Riding on a light beam

Some of you probably have read about a project called Breakthrough Starshot that began perhaps eight years ago (and which was championed by none other than Stephen Hawking), which proposed sending small remote-controlled cameras to nearby star systems, powered by lasers that could propel them up to twenty percent of the speed of light.

If something like this were launched today, it would mean we could be getting photographs back from Proxima Centauri in twenty years.

[Image licensed under the Creative Commons ESO/M. Kornmesser, Artist's impression of the planet orbiting Proxima Centauri, CC BY 4.0]

It's an ambitious project, and faces significant hurdles.  Even if propelled by lasers -- which, being light, travel at the speed thereof -- navigation becomes increasingly difficult the farther away it gets.  Just at the distance of Pluto, our intrepid little spacecraft would be 4.5 light-hours from Earth, meaning if we tried to beam it instructions to dodge around an incoming meteor, it would be 4.5 hours until the command arrived, at which point all that would be left is intrepid scrap metal.  And Proxima Centauri is 4.3 light years away.

You see the problem.  The Starshot spacecraft would have to be able, on some level, to think for itself, because there simply wouldn't be time for Mission Control to steer it to avoid danger.

There are other obstacles, though.  Besides the obvious difficulties of being in the cold vacuum of interstellar space, contending with cosmic rays and the like, there's the problem engendered by its speed.  Assuming the estimate of a maximum velocity of twenty percent of light speed is correct, even tiny particles of dust would become formidable projectiles, so Starshot is going to require some heavy-duty shielding, increasing its mass (and thus the amount of energy needed to make it go).

Three years ago we got an encouraging proof of concept, when the group working on the mission -- Russian entrepreneur Yuri Milner's Breakthrough Foundation -- launched a test of the Starshot craft.  It was a tiny little thing, small enough to fit in your hand and weighing about the same as a stick of gum, designed and built by engineers at the University of California - Santa Barbara.  In the test flight it achieved an altitude of nineteen miles, all the while functioning flawlessly, returning four thousand images of the Earth taken from aloft.

And just last week, a paper in Nature Photonics describes further research on how to overcome the weight/propulsion issue, with the creation of a fifty-nanometer-thick membrane of silicon nitride that was tested to measure the actual thrust a laser could create on something that lightweight -- a feat that has never been done before.  The miniature sail passed with flying colors.

"There are numerous challenges involved in developing a membrane that could ultimately be used as lightsail," said Harry Atwater of Caltech, who led the study.  "It needs to withstand heat, hold its shape under pressure, and ride stably along the axis of a laser beam.  But before we can begin building such a sail, we need to understand how the materials respond to radiation pressure from lasers.  We wanted to know if we could determine the force being exerted on a membrane just by measuring its movements.  It turns out we can."

The most significant remaining hurdle is to design the laser system to make Starshot move -- lasers that are extremely powerful yet so finely collimated that they can still strike a ten-centimeter craft square-on from several light years away.  The engineering director for Breakthrough, Peter Klupar, is designing a 100,000 gigawatt laser -- to be located, he says, in Chile -- that could be the answer.  Of course, such a powerful device is not without its dangers.  Reflected off a mirror in space, Klupar says, such a laser could "ignite an entire city in minutes."

Not that there's a mirror out there.  So you shouldn't worry at all about that.

"You would think that this is all impossible, but we have folks at Caltech and the University of Southampton and Exeter University working on about fifty contracts on making all [of] this happen," Klupar said.  "No one has come up with a deal-breaker that we can find yet.  It all seems real."

All of which may seem like science fiction, but it's phenomenal how fast things go from the realm of Star Trek to reality.  Klupar compares his light sails to CubeSats, tiny (ten by ten centimeters, weighing a little over a kilogram) orbiting telemetry devices that are now common.  "It feels a lot like the way CubeSats felt twenty years ago," he said.  "People were saying, 'Those are toys, they're never going to develop into anything, there's no way I can see that ever working.'  And today and look them: hundreds of millions of dollars is being spent on them."

So keep your eye on this project.  If there's a chance at a remote visit to another star system, I think this is our best bet.  The Breakthrough Foundation estimates an actual, honest-to-goodness launch toward a nearby star as early as 2030.  Meaning perhaps we could get our first photographs of planets around another star by 2050.

I'll be ninety years old at that point, but if that's what I'm waiting for, I can make it till then.

