Patterns out of noise

We all have intuition and common sense about how the world works, and it is fascinating how often that intuition is wrong.

Not that I like having my worldview called into question, mind you; but I have to admit there's a certain thrill in discovering that there are subtleties I had never considered.  Take, for example, Benford's Law, that I first heard about a while back while listening to the radio program Freakonomics.  In any reasonably unrestricted data set, what should be the relative frequencies of the first digit?  Put another way, if I was to take a set of numbers (like the populations of all of the incorporated villages, towns, and cities in the United States) and look only at the first digits, how many of them would be 1s, 2s, 3s, and so on?

On first glance, I saw no reason that the distribution shouldn't be anything but equal.  That's what a set of random numbers means, right?  And how are the populations of municipalities ranging from ten people all the way up to several million anything other than a collection of random numbers?

Well, you've probably already guessed this isn't right.  Lining up the frequencies of 1s through 9s in order, you get a perfect inverse relationship.  About 30% of the first digits are 1s, all the way down to only 5% being 9s.

Why is this?  Well, the simple answer is that the statisticians are still arguing about it.  But it does give a way to catch when a supposedly real data set has been altered or fudged; the real data set will conform to Benford's Law, and (very likely) the altered one won't.

Another interesting one, and in fact the reason why I was thinking about this topic, is Zipf's Law, named after American linguist George Kingsley Zipf, who first attempted a mathematical explanation of why it works.  Zipf's Law looks at the frequencies of different words in long passages of text, and finds that there's an inverse relationship, similar to what we saw with Benford's Law.  In English, the most commonly used word is "the."  The next most common ("of") has half that frequency.  The third ("and") has one-third the frequency.  And on down the line; the tenth most frequent word occurs at one-tenth the frequency of the most common one, and so forth.

Zipf's Law has been tested in dozens of different languages, including conlangs like Esperanto, and it always holds.  So does the related pattern called the Brevity Law (there's an inverse relationship between the length of a word and how commonly it's used), and -- to me the most fascinating -- the Law of Hapax Legomenon, which states that in long passages of text, about half of the words will only occur once (the name comes from the Greek ἅπαξ λεγόμενον, meaning "being said once").

Where things get really interesting is that these three laws -- Zipf's Law, the Brevity Law, and the Law of Hapax Legomenon -- may have relevance to the search for extraterrestrial intelligence.  Say we pick up what seems like radio-wave-encoded language from another star system.  The difficulty is obvious; translating a passage from another language when we don't know the sound-to-meaning correspondence is mind-bogglingly difficult (although it has been accomplished, most famously Alice Kober's and Michael Ventris's decipherment of the Linear B script of Crete).  

The task seems even more hopeless for an alien language, that shares no genetic roots with any human language, and thus the most useful tool we have -- noting similarities with known related languages -- is a non-starter.  Just like Dr. Ellie Arroway in Contact, we'd be faced first with the seemingly insurmountable problem of figuring out if it is an actual alien language, and not just noise or gibberish.

The three laws I mentioned may solve at least that much of the problem.  The fact that they've been shown to govern the frequency distribution of every language tested, including completely unrelated ones like Japanese and Swahili, suggests that they might represent a universal tendency.  Just as Benford's Law can help statisticians identify falsified data sets, the three laws of word frequency distribution might help us tell if what we've picked up is truly language.

It still leaves the linguists with the daunting task of figuring out what it all means, but at least they won't be working fruitlessly on something that turns out to be mere noise.

I find the whole thing fascinating, not only from the alien angle (which you'd probably predict I'd love) but because it once again demonstrates that our intuition about things can lead us astray.  Who would have guessed, for example, that half of the words in a long passage of text would occur only once?  I love the way science, and scientific analysis, can correct our fallible "common sense" about how things work.

And, as with Zipf, Brevity, and Hapax Legomenon, open up doors to understanding things we never dreamed of.

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

Ever get frustrated by scientists making statements like "It's not possible to emulate a human mind inside a computer" or "faster-than-light travel is fundamentally impossible" or "time travel into the past will never be achieved?"

Take a look at physicist Chiara Marletto's The Science of Can and Can't: A Physicist's Journey Through the Land of Counterfactuals.  In this ambitious, far-reaching new book, Marletto looks at the phrase "this isn't possible" as a challenge -- and perhaps, a way of opening up new realms of scientific endeavor.

Each chapter looks at a different open problem in physics, and considers what we currently know about it -- and, more importantly, what we don't know.  With each one, she looks into the future, speculating about how each might be resolved, and what those resolutions would imply for human knowledge.

It's a challenging, fascinating, often mind-boggling book, well worth a read for anyone interested in the edges of scientific knowledge.  Find out why eminent physicist Lee Smolin calls it "Hugely ambitious... essential reading for anyone concerned with the future of physics."

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

 

Guest post: That's my left hand, right?

The running coach I work with has a good laugh at me nearly every week because I'm directionally impaired.  He tells me, "Okay, ten lateral lunges, starting on the right side," and the chance is 50/50 I'll lunge to the left.  I was talking with my dear friend, the amazing writer K. D. McCrite, about this -- turns out she suffers from the same malady, and we're not alone.  Current research has found that about twelve percent of adults have poor left-right discrimination, which can lead to some embarrassment... or worse.  A 2011 report found that forty wrong-side surgeries are done in the United States every week.  We're talking well-educated, highly trained professionals here, so clearly, it's nothing to do with intelligence.

K. D. is our guest here on Skeptophilia today, sharing her experiences of having issues with knowing which side is which.  And as an aside: when you're done reading this, check out her books...!

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

Just outside the open window next to my desk, water dribbled from the spray nozzle of the hose and drove me nutty.  The man of the house told me the nozzle needs to be either replaced or adjusted.  I lack the strength to turn off the outdoor spigot to halt the flow, the hubs wasn’t home to take care of it, so when the young man next door came home from school, I asked him for help.  Tall and strong, this high schooler would be able to take care of the problem.

I reminded him that he needed to turn it to the right to shut off the water.  So why did he keep turning it to the left?  I kept muttering, silently, “To the right, to the right!”

He accomplished the task, and then…

And then I was so relieved I had not hollered “TO THE RIGHT!” because he’d been doing just that.

I have always had a hard time with left and right.  It’s so much easier for me to understand north and south, or landmarks, or if you simply point.  This left and right mess causes me to pause every time.  It will congeal in my brain especially when I’m under stress or someone is watching me.  It’s confounding, embarrassing, and hard to explain to that person sneering at you.

One time stands out sharply in my memory.  I was visiting a friend, an older man whom I highly regarded and respected.  He asked me to turn down the radio on the other side of the room.  There were several knobs along the front of that old radio, but none of them were marked for volume control.

“It’s on the left,” he said.

Of course, I immediately reached for the knobs on the right.

“On the left, on the left!” he screamed.  “Are you some kind of moron??”

Immediately, I froze, unable to make the adjustment he asked for.  He’d never been verbally abusive to me before.  My frozen state made him even angrier and more abusive.  His wife quickly adjusted the volume, then touched my shoulder and told me it was okay, she understood.  He, on the other hand, continued to mumble and curse, and I truly believed my intellect was deeply flawed if I couldn’t grasp something as simple as right and left.  Later, I realized I didn’t need that abusive friend in my life, nor did he deserve my respect.

It stays with me, though, those times when I’ve been berated for this inability to differentiate quickly between left and right.  Believe me, I beat myself up plenty, and still do, even though there is a scientific reason for this disability.

[Image licensed under the Creative Commons Evan-Amos, Human-Hands-Front-Back, CC BY-SA 3.0]

If you have a friend or loved one who struggles with this, the last thing they need is to feel foolish or ignorant, so be patient.  You will likely have to be patient about this all their lives because I don’t think there is a pill, procedure, counseling, or surgery that can take care of it.  Aging certainly doesn’t make it any easier for us.  It might help if you consider for a moment how you might feel if it was your struggle.  Suppose someone told you to turn left, but before you could do that, you had to think about it, had to look at your hands to see which one had the ring or which one you write with or which one has that little birthmark?

I’ve thought of getting L and R tattooed on the appropriate hands, but I’d still have to pause and look.

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

Ever get frustrated by scientists making statements like "It's not possible to emulate a human mind inside a computer" or "faster-than-light travel is fundamentally impossible" or "time travel into the past will never be achieved?"

Take a look at physicist Chiara Marletto's The Science of Can and Can't: A Physicist's Journey Through the Land of Counterfactuals.  In this ambitious, far-reaching new book, Marletto looks at the phrase "this isn't possible" as a challenge -- and perhaps, a way of opening up new realms of scientific endeavor.

Each chapter looks at a different open problem in physics, and considers what we currently know about it -- and, more importantly, what we don't know.  With each one, she looks into the future, speculating about how each might be resolved, and what those resolutions would imply for human knowledge.

It's a challenging, fascinating, often mind-boggling book, well worth a read for anyone interested in the edges of scientific knowledge.  Find out why eminent physicist Lee Smolin calls it "Hugely ambitious... essential reading for anyone concerned with the future of physics."

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

 

The stellar whirlpool

In today's installment of "The Universe Is A Really Weird Place," we have: a piece of our own galaxy that we didn't even know existed until now.

It's called the "Cepheus Spur" after the constellation Cepheus, in which (from the Earth perspective) the structure seems to reside.  It's a spiral of stars lying above the galactic plane, and at the moment, astronomers don't know how it got there.   "Possibly these are oscillations of the galactic disk resulting from the convulsive evolution of the galaxy," said co-discoverer Michelangelo Pantaleoni González, of the Spanish Astrobiology Center.  "Perhaps they are the echoes of collisions with other galaxies billions of years ago, or maybe it’s something else."

The befuddlement of the experts is indicative that this structure has some seriously odd characteristics.  One of the strangest is that it seems to be mostly composed of type-OB blue supergiant stars, which are amongst the rarest star types known; from observations of the Milky Way, only one star in a million is a type-OB blue supergiant.

That's even taking into account the fact that the ones we know about are visible from a long way off.  They have masses between twenty and fifty times that of the Sun, and luminosities on the order of a hundred thousand times higher.  One familiar example is Rigel, in Orion, which is the brightest star in the constellation despite being 860 light years away.

The constellation Orion, with Rigel at the lower right [Image licensed under the Creative Commons Rogelio Bernal Andreo, Orion Head to Toe, CC BY-SA 3.0]

Their rarity isn't just because it's unusual to have such a huge clump of matter form; they're also exceedingly short-lived.  Because of their mass, they burn through their hydrogen fuel quickly, which makes them the hottest stars -- with surface temperatures of between 10,000 and 50,000 K (the Sun's surface is on the order of 5770 K).  It's estimated that a typical type-OB blue supergiant goes from formation to supernova in something between a few hundred thousand and thirty million years; again, by contrast, the Sun is estimated at 4.6 billion years in age, and is only about halfway through its life.

So to have a swirl of these rare and short-lived stars whirling above the plane of the galaxy is a significant puzzle.

"When we discovered the spur, there was no explosive revelation, but something inside me was transformed.  That’s what draws you in and gives meaning to so much effort," said Pantaleoni González.  "We were in front of [astrophysicist] Jesús [Apellániz]’s computer when he began to inspect this density of dots on the map. I ran to make a special diagram to see if it was consistent with the idea that there was a structure there, and it appeared."

The presence of these stars outside of the galactic plane has yet to be explained, and it's still unknown if the Cepheus Spur really is composed primarily of rare type-OB blue supergiants, or if we're overestimating their frequency because they're so luminous.  It could be that there are a lot of other, dimmer stars in the Spur that we're not seeing because of its distance (estimated at an average of 100,000 light years).  In any case, what seems certain is that this discovery will keep the astrophysicists working for a long while -- and illustrates that once again, the universe is full of surprises.

Which is one of the reasons that science is so endlessly fascinating.

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

When people think of mass extinctions, the one that usually comes to mind first is the Cretaceous-Tertiary Extinction of 66 million years ago, the one that wiped out all the non-avian dinosaurs and a good many species of other types.  It certainly was massive -- current estimates are that it killed between fifty and sixty percent of the species alive at the time -- but it was far from the biggest.

The largest mass extinction ever took place 251 million years ago, and it destroyed over ninety percent of life on Earth, taking out whole taxa and changing the direction of evolution permanently.  But what could cause a disaster on this scale?

In When Life Nearly Died: The Greatest Mass Extinction of All Time, University of Bristol paleontologist Michael Benton describes an event so catastrophic that it beggars the imagination.  Following researchers to outcrops of rock from the time of the extinction, he looks at what was lost -- trilobites, horn corals, sea scorpions, and blastoids (a starfish relative) vanished completely, but no group was without losses.  Even terrestrial vertebrates, who made it through the bottleneck and proceeded to kind of take over, had losses on the order of seventy percent.

He goes through the possible causes for the extinction, along with the evidence for each, along the way painting a terrifying picture of a world that very nearly became uninhabited.  It's a grim but fascinating story, and Benton's expertise and clarity of writing makes it a brilliant read.

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

The child on the road

One of the creepiest urban legends is the tale of the Black-eyed Children.

The whole thing seems to have begun with a Texas man named Brian Bethel, who reported back in 1996 that he had an encounter with what appeared to be a ten-year-old child on the side of a highway near Abilene.  When he stopped to see if the child was okay, or needed a ride or something, the kid came up to Bethel's open window and said, "Please, can you help me?  I'm lost."

But when Bethel looked closer, he saw that the child's eyes were entirely black.  No white, no iris, just solid, glossy black.  Understandably, he gunned the engine and took off.

[Image licensed under the Creative Commons Megamoto85, Black eyes by megamoto85 (cropped), CC BY-SA 4.0]

Since then, the legend has grown by accretion, with other people pitching in with their own stories of the Black-eyed Children.  The claim is that if you let one into your car or house, you'll never be seen again, although it's hard to understand how they'd know that, given that the only ones who could verify this are the ones who did let them in.

And they were never seen again.  Right?  Or am I missing some part in the logical chain, here?

The plausibility issues notwithstanding, the idea was creepy enough that I made it the basis of my trilogy of novels called The Boundary Solution -- Lines of Sight, Whistling in the Dark, and Fear No Colors.  I hope I did it justice, because whatever else you can say about it, the concept is scary as hell.

The topic comes up because of a report out of Australia, where something really peculiar is alleged to have happened last weekend.  According to a man named Mitch Kuhne, he was driving on the Hume Highway south of Sydney when he saw what looked like a child on the road.  Here's what Kuhne said:

In the video you’ll see what we seen on our way home from racing what looked to be a child on the middle of the highway!

Instantly called 000 as we couldn’t stop as we had a huge toy hauler we were carrying and would have caused an accident, police said they were putting patrols out immediately, I called the local station after realising the dash cam would have footage and called to see where I could send it to help them so they know what it is we saw and could pinpoint the location.  I was told on the phone by the officer that there is no need to send it as the child had been collected safely and was on its way home, I felt absolutely sick when all this happened I instantly felt so much better when I was told the kid had been collected.

If you want to see the dashcam footage, you can check it out at News.com.au, at the link I posted above.  But here's a still:

There's no doubt that the video is creepy.  The figure moves as the car passes it, and you can see its shadow rotating beneath its feet, indicating it's a solid object (i.e. not a lens flare or some camera glitch).  But this isn't as creepy as the postscript -- because the Australian media covering the story contacted the police, and they denied the entire thing.

They'd searched the area after Kuhne's call, they said, and found nothing.  Furthermore, there'd been no reports of a missing person in the area.

Case closed.

If it weren't for the discrepancy, the story wouldn't be that odd; just a kid wandering where (s)he shouldn't, and getting rescued by the police.  But the police at the Macquarie Fields Police Station are now saying there was no child found, and furthermore, that Kuhne was told that after the search was complete.

"The only reason I posted the video [of the dashcam footage on social media] is because I thought the kid was safe and felt okay posting it," Kuhne said.  "Now to see that they are claiming I was never told this makes me sick."

So it's a weird story, I'll give it that.  There may not be anything to it; it could be that Kuhne made up the part about the police having confirmed they'd found a child.  (I don't mean to impugn the honesty of someone I don't know, but we have to admit that as a possibility.)  If it's the police who are lying, the next obvious question is, "Why?"  What would they have to gain by telling Kuhne the child was safe if they hadn't found any child -- or, conversely, denying the existence of the child to the media if they had found one and gotten him/her home safely?  Either way, there's something about this whole situation that doesn't add up.

Take a look at the video, and let me know what you think in the comments.  Skeptics are saying it isn't a child at all, but a bit of rubbish being blown on the wind, an animal, or a statue (although what a statue was doing in the middle of the road is a question in and of itself).  Other, less skeptical types are saying it was a ghost or an alien.

Or, possibly, a Black-eyed Child.  Gotta watch out for those.  And if that's what it was, it's a good thing Kuhne didn't stop.  Maybe that's what happened to the police -- the ones who picked up the child were never seen again.

I hear that happens sometimes.

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

When people think of mass extinctions, the one that usually comes to mind first is the Cretaceous-Tertiary Extinction of 66 million years ago, the one that wiped out all the non-avian dinosaurs and a good many species of other types.  It certainly was massive -- current estimates are that it killed between fifty and sixty percent of the species alive at the time -- but it was far from the biggest.

The largest mass extinction ever took place 251 million years ago, and it destroyed over ninety percent of life on Earth, taking out whole taxa and changing the direction of evolution permanently.  But what could cause a disaster on this scale?

In When Life Nearly Died: The Greatest Mass Extinction of All Time, University of Bristol paleontologist Michael Benton describes an event so catastrophic that it beggars the imagination.  Following researchers to outcrops of rock from the time of the extinction, he looks at what was lost -- trilobites, horn corals, sea scorpions, and blastoids (a starfish relative) vanished completely, but no group was without losses.  Even terrestrial vertebrates, who made it through the bottleneck and proceeded to kind of take over, had losses on the order of seventy percent.

He goes through the possible causes for the extinction, along with the evidence for each, along the way painting a terrifying picture of a world that very nearly became uninhabited.  It's a grim but fascinating story, and Benton's expertise and clarity of writing makes it a brilliant read.

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

Watching the clock

 If I had to pick the scientific law that is the most misunderstood by the general public, it would have to be the Second Law of Thermodynamics.

The First Law of Thermodynamics says that the total quantity of energy and mass in a closed system never changes; it's sometimes stated as, "Mass and energy cannot be destroyed, only transformed."  The Second Law states that in a closed system, the total disorder (entropy) always increases.  As my long-ago thermodynamics professor put it, "The First Law says you can't win; the Second Law says you can't break even."

Hell of a way to run a casino, that.

So far, there doesn't seem to be anything particularly non-intuitive about this.  Even from our day-to-day experience, we can surmise that the amount of stuff seems to remain pretty constant, and that if you leave something without maintenance, it tends to break down sooner or later.  But the interesting (and less obvious) side starts to appear when you ask the question, "If the Second Law says that systems tend toward disorder, how can a system become more orderly?  I can fling a deck of cards and make them more disordered, but if I want I can pick them up and re-order them.  Doesn't that break the Second Law?"

It doesn't, of course, but the reason why is quite subtle, and has some pretty devastating implications.  The solution to the question comes from asking how you accomplish re-ordering a deck of cards.  Well, you use your sensory organs and brain to figure out the correct order, and the muscles in your arms and hands (and legs, depending upon how far you flung them in the first place) to put them back in the correct order.  How did you do all that?  By using energy from your food to power the organs in your body.  And to get the energy out of those food molecules -- especially glucose, our primary fuel -- you broke them to bits and jettisoned the pieces after you were done with them.  (When you break down glucose to extract the energy, a process called cellular respiration, the bits left are carbon dioxide and water.  So the carbon dioxide you exhale is actually broken-down sugar.)

Here's the kicker.  If you were to measure the entropy decrease in the deck of cards, it would be less -- way less -- than the entropy increase in the molecules you chopped up to get the energy to put the cards back in order.  Every time you increase the orderliness of a system, it always (1) requires an input of energy, and (2) increases the disorderliness somewhere else.  We are, in fact, little chaos machines, leaving behind a trail of entropy everywhere we go, and the more we try to fix things, the worse the situation gets.

I've heard people arguing that the Second Law disproves evolution because the evolutionary model claims we're in a system that has become more complex over time, which according to the Second Law is impossible.  It's not; and in fact, that statement betrays a fundamental lack of understanding of what the Second Law means.  The only reason why any increase in order occurs -- be it evolution, or embryonic development, or stacking a deck of cards -- is because there's a constant input of energy, and the decrease in entropy is offset by a bigger increase somewhere else.  The Earth's ecosystems have become more complex in the 4.5 billion year history of life because there's been a continuous influx of energy from the Sun.  If that influx were to stop, things would break down.

Fast.

The reason all this comes up is because of a paper this week in Physical Review X that gives another example of trying to make things better, and making them worse in the process.  This one has to do with the accuracy of clocks -- a huge deal to scientists who are studying the rate of reactions, where the time needs to be measured to phenomenal precision, on the scale of nanoseconds or better.  The problem is, we learn from "Measuring the Thermodynamic Cost of Timekeeping," the more accurate the clock is, the higher the entropy produced by its workings.  So, in effect, you can only measure time in a system to the extent you're willing to screw the system up.

[Image licensed under the Creative Commons Robbert van der Steeg, Eternal clock, CC BY-SA 2.0]

The authors write:

All clocks, in some form or another, use the evolution of nature towards higher entropy states to quantify the passage of time.  Due to the statistical nature of the second law and corresponding entropy flows, fluctuations fundamentally limit the performance of any clock.  This suggests a deep relation between the increase in entropy and the quality of clock ticks...  We show theoretically that the maximum possible accuracy for this classical clock is proportional to the entropy created per tick, similar to the known limit for a weakly coupled quantum clock but with a different proportionality constant.  We measure both the accuracy and the entropy.  Once non-thermal noise is accounted for, we find that there is a linear relation between accuracy and entropy and that the clock operates within an order of magnitude of the theoretical bound.

Study co-author Natalia Ares, of the University of Oxford, summarized their findings succinctly in an article in Science News; "If you want a better clock," she said, "you have to pay for it."

So a little like the Heisenberg Uncertainty Principle, the more you try to push things in a positive direction, the more the universe pushes back in the negative direction.  

Apparently, even if all you want to know is what time it is, you still can't break even.

So that's our somewhat depressing science for the day.  Entropy always wins, no matter what you do.  Maybe I can use this as an excuse for not doing housework.  Hey, if I make things more orderly here, all it does is mess things up elsewhere, so what's the point?

Nah, never mind.  My wife'll never buy it.

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

When people think of mass extinctions, the one that usually comes to mind first is the Cretaceous-Tertiary Extinction of 66 million years ago, the one that wiped out all the non-avian dinosaurs and a good many species of other types.  It certainly was massive -- current estimates are that it killed between fifty and sixty percent of the species alive at the time -- but it was far from the biggest.

The largest mass extinction ever took place 251 million years ago, and it destroyed over ninety percent of life on Earth, taking out whole taxa and changing the direction of evolution permanently.  But what could cause a disaster on this scale?

In When Life Nearly Died: The Greatest Mass Extinction of All Time, University of Bristol paleontologist Michael Benton describes an event so catastrophic that it beggars the imagination.  Following researchers to outcrops of rock from the time of the extinction, he looks at what was lost -- trilobites, horn corals, sea scorpions, and blastoids (a starfish relative) vanished completely, but no group was without losses.  Even terrestrial vertebrates, who made it through the bottleneck and proceeded to kind of take over, had losses on the order of seventy percent.

He goes through the possible causes for the extinction, along with the evidence for each, along the way painting a terrifying picture of a world that very nearly became uninhabited.  It's a grim but fascinating story, and Benton's expertise and clarity of writing makes it a brilliant read.

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

Twinkle, twinkle, little antistar

It's a big mystery why anything exists.

I'm not just being philosophical, here.  According to the current most widely-accepted cosmological model, when the Big Bang occurred, matter and antimatter would have formed in equal quantities.  As anyone who has watched Star Trek knows, when matter and antimatter come into contact, they mutually annihilate and all of the mass therein is converted to a huge amount energy in the form of gamma rays, the exact quantity of which is determined by Einstein's law of E = mc^2.

So if we started out with equal amounts of matter and antimatter, why didn't it all eventually go kablooie, leaving a universe filled with nothing but gamma rays?  Why was there any matter left over?

The answer is: we don't know.  Some cosmologists and astrophysicists think that there may have been a slight asymmetry in favor of matter, driven by random quantum fluctuations early on, so while most of the matter and antimatter were destroyed by collisions, there was a little bit of matter left, and that's what's around today.  (And "a little bit" is honestly not an exaggeration; the vast majority of the universe is completely empty.  An average cubic meter of space is very unlikely to have much more than an atom or two in it.)

One question this sometimes brings up is whether the stars and galaxies we see in the night sky are matter; if, perhaps, some entire galaxies are made of antimatter, and there really are equal amounts of the two.  After all, antimatter is predicted to act exactly like matter except that its fundamental particles have the opposite charges -- its protons are negative, its electrons positive, and so forth.  So a planet entirely formed of antimatter would look (from a safe distance) exactly like an ordinary planet.

And just to throw this out there, an antiplanet wouldn't have copies of all of us except for having the opposite personalities, for example some people who are good guys being evil and/or having beards, as outlined in the highly scientific Lost in Space episode "The Antimatter Man:"

Nor would there be a creepy bridge between the two universes, covered with fog and backed by eerie music:

Which is a shame, because I always kinda liked that episode.

Considerations of evil Major Don West with a beard notwithstanding, here are two arguments why most physicists believe that the stars we see, even the most distant, are made of ordinary matter.  The first is that there is no known process that would have sorted out the matter from the antimatter early in the universe's life, leaving isolated clumps of each to form their respective stars and galaxies.  Secondly, if there were antistars and antigalaxies, then there'd be an interface between them and the nearest clump of ordinary stars and galaxies, and at that interface matter and antimatter would be constantly meeting and mutually annihilating.  This would produce a hell of a gamma ray source -- and we haven't seen anything out there that looks like a matter/antimatter interface (although I will return to this topic in a moment with an interesting caveat).

A paper last year found that the key to understanding why matter prevailed might lie in the mysterious "ghost particles" called neutrinos.  There are three kinds of neutrinos -- electron neutrinos, muon neutrinos and tau neutrinos -- and one curious property they have is that they oscillate, meaning they can convert from one type to another.  The rate at which they do this is predicted from current theories, and it's thought that antineutrinos do exactly the same thing at exactly the same rate.

The experiment described in the paper took place in Japan, and found that there is an unexpected asymmetry between neutrinos and antineutrinos.  Beams of muon neutrinos and muon antineutrinos were sent on a six-hundred-kilometer journey across Japan, and upon arriving at a detector, were analyzed to see how many had converted to one of the other two "flavors."  The surprising result was that the neutrinos had oscillated a lot more than predicted, and the antineutrinos a lot less -- something called a "CP (charge-parity) violation" that shows antimatter doesn't, in fact, behave exactly like matter.  This asymmetry could lie at the heart of why the balance tipped in favor of matter.

But now a new analysis of data from the Fermi Gamma-ray Space Telescope has thrown another monkey wrench into the works.  The study was undertaken because of a recent puzzling detection by an instrument on the International Space Station of nuclei of antihelium, which (if current models are correct) should be so rare in the vicinity of ordinary matter that they'd be entirely undetectable.  But what if the arguments against antistars and antigalaxies I described earlier aren't true, and there are such odd things out there?  Antistars would be undergoing fusion just like the Sun does, and producing antihelium (and other heavier antielements), which then would be shed from the surface just like our Sun sheds helium.  And some of it might arrive here, only to fall into one of our detectors.

But what about the whole gamma-rays-at-the-interface thing?  Turns out, the study in question, the subject of a paper last week in the journal Physical Review D, found that there are some suspicious gamma-ray sources out there.

Fourteen of them, in fact.

These gamma-ray sources are producing photons with an energy that's hard to explain from known sources of gamma rays -- pulsars and black holes, for example.  In fact, the energy of these gamma rays is perfectly consistent with the source being ordinary matter coming into contact with an antistar.

Curiouser and curiouser.

It doesn't eliminate the problem of why the universe is biased toward matter; even if these are antistars, their frequency in the universe suggests that only one in every 400,000 stars is an antistar.  So we still have the imbalance to explain.

But it's a strange and fascinating finding.  Astrophysicists are currently re-analyzing the data from every angle they can think of to try and account for the odd gamma-ray sources in any way other than it being evidence of antistars, so it may be that the whole thing will fizzle.  But for now, it's a tantalizing discovery.  It brings to mind the famous quote from J. B. S. Haldane -- "The universe is not only queerer than we imagine, it's queerer than we can imagine."

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When people think of mass extinctions, the one that usually comes to mind first is the Cretaceous-Tertiary Extinction of 66 million years ago, the one that wiped out all the non-avian dinosaurs and a good many species of other types.  It certainly was massive -- current estimates are that it killed between fifty and sixty percent of the species alive at the time -- but it was far from the biggest.

The largest mass extinction ever took place 251 million years ago, and it destroyed over ninety percent of life on Earth, taking out whole taxa and changing the direction of evolution permanently.  But what could cause a disaster on this scale?

In When Life Nearly Died: The Greatest Mass Extinction of All Time, University of Bristol paleontologist Michael Benton describes an event so catastrophic that it beggars the imagination.  Following researchers to outcrops of rock from the time of the extinction, he looks at what was lost -- trilobites, horn corals, sea scorpions, and blastoids (a starfish relative) vanished completely, but no group was without losses.  Even terrestrial vertebrates, who made it through the bottleneck and proceeded to kind of take over, had losses on the order of seventy percent.

He goes through the possible causes for the extinction, along with the evidence for each, along the way painting a terrifying picture of a world that very nearly became uninhabited.  It's a grim but fascinating story, and Benton's expertise and clarity of writing makes it a brilliant read.

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

Unreal estate

Thanks to a friend and loyal reader of Skeptophilia, I found out yesterday that those of you who would like a nice place to retire can now buy property...

... on Mars.

I'm not joking, although the people who set up the site may well be.  Here's the idea:

Own an acre of land in our Solar System’s 4th planet; package includes the deed, a map with location of your land, and a Mars info eBook.

Which sounds like it's completely aboveboard, given that it comes with an official deed and an informational booklet and all.

Home, sweet home.  [Image is in the Public Domain courtesy of NASA/JPL]

They go on to give us more details:

Buying land on Mars sounds like a plot line in some futuristic sci-fi flick about billionaires.  In truth, it's a modern-day possibility for thousandaires.  Buy Planet Mars gives astrophiles the chance to buy one acre of land on the Red Planet.  Much like the purchase of a star, Martian Land Packages include a map charting your acre's location, an owner's deed, a NASA report on Mars exploration, and a photo eBook.  These packages are issued digitally, meaning they're available for download immediately after purchase.

Yes, thousandaires, as long as they have more money than sense.  An acre of land on Mars costs $35, which sounds pretty cheap, until you realize that (1) you're never going to go there, and (2) even after you purchase it, you don't really own land on Mars, because (3) the person selling the property on Mars doesn't technically own what he's selling.

Which evidently is not apparent to the 210 people who have paid actual money for this unreal estate.  The seller's Groupon page has a lot of positive testimonials, such as the following:

• When you can't afford land in California, might as well invest in the future!
• It's fun, thought provoking, unique and a great conversation peace [sic] I have never owned property, how could I pass it up?
• Fun gift, who knows what it could be in the future?

Worthless!  Yay!  Isn't that fun?

Okay, I know I'm coming across as a sarcastic, grumpy, humorless, sour-tempered curmudgeon here.  Which is hardly fair, because I am not humorless.  As far as the others, well, okay, maybe.  For example, my wife contends that I've been a curmudgeon since infancy.  I can't quite dodge the "sarcastic" thing, either, given that it's in the tagline of this blog.

But in my own defense, I'm not immune to pointless stuff sometimes.  After all, I'm the guy who was fully in favor of everyone purchasing alien abduction insurance.  (After posting that one, an anonymous reader of Skeptophilia purchased alien abduction insurance for me, and made my dog the beneficiary.)

So maybe I should be encouraging people to buy property on Mars.  You never know, maybe one day we'll have manned missions to Mars, and you could go visit your homestead.  Although this didn't work out so well for Matt Damon in The Martian.  As I recall, it became uncomfortably breezy.  He ended up having to do some impromptu self-surgery with a staple gun.  And he learned that Mars is really not the place if your lifelong dream is growing potatoes.

Anyhow.  If you've got an extra $35 that you can't think of doing something more productive with, which in my opinion would include using it to start a campfire, you can buy an acre of land on Mars.  If you do, make sure to post here and let me know the details.  I'm especially curious about the deed, because you have to wonder under whose jurisdiction it's being issued.

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

When people think of mass extinctions, the one that usually comes to mind first is the Cretaceous-Tertiary Extinction of 66 million years ago, the one that wiped out all the non-avian dinosaurs and a good many species of other types.  It certainly was massive -- current estimates are that it killed between fifty and sixty percent of the species alive at the time -- but it was far from the biggest.

The largest mass extinction ever took place 251 million years ago, and it destroyed over ninety percent of life on Earth, taking out whole taxa and changing the direction of evolution permanently.  But what could cause a disaster on this scale?

In When Life Nearly Died: The Greatest Mass Extinction of All Time, University of Bristol paleontologist Michael Benton describes an event so catastrophic that it beggars the imagination.  Following researchers to outcrops of rock from the time of the extinction, he looks at what was lost -- trilobites, horn corals, sea scorpions, and blastoids (a starfish relative) vanished completely, but no group was without losses.  Even terrestrial vertebrates, who made it through the bottleneck and proceeded to kind of take over, had losses on the order of seventy percent.

He goes through the possible causes for the extinction, along with the evidence for each, along the way painting a terrifying picture of a world that very nearly became uninhabited.  It's a grim but fascinating story, and Benton's expertise and clarity of writing makes it a brilliant read.

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