It's Been a Long Half Century Since We Went to the Moon...But We May Finally Be Going Back

Exactly fifty years ago at this time, American astronauts Gene Cernan and Harrison Schmitt were on the surface of the Moon while fellow astronaut Ronald Evans orbited the Moon in the command module. Cernan and Schmitt were the eleventh and twelfth people to walk on the Moon, while Evans was one of another twelve to fly to the Moon without landing on it. Cernan and Schmitt spent over three days on the Moon, and nearly a day of that was spent outside actually walking or driving out on the surface, with both their total time and time outside exceeding the records set in previous missions. But on late on December 14, 1972 (Coordinated Universal Time; in Asia and much of Europe and Africa it was early December 15), Cernan and Schmitt lifted off in the lunar module to rendezvous with Evans a few hours later. Late on December 16, the three left lunar orbit for the return journey to Earth. 

Apollo 17 astronaut Gene Cernan with the Lunar Rover (NASA)

Since that time half a century ago, humans have not been back to the Moon. Of the twelve people who walked on the Moon, only four are still alive: Schmitt, Apollo 11's Buzz Aldrin, Apollo 15's Dave Scott, and Apollo 16's Charlie Duke. Of the twelve others who flew to the Moon without landing, six are still alive: Frank Borman (Apollo 8), Jim Lovell (Apollos 8 and 13), Bill Anders (Apollo 8), Tom Stafford (Apollo 10), Fred Haise (Apollo 13) and Ken Mattingly (Apollo 16). The three youngest are Mattingly (86), Duke (87) and Schmitt (87); most of the others are over 90. For that matter, everyone who can actually remember watching or hearing about the Moon landings at the time they were happening is well over fifty now; those of us who recently hit that milestone were too young at the time to have any memory of it, and anyone younger was of course not even born yet. Human exploration of the Moon is not yet gone from living memory, but it is becoming more and more distant in the past. 

This is very unfortunate. Not so much because being in the distant past will make it easier for some to claim it never happened; people who claim such things are idiots and fools — after all, only a tiny handful of people alive today are old enough to have even a vague memory of World War I, but only complete idiots would claim that World War I never happened. However, humans landing on the Moon was, at least in terms of physical exploration of our surroundings, our peak achievement as a species, and it is something of a tragedy that in half a century since we have not even managed to replicate it, much less surpass it. 

But that may finally be about to change. As those who still manage to keep abreast of a wide range of headlines — or those whose information bubbles include news relating to science and technology — may have heard, the US space agency NASA, responsible for the Apollo missions half a century ago, recently launched the Artemis 1 mission to the Moon, this time with major contributions from the European Space Agency. While this mission was uncrewed, the Orion spacecraft that flew to and orbited the Moon over the past few weeks, returning to Earth exactly 50 years to the day and almost to the hour after Cernan and Schmitt landed on the Moon (December 11 UTC), is designed to eventually carry humans, and if all goes well, the next Artemis mission will take humans back to the Moon again. We will have to wait until at least 2024 for this to happen, and that first mission back, like Apollo missions 8 and 10 (and 13, though for less fortunate reasons), won't involve landing on the Moon, just flying there and coming back. But that's far more than we've done in half a century, and the mission after that, perhaps in 2025 or 2026, should see humans landing on the Moon once more, and this time those going will include women and people of color, unlike the Apollo missions, which were exclusively crewed by white men. 

I fervently hope that most of the remaining Apollo astronauts will still be around to see humans return to the Moon. But just as importantly, I hope that once we as a species do get back to the Moon, we will continue to explore it regularly, and even go beyond it, to Mars or the asteroids. Of course if we want to maintain a regular presence in space beyond low Earth orbit (there have already been in low Earth orbit continuously for the entire 21st century) for decades or even centuries, we will have to solve the many problems we have created for ourselves down on Earth, including the climate crisis, the biodiversity crisis, and many more. But despite what some people might say, and indeed have been saying since the Apollo era, that doesn't mean we shouldn't be going to the Moon. Going to the Moon and solving problems on Earth are not mutually exclusive goals; in fact, our exploration of space, including figuring out how to sustain human life far from Earth, can be directly useful in finding ways to deal with Earth-bound problems (and it can also just provide inspiration — the famous Blue Marble photo of Earth, which helped inspire the environmental movement, was taken by the Apollo 17 astronauts).

So let's celebrate the anniversary of Apollo 17 with the hope that in the next two or three years, humans will finally follow in the footsteps of Cernan, Schmitt, and their fellow Apollo astronauts, and we will get to see people walking on the Moon, not as distant history but as part of our present.

Reflections on the 50th Anniversary of the First Moon Landings

It's been quite some time since I've written anything here; while I've felt the inspiration to write something on a few occasions, I've always ended up distracted by something else. But the 50th anniversary of the first Moon landing really is too good an opportunity to pass up. A few years ago I posted something on the last Moon landing, which took place in December 1972; since I am writing this without referring to that piece, I may repeat myself on a few points, but then they are likely to be worth repeating.

Apollo 11 lifted off on July 16, 1969 and entered lunar orbit on July 19. Neil Armstrong and Buzz Aldrin went down to the surface in the lunar module on July 20, leaving Michael Collins in the command module, and Armstrong and then Aldrin stepped out onto the surface a few hours after landing (the time was late in the evening on July 20 in the US, but in most of the world it was July 21). After a few hours on the surface, Armstrong and Aldrin returned to the LM and then ascended from the surface to rendezvous with Collins for the return to Earth, which they reached on July 24, fifty years ago today. This was indeed a momentous journey, arguably the greatest single achievement by humans in the few hundred thousand years we've been in existence. But despite the attention that Apollo 11 as a mission and Aldrin and especially Armstrong as individuals receive, it's worth remembering that this was not the only mission to the Moon, and Armstrong and Aldrin were not the only people to walk on its surface.

Though Armstrong and Aldrin were the first to walk on the Moon, they and Collins were not the first humans to travel there. The first flight to the Moon took place in December 1968 during the Apollo 8 mission, with Frank Borman, Jim Lovell and Bill Anders becoming the first people to orbit the Moon. The Apollo 9 mission stayed in Earth orbit, as had the Apollo 7 mission (both were still important tests of the hardware needed for the later missions), but Apollo 10 was a full dress rehearsal for the first Moon landing, in which Tom Stafford, Gene Cernan, and John Young flew to the Moon and did everything short of actually landing, including taking the lunar module down towards the surface before returning to the command module. The lunar module's ascent stage was sent into orbit around the Sun, unlike later ascent stages, which were left in lunar orbit to later crash on the Moon's surface, meaning the Apollo 10 ascent stage is the only derelict once-crewed spacecraft still somewhere in space (a recent study indicates that the asteroid 2018 AV2 is probably the spacecraft). This Apollo mission has special significance for me personally, since I was born while it was taking place.

Not only were there missions to the Moon before Apollo 11, but there were quite a few afterwards. From Apollo 12 in November 1969 to Apollo 17 in December 1972, there were five more successful Moon landings in which Pete Conrad, Alan Bean, Alan Shepard, Edgar Mitchell, David Scott, John Young, Charlie Duke, Gene Cernan, and Harrison Schmidt walked on the Moon, in the later cases staying for as long as three days on the surface of the Moon. The one mission without a Moon landing was Apollo 13, in which an explosion in the service module forced an emergency return to Earth, though they have to fly by the Moon in order to gain the velocity to make it back to the Earth. This meant that Jim Lovell, who commanded the mission, became the first person to fly to the Moon twice (Young and Cernan did it later), and the only one to go twice without landing. In all, in addition to the 12 people mentioned above who walked on the Moon, there were 12 more, including Lovell, Borman, Stafford, Collins, et al, who flew to the Moon without landing. What's unfortunate is that of the 12 who walked on the Moon, only Aldrin, Scott, Duke and Schmidt are still alive, though eight of the 12 who flew to the Moon without landing are still alive (oddly enough, the only Moon mission with all three members of its crew still alive is the earliest, Apollo 8; on the other hand, all three astronauts who flew on Apollos 12 and 14 have died). Lovell and Borman are 91, and Aldrin at 89 is the oldest of the remaining moonwalkers. Charlie Duke is the youngest, but even he is 83. As I noted in my previous post on the subject, there's a danger that if humans don't make it back to the Moon in the near future that there will come a time when there's no one alive who has been there. For now, at least, many of them seem to be in good health for their age. Late last month I attended the Starmus festival in Zurich, and Aldrin, Duke, Schmidt, and Al Worden (command module pilot on Apollo 15) all attended and seemed in good shape. Collins was supposed to come but his trip was vetoed by his doctor, though it was seemingly nothing serious. Regrettably, I didn't manage to meet any of the Apollo guys, though I saw them all up close and did interact a bit with a few of the other speakers.