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Goldilocks next door

Springboarding off yesterday's post, about how easy it is to form organic compounds abiotically, today we have: our nearest neighbor might be a decent candidate for the search for extraterrestrial life.

At only 4.24 light years away, Proxima Centauri is the closest star to our own Sun.  It's captured the imagination ever since it was discovered how close it is; if you'll recall, the intrepid Robinson family of Lost in Space was heading toward Alpha Centauri, the brightest star in this triple-star system, which is a little father away (4.37 light years) but still more or less right next door, as these things go.

It was discovered in 2016 that Proxima Centauri has a planet in orbit around it -- and more exciting still, it's only a little larger than Earth (1.17 times Earth's mass, to be precise), and is in the star's "Goldilocks zone," where water can exist in liquid form.  The discovery of this exoplanet (Proxima Centauri b) was followed in 2020 by the discovery of Proxima Centauri c, thought to be a "mini-Neptune" at seven times Earth's mass, so probably not habitable by life as we know it.

And now, a paper in Nature has presented research indicating that Proxima Centauri has a third exoplanet -- somewhere between a quarter and three-quarters of the Earth's mass, and right in the middle of the Goldilocks zone as well.

"It is fascinating to know that our Sun’s nearest stellar neighbor is the host to three small planets," said Elisa Quintana, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who co-authored the paper.  "Their proximity make this a prime system for further study, to understand their nature and how they likely formed."

The newly-discovered planet was detected by observing shifts in the light spectrum emitted by the star as the planet's gravitational field interacted with it -- shifts in wavelength as little as 10 ^-5 ångströms, or one ten-thousandth the diameter of a hydrogen atom.  The device that accomplished this is the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO -- because you can't have an astronomical device without a clever acronym) at the European Southern Observatory in Cerro Paranal, Chile.  

"It’s showing that the nearest star probably has a very rich planetary system," said co-author Guillem Anglada-Escudé, of the Institute of Space Sciences in Barcelona.  "It always has a little bit of mystique, being the closest one."

What this brings home to me is how incredibly common planets in the Goldilocks zone must be.  It's estimated that around two percent of spectral class F, G, and K stars -- the ones most like the Sun -- have planets in the habitable zone.  If this estimate is accurate -- and if anything, most astrophysicists think it's on the conservative side -- that means there's five hundred million habitable planets in the Milky Way alone.

Of course, "habitable" comes with several caveats.  Average temperature and proximity to the host star isn't the only thing that determines if a place is actually habitable.  Remember, for example, that Venus is technically in the Goldilocks zone, but because of its atmospheric composition it has a surface temperature hot enough to melt lead, and an atmosphere made mostly of carbon dioxide and sulfuric acid.  Being at the right distance to theoretically have liquid water doesn't mean it actually does.  Besides atmospheric composition, other things that could interfere with a planet having a clement climate are the eccentricity of the orbit (high eccentricity would result in wild temperature fluctuations between summer and winter), the planet being tidally locked (the same side always facing the star), and how stable the star itself is.  Some stars are prone to stellar storms that make the ones our Sun has seem like gentle breezes, and would irradiate the surface of any planets orbiting them in such a way as to damage or destroy anything unlucky enough to be exposed.

But still -- come back to the "life as we know it" part.  Yeah, a tidally-locked planet that gets fried by stellar storms would be uninhabitable for us, but perhaps there are life forms that evolved to avoid the dangers.  As I pointed out yesterday, the oxygen we depend on is actually a highly reactive toxin -- we use it to make our cellular respiration reactions highly efficient, but it's also destructive to tissues unless you have ways to mitigate the damage.  (Recall that burning is just rapid oxidation.)  My hunch -- and it is just a hunch -- is that just as we find life even in the most inhospitable places on Earth, it'll be pretty ubiquitous out in space.

After all, remember what we learned from Ian Malcolm in Jurassic Park:

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People made fun of Donald Rumsfeld for his statement that there are "known unknowns" -- things we know we don't know -- but a far larger number of "unknown unknowns," which are all the things we aren't even aware that we don't know.

While he certainly could have phrased it a little more clearly, and understand that I'm not in any way defending Donald Rumsfeld's other actions and statements, he certainly was right in this case.  It's profoundly humbling to find out how much we don't know, even about subjects about which we consider ourselves experts.  One of the most important things we need to do is to keep in mind not only that we might have things wrong, and that additional evidence may completely overturn what we thought we knew -- and more, that there are some things so far out of our ken that we may not even know they exist.

