Whispers, tingles, and brain orgasms

My wife sent me a link to an article a couple of days ago about a phenomenon that I'd heard a bit about, but never really researched.

It's called an "Autonomous Sensory Meridian Response," ASMR for short.  The nickname, though, is more telling; people call it a "brain orgasm."

Of course, on some level, all orgasms are about what happen in the brain.  fMRI studies of people during orgasm show that during arousal and climax people experience a surge of neurotransmitters like dopamine and endorphin, as well as the "cuddle hormone" oxytocin (explaining why most of us feel snuggly after doing the deed, not to mention sleepy).  Without a brain response, there's no arousal, and I think just about everyone can think of times when what was going on in their brains -- worry, fatigue, frustration, anger -- interfered with their desire, or even ability, to have sex.

Gustav Klimt, The Kiss (1908) [Image is in the Public Domain]

It brings up the question, however, of who is volunteering for those studies.  I mean, I'm as comfortable in my skin as the next guy, and in fact in my twenties would have been voted the captain of the co-ed skinnydipping team.  But doing a solo performance while hooked up to a fMRI, with lots of people wearing white lab jackets and holding clipboards and peering at me and taking notes, gives new meaning to the phrase, "no way, José."  I mean, if getting off with an audience turns you on, more power to you, but even with a significant cash incentive I don't think I'd participate.

But I digress.

Anyhow, my point is, there have been a good many studies of the neurochemistry of the human sexual response, so this ASMR thing is interesting because apparently for some people, hearing certain noises (or, less commonly, seeing particular images) triggers a brain response that is very similar to orgasm but without the involvement of your naughty bits.  Here's how one person describes it:

While watching videos of space... a tingling spreads through my scalp as the camera pulls back to show the marble of the earth.  It comes in a wave, like a warm effervescence, making its way down the length of my spine and leaving behind a sense of gratitude and wholeness.

The similarity to an actual orgasm is obvious.  But why was it happening?

Turns out, we don't know.  Also unknown is why the people who experience ASMR are (1) nearly all female, and (2) have particular triggers that are specific to them.  The article in the New York Times (linked above) said that there are five hundred new ASMR-inducing videos uploaded to YouTube every day, which I suppose is understandable given what they can allegedly do to you.  Most of them are some combination of people whispering, rubbing fabric or combs or the like across microphones, stroking rough surfaces with fingernails, crunching paper, brushing hair, or chewing food.

This last one was a little puzzling right from the get-go.  A lot of people hate the sound of others chewing.  My older son, for example, was as a teenager really sensitive to sounds like that, and became nearly homicidal when he was around someone eating Doritos.  But apparently not everyone responds that way, and some people feel exactly the opposite.

So I was intrigued, and got onto YouTube and checked out a couple of the videos.  Here's a typical one:

 I went into it figuring I wouldn't respond, given that I'm male, also was a little dubious from the outset, and...

... sure enough, nothing, or at least nothing positive.  In fact, I found the noises intensely annoying.  Not only was I not soothed or tingly, after about 45 seconds I wanted to climb out of my skin.  So if you watched the video and had a brain orgasm or whatever, I'm happy for you, but that was certainly not my experience.

It does bring up the fascinating question of how the same stimuli can provoke entirely different responses in different people.  And this applies outside of the realm of listening to people brush their hair, or even what specific things are a sexual turn-on; consider how unique people's reactions are to music.  My wife and I, for example, both love music, but what particular pieces of music grab us are completely different.  When I find a piece of music I love, it definitely gives me chills, and has been known to bring me to actual tears.  The first time I heard Vaughan Williams's Fantasia on a Theme by Thomas Tallis, for example, I ended up sobbing, and couldn't have explained why.

Now there's something I'd be willing to do while hooked up to a fMRI machine.

My point, though, is that these kinds of emotional and physical reactions are pretty common in humans, as is the fact that what specifically triggers them is highly personal.  I think we're a long, long way from figuring out why that is, though, even on the level of being able to comprehend as individuals why a particular trigger is a turn-on for us.

In any case, the whole ASMR thing is curious enough that it deserves more research.  It's understandable that scientists have been reluctant to do so, I suppose; both the variability of response, and the general oddity of the phenomenon, probably pushes researchers to look into phenomena that are more likely to get grant approval.  (In fact, the New York Times article said that there have only been ten academic papers addressing ASMR ever published.)

But given the popularity of the videos, there has to be something to it, and it'd be cool to find out what that something is.  So even if the sound of someone whispering or twisting bubble wrap or chewing gum doesn't turn me on, I'd sure like to know why it has that effect on others.

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This week's Skeptophilia book recommendation is a fun one; Atlas Obscura by Joshua Foer, Dylan Thuras, and Ella Morton.  The book is based upon a website of the same name that looks at curious, beautiful, bizarre, frightening, or fascinating places in the world -- the sorts of off-the-beaten-path destinations that you might pass by without ever knowing they exist.  (Recent entries are an astronomical observatory in Zweibrücken, Germany that has been painted to look like R2-D2; the town of Story, Indiana that is for sale for a cool $3.8 million; and the Michelin-rated kitchen run by Lewis Georgiades -- at the British Antarctic Survey’s Rothera Research Station, which only gets a food delivery once a year.)

This book collects the best of the Atlas Obscura sites, organizes them by continent, and tells you about their history.  It's a must-read for anyone who likes to travel -- preferably before you plan your next vacation.

(If you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!)

Tales from a white dwarf

This week we've focused on some cool scientific discoveries, which is, honestly, my happy place.  So we'll round out the week with a new piece of research that is kind of a double-edged sword.  It is (1) fascinating, but (2) tells us about how the Earth is going to be destroyed.  So while it's interesting, cheerful it isn't.

Of course, the upside is that the Earth isn't going to be destroyed for another few billion years.  So even in the best-case scenario, I won't be around when it happens.

The research was led by Christopher Manser of the University of Warwick, and is based on observations done of a white dwarf star at the 10.4-meter Gran Telescopio Canarias on La Palma in the Canary Islands.  White dwarfs are the remnants of stellar cores for stars smaller than about 10 times the mass of the Sun.  At the end of their lives, stars in this range exhaust the hydrogen fuel in their cores, and switch to burning helium -- this gives an added kick to the core temperature, and the outer atmosphere balloons out into what's called a red giant.  But eventually, it becomes a nova -- it exhausts the helium as well, the core collapses and heats up (dramatically), and that blows the outer atmosphere away (forming what's called a planetary nebula), in an expanding cloud of gas and dust surrounding the exposed core -- the white dwarf star.

[Image licensed under the Creative Commons, ESA/Hubble, Artist’s impression of debris around a white dwarf star, CC BY 4.0]

It was long thought that a star that becomes a white dwarf will in the process completely destroy any planets that happen to be orbiting around it.  When the Sun becomes a red giant, for example, it's believed that its outer edges will be somewhere between the orbits of Mars and Jupiter.  So where you are sitting right now will be inside the Sun.

I like it warm, but that's a bit toasty even my my standards.

So it was quite a shock when Manser et al. found that the white dwarf they were studying, the euphoniously named SDSS J122859.93+104032.9, had a planet orbiting it.

The fact that they could even tell that is pretty extraordinary.  As I explained in a previous post, the two most common ways of detecting planets are by occlusion (the star dimming because the planet has passed in front of it) or by Doppler spectroscopy (seeing shifts in the frequency of light from the star because it's being pulled around by the planet as it orbits).  Both of these work better when the planet is massive -- so for a little planet around a littler star, it's kind of amazing they even figured out it was there.

What they found was that there was light coming from the star system that was consistent with the emission spectrum of calcium, but oddly, the calcium spectral lines were split in two -- and the two lines oscillated back and forth with a period of almost exactly two hours.  The best explanation, say Manser et al, is that there is a planetesimal -- probably the iron-rich core of a planet that once orbited the star prior to its demise -- that is dragging around a cloud of calcium-rich gas that is being Doppler shifted first one way and then the other every time the planet circles the star.

As Luca Fossati, writing for Science magazine, describes the research:

The method of Manser et al. has revealed the presence of planetesimals without the need for the particular orbital geometry that is required by the transit method.  It could therefore be used to identify the presence of planetesimals orbiting other polluted white dwarfs and advance the study of the planetary systems evolution.  Furthermore, because planetesimals orbiting white dwarfs are believed to be the remnant cores of shattered planets, studying the spectra of polluted white dwarfs known to be surrounded by planetesimals enables one to gain information about the chemical composition and metal abundances of the infalling material—that is, planetary cores.

The most awe-inspiring part of this research is that this will be the likely fate of the Earth -- assuming that the red giant and nova phases of the Sun don't destroy it completely.  All that will be left is the remnant core of the Sun and the remnant core of the Earth, circling each other and gradually cooling, becoming a whirling pair of cinders forever spinning in the infinite dark, cold vacuum of space.

Have a nice day.

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This week's Skeptophilia book recommendation combines science with biography and high drama.  It's the story of the discovery of oxygen, through the work of the sometimes friends, sometimes bitter rivals Joseph Priestley and Antoine Lavoisier.   A World on Fire: A Heretic, an Aristocrat, and the Race to Discover Oxygen is a fascinating read, both for the science and for the very different personalities of the two men involved.  Priestley was determined, serious, and a bit of a recluse; Lavoisier a pampered nobleman who was as often making the rounds of the social upper-crust in 18th century Paris as he was in his laboratory.  But despite their differences, their contributions were both essential -- and each of them ended up running afoul of the conventional powers-that-be, with tragic results.

The story of how their combined efforts led to a complete overturning of our understanding of that most ubiquitous of substances -- air -- will keep you engaged until the very last page.

[Note:  If you purchase this book by clicking on the image/link below, part of the proceeds will go to support Skeptophilia!]

Snapshot of a very bad day

Some of you have probably bumped into articles in the last week or so about a phenomenal discovery in paleontology -- a fossil bed in North Dakota that may have been created the day the Chicxulub Meteor Strike occurred, 66 million years ago.  This single event is thought to have flash-fried everything in the southern half of what is now North America, changed climates worldwide, and was the death blow to the dinosaurs, with the exception of the lineage that led to modern birds.

The deposit contains exquisitely preserved remains of a variety of fish, plants, dinosaurs, and mollusks.  The gills of the fish contained huge numbers of tektites -- tiny spheres of glass formed during a meteorite collision and ejected into the atmosphere.  The impact is thought to have caused a magnitude 10 earthquake (almost unimaginable to me), which took the shallow ocean that crossed what is now the central United States and "agitated it like a washing machine" -- creating a seiche, a standing wave like the sloshing of water in a giant bathtub.

The seiche caused the repeated exposure and inundation of shallow regions, and while exposed, the stranded animals were subjected to a rain of tektites and other debris thrown up by the collision.

"This is the first mass death assemblage of large organisms anyone has found associated with the K-T boundary," Robert DePalma, curator of paleontology at the Palm Beach Museum of Natural History in Florida and a doctoral student at the University of Kansas, said in a press release.  "At no other K-T boundary section on Earth can you find such a collection consisting of a large number of species representing different ages of organisms and different stages of life, all of which died at the same time, on the same day."

One of the fish from the Hell Creek fossil bed

"The seismic waves start arising within nine to ten minutes of the impact, so they had a chance to get the water sloshing before all the spherules (small spheres) had fallen out of the sky," said Mark Richards, professor emeritus of earth and planetary science at the University of California - Berkeley.  "These spherules coming in cratered the surface, making funnels — you can see the deformed layers in what used to be soft mud — and then rubble covered the spherules.  No one has seen these funnels before...  You can imagine standing there being pelted by these glass spherules.  They could have killed you."

It's amazing to think that if these scientists are correct -- and the consensus amongst paleontologists is that they are -- we're seeing a remnant of a catastrophe initiated at a single moment in time.  The simulations of what happened are astonishing enough:

But somehow, to see the remains of animals that were directly killed by the collision, who were there when it happened, gives it an immediacy that is stunning.

So this is cool enough, right?  But what makes it even more personal for me is that one of the researchers who has worked the Hell Creek fossil bed, and was a co-author of the paper...

... is Loren Gurche, who is a former student of mine.

I distinctly remember Loren's contributions to my AP Biology class -- whenever the topic was prehistory, I always deferred to his greater knowledge.  Even then, when he was in 11th grade, he clearly knew way more paleontology than I did, or probably, than I ever would.  The presence of a true expert enriched both my experience and the other students', and it's thrilling to see that he is making significant contributions in a field about which he is so deeply passionate.

So the whole thing is doubly cool for me to read about.  I'm looking forward to more discoveries by Loren and the team he's working with, although it must be said it'll be hard to top this one.  This snapshot of one of the worst disasters ever to strike the Earth is the find of a lifetime.

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

This week's Skeptophilia book recommendation combines science with biography and high drama.  It's the story of the discovery of oxygen, through the work of the sometimes friends, sometimes bitter rivals Joseph Priestley and Antoine Lavoisier.   A World on Fire: A Heretic, an Aristocrat, and the Race to Discover Oxygen is a fascinating read, both for the science and for the very different personalities of the two men involved.  Priestley was determined, serious, and a bit of a recluse; Lavoisier a pampered nobleman who was as often making the rounds of the social upper-crust in 18th century Paris as he was in his laboratory.  But despite their differences, their contributions were both essential -- and each of them ended up running afoul of the conventional powers-that-be, with tragic results.

The story of how their combined efforts led to a complete overturning of our understanding of that most ubiquitous of substances -- air -- will keep you engaged until the very last page.

[Note:  If you purchase this book by clicking on the image/link below, part of the proceeds will go to support Skeptophilia!]

Thawing the snowball

One of the frightening things about a system in equilibrium is what happens when you perturb it.

Within limits, most systems can recover from perturbation through some combination of negative feedbacks.  An example is your body temperature.  If something makes it goes up -- exercise, for example, or being outside on a hot, humid day -- you sweat, bringing your temperature back down.  If your body temperature goes down too much, you increase your rate of burning calories, and also have responses like shivering -- which brings it back up.  Those combine to keep your temperature in a narrow range (what the biologists call homeostasis).

Push it too much, though, and the whole thing falls apart.  If your temperature rises beyond about 105 F, you can experience seizures, convulsions, brain damage -- or death.  Your feedback mechanisms are simply not able to cope.

This, in a nutshell, is why climate scientists are so concerned about the effects of anthropogenic carbon dioxide.  Within limits -- as with your body temperature -- an increase in carbon dioxide results in an increase in processes that remove the carbon dioxide from the atmosphere, and the whole system stays in equilibrium.  There is a tipping point, however.

The problem is that no one knows where it is -- and whether we may have already passed it.

A new piece of research from the Virginia Polytechnic Institute has indicated that this flip from stability to instability may be fast and unpredictable.  A paper authored by a team led by paleobiologist Shuhai Xiao, that came out last month in Geology, looks at one of the main destabilization events that the Earth has ever experienced -- when the "Snowball Earth" thawed out in the late Precambrian Period,  635 million years ago.

Artist's conception of the Precambrian Snowball Earth [Image is in the Public Domain, courtesy of NASA/JPL]

Xiao and his team studied rocks from Yunnan and Guizhou, China, that are called cap carbonates.  They are made of limestone and dolomite and are deposited quickly in marine environments when the carbon dioxide content of the atmosphere spikes, leading to a dramatic temperature increase and a subsequent increase in absorption of carbonates into seawater (and ultimately deposition of those carbonates on the seafloor).  The cap carbonates Xiao et al. studied were dated to between 634.6 and 635.2 million years old, which means that the entire jump in both temperature and carbon dioxide content took less than 800,000 years.

So in less than a million years, the Earth went from being completely covered in ice to being subtropical.  The jump in global average temperature is estimated at 7 C -- conditions that then persisted for the next hundred million years.

Xiao et al. describe this as "the most severe paleoclimatic [event] in Earth history," and that the resulting deglaciations worldwide were "globally synchronous, rapid, and catastrophic."

Carol Dehler, a geologist at Utah State University, is unequivocal about the implications.  "I think one of the biggest messages that Snowball Earth can send humanity is that it shows the Earth’s capabilities to change in extreme ways on short and longer time scales."

What frustrates me most about today's climate change deniers is that they are entirely unwilling to admit that the changes we are seeing are happening at an unprecedented rate.  "It's all natural," they say.  "There have been climatic ups and downs throughout history."  Which is true -- as far as it goes.  But the speed with which the Earth is currently warming is faster than what the planet experienced when it flipped between an ice-covered frozen wasteland and a subtropical jungle.  It took 800,000 years to see an increase of the Earth's average temperature by 7 degrees C.

The best climate models predict that's what we'll see in two hundred years.

And that is why we're alarmed.

It's unknown what kind of effect that climate change in the Precambrian had on the existing life forms.  The fossil record just isn't that complete.  But whatever effect it had, the living creatures that were around when it happened had 800,000 years to adapt to the changing conditions.  What's certain is that an equivalent change in two centuries will cause massive extinctions.  Evolution simply doesn't happen that quickly.  Organisms that can't tolerate the temperature fluctuation will die.

We can only speculate on the effects this would have on humanity.

This is clearly the biggest threat we face, and yet the politicians still sit on their hands, claim it's not happening, that remediation would be too costly, that we can't prevent it, that short-term profits are more important than the long-term habitability of the Earth.  Our descendants five hundred years from now will look upon the leaders from this century as having completely abdicated their responsibility of care for the people they represent.

Presuming we still have descendants at that point.

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This week's Skeptophilