Flash in the pan

I introduced yesterday's post, about the discovery that a large percentage of the meteorites seem to have come from a single collision event in the distant past, as "a question without an answer."  Today we're going to look at another one; fast radio bursts.

They're pretty much what they sound like; quick, high-energy flashes in the radio region of the electromagnetic spectrum.  What the name doesn't tell you, however, is how quick and high-energy they are.  They have a duration of only a few milliseconds at most; there and gone faster than a camera flash.  And their energy output is enormous -- the average fast radio burst releases as much energy in a few milliseconds as the Sun does in three days.

The trouble with studying these events is that they're over before you can get your radio telescope pointed toward them.  Until recently, there had been no coordinated effort to find fast radio bursts; how can you find them if they come from seemingly random spots in the night sky?  You would have to have the radio telescope pointed in the exactly right direction at exactly the right time in order to know one had even happened.

[Image licensed under the Creative Commons ESO/M. Kornmesser, Artist’s impression of a fast radio burst traveling through space and reaching Earth, CC BY 4.0]

This is why the first ones weren't even observed until 2007, and the number recorded in the fourteen years since was quite small.  But it was just announced this week that CHIME, the Canadian Hydrogen Intensity Mapping Experiment, has recorded 535 fast radio bursts in the one year of its operation -- quadrupling the total number ever detected.

"Before CHIME, there were less than a hundred total discovered FRBs; now, after one year of observation, we've discovered hundreds more," said study contributor Kaitlyn Shin, a graduate student in MIT's Department of Physics.  "With all these sources, we can really start getting a picture of what FRBs look like as a whole, what astrophysics might be driving these events, and how they can be used to study the universe going forward."

Because that's the problem with fast radio bursts; no known astrophysical process could produce such a sudden, short-duration explosion in the radio region of the spectrum.  More interesting still, the CHIME study showed that they seem to fall into two classes; "one-offs" and "repeaters."  So even if we figure out how they happen, we'll still be left with why some of them happen only once, and others seem to be on some kind of regular cycle.

The most perplexing thing about them, though, is how common they appear to be.  For something that is caused by a completely unknown mechanism, they're pretty much everywhere.  "That's kind of the beautiful thing about this field -- FRBs are really hard to see, but they're not uncommon," said Kiyoshi Masui, another study contributor, and a member of MIT's Kavli Institute for Astrophysics and Space Research.  "If your eyes could see radio flashes the way you can see camera flashes, you would see them all the time if you just looked up."

So there you have it; another as-yet unsolved mystery.  It seems like no matter where we look, there are three new conundrums for every one we solve.  It brings to mind the quote from biologist J. B. S. Haldane: "The universe is not only queerer than we imagine, it is queerer than we can imagine."

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I'm in awe of people who are true masters of their craft.  My son is a professional glassblower, making precision scientific equipment, and watching him do what he does has always seemed to me to be a little like watching a magic show.  On a (much) lower level of skill, I'm an amateur potter, and have a great time exploring different kinds of clays, pigments, stains, and glazes used in making functional pottery.

What amazes me, though, is that crafts like these aren't new.  Glassblowing, pottery-making, blacksmithing, and other such endeavors date back to long before we knew anything about the underlying chemistry and physics; the techniques were developed by a long history of trial and error.

This is the subject of Anna Ploszajski's new book Handmade: A Scientist's Search for Meaning Through Making, in which she visits some of the finest craftspeople in the world -- and looks at what each is doing through the lenses of history and science.  It's a fascinating inquiry into the drive to create, and how we've learned to manipulate the materials around us into tools, technology, and fine art.

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

Fermi's Paradox, fast radio bursts, and extraterrestrial intelligence

Just because I believe that science works, and that its methods are sound, doesn't mean that I have to like its conclusions.  And one of my least favorite pieces of sound scientific reasoning is Fermi's Paradox.

Named after the Nobel Prize-winning physicist Enrico Fermi, Fermi's Paradox originally took the form of a succinct response to all of the speculation about life in other star systems.  According to everything we know about stellar evolution, planet formation, biochemistry, and evolutionary biology, life should be common out there.  And just considering the fact that some star systems with planets are likely to be considerably older than ours, it also stands to reason that there should be civilizations out there considerably more advanced than ours.

Upon hearing this sort of argument, Fermi responded with a simple question:  "Where is everybody?"  If life, and intelligent life, is as common as all that, we should be bombarded with signals from extraterrestrials.  And in fact, despite decades of searching the skies, there has never been a single unequivocal transmission found from an intelligent life-form.  (Although the "WOW Signal" might be a contender; it's yet to be explained.)

There are a number of possible explanations for the lack of extraterrestrial communications, and most of them are depressing.  It could be that the likelihood of intelligent life developing on planets is, for some reason, a great deal less likely than we think it is (i.e. we here on Earth were just damn lucky).  It could be that most civilizations destroy themselves shortly after achieving the capacity for long-distance communication.  Some astronomers even think that there are cosmic reset switches -- natural phenomena that periodically wipe the galaxy clean of life, requiring a prolonged reboot, and preventing most life ever from achieving technology.  (For example, consider gamma-ray bursters, but only if you want to spend the next few days worrying about the entire solar system suddenly getting fried.)

Being someone who would love nothing better than to witness the discovery of extraterrestrial intelligence, I find the Fermi Paradox a significant downer.  I do have one possible answer that may still allow for a rich diversity of intelligent life in the galaxy, however; because we are looking for communication in the radio region of the spectrum (the fashion in which we as a species first learned to do long-distance transmission of information), it might be that such discernible, signal-producing modes of communication are quickly superseded by more sophisticated technologies that produce much less in the way of a footprint when observed from light years distant.  In other words; societies might only be detectable during the first few decades of their technological existence, when they're communicating with each other by shouting from the rooftops.  After they learn more efficient means of transmitting information, they seem to go silent.

I hope.  Because otherwise, it's mighty lonely here, you know?

All of this comes up because of a paper published just last week by Michael Hippke, Wilfried Domainko, and John Learned called "Discrete Steps in Dispersion Measures of Fast Radio Bursts."  In this interesting bit of research, an analysis was done of the dispersion measures of microseconds-long pulses in the radio region of the spectrum.  The paper is quite technical -- even with a B.S. in physics, it was over my head -- but insofar as I understand it, the curious thing about the eleven radio pulses thus far detected is that their dispersion measures are all integer multiples of 187.5 parsec/cm3 -- something that admits of no particularly obvious natural explanation.

Carl Sagan, in his wonderful novel (and later movie) Contact, used the idea of encoding a signal with some mathematical pattern as a way of broadcasting a "We're Here" signal into space -- or, conversely, looking for such a signal as a way of detecting life that's out there.  If a radio signal could be encoded with the first ten digits of pi, or (as in Contact) the first few prime numbers, that would be instantly recognizable as an unequivocal signal from an intelligence.  So the discovery of the 187.5 pattern in dispersion measures for FRBs was immediately jumped upon as evidence that the radio bursts originate from some alien civilization.  (The International Business Times, for example, was all a-quiver with the possibility.)

The astrophysicists, of course, are being more circumspect.  All that Hippke, Domainko, and Learned concluded from their research is that the pattern is currently unexplained, if suggestive:

(A)n extragalactic origin would seem unlikely, as high (random) DMs would be added by intergalactic dust.  A more likely option could be a galactic source producing quantized chirped signals, but this seems most surprising.  If both of these options could be excluded, only an artificial source (human or non-human) must be considered, particularly since most bursts have been observed in only one location (Parkes radio telescope)...  In the end we only claim interesting features which further data will verify or refute. 

They also suggest that the FRBs might actually be perytons, signals that appear to originate from space when they actually are entirely terrestrial in origin -- i.e. human-generated signals that are being misinterpreted, or simple radio telescope glitches.

Whatever the explanation is, the FRBs are an interesting phenomenon, and give me hope that there might be an eventual answer to Fermi's Paradox.  I have to be careful about letting my desire for there to be intelligent life elsewhere in the universe get in the way of my objectivity in evaluating the evidence at hand; but even so, the strange mathematical pattern that Hippke et al. have discovered might be the best contender we currently have for an alien civilization saying, "Here we are!"