These ideas -- the perimeter of human knowledge, and the importance of being able to learn, relearn, change directions, and accept new information -- are the topic of psychologist Adam Grant's book Think Again: The Power of Knowing What You Don't Know.  In it, he explores not only how we are all riding around with blinders on, but how to take steps toward removing them, starting with not surrounding yourself with an echo chamber of like-minded people who might not even recognize that they have things wrong.  We should hold our own beliefs up to the light of scrutiny.  As Grant puts it, we should approach issues like scientists looking for the truth, not like a campaigning politician trying to convince an audience.

It's a book that challenges us to move past our stance of "clearly I'm right about this" to the more reasoned approach of "let me see if the evidence supports this."  In this era of media spin, fake news, and propaganda, it's a critical message -- and Think Again should be on everyone's to-read list.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

False alien alarm

In yet another blow to those of us who would dearly love to find incontrovertible evidence of extraterrestrial intelligence, the signal that the Breakthrough Listen project detected in 2019 and which seemed to be coming from Proxima Centauri (the nearest star to the Sun) turns out to be...

... not aliens.

The signal was certainly intriguing.  Proxima Centauri is not only close, at only 4.2 light years away, it is known to have a planet orbiting in the "Goldilocks Zone" -- not too hot, not too cold, juuuuuust right -- i.e., at the a distance that allows it to have liquid water on its surface.  The nature of the signal was curious in and of itself; it was at around 982 megahertz, and lasted for five months, giving the scientists at Breakthrough Listen a long time to study it.  "My first thought was that it must be interference, which I guess is a healthy attitude, to be skeptical," said Danny Price, an astronomer at the University of California - Berkeley.  "But after a while I started thinking, this is exactly the kind of signal we’re looking for."  After significant analysis, the signal -- BLC1 (Breakthrough Listen Candidate 1) -- was the first to pass all of the project's screening benchmarks.

When you have a bunch of hard-headed scientists saying, "Okay, maybe," to the rest of us extraterrestrial aficionados it seems tantamount to an outright admission.

Sadly, though, our hopes were doomed to be dashed once again.  Turns out, BLC1 isn't from Proxima Centauri; it's a radio signal originating right here on Earth.  The Breakthrough Listen team found that the signal showed a frequency drift similar to that exhibited by inexpensive crystal oscillators commonly used in computers, phones, and radios.  The scientists suspect that it came from a malfunctioning or poorly-shielded piece of electronics, and the signal stopped when its owner either repaired it or shut it down entirely.

"It definitely had me wondering ‘what if?’ for a bit," said Sofia Sheikh, also of UC-Berkeley.  "Many groups assumed that if you had a detection that only showed up when you were pointed at the source, that was it, break out the champagne, you’re done.  As technology changes, the way we vet signals also has to change — and that hadn’t come together until BLC1."

Surprisingly, the scientists didn't appear to be as disappointed as us laypeople.  "It’s really valuable for us to have these dry runs," said Jason Wright, an astronomer at Pennsylvania State University.  "We need these candidate signals so we can learn how we will deal with them — how to prove they are extraterrestrial or human-made."

So what we need is a real-life Ellie Arroway to keep analyzing the data until we do find a signal that comes from extraterrestrial intelligence.

But until she comes along, the scientists over at Breakthrough Listen will continue listening -- and hoping for a breakthrough.  Me, I hope it happens soon.  I'd love to live to see evidence of extraterrestrial intelligence, because some days, terrestrial intelligence seems to be in awfully short supply.

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Some of the most enduring mysteries of linguistics (and archaeology) are written languages for which we have no dictionary -- no knowledge of the symbol-to-phoneme (or symbol-to-syllable, or symbol-to-concept) correspondences.

One of the most famous cases where that seemingly intractable problem was solved was the near-miraculous decipherment of the Linear B script of Crete by Alice Kober and Michael Ventris, but it bears keeping in mind that this wasn't the first time this kind of thing was accomplished.  In the early years of the nineteenth century, this was the situation with the Egyptian hieroglyphics -- until the code was cracked using the famous Rosetta Stone, by the dual efforts of Thomas Young of England and Jean-François Champollion of France.

This herculean, but ultimately successful, task is the subject of the fascinating book The Writing of the Gods: The Race to Decode the Rosetta Stone, by Edward Dolnick.  Dolnick doesn't just focus on the linguistic details, but tells the engrossing story of the rivalry between Young and Champollion, ending with Champollion beating Young to the solution -- and then dying of a stroke at the age of 41.  It's a story not only of a puzzle, but of two powerful and passionate personalities.  If you're an aficionado of languages, history, or Egypt, you definitely need to put this one on your to-read list.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

A signal from our neighborhood

I try to keep my rational brain engaged, but man, sometimes it's hard going.

Like when I read the story that popped up over at Scientific American last Friday.  My ears perked up at the very first line: "It's never aliens, until it is."

Written by Jonathan O'Callaghan and Lee Billings, it tells about a recent discovery made by "Breakthrough Listen," the search-for-extraterrestrial-intelligence program launched by entrepreneur Yuri Milner in 2015.  Despite scanning the skies for five years looking for something that might be a sign of alien intelligence, Breakthrough Listen hasn't found anything that couldn't be explained using ordinary astrophysics...

... until now.

Maybe.  I hate to add that word, but... "rational brain engaged," and all.  There's a lot that's exciting about what they discovered, not least that the signal they found comes from Proxima Centauri -- the nearest star to the Sun, right in our own neighborhood at only 4.2 light years' distance.  (Okay, I probably shouldn't say "only."  4.2 light years is about 25,000,000,000,000 miles.  One of the fastest spacecraft ever made by humans, Voyager 2, would still take 73,000 years to reach Proxima Centauri -- if it were heading that way, which it's not.)

The proximity of the signal's source is hardly the only exciting thing about it.  After all, the universe has plenty of radio sources, and all the ones we've found so far have purely prosaic explanations.  The signal is weirdly compressed, occupying a narrow band of frequencies centering around 982 megahertz.  Interestingly, this is a frequency range that is usually fairly empty of transmissions, which is one of the reasons the signal stood out, and decreases the likelihood that it's some kind of human-made source being picked up accidentally.  "We don’t know of any natural way to compress electromagnetic energy into a single bin in frequency,” said astrophysicist Andrew Siemion, who is on the team that analyzed the signal.  "Perhaps, some as-yet-unknown exotic quirk of plasma physics could be a natural explanation for the tantalizingly concentrated radio waves, but for the moment, the only source that we know of is technological."

The "tantalizing" part is that we know for sure that Proxima Centauri has at least one Earth-like planet -- Proxima b, which is 1.2 times the size of the Earth, and orbits its star in eleven days.  (If that doesn't sound very Earth-like, remember that Proxima Centauri, as a red dwarf, is a lot less massive than the Sun, so its "Goldilocks zone" -- the band of orbital distances that are "just right" for the temperatures to allow liquid water" -- is a lot closer in, and the planets in that region travel a lot faster.)  Red dwarf stars are prone to solar flares, so some of the more pessimistic astrophysicists have suggested that the radiation flux and general turbulence would destroy any nearby planets' atmosphere, or at least shower the surface with sufficient ionizing radiation to prevent the development of complex biochemistry, let alone life.

But it's important to realize that this, too, is a surmise.  Truthfully, we don't know what's down there on Proxima b -- just that it's got a rocky surface and a temperature range that would allow for liquid oceans, rivers, and lakes.

Just like here.

In short, finding a suspicious radio signal from the nearest star to our own is pretty amazing, even if I *wince* *grimace* keep my rational brain engaged.

The fact is, even the scientists -- normally the most cautious of individuals -- are sounding impressed by this.  "It’s the most exciting signal that we’ve found in the Breakthrough Listen project, because we haven’t had a signal jump through this many of our filters before," said Sofia Sheikh of Pennsylvania State University, who led the team that analyzed the signal and is the lead author on an paper describing it, scheduled for publication this spring.

Honestly forces me to add that there's one bit of information about the signal that points away from it being a technosignature: unlike the signal detected at the beginning of the movie Contact, it has no internal fine structure.  “BLC1 [Breakthrough Listen Candidate 1] is, for all intents and purposes, just a tone, just one note," Siemion says.  "It has absolutely no additional features that we can discern at this point."

But even the doubters are saying it's worthy of further study.  "If it’s an ETI it must eventually be replicable, because it’s unlikely it would be a one-off,” said Shami Chatterjee, a radio astronomer at Cornell University.  "If an independent team at an independent observatory can recover the same signal, then hell yes.  I would bet money that they won’t, but I would love to be wrong."