Incidentally, I have almost finished reading Michael Collins' autobiography Carrying the Fire, which is widely regarded as one of the best if not the best Apollo astronaut autobiography, and is also notable for being written by Collins alone, without help from a ghostwriter or co-author. It is indeed very good and is fascinating reading, doing much to support a reference I once saw to Collins as the most articulate of the Apollo astronauts. He certainly comes across as very knowledgeable on a variety of topics. While a professional co-author might have smoothed out some of his transitions in topics, in many ways his occasional tangents and throwaway remarks make the book more interesting than they would be otherwise. He also manages to inject a fair amount of humor as well as managing to keep up the pacing throughout the book. There are a few bits that are not exactly politically correct by today's standards, but are pretty standard fare for the time it was written in the early 1970s. Collins himself said in a recent interview that he hasn't read it in years and if he did would probably find things he thought were wrong or that he disagreed with, and perhaps those might include his slightly disdainful attitude towards hippies or his relief that women weren't recruited into the Apollo program (his chief reasons were the need to redesign the spacesuits and the awkwardness of having to relieve oneself in mixed company). On the other hand, he expressed regret that they didn't have any black astronauts in the program, and other parts of the book show that he had a fairly progressive outlook for the time.

One of the most impressive parts of the book was the very end, where he talks about the effect that going to the Moon had on him personally; delves into the question of whether the Apollo program was worth it, giving an even-handed overview of the arguments on both sides, though naturally concluding that it was; explains the foolishness of an "either/or" mentality ("Either cure cancer or fly in space") when it's possible to try to do both; and talks about the fragility of Earth as a planet, including the danger of polluting it without restraint (he refers to the pollution residues from use of fossil fuels as "unholy evidence of our collective insanity") and how our common interest in keeping our home planet habitable outweighs the things that separate us. Another impressive part of the book was his prefaces to the 40th and 50th anniversary editions, which make even more apparent that he has a clear and even progressive view of the world's major problems. For instance, he stated in 2009 and restated in 2019 that "we need a new economic paradigm to produce prosperity without growth", a sentiment I heartily agree with, "socialist" though some might think it. He also cited rising global temperatures as a serious problem in his 2019 preface, a refreshing change from a few of his fellow Apollo astronauts, who despite being otherwise very intelligent have in a couple of cases made comments indicating they are (or at least were) climate change deniers. Collins, on the other hand, very wisely recognizes that global warming, overpopulation and endless, unsustainable growth are serious problems.

But to return to the Moon landings, it is easy to underestimate their importance. Yes, to a large extent they were a one-off (even though there were six of them), an outgrowth of the Cold War that were motivated as much or more by geopolitics as a genuine urge to accomplish the incredible. But nevertheless, not only did they force a much more rapid advance in many areas of technology than might have occurred (among many other things, computers had to be miniaturized far beyond what had been previously achieved, though of course now Apollo-era computers seem incredibly primitive), but they inspired a whole generation of scientists, engineers, and innovators, something which is far more important than people realize. Apollo also showed that with a concentrated effort by many intelligent, dedicated people we can things that seem almost impossible at the outset. This is a lesson that we should take to heart today.

Of course, even at the time, there was considerable opposition to the Apollo program, and both then and now people talk about the contrast between the amazing achievement of putting humans on the Moon and the enormous problems that we can't seem to solve on Earth, a contrast that is captured well in John Stewart's contemporary song "Armstrong". Many argued and sometimes still argue that the money spent on Apollo would have been better spent on Earth. But this criticism was and is misguided. Yes, both then and now, more should be spent on addressing poverty, disease, and environmental degradation, among other things. But there are many much more wasteful things that we could take money from to do so, whether it's public spending on the military or tax breaks for the wealthy, or private spending on frivolities like sports and cosmetics. Space exploration, on the other hand, provides profound benefits to humanity, both practical and abstract, and is worth every penny. And as Michael Collins stated in his speech to a joint session of Congress a few months after Apollo 11, "We cannot launch our planetary probes from a springboard of poverty, discrimination or unrest; but neither can we wait until each and every terrestrial problem has been solved." As he says, we can both work to solve our problems on Earth and continue to explore space at the same time.

Another point worth remembering is that while Apollo shows what we can do if we put our minds to it, that doesn't mean that even an all-out, Apollo-type effort will be met with the same success if we try it in other areas. Despite the immense difficulty of landing people on the Moon, it had the advantage of being a clear goal that would either be achieved or not, with no ambiguity. If we set out to eliminate poverty, on the other hand, not only would we be taking on a task that is even more massive than going to the Moon, we would have to agree not only on how to do it, but how to know if we'd succeeded. After all, it's not as if there's even a consensus on how to define poverty. Another advantage we had with Apollo was that there was no active opposition in the sense of people working directly against the goal, though there were many who considered it a waste of resources. But if we set out to bring carbon emissions to zero by a certain date, as indeed we should, while the goal is clear enough there will be many forces actively trying to work against it, such as the powerful interests that make their money from fossil fuels. This is not to say that we shouldn't use Apollo as inspiration for future transformative projects like addressing the climate crises, just that we should understand that as hard as Apollo was, it was considerably easier than some of the things we should now be trying to do.

Finally, there's the question of going back to the Moon itself. Of course this is something I'd like to see happen, and the sooner the better, since as noted above it's hard to tell how much longer the last few living moonwalkers will be around and I'd like to see someone get to the Moon while at least one or two of them are still alive. I will admit that I'd rather it not be the Chinese who get there first, though if they make it there afterwards is fine, and I also certainly wouldn't want to see the current US administration get credit for an American return to the Moon. While it'd be nice to view the exploration of space as something that transcends politics, the truth is even a wonderful achievement like going to the Moon could be misused, particularly by nationalist types like those running both the Chinese and US governments. Of course if the US doesn't have a new president in less than two years we're all in trouble anyway. But I digress. As I said above, space exploration is definitely worth the money, so ideally we'll see more of it by the US, the European Union, Japan, India, and, yes, China too, alongside private companies like Space X and Blue Origin. There are a lot of serious questions to be addressed as soon as possible, like how exploitation of resources in space will be regulated and what measures we need to take in terms of planetary protection (i.e., the contamination of other places by Earth organisms or vice versa), but those should only affect how we explore space, not whether we do so. After all, while the Apollo missions to the Moon may be the pinnacle of human achievement so far, we don't want them to always be so. 

The Planets of TRAPPIST-1: Multiple Potentially Habitable Earth-like Worlds in a Single System

Though there’s plenty happening on Earth to write about, considering how grim much of it is, it’s something of a relief to be able to instead comment on some fascinating astronomy news. I’m of course referring to the announcement that seven apparently Earth-like planets have been identified orbiting a single star, and one that is on a cosmic scale quite close (though on a human scale the star and its planets are still very, very far away, a point I will come back to later). To put this in perspective, prior to this discovery, the star with the greatest number of terrestrial (i.e., rocky and relatively similar to Earth in size) planets was our own Sun with four, namely Mercury, Venus, Earth itself, and Mars. There are no doubt other systems with multiple terrestrial planets, but due to the relative difficulty of spotting such planets, most discoveries to date have been of larger planets, though there are a few known systems with one or more super-Earths (planets somewhat larger than Earth which may also be rocky). What makes this newly discovered system even more fascinating is the fact that several of the worlds appear to be in the star’s habitable zone, and the relative closeness of the system and the nature of its parent star means that we will be able to study their possible atmosphere is in the near future, and maybe determine if the gases present in those atmospheres indicate the presence of life.

The star that the newly discovered planets are orbiting is called Trappist-1 (technically it should be capitalized as TRAPPIST-1, but I will use the lower case form) and it is located 39 light years away. Though most of its planets seem to be similar to Earth in mass and radius, the star itself is nothing like the Sun. It is a very cool red dwarf star, which means that it produces far less energy than the Sun. One of the charts used in some articles about Trappist-1 and its planets compared the orbits of the latter not only to those of the four terrestrial planets orbiting the Sun but also to the orbits of the four Galilean satellites of Jupiter. This makes sense when you realize that Trappist-1 is in many ways as similar to Jupiter as it is to the Sun. In fact its diameter is only slightly greater than Jupiter’s, and the orbits of its planets resemble those of the Galilean satellites more than they do those of the four terrestrial planets in our Solar System, though they are still considerably further out from the star than Jupiter’s moons are from Jupiter. The ratio of their masses in comparison to their star is also similar to that of the Galilean moons in comparison to Jupiter. Nevertheless, while Jupiter is just a planet (though a very big one), Trappist-1 is a star powered by nuclear fusion in its core, and it is still more than 80 times as massive as Jupiter, though it is only 8% as massive as the Sun. So it gives off enough energy that many of its planets, given their close orbits, could potentially have liquid water on their surfaces, unlike the moons of Jupiter, which remain frozen on their surfaces (though Europa at least almost certainly has liquid water underneath its icy crust).

The planets, designated b to h in order of their distance from the star, orbit at distances that are a fraction of Mercury’s distance from the Sun. They were discovered by the transit method, which involves observing the dimming of the star’s light as a planet passes in front of it. Trappist-1b orbits the star in just 1.5 Earth days, and even the most distant planet, Trappist-1h, takes only about 20 days to complete on orbit (though this planet is the one about which there is the greatest uncertainty). Though at this point we only have rough estimates of the planets’ masses and diameters, it appears that c and g are somewhat larger than Earth but not by very much, and the other planets are slightly smaller than Earth, though even the smallest two, d and h, are larger than Mars. The planets are likely to be tidally locked so that they always show the same face to their star, just as the Moon does toward Earth. However, if they have atmospheres the temperature contrast may not be as great as it would be otherwise.

The planets d, e and f receive similar amounts of energy from Trappist-1 as the Earth does from the Sun, putting them in what is known as the habitable zone. Some of the other planets could potentially have moderate temperatures and liquid water, depending on their particular circumstances (for instance, if g has a thick enough atmosphere it might retain enough heat to stay above water’s freezing point). However, there is a lot of uncertainty involved. If Earth didn’t have an atmosphere with a greenhouse effect, it would be frozen despite the amount of energy it receives from the Sun (of course our problem now is that we are increasing the amount of greenhouse gases, which could disrupt the climate’s equilibrium in the other direction). It is uncertain how many of these planets have atmospheres or how thick they might be. Red dwarf stars are prone to violent flares, which may strip atmospheres from close in planets. The planets closer in may also have lost all their water or have undergone a runaway greenhouse effect like that on Venus in our solar system. The ones further out may have ended up like Mars if their atmospheres are too thin.

Despite these caveats, given the number of planets, it seems likely that at least one or two have moderate, Earth-like temperatures and high potential for liquid water on their surfaces. What’s more, since these planets are much closer to us than many other exoplanets (planets orbiting stars other than the Sun) that are in their star’s habitable zones – for example, the probable super-Earth Kepler-452b, which orbits a Sun-like star, is about 1400 light years away – and they orbit close to a dim star and transit it frequently, they are much easier to study. With slightly improved telescopes such as the ones that should be coming online in the next few years, it should be possible to analyze the components of these planets’ possible atmospheres and determine whether gases commonly produced by living things are present. There are a few other potentially habitable exoplanets that are closer these ones, notably the one orbiting the closest star other than the Sun, Proxima Centauri (or Alpha Centauri C), but not all of these transit their stars from the perspective of Earth (for example, Proxima Centauri b, which was discovered by the radial velocity method which measures changes in a star’s apparent velocity due to the gravitational effects of a planet, apparently does not transit its star), and most are super-Earths, rather than being truly Earth-like. What’s more, the presence of multiple Earth-like planets in the habitable zone of the same system makes it a uniquely attractive target for study.

Of course, just because the planets are potentially habitable does not mean that they are actually inhabited by any form of life. As noted, they may be in fact either too hot or too cold, too lacking in water, or too heavily irradiated, for life to have developed. We still don’t know what conditions are required for life to appear, though from what we see on Earth we know that life is amazingly tenacious and adaptable once it does appear. Furthermore, even if one or more of the planets has some form of life, the chances that they have intelligent life are much smaller, and the chances of a technological civilization like that of humanity are even smaller. As I have argued before, I suspect that the real reason we’ve seen no signs of advanced alien civilizations all over the galaxy is that while life itself may turn out to be common, multicellular life (which only appeared on Earth billions of years after single-celled life forms) is much rarer, and intelligent life that happens to evolved the physical characteristics for building a civilization (a condition that prevents, say, dolphins from making tools or building spaceships) and lives on a planet with the right resources (a lack of iron on the planet’s surface, for instance, would make it hard for even human-like creatures to get very far towards developing advance technology) may be so rare that it only exists on a few planets out of all the billions in the entire galaxy at any given time. But even evidence of “primitive” life would be an incredibly exciting discovery, and these planets give us the best chance of discovering it outside our solar system in the near future that we have yet seen.

Perhaps inevitably, a number of articles about this discovery mentioned jokingly the possibility of escaping the growing mess created by the new US administration and the threat of right-wing populism in Europe by colonizing these potentially habitable planets, or alternately sending all the troublemakers on Earth to them and thus ridding ourselves of them. Unfortunately, direct exploration of these planets, even by robotic spacecraft, remains an extremely distant prospect. As I explained in my commentary on the discovery of Proxima Centauri b, we are a long way from being able to travel to other stars in a reasonable time frame. One article on the Trappist-1 planets noted that one of the fastest spacecraft ever launched, the New Horizons probe that explored Pluto (reaching that distant planet in a little less than 10 years after its launch from Earth), would take about 750,000 years to reach Trappist-1. It’s possible that an effort like Breakthrough Starshot might actually see miniature spacecraft traveling to the closest star systems, such as Alpha Centauri, before this century is over, but even if that ambitious project succeeds, it would still take a couple of centuries for spacecraft traveling at the speeds targeted by the project to reach Trappist-1, which is almost 10 times as distant as Alpha Centauri. Nevertheless, simply by studying the planets from Earth, we may be able to discover if any of them host life. If we do find solid evidence of life on any of them (which, it must be emphasized again, is not guaranteed), it may provide the motivation for even more intense efforts at finding better methods of starship propulsion. Even the knowledge that life exists on a planet or, even more excitingly, multiple planets orbiting a nearby star would have a dramatic effect on our view of our place in the universe.

Big Astronomy News: A Planet Has Been Found Orbiting Proxima Centauri

I’d originally intended to finish my much delayed overview of some of the books I’ve read this year, or perhaps comment on the US presidential race (particularly the incredible blathering of the Republican candidate), but instead I’ve decided on a very interesting piece of recent news in the field of astronomy. Last week it was announced that a planet had been found orbiting Proxima Centauri, which is the closest star other than the Sun (hence its name). Not only is this the closest exoplanet that has ever been discovered or will be discovered (unless we find a closer free floating planet or one orbiting a currently undiscovered nearby brown dwarf), it is at the right distance from Proxima Centauri to have a reasonable chance of having liquid water on its surface and thus being habitable to life as we know it (though as I will get into below, a number of factors could substantially increase or decrease its habitability). All things considered, this looks like the most important exoplanet discovery yet.

Proxima Centauri is just over 4.2 lightyears from our solar system. It is also sometimes called Alpha Centauri C, as it probably (though not certainly) is gravitationally bound to the binary star Alpha Centauri, orbiting the other two stars (known as Alpha Centauri A and Alpha Centauri B) at a distance. The Alpha Centauri binary is about a tenth of a light year further away and is one of the brightest stars in Earth’s sky. Proxima Centauri, on the other hand, is not visible to the unaided eye. This might seem surprising considering the proximity it is named for, but not quite as much so if we keep in mind that it is a red dwarf. Such stars are actually by far the most common in the galaxy (and presumably the rest of the universe), but they are much smaller and cooler, and thus much dimmer than even the Sun, which is less intrinsically bright than the majority of stars that are prominent in our skies.

Since Proxima Centauri is a red dwarf, its habitable zone – as the range of distances at which an orbiting planet might be reasonably expected to have liquid water on its surface is known – is far closer in than it is in the case of the Sun. The newly discovered planet, for now simply known as Proxima Centauri b (or just Proxima b), is much closer to its star than Mercury is to the Sun, and its year is just 11 Earth days. This means that it is probably tidally locked with one side always facing Proxima Centauri. Though this means that the planet would have one hot side and one cold side, if it has a substantial atmosphere that could moderate temperatures enough for it to remain habitable. Nevertheless, it is still unlikely to be as comfortable an environment for life as Earth. This is even more so because of a major issue with Proxima Centauri itself, namely the fact that is a flare star, prone to outbursts that would bathe the planet in intense radiation. Some astronomers think this alone may make it unlikely that life has arisen on the planet, but others note that if the star hasn’t always been as active as it is now, life on the planet may have had a chance to evolve some resistance, or other factors might help mitigate the radiation problem.

Another difference between Proxima b and Earth is that the former is more massive. The figure that has appeared in reports about the planet is 1.3 Earth masses, but this is actually the minimum mass – it could be quite a bit more massive, depending on the angle from which we are viewing its orbit. However, it is at least 90% likely to be less than 3 Earth masses, which is still closer to Earth in size than most known exoplanets, so in this respect at least it’s one of the most Earth-like planets found yet (on the negative side, the most Earth-like planet in terms of mass that I know of is Venus, which is not at all habitable now, though it might have been in the remote past). What we don’t know is what kind of atmosphere it has, and that is naturally a crucial piece of information in determining its habitability. It needs to have enough of an atmosphere to warm the planet up past the freezing point of water (the Earth itself would be frozen if it didn’t have an atmosphere that trapped heat, though of course our current problem is that we’re changing it so that it traps too much) and to spread heat around if it is tidally locked. Other factors that may affect how habitable Proxima b is include whether it has a strong magnetic field (which would help stop some of that deadly radiation from hitting the surface of the planet), whether it has plate tectonics (which keep things stirred up inside the planet, ensuring that elements essential to life as we know it get to the surface), and how much water is in the system.

Despite all the unknowns which could potentially lower or even eliminate the chance of life having developed on the planet, it is clear that based on what we know now, this is the most exciting discovery yet in terms of potential life bearing planets outside our solar system. Proxima b is, as noted above, fairly close to Earth in mass, orbits in the habitable zone, and is closer than any other potentially habitable exoplanet we have found or that we will ever find in the future. The only discovery that could beat this one would be an Earth-sized planet in the habitable zone of Alpha Centauri A or Alpha Centauri B. Why? Because these two stars, unlike Alpha Centauri C (Proxima Centauri), are much like the Sun, with A being a little larger and B being a little smaller. However, my understanding is that even if there is such a planet around either of these stars, it would be undetectable with the technology we have now. This is because an Earth-sized planet at that distance would not tug on its star enough for us to detect it. There was an announcement several years ago that a planet had been found orbiting Alpha Centauri B; I even wrote a blog post on it. But that discovery has never been confirmed, and later analysis seems to indicate it doesn't exist. In any case, it was said to be orbiting very close in (making it much easier, though not actually easy, to detect than a planet in the habitable zone). So until in the (we hope near) future advances in technology make it possible for Earth-like planets, if they exist, to be found in the right orbits around the Sun-like Alpha Centauri stars, Proxima b is our best bet for exploring a potentially life-bearing exoplanet.

One thing must be kept in mind, though, when we use words like “close” to describe Proxima Centauri and its planet, and that is they are only close in comparison to other stars and their planets. They are still extremely far away. As I’ve mentioned in several previous posts, it’s important to keep in mind that interstellar distances are enormous, so much so that even Proxima Centauri is currently far beyond our reach. It took New Horizons almost 10 years to reach Pluto, while light makes the same journey in just over five hours. By contrast, it takes light over four years to travel from the Sun to Proxima Centauri. Voyager 1, the most distant spacecraft humanity has launched, has traveled more than 100 AU since its launch in 1977, but that’s a tiny fraction of the distance to Proxima Centauri. Neither Voyager 1 nor New Horizons is aimed at th is e Alpha Centauri system, but if they were, it would take them tens of thousands of years to get there. As for exploration by humans, we haven’t gotten as far as Mars yet, so it will take some really big technological advances to send humans to Proxima b, if it ever becomes possible at all.

However, this isn’t to say that Proxima b will remain beyond our reach forever. While humans are unlikely to go there in the foreseeable future, we might send robotic spacecraft there as soon as the next half century. Unless we make a major effort, we probably won’t find a way to accelerate New Horizons-type craft to the speeds necessary to reach the Alpha Centauri region this century, but we might pull it off with something smaller, such as the miniature spacecraft of the Breakthrough Starshot project. By the (possibly optimistic) timeline that those involved have suggested, a fleet of these laser-propelled probes could be launched within a few decades, if all the difficulties can be overcome. If they are launched, are successfully accelerated to a significant fraction of the speed of light, and a few of them make it all the way without incident (a collision with even a piece of dust at that speed would likely destroy the craft), we might be getting some kind of pictures and other data (depending on how successful the project is at miniaturizing the science instruments to fit on such small probes) from Proxima b forty to fifty years from now. I hope, however, that a few craft are sent on to Alpha Centauri A and B, since whether or not a planet has been found in the habitable zone around either star by launch time, if no search has been able to rule such a planet out, it would be worthwhile to look for one, since as noted above these two stars are much more similar to the Sun than their dim companion Proxima (or for that matter any other star within ten light years). There’s even a slim chance that all three stars have habitable planets or even inhabited ones. If just one planet in the Alpha Centauri system, whether it’s Proxima b or a planet orbiting the other two stars, is indeed home to life, it will drastically change our view of the universe. Even if the system is without life, close-up views of a planet orbiting another star would be well worth the time it would take to get there.

Political News from the US, the Philippines and Taiwan, Plus More Planet Discoveries

In the last few weeks, there have been quite a few interesting news items, some good, some not so good, but all worthy of talking about in some depth. Unfortunately, I’ve been too busy lately to do a lot of writing, so for now I’ll settle for a few quick comments on some of them.

In the US, it looks more and more like the US presidential election is going to come down to Hillary Clinton and Donald Trump (aka Donald Drumpf). While Bernie Sanders is still in the race, looking at the math it is highly improbable that he could end up winning a majority of the pledged delegates, and if Clinton ends up with a majority of the pledged delegates (as she is almost certain to do), there is no reason for any of the superdelegates who support Clinton to change sides, and no justification for protests by Sanders supporters that the establishment (in the form of the superdelegates) somehow stole the nomination for Sanders. I do think Sanders should stay in the race until the primaries are over, but I hope he and his campaign will focus on policies, rather than attacking Clinton, and I hope Clinton will make an effort to win over Sanders’s followers (the open-minded ones at least) by taking even more strongly progressive stands. As for how Clinton compares to Trump, I’ve addressed the question some in previous posts, and I will no doubt do so again. But to put it succinctly, anyone who thinks that, whatever Clinton’s real or imagined flaws, Trump would be in any way a better president for anyone inside or outside the US other than Trump himself and a very narrow group of other people (e.g., those who would rather see the country collapse and the Earth overheat than have to live near Muslims, undocumented people or other “undesirables”) is either ignorant, delusional, somewhat lacking in intellectual capacity or, in the most charitable interpretation possible, not thinking clearly. Trump would be a disaster, and Clinton would be at worst adequate and possibly even excellent.

Speaking of terrible presidential candidates, the Philippines not only managed to elect one, but did so in a landslide. Former Davos city mayor Rodrigo Duterte is supposedly a socialist, so his economic policies at least shouldn’t blatantly favor the elite, but his complete and open disregard for human rights and the rule of law is appalling. He claims he will wipe out crime through summary execution of criminals (he claims to prefer hanging them), and considering his seeming support for virtual death squads as mayor, he is likely to at least try to do what he has said, no matter how many innocent people get killed by “mistake”. Then there was his utterly appalling rape joke, which alone should have been enough to turn off most reasonable voters. He even aimed a crude insult at Pope Francis. It’s no wonder he has been compared to Trump. Unfortunately, the Philippines is now stuck with him. While it’s tempting to say that they deserve him because they elected him, there were plenty of Filipinos who didn’t vote for him, and even some of those who did may come to regret it. Unfortunately, tough talk appeals to a lot of people, especially those who want simple solutions to complex problems – here in Taiwan that has manifested in the form of bizarre statements by all sorts of people in support of the death penalty, such as asserting that executing one particular criminal will somehow prevent random killings in the future, despite there being no evidence that the death penalty in general (let alone a single execution) has a significant deterrent effect.

Meanwhile in Taiwan, we're finally getting a new President, as Tsai Ing-wen of the Democratic Progressive Party is taking office four months after her landslide election victory. This will be the first time since Japanese rule ended in 1945 that the KMT (the Kuomintang, i.e., the Chinese Nationalist Party that fled to Taiwan after losing power in China) controls neither the presidency or the legislature, as during the previous DPP administration of Chen Shui-bian, the KMT held a solid majority in the legislature, whereas this time the DPP won a solid majority. Of course China is not happy about this, since the DPP is more inclined to stand up to them on sovereignty issues, but hopefully Tsai will not bow to the pressure China is already attempting to exert. In any case, while it's fair to expect some improvement under Tsai, outside groups still have to keep an eye on the DPP to make sure it remains responsive to the public.

A more unequivocally positive piece of news was the announcement of 1284 new exoplanet discoveries. While we still haven’t found a true twin of Earth (i.e. a planet with a size and mass very similar to Earth’s orbiting a star like the Sun at a distance similar to that of Earth’s distance from the Sun), in part because the methods used make detecting such a planet difficult, we are finding more and more planets that are comparable to Earth, and some that at least theoretically could be habitable by life as we know it. What’s particularly amazing is the Kepler telescope that has made these discoveries focused on what it actually a very small slice of the Milky Way galaxy, so the actual number of planets in the entire galaxy is vastly greater. It’s easy to forget how truly huge the galaxy is. The number of stars that Kepler observed for evidence of planets is a tiny fraction of the total number in the Milky Way, and from what I can tell, even some of these parent stars of the newly discovered planets had never been specifically catalogued, despite the fact that they are for the most part relatively near to us (relatively being a key word here, as the distances are still vast). The huge number of stars in the galaxy, not to mention the huge number of galaxies in the universe, is why I am pretty sure that there is certainly some form of alien life out there somewhere. The problem, as I have observed in the past, is that intelligent life capable of creating a technological civilization (and not destroying it again relatively quickly through environmental degradation, war, or some other means) may still be extremely rare, and given the distances involved, our closest neighbors of that sort may be too far for us to find them anytime in the immediate future. But just by searching we will learn a lot, and I suspect that in the next half century or so we’ll at least have found strong evidence of life (though not necessarily intelligent life) on planets beyond our Solar System. That at least will be some consolation if things are not going well here – though we should do our best to ensure that is not the case, by preventing the Trumps and Dutertes of the world from getting too much power.

From Space X to Starshot, Plus Some Sobering Earth Day News

There have been two exciting bits of news in the field of space exploration in the last few weeks, though one of them is considerably more immediate than the other. The first is that after several attempts that narrowly failed, Space X finally managed to land one of its rockets on a floating barge at sea. This is only the second time a rocket used to launch objects into orbit has landed again successfully and the first time anyone has landed a rocket at sea. A few months ago, Space X landed a rocket on land, and its rival Blue Origins has landed and reused a rocket, though theirs was a suborbital one. While landing a suborbital rocket is a significant achievement, it is still easier than landing one that has been used to boost an object into orbit, as the latter return to Earth at a much higher speed. And naturally landing a rocket on land is easier than landing one on a moving platform at sea. But as Space X founder Elon Musk and others have explained, if these rockets are to be fully reusable, it will often be necessary to land at sea, as returning to the original launch site to land requires more fuel than may be left in the rocket, depending on the circumstances of the launch.

So why is this a big deal? A rocket costs tens of millions of US dollars or more, and yet up till now, every rocket that has been launched has been a one-shot deal. If Space X is able to regularly reuse rockets, that will reduce the costs of launching objects into space dramatically. This will lead to space becoming more widely accessible, and will open up all sorts of possibilities. Of course, one success doesn’t mean that Space X will manage to land and reuse all of their rockets in the future, but even if they do so with a significant percentage, that will make a big difference. Maybe within as little as a decade, advances by companies like Space X will lead to a huge increased human presence in space. Besides that, watching a rocket land on a barge is cool, all the more so when the barge is named for one of the humorously and idiosyncratically named intelligent spaceships from Iain M. Banks’s Culture novels, in this case “Just Read the Instructions” (Space X’s other barge is named “Of Course I Still Love You”).

The other exciting piece of space news is admittedly much less likely to lead to any actual results in the near future, but if it does come to fruition, it could potentially be as exciting as a human mission to Mars. This is a project announced by Nobel laureate Steven Hawking and Russian billionaire space enthusiast and physicist Yuri Milner called Breakthrough Starshot. They propose to develop and launch a fleet of miniature spacecraft equipped with light sails, and to use a giant laser array to accelerate them to a significant fraction of the speed of light (as much as 0.2c, or 20% of light speed) in the direction of Alpha Centauri, the star system nearest to the Sun. The spacecraft will be tiny – a mere centimeter or so in size – which is what will make it possible to accelerate them to such a high speed. The basic technology for the project already exists, but it will still need considerable refinement and improvement, and there are numerous engineering obstacles to overcome, from construction of the laser array to avoiding overheating the spacecraft to aiming the spacecraft. It will probably take several decades before anything is actually launched, even assuming the difficulties can be overcome.

If Hawking, Milner and their cohorts succeed, however, it could be a transformative moment for humanity. As I have discussed before, even Alpha Centauri is incredibly far away. A spacecraft like New Horizons, which recently flew by Pluto after a nine year journey from Earth, would take many tens of thousands of years to reach Alpha Centauri. The Starshot miniature spacecraft would get there a thousand times faster, perhaps arriving as soon as half a century from now. While such tiny ships would be limited in what they could do, they should at least be able to take a few pictures and gather basic data. If there are planets orbiting either of the main components of the Alpha Centauri system, that would be incredibly exciting. Even if the only planets present are uninhabitable ones, it would be extremely dramatic to get our first relatively close up pictures of an alien world outside our solar system. But if there is an Earth-like planet in the habitable zone of either star, pictures of it would almost certainly inspire an all-out effort towards further interstellar exploration, perhaps even eventually by humans – though without some unforeseeable breakthrough, that will take centuries, even with the knowledge of a potentially habitable (or even inhabited!) planet a few light years away to motivate us.

But we will certainly not be able to launch any large scale interstellar missions in the coming centuries or even take advantage of cheaper space travel to colonize the Moon or Mars in the coming decades if our civilization can’t survive climate change. As it’s Earth Day, I’ll close with a much more sobering piece of news. Not only was this past March the warmest March on record, making it 11 months in a row that a new monthly record has been set, it surpassed the average by more than any month ever. While even past record setting months have seen a few parts of the globe where temperatures were noticeably cooler than average, it was warmer than average nearly everywhere last month, and in many places regional temperatures also set an all-time record for the month. While part of this is because of El Nino, this past year has been far warmer than 1998, the last year with a strong El Nino, and the first three months of 2016 have been easily the warmest three month period ever. If this keeps up, 2016 could beat 2015 as the hottest year ever, just as 2015 beat out 2014. Even with the end of El Nino, global temperatures are unlikely to drop back to the levels of even the 1990s any time soon. Since even if humans do manage to colonize space in the near future the Earth will remain the home of the vast majority of humanity, we really have to get cracking if we want to keep it livable in future centuries.

A New Planet in Our Solar System?

Astronomy being a long-time interest of mine (as should be obvious by the number of related posts on this blog), I was naturally intrigued by the flurry of news reports on an announcement by astronomers Konstantin Batygin and Michael Brown that their calculations show a large planet (which they rather provocatively are calling "Planet Nine") exists in the outer Solar System, far beyond Pluto and Eris. The proposed planet is believed to orbit between about 200 AU (300 billion km) at perihelion and as much as 1200 AU (1.2 trillion km) at aphelion, with an orbital period of between 10,000 and 20,000 Earth years, a period comparable or even more than that of Sedna, which at around 11,400 Earth years has the longest orbital period of any known large object (for comparison, Pluto takes 248 Earth years to orbit the Sun and Eris takes 558 Earth years). Batygin and Brown estimate that the planet should be about ten times as massive as Earth, putting it between Earth and Neptune (17 Earth masses) in size, making it a super-Earth or more properly a mini-Neptune, a category of planet that has been found in many star systems but is (so far) unknown in our own Solar System.

Some of the initial headlines about this hypothetical planet were a bit exaggerated, to say the least. One even stated that a new planet had been “discovered” even though the article to which headline was attached made it fairly clear that it had only been predicted and is not known for certain to exist. As another article pointed out, despite the famous and impressive prediction and discovery of Neptune, no other prediction of a planet in our Solar System has turned out to be accurate, as even Pluto’s discovery by Clyde Tombaugh while searching for a planet predicted by Percival Lowell turned out to be just a fortunate coincidence. Neptune was discovered due to residuals in the orbit of Uranus, that is to say, Uranus was not moving as it should have been based on the gravitational effects of the Sun and the known planets, meaning that there was something else affecting it. As impressive as the mathematical prediction leading to Neptune’s discovery was, the residuals in that case were fairly substantial, allowing a precise prediction of the unknown planet’s size and position. Attempts to find other planets by similar methods have been based on much slimmer evidence that in many cases was later to shown to be wrong anyway (for example, the problems with Mercury’s orbit which led to predictions of a planet closer to the Sun disappeared when Einsteinian physics was applied, and the apparent remaining problems with Uranus’s orbit that led to predictions of an additional planet beyond Neptune disappeared after estimates of Neptune’s mass were corrected following Voyager 2’s encounter with the planet). In other cases, even at the time the supposed evidence upon which the claims were based was dubious, such as in the case of Nemesis, the claim that the Sun has a distant red dwarf or brown dwarf companion that is causing periodic extinction events on Earth by sending showers of comets toward the Earth from the Oort cloud in the far outer reaches of the Solar System. Many experts doubt the claim that extinctions occur on a regular, periodic basis, and some astronomers have pointed out that an object like the predicted one would have measurable effects on objects closer to the Sun, effects that are clear not happening. Finally, infrared surveys of the Sun’s neighborhood seem to have pretty much ruled out anything of Jupiter-size or greater to a distance far beyond that predicted.

So historically speaking the record for planet predictions, despite the one spectacular success in the case of Neptune, is pretty poor. However, in this case Batygin and Brown do seem to have a slightly stronger case than that made for most previous hypothetical planets. Their prediction is based on the odd grouping of the orbits of half a dozen extremely distant objects, including Sedna. They calculate that it is extremely unlikely that this correlation in orbits would occur by chance. One might argue that we simply haven’t found enough of the objects that may exist in that region of the Solar System to be sure that the correlation holds true for all or even most of them, but then the odds against our first discoveries out of a large population just coincidentally having similar orbits also has to be very small. Another factor perhaps just as strongly in favor is the fact that Batygin and Brown did not start out by looking for evidence of a planet; instead they were originally hoping to disprove a suggestion made by Scott Sheppard and Chad Trujillo that a large, distant planet might be responsible for the orbits of Sedna and similar objects. Instead, their simulations showed the opposite of what they expected. Why do their original intentions matter? Because even scientists can fall prey to confirmation bias. If a scientist starts out hoping to find a planet, they may tend to exaggerate the reliability of the evidence they are using. Since Batygin and Brown, at least by their own account, started out hoping to disprove the idea that there might be a planet, the evidence that changed their minds would have to be at least somewhat more convincing than for someone who was hoping to prove there was a planet.

If this planet exists, it is probably near to aphelion, the part of its orbit farthest from the Sun, which would explain why it hasn’t been found yet. If it is of the speculated size, it could possibly be seen in a good amateur telescope near perihelion (when it is closest to the Sun). A planet that bright would have been found long ago, perhaps by Clyde Tombaugh, who covered much of the sky after finding Pluto. But if this planet is at aphelion, its last perihelion was at least 5,000 years ago, long before telescopes were invented. At its probable current distance, it would be much harder to see and it may be lost among the stars of the Milky Way. Nevertheless, a determined search will probably find it – if it is there.

Of course, even if the planet exists and is actually spotted, it won’t resolve the controversy over how many planets there are in the Solar System. Brown takes what I must say (despite my great respect for his work in planetary astronomy) is somewhat juvenile pride in being the “Pluto killer”, since it was his discovery of Eris that led to the “demotion” of Pluto from full planetary status. But as I have discussed in the past, a good case can be made for a definition of “planet” that includes Pluto, Charon, Eris and a few other of the larger trans-Neptunian objects, or alternatively for saying that while Pluto et al may be called “dwarf planets”, that is still a kind of planet. As there are still many, including at least some astronomers, who still consider Pluto (and presumably the similarly sized Eris) a planet, the term “Planet Nine” given by Batygin and Brown to their hypothetical planet is, as I noted at the beginning, somewhat provocative. Nevertheless, if the planet really turns up, it will be a fascinating addition to our Solar System, even though it may be many decades before we are able to explore it more closely, considering how incredibly far away it is, even in comparison with Pluto.

KIC 8462852 And the Likelihood of Finding Alien Civilizations

Over the past few weeks a number of articles have appeared in various news sources about the star KIC 8462852. This was one of the thousands of stars observed by the Kepler telescope in its search for extrasolar planets. For those who are unfamiliar with Kepler and how it works, the telescope observed stars over a long period of time, watching for periodic dips in their brightness that indicated the presence of planets passing in front of the stars and blocking a tiny portion of their light. Kepler’s initial observation period came to an end when two of the reaction wheels used to maintain the stability necessary for precise observations failed, though since then it has been re-purposed for more limited observations. The initial haul of data is still being analyzed and has already resulted in the discovery of hundreds of planets. Some of these planets are super-Earths (planets not much larger than Earth, as opposed to gas giants like Jupiter), and a few are in the theoretical habitable zones around their stars where liquid water could exist on their surfaces, though we as yet have no way of knowing if it actually does.

What stood out about KIC 8462852, a star somewhat larger than the Sun (spectral class F3 as compared to the Sun's G2) that is about 1480 light years away, was that the observed dips in its brightness were too substantial to have been caused by a planet, and they were irregular. In other words, in the two observed dimming events, which came about 750 days apart, the star dimmed, brightened and then dimmed again several times. This is extremely odd, and astronomers have struggled to come up with an explanation that fits the data. This uncertainty led a few astronomers to note that there was an additional possibility that didn’t involve natural phenomena. This was that the star was surrounded by some sort of alien megastructure designed to capture the star’s light for use as an energy source. This sort of construction has been proposed as a theoretical possibility before, with the most complete version being what is known as a Dyson sphere (after Freeman Dyson, who helped popularize the concept), which would totally surround the star in order to capture all or nearly all of its light. This is obviously not what is being observed here, but as Dyson himself later noted that a solid sphere or even ring around a star was "mechanically impossible", so a practical Dyson sphere would have be something like a swarm or bubble of constructs around the star, so the possibility remains open. Furthermore, some have pointed out that the megastructure could be incomplete (whether because it’s still under construction or because it is abandoned and derelict). In any case the idea is that it is something like a "Dyson swarm" that is being seen here.

Most likely, though, the explanation is something far more prosaic. Even the astronomers who have talked about the possibility that what is being seen at KIC 8462852 is an alien artifact have emphasized that the true explanation is likely to be something natural. The leading theories seems to be a unusually large swarm of comets, presumably disturbed by a recent passing star, though some question whether it is possible for a large enough number of comets to account for the data to have been disrupted, or simply dust, though astronomers are not sure why a seemingly older star (KIC 8462852 is thought to be at least as old as the 5-billion-year-old Sun, though there is still some uncertainty about that) would have so much dust around it. Despite the difficulties with both ideas, dust seems to be the most likely cause. Certainly we should want to see a lot more evidence before leaping to the extraordinary conclusion that aliens are the cause, or even anything more than a remote possibility; as Carl Sagan once said, extraordinary claims require extraordinary evidence.

But all the talk about KIC 8462852 does bring up once again the long-running debate over life in the universe, and specifically the likelihood that there are alien civilizations capable of space travel (obviously necessary to build any kind of structures around even the local star) out there somewhere. Of course, there are a lot of uncertainties involved, spelled out most clearly in the famous Drake equation. How many habitable planets are there? How many of those have life? How many planets with life give rise to technological civilizations capable of space travel? How long do such civilizations typically last? Everyone has different answers to these questions, but no one knows for sure. However, I’m willing to give my own take on the matter, even if I can’t claim to be an expert.

From all the planets we have discovered over the past two decades, we can estimate that there are over a hundred billion planets in the Milky Way, which is home to several hundred billion stars, many or even most of which are likely to have planets. Most of these planets will not be at all Earth-like, but it still seems likely that there could be billions in our galaxy that are similar enough to Earth to be considered habitable. The next question is how likely it is that life has arisen on these planets. We’re still not certain exactly how life arose here (though we’re getting closer all the time) and we still haven’t found definitive evidence of life originating anywhere other than Earth. Given how pervasive life is on Earth, though, I would not be surprised if we find traces of it elsewhere in the solar system, such as on Mars, Europa or Enceladus, and the fact that life seems to have appeared fairly early in Earth’s history is also a positive sign for how likely it is to arise in the first place.

But so far we are only talking about life in its most primitive, single-celled form. There is a rather large leap from this to a technological civilization capable of space travel. In fact, even if life in general turns out to be fairly common in the universe, we may find that on the vast majority of planets it consists entirely of single-celled organisms. After all, life existed on Earth for over 3 billion years before multi-cellular life appeared around 600 million years ago. To put that in perspective, life appeared within a billion years of the Earth’s formation and quite soon after the end of the hypothetical Late Heavy Bombardment era, during which it may have been difficult for even primitive life to survive (and even harder for any traces of life that may have arisen to survive for us to find), but for the vast majority of Earth’s history, there were only single-celled organisms – no plants or animals of any sort, much less intelligent life. This may indicate that it takes special conditions that are not easily fulfilled for multicellular life to evolve, and on many planets where life appears, these conditions may never arise.

Even if multicellular organisms appear, there is no guarantee that intelligent life forms will evolve – particularly intelligent life forms capable of constructing spaceships. Multicellular life had been on Earth for over half a billion years before humans evolved, so obviously intelligent life takes some time to appear. Of course on Earth there have been periodic mass extinctions that have wiped out most life, essentially setting back the evolutionary clock, so it isn’t as if we’ve had half a billion years of continuous evolution. On the other hand, other planets are likely to also suffer from periodic mass extinctions, and intelligent life would have to evolve in the periods between such events, which might be difficult if they were more frequent than they are on Earth. And even if intelligent life evolved, it would not necessarily be capable of developing advanced technology. It is often argued that dolphins are highly intelligent, but even if they are as smart as humans, they obviously can’t build spaceships. For that matter, even humans existed for hundreds of thousands of years before developing advanced technology, and we couldn’t have done that without the right raw materials (for instance, sufficient amounts of iron that could be easily mined). Then there is the obvious danger of an advanced civilization destroying itself in a relatively short period of time, just as we could end up destroying ourselves (or at least sending ourselves back to a low level of technology) through nuclear weapons or catastrophic climate change. After all, we've been capable of space travel for only half a century. That's 0.025% of the time modern humans have been around, and 0.000001% of Earth's history. For us to have a chance of encountering (even from a distance) any alien civilizations, some of them would have to last a lot longer than that.

So there probably are a lot of barriers to advanced technological civilizations arising, to the point that they may only appear on a tiny fraction of habitable planets. But on the other hand, if there are 10 billion habitable planets in the galaxy, even a one in a hundred million chance that an advanced civilization had arisen and survived long enough to be around now would mean that there would be a hundred such civilizations. That’s not a particularly huge number, considering how large our galaxy is, and if they are that rare we may have trouble finding them, especially if we keep in mind how huge the distances between stars are - even talking to any aliens living in the KIC 8462852 system would take 3000 years for a single exchange of messages. As for alien civilizations in other galaxies, they would be so far away as to be completely inaccessible even for any form of communication, unless wormholes or other forms of exotic travel turn out to be possible. Still, while it seems too much to hope that KIC 8462852 will turn out to have advanced alien life, it almost certainly does exist somewhere else in the universe, and probably even exists somewhere else in our galaxy. Whether we will ever find it is another matter; however, I am all in favor of continuing to look.

Drawing the Curtain Back on Pluto and Charon

I have been interested in space and astronomy, particularly the solar system, for as long as I can remember; at least since I was in preschool. And of all the planets and other bodies in the solar system, the one that I found most fascinating in childhood was Pluto. Of course I am hardly alone in having Pluto as my “favorite planet”, but as to why I especially liked Pluto, it is a little difficult to say. I think it was in part simply that it was different; it was clearly unlike either the so-called terrestrial planets close to the Sun or the gas giants in the outer solar system. It’s status as the most distant planet, with an incredibly long orbit of 248 Earth years, may have played a role. Or maybe it was just that Pluto was so mysterious. When I first became interested in astronomy, most books had practically no information about Pluto at all, as next to nothing was known. Some of the astronomy books I would check out of the library, books that were already somewhat out of date at the time, even included some of the more wild early theories about Pluto, such as the suggestion that Pluto was in fact a fairly large planet, but was almost perfectly black, so that we were seeing the reflection of the sun off its surface like a mirror. This theory was developed to accommodate the idea that Pluto was indeed the theorized Planet X that was supposedly affecting the orbits of Uranus and Neptune (which would require a fairly massive planet) and yet failed to show a disc in even the largest telescopes of the day. More commonly, books of the time would declare Pluto to have a diameter of about 5000 km (3600 miles), which was in truth more of an upper limit than an estimate based on any concrete evidence, or repeat the then-common theory that Pluto was an escaped satellite of Neptune (this idea even crops up occasionally today in articles by non-scientists despite being long discredited; the truth is Pluto never comes anywhere remotely close to Neptune due to an orbital resonance, and actually gets closer to Uranus than it ever does to Neptune). In truth, even though it had been almost 5 decades since Pluto had been discovered by Clyde Tombaugh, the only things known with any degree of certainty about Pluto in those days was its orbital characteristics and that it had a rotation period of 6.39 days.

The mystery around Pluto began to clear up ever so slightly in the late 1970s. First methane was detected on its surface. Since methane ice is highly reflective, this was the first hint that Pluto was in fact even smaller than had been previously thought (with the constant downward revisions in estimates of Pluto's mass from the time of its discovery, at some point an astronomer joked that if the trend continued, it would soon disappear entirely!). Then in 1978 came the dramatic discovery of Pluto’s satellite - or perhaps companion would be a better term - Charon, which at half the diameter of Pluto is the largest moon with respect to its parent planet in the solar system (how hard it is to get a decent image of Pluto from Earth is illustrated by the fact that in the discovery photos of Charon, it appears as a fuzzy lump on the bigger fuzzy lump of Pluto - it took the Hubble Space Telescope to get a picture of the two clearly separated). The discovery of Charon in turn allowed Pluto’s mass to be calculated with some precision, showing that it was actually quite small for a planet, being considerable less massive than even the Earth’s Moon, let alone Mercury, the smallest inner planet, though still much larger than Ceres, the biggest asteroid. This discovery gave rise to the first arguments among astronomers about whether Pluto should be classified as a planet. But for me, while Pluto was now a little less mysterious, it remained as fascinating as ever, especially with the relative size of Charon making it more like a double planet system, if a small one (see here for an example of how Pluto and Charon orbit each other).

I don’t want to delve into the debate over Pluto’s planetary status in great detail here, but there are a few things worth pointing out. First of all, as I mentioned above, while Pluto certainly is very small in comparison with the eight universally recognized major planets, it is still much larger than any asteroid, even Ceres (by far the biggest asteroid). At least one other recently discovered body in the outer solar system, Eris, is somewhat more massive than Pluto (though slightly smaller in diameter), but that alone doesn’t disqualify Pluto from planetary status, it just means that Eris itself also needs to have its status determined, and that it should be classified with Pluto. It should also be noted that the eccentricity of Pluto’s orbit is also irrelevant to whether or not it is a planet, as quite a few extrasolar planets have similarly eccentric orbits. I am not so attached to Pluto’s planetary status that I don’t recognize that it, along with Eris and several other large trans-Neptunian objects, are distinct from the major planets; in fact way back at the end of the 1980s I distinctly remember doing a high school project in which I suggested that Pluto belonged to a completely new class of objects (even though, with the possible exception of Chiron, an asteroid-like body orbiting between Saturn and Uranus, no other similar objects had been discovered at that time) which I think I called cometoids or something like that. But essentially I think both sides are arguing about the wrong question. The argument shouldn’t be about Pluto per se; it should be about the minimum characteristics for a planet, wherever it is located. The definition that the IAU came up with when it reclassified Pluto, Eris and several other objects (including Ceres) as “dwarf planets” is vague and unsatisfactory. While any definition is going to be somewhat arbitrary, I think it makes more sense to define a planet based on its own physical characteristics, instead of vague criteria like “clearing its orbit”, as even in the outer reaches of our own solar system we may someday find an object the size of Mercury or Mars orbiting among smaller objects in the way Pluto does, and extrasolar planetary system will no doubt have all kinds of mixes of objects, whereas I think a definition of a planet should such that the same object would always be a planet if it is orbiting a star, regardless of what else may be orbiting in its neighborhood. What the qualifying characteristics should be is of course debatable, though several good possibilities, such as the object being large enough to maintain hydrostatic equilibrium, would result in Pluto and similarly sized objects being classified as planets. The point is that the definition should not be written either to deliberately include or exclude Pluto, but should be based as much as possible on clearly defined physical characteristics. Probably the easiest solution for the time being would be to keep the term “dwarf planet”, but to acknowledge that, as the name implies, a dwarf planet is still a planet, while we can refer to the eight bigger planets as “major planets” (though in that case we'd still need a definition for "major planets"). But in the end what we call Pluto is not that important, as it remains equally interesting regardless (for more arguments on both sides, see here and here).

In subsequent decades we learned even more about Pluto, first through mutual occultation events between Pluto and Charon, and then in the past few years through observations by the Hubble Space Telescope, including the discovery of four small moons of Pluto, Nix, Hydra, Kerberos and Styx. But despite these advances, our knowledge of Pluto and its companions remained extremely limited, and the best images we had of it were extremely fuzzy, due to its great distance and small size. All of that has finally changed with the flyby of the Pluto system by the New Horizons spacecraft on July 14. As a longtime “Plutophile”, it goes without saying that this is an event I have long awaited. But rather than attempting to summarize New Horizons’ discoveries so far myself (after all, one of the most exciting and dramatic things about it is the pictures, which are best seen elsewhere), I am providing some links to articles about the flyby and some of the discoveries that have been made so far, with many more to come as data continues to be sent back by New Horizons over the coming months.

Articles on Pluto's moons from the months prior to the close encounter can be found here and here.

An article on the significance of the New Horizons mission can be found here, and one about how great a value it is for the money is here.

Articles reporting on the flyby can be found here, here, here and here, with articles focusing on Pluto's atmosphere here and here, articles on the strange mountain on Charon here and here, and an article about the first relatively close-up picture on Nix here (one with pictures of both Nix and Hydra is here). A picture gallery of photos from the New Horizons mission, starting from the most recent images, can be found here.

An article on reactions to the flyby can be found here, and an article on possible future exploration by New Horizons can be found here. Unfortunately, there are no near future plans to send probes to Eris, now the largest object in the solar system that has never been visited by a space probe, or Sedna, which has by far the greatest average distance from the Sun of any known object of substantial size (it probably qualifies as a dwarf planet), but with this flyby of Pluto we have at least begun the exploration of the bodies of the far outer solar system, and after decades of wondering what they were like, I personally am happy to finally get to see what Pluto and Charon look like up close.

A Whole Bunch of Space and Astronomy Links

Since I haven't had time to write anything lately, instead I'm posting links to a whole lot of interesting articles about space and astronomy from the past month or so, ranging from stories about new discoveries on Mars, the ESA's comet probe, and the NASA probes approaching Pluto and Ceres to ones about extrasolar planet discoveries, speculations about alien life, and one of my favorites, a new idea about sending people to live in a floating city in the atmosphere of Venus, far above the inhospitable surface.

Mars:
http://news.yahoo.com/found-ancient-lake-mars-sign-143002982.html
http://news.yahoo.com/curiosity-rover-drills-mars-rock-finds-water-122321635.html
http://www.space.com/28019-mars-methane-disovery-curiosity-rover.html
http://www.space.com/28033-mars-life-building-blocks-curiosity-rover.html?cmpid=558746
http://www.cnet.com/news/curiosity-has-discovered-organic-matter-on-mars/#ftag=YHF65cbda0

Comet:
http://news.yahoo.com/european-comet-lander-may-wake-space-slumber-232545821.html

Pluto and Ceres:
http://news.yahoo.com/nasa-s-new-horizons-mission-to-pluto-to-illuminate-mysterious-reaches-of-solar-system-151951810.html
http://news.yahoo.com/nasa-spacecraft-almost-pluto-smile-camera-153919436.html
http://news.yahoo.com/nasa-finds-mysterious-bright-spot-dwarf-planet-ceres-191633834.html

Extrasolar planets:
http://news.yahoo.com/planets-odd-mercury-orbits-could-host-life-053306188.html
http://www.vox.com/2015/1/2/7474501/exoplanet-simulator
http://www.space.com/28185-rocky-alien-planets-habitable-zone.html?cmpid=558939
http://news.yahoo.com/mars-rover-photos-show-potential-signs-ancient-life-210713579.html
http://news.yahoo.com/astronomers-oldest-known-star-earth-planets-191903312.html
http://news.yahoo.com/faraway-planet-lord-rings-152706151.html

Alien life:
http://news.yahoo.com/scientists-think-well-signs-aliens-152001079.html
http://news.yahoo.com/did-life-become-complex-could-happen-beyond-earth-124952260.html

Floating city on Venus:
http://www.cnet.com/news/nasa-wants-to-build-a-floating-city-above-the-clouds-of-venus/

Current Events: Taiwanese Elections, Obama Tackles Immigration, and Comet Landing

A lot has been going on in the past few weeks that is worth of comment, and if I had unlimited time I could write a half a dozen essays around current events. But for now I’ll just settle for some (relatively) brief observations on a few news items. Starting with news from home, Taiwan held local elections in cities and counties around the country this past Saturday, and the ruling Kuomintang (KMT) did much worse than expected, losing most of the mayoral and county commissioner races, including in usually KMT-leaning areas such as Taipei and Taoyuan. At the risk of over generalizing, this result can be ascribed to disapproval of the governments’ performance, with food scandals, economic issues, corruption, expropriation of land with poor justification, and attempts to force through the service trade agreement with China all contributing factors. I should point out, however, that it would be a mistake to overestimate the importance of Taiwan-China relations in voters’ minds, as a lot of people in Taiwan, like elsewhere in the world, are more concerned with local issues (in other words, the food scandals probably hurt the KMT more than the service trade agreement did). In any case, the results were good news for Taiwan as a whole, even though in places such as Taipei it was a matter of a mediocre candidate beating a terrible one, and places like Hualian and Taidong on the east coast remain in the hands of terrible politicians. Our local Green Party candidate unfortunately didn’t win election to the city council (though one Green Party candidate in Taoyuan was elected to their council with a high vote total) and the KMT mayor in our city won, though by an unexpectedly narrow margin. Still, while the KMT and KMT-leaning independents hung on in many places and even the winning DPP and DPP-leaning candidates who won around the country are in many cases just the lesser of two evils, I’m certainly much more happy with these election results than those in the US at the beginning of the month.

Speaking of the US, I have been glad to see US President Barack Obama take strong actions in a number of important areas, even if it is overdue and often insufficient. The one which garnered the most attention, of course, was his executive order allowing some 5 million undocumented residents of the US to remain in the country without fear of deportation. Many Republicans had a predictably hysterical reaction to this. But contrary to their claims, Obama’s action was neither unprecedented nor illegal, and it was clearly justified. Many presidents have taken executive action relating to immigration, and both Reagan and the first Bush took actions very similar to Obama’s. The Supreme Court just a few years ago ruled that the executive branch had discretion in determining when to pursue deportation and that the law did not obligate authorities to deport all undocumented people. Many Republicans also complained that Obama should have left immigration reform to Congress. The problem with this complaint is that he did leave it to Congress for a long time, and Congress – more specifically, the House Republican leadership – did nothing. The Senate passed a comprehensive immigration bill (an imperfect one which placed far too much weight on “border security”, but better than nothing) almost two years ago, and the House never even voted on it. So how long was Obama supposed to wait for Congress to act? If anything, Obama should be criticized for waiting as long as he did, and for not covering more people with his executive order.

In news (much) further afield, last month saw the first soft landing of a probe on the surface of a comet when the European Space Agency’s Philae lander, dispatched from the orbiting Rosetta probe, touched down on 67P/Churyumov-Gerasimenko. Admittedly, the landing was not without a hitch; the harpoons that were supposed to anchor the probe to the comet’s surface failed to deploy, so the probe bounced twice before coming to rest, the first time traveling as far as a kilometer before landing and bouncing a shorter distance the second time. This was because due to the small size of the comet, its gravity is extremely weak. It is estimated to be about one meter per second, meaning you could easily throw a ball into space and with a hard enough jump you might be able to launch yourself. In any event, the probe ended up next to a cliff that left it mostly in shadow, so it could not recharge its batteries with its solar panels. However, it managed to send off some data before its power ran out, and simply by landing the probe made history. We can look forward to more space exploration milestones in the near future, as an unmanned test flight of the Orion capsule that NASA is developing for future crewed space exploration is coming up which will send the capsule further than any such capsule has traveled from Earth since the Apollo missions ended in 1972. While this would be even cooler if it actually had a crew (after all, unmanned probes have traveled thousands of times farther), if the test goes as planned it will be an encouraging sign that we may say real human crewed space missions to destinations beyond low Earth orbit in the not too distant future. Finally, looking further ahead, next year the New Horizons probe will make its rendezvous with Pluto on the edge of the Solar System, and the Dawn probe will visit Ceres. While humanity is still trying to get its act together on Earth, it’s good to see us continuing to explore beyond our home world.

Voyager 1 Enters Interstellar Space

I was originally planning to write about how the Syrian crisis shows up serious flaws in the international system, or else about the recent political crisis in Taiwan. But while I may write about these things later, this time I decided to write about a completely different and rather more positive news item.

One of the cooler bits of news lately was the announcement by NASA that Voyager 1 has entered interstellar space. For those who aren't familiar with it, the robotic spacecraft Voyager 1 was launched in 1977 and visited Jupiter in 1979 and Saturn in 1980, making major discoveries at those two planets (its twin, Voyager 2, also became the first and so far only spacecraft to visit Uranus and Neptune). Since then it has been heading out of the Solar System at a velocity of about 17 kilometers per second (11 miles per second), or about 3.6 AU per year (an AU or astronomical unit is the mean distance from the Earth to the Sun, or roughly 150 million kilometers). Over the past couple of years there has been debate over the indications that Voyager 1, which is moving slightly faster than Voyager 2 or the earlier but slower Pioneer 10 and 11 (though Pioneer 10 is currently still more distant than Voyager 2), had left the heliosphere, the bubble in space created by the solar wind, but in the latest announcement NASA stated that they finally have definitive evidence that Voyager 1 is now beyond the heliosphere and the boundary area known as the heliopause and has entered interstellar space.

This is a pretty amazing achievement. Voyager 1 is currently almost 19 billion kilometers from the Sun, about 125 times the distance from the Earth to the Sun and over three times the average distance of Pluto, and it is still functioning after 36 years in space. At the speed of light, it now takes signals about 17 hours to travel from Voyager 1 to the Earth, and we are still receiving them. As one article pointed out, Voyager 1 has accomplished this with far less computing power than a so-called smartphone. It is incredible to contemplate that a human-made object has traveled so far into space.

On the other hand, the Voyagers and the Pioneers (and the other, more recent spacecraft on a recent trajectory toward interstellar space, New Horizons) also serve to remind us of how huge the distances in space are. While many headlines have reported that Voyager 1 has left the solar system, this is not really accurate. As others have pointed out, while it is in interstellar space in the sense that it is beyond the solar wind, it is still well within the region gravitationally dominated by the Sun. For example, the most distant substantial object that we know of in the solar system is Sedna, a trans-Neptunian object that probably qualifies as a dwarf planet under the current classification system. Sedna is currently "only" 80-some AU away, but it is now nearing its perihelion, or closest approach to the Sun. At the most distant point in its orbit, Sedna is 937 AU or 140 billion kilometers from the Sun, something like seven times the current distance of Voyager 1. The comets in the Oort Cloud at the edge of the Sun's gravitational grip are many times further than that. So in this sense, it will be thousands of years before Voyager 1 truly leaves the solar system (a point mentioned even in one or two mainstream news articles).

Another way of looking at it is to remember that while Voyager 1 is an impressive 17 light hours away, meaning it takes light 17 hours to reach us from it at a velocity of 300,000 kilometers per second, it won't reach the distance of 1 light day (about 172 AU) for well over a decade, around the time it is expected to cease functioning completely, even if it suffers no glitches in the meantime. The nearest star other than the Sun is over 4 light years away. Even if Voyager 1 were heading directly toward it (which it isn't), it would take it tens of thousands of years to reach it. So while this milestone could be said to mark humanity's first step toward the stars, it is a very tiny step. If we really want to explore the stars, it will take a major leap forward in propulsion technology. This isn't to say we shouldn't be impressed at Voyager 1's achievement, but rather than just patting ourselves on the back, we should be inspired to go even further and faster in the future. If we make the effort, maybe by the end of this century we'll have one or more spacecraft passing the Voyagers on the way to the stars.