So would a lot of us, Dr. Chatterjee.  I know we've had other strange signals before, stretching all the way back to the beginnings of radio astronomy and the discovery of incredibly rapid-fire "blinking" of a radio source discovered at Jodrell Bank by astrophysicist Jocelyn Bell Burnell in 1967.  That one also elicited the comment of "we don't know a natural process that could generate such fast oscillation" -- and the source was actually nicknamed "LGM" (Little Green Men) until Burnell showed that the signal was coming from a pulsar, a rapidly-spinning neutron star.

So it was bizarre, perhaps, but not a message from an extraterrestrial intelligence.

In any case, I'll be eagerly awaiting replication and confirmation of the discovery.  Even if it doesn't turn out to be aliens *heavy sigh* it'll probably turn out to be something interesting.  But until then... well, I guess it's premature to request transport to the mother ship, but I can still keep hoping.

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Not long ago I was discussing with a friend of mine the unfortunate tendency of North Americans and Western Europeans to judge everything based upon their own culture -- and to assume everyone else in the world sees things the same way.  (An attitude that, in my opinion, is far worse here in the United States than anywhere else, but since the majority of us here are the descendants of white Europeans, that attitude didn't come out of nowhere.)  

What that means is that people like me, who live somewhere WEIRD -- white, educated, industrialized, rich, and democratic -- automatically have blinders on.  And these blinders affect everything, up to and including things like supposedly variable-controlled psychological studies, which are usually conducted by WEIRDs on WEIRDs, and so interpret results as universal when they might well be culturally-dependent.

This is the topic of a wonderful new book by anthropologist Joseph Henrich called The WEIRDest People in the World: How the West Became Psychologically Peculiar and Particularly Prosperous.  It's a fascinating lens into a culture that has become so dominant on the world stage that many people within it staunchly believe it's quantifiably the best one -- and some act as if it's the only one.  It's an eye-opener, and will make you reconsider a lot of your baseline assumptions about what humans are and the ways we see the world -- of which science historian James Burke rightly said, "there are as many different versions of that as there are people."

[Note:  If you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

The planet detectors

Are you looking for something to occupy you while you're stuck home?  For the month of April, I'm putting my online course An Introduction to Critical Thinking on sale for $12.99 (it's ordinarily $49.99).  It includes an hour and a half of video lectures, some (fun) problem sets and readings, and you'll come away with a better ability to detect such things as hoaxes, pseudoscience, ripoffs, and fake news.  Use the coupon code STUCKATHOME4APR to get your discount!

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Long-time readers of Skeptophilia know I'm kind of obsessed with the idea of extraterrestrial life.  I guess it's natural enough; I'm a biologist who's also an amateur astronomer, and grew up on Lost in Space and Star Trek and The Invaders, and later The X Files and Star Wars.  (Although I'm aware this is kind of a chicken-and-egg situation, so what the ultimate origin of my obsession is, I'm not certain.)

Until fairly recently, there was no particularly good way to determine the likelihood of life on other worlds.  Decades ago astronomer Frank Drake came up with the famous Drake Equation, which uses the statistical principle that if you know the probabilities of various independent occurrences, to find the probability of all of them happening, you multiply them together.  Here's the Drake Equation:

[Image is in the Public Domain courtesy of NASA/JPL]

The problem, of course, is that the more uncertainty there is in the individual probabilities, the more uncertainty there is in the product.  And there was no way known to get even a close value -- or, worse, to know if the value you had reflected reality or was just a wild guess.

What's cool for us alien enthusiasts, though, is that our research and techniques have improved to the point where we do have decent estimates for the values of some of these.  Even better, every time one of them is revised, it's revised upward.  Today I'd like to look at two of them -- f(p) and n(e) -- respectively, the fraction of stars that have planetary systems, and the fraction of those systems that have at least one planet in the habitable zone.

Given that we started out with a sample size of one (1) solar system, no one knew whether the coalescence of stellar debris into planets was likely, or simply a lucky fluke.  Same for planets in the habitable zone; here we have only a single planet that is habitable for organisms like ourselves.  Again, is that some kind of happy accident, or would most planetary systems have at least one potentially habitable planet?

Once we started to find exoplanets, though, they seemed to be everywhere we looked.  The earliest ones were massive (probably Jupiter-like) planets, often in fast, close orbit, so they'd be pretty hostile places from our perspective.  (Although, as I dealt with in a recent post, what we're finding out about the resilience of life may mean we'll have to revise our definition of what constitutes the "habitable zone.")

So the estimates for f(p) and n(e) crept upward, but still, it was hard to get reliable numbers.  But just last week, two studies have suggested that f(p) -- the percentage of stars with multiple-planet systems -- may be very close to 100%.

In the first, we hear about a recently-developed technique to improve our ability to detect exoplanets even at great distances.  Before this, most exoplanets were discovered using one of two methods -- looking for stellar wobble as a planet and its star circle their mutual center of gravity (which only works for nearby stars with massive planets capable of generating a detectable wobble), and luminosity dips as a planet occludes (passes in front of) its host star (which only works if the orbital plane is lined up in such a way that the planet passes in front of the star as seen from Earth).  As you might imagine, those restrictions mean that we might well be missing most of the exoplanets out there.

Now, a new orbiting telescope developed by NASA -- called WFIRST (Wide Field Infrared Survey Telescope) -- has the capability to detect microlensing.  Microlensing occurs because of the warping of the fabric of space-time by massive objects.  As a planet rotates around its host star, that warp moves, creating a ripple -- and the light from any stars behind the planet gets deflected.  An analogy is when you're looking down to the bottom of a clear pond and a ripple on the surface passes you; the image of the pebbles on the bottom appears to waver.  That wavering of light from distant stars is what WFIRST is designed to detect.

The nice thing is that WFIRST isn't dependent on visible wobbles or planets with precisely-aligned orbital planes; it can see pretty much any planet out there with sufficient mass.  And it can detect them from much farther away than previous telescopes -- the Kepler Space Telescope could detect planets up to around a thousand light years away, while WFIRST extends that reach by a factor of ten.  It's also capable of scanning a great many more stars; the estimate is that the first sweep will look at two hundred million stars, which is a thousand times the number Kepler studied.

So chances are, we're going to see an exponential jump in the number of exoplanets we know of, and a corresponding uptick in the estimate for f(p).

The second study is much closer to home -- about as close as you can get without being in our own Solar System.  Proxima Centauri is the nearest star to us other than the Sun, at 4.244 light years away.  In 2016 we were all blown away by the announcement that not only did Proxima Centauri have a planet, it was (1) Earth-sized, and (2) in the habitable zone.  (Anyone want to board the Jupiter 2?)

Now, astronomers have discovered a second planet around Proxima, at a distance about 1.5 times the orbit of the Earth, and a mass of about twelve times Earth's.  This means it's probably something like Neptune, and very cold -- Proxima is a dim star, so the habitable zone is a lot closer to it than the Sun's is -- the estimate is that its average temperature is -200 C.

Even though it probably doesn't host life, it's exciting from the standpoint that Proxima's planetary system is looking more and more like ours.  As astronomer Phil Plait put it, over at his fantastic blog Bad Astronomy, "I hope this new planet candidate turns out to be real.  Having one planet orbiting the star is already pretty amazing, but having two?  In my mind that makes it a solar system.  And if two, why not more?  How about moons orbiting the planets, or asteroids and comets around the star, too?"

The impression I'm getting is that f(p) (the fraction of stars with planetary systems) and n(e) (the fraction of stars with at least one planet in the habitable zone) are both extremely high.  This bodes well for our search for life -- and as the techniques improve, my sense is that we'll find planets like ours pretty much everywhere we look.  So life is looking more and more likely to be plentiful out there.  Now, intelligent life that is sufficiently technological to communicate across interstellar space... that's another matter entirely.

But in my opinion, any time we can revise some part of the Drake Equation upward, it's a good thing.

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This week's Skeptophilia book recommendation of the week is brand new -- only published three weeks ago.  Neil Shubin, who became famous for his wonderful book on human evolution Your Inner Fish, has a fantastic new book out -- Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA.

Shubin's lucid prose makes for fascinating reading, as he takes you down the four-billion-year path from the first simple cells to the biodiversity of the modern Earth, wrapping in not only what we've discovered from the fossil record but the most recent innovations in DNA analysis that demonstrate our common ancestry with every other life form on the planet.  It's a wonderful survey of our current state of knowledge of evolutionary science, and will engage both scientist and layperson alike.  Get Shubin's latest -- and fasten your seatbelts for a wild ride through time.

Starshot update

Two years ago I wrote about a project called Breakthrough Starshot, which proposed sending small remote-controlled cameras to nearby star systems, powered by lasers that could propel them up to twenty percent of the speed of light.

Which means we could be getting photographs back from Proxima Centauri in twenty years.

[Image licensed under the Creative Commons ESO/M. Kornmesser, Artist's impression of the planet orbiting Proxima Centauri, CC BY 4.0]

It's an ambitious project, and faces significant hurdles.  Even if propelled by lasers -- which, being light, travel at the speed thereof -- navigation becomes increasingly difficult the farther away it gets.  Even at the distance of Pluto, our intrepid little spacecraft would be 4.5 light-hours from Earth, meaning if we tried to beam it instructions to dodge around an incoming meteor, it would be 4.5 hours until the command arrived, at which point all that would be left is intrepid scrap metal.  And Proxima Centauri is 4.3 light years away.

You see the problem.  The Starshot spacecraft would have to be able, on some level, to think for itself, because there simply wouldn't be time for Mission Control to steer it to avoid danger.

There are other obstacles, though.  Besides the obvious difficulties of being in the cold vacuum of interstellar space, contending with cosmic rays and the like, there's the problem engendered by its speed   Assuming the estimate of a maximum velocity of twenty percent of light speed is correct, even tiny particles of dust would be formidable projectiles, so Starshot is going to require some heavy-duty shielding, increasing its mass (and thus the amount of energy needed to make it go).

But last month we got an encouraging proof of concept, when the group working on the mission -- Russian entrepreneur Yuri Milner's Breakthrough Foundation -- launched a test of the Starshot craft.  It was a tiny little thing, small enough to fit in your hand and weighing about the same as a stick of gum, designed and built by engineers at the University of California - Santa Barbara, and in the test flight achieved an altitude of nineteen miles, all the while functioning flawlessly, returning four thousand images of the Earth taken from aloft.

The Breakthrough Foundation is planning a suborbital test next year, and perhaps a full orbit the year after that.  So things are moving along.  But the most significant hurdle is to design the laser system to make Starshot move -- lasers that are so finely collimated that they can still strike a ten-centimeter craft square-on from several light years away.  The engineering director for Breakthrough, Peter Klupar, is designing a 100,000 gigawatt laser -- to be located, he says, in Chile -- that could be the answer.  Of course, such a powerful device is not without its dangers.  Reflected off a mirror in space, Klupar says, such a laser could "ignite an entire city in minutes."

Not that there's a mirror out there.  So you shouldn't worry at all about that.

"You would think that this is all impossible, but we have folks at Caltech and the University of Southampton and Exeter University working on about 50 contracts on making all [of] this happen," Klupar said.  "No one has come up with a deal-breaker that we can find yet. It all seems real."

One possible way to increase the thrust generated by the laser is to increase the surface area that the beam strikes, and Klupar thinks he knows how to do that -- using a "light sail."  He's already built a prototype.  "The sail is very thin. It's about 400 atoms thick, it weighs about a half a gram, and it's four meters in diameter," he said.  "I think of it as 'reflective smoke.'"

All of which may seem like science fiction, but it's phenomenal how fast things go from the realm of Star Trek to reality.  Klupar compares his light sails to CubeSats, tiny (ten by ten centimeters, weighing a little over a kilogram) orbiting telemetry devices that are now common.  "It feels a lot like the way CubeSats felt twenty years ago," he said.  "People were saying, 'Those are toys, they're never going to develop into anything, there's no way I can see that ever working.'  And today and look them: Hundreds of millions of dollars is being spent on them."

So keep your eye on this project.  If there's a chance at a remote visit to another star system, I think this is our best bet.  The Breakthrough Foundation estimates an actual, honest-to-goodness launch toward a nearby star as early as 2030.  Meaning perhaps we could get our first photographs of planets around another star by 2050.

I'll be ninety years old at that point, but if that's what I'm waiting for, I can make it till then.

**************************

When the brilliant British neurologist and author Oliver Sacks died in August of 2015, he was working on a collection of essays that delved into some of the deepest issues scientists consider: evolution, creativity, memory, time, and experience.  A year and a half ago, that collection was published under the title The River of Consciousness, and in it he explores those weighty topics with his characteristic humor, insight, and self-deprecating humility.

Those of us who were captivated by earlier works such as The Man Who Mistook His Wife for a Hat, Musicophilia, Awakenings, and Everything in its Place will be thrilled by this book -- the last thoughts of one of the best thinkers of our time.

[Note:  If you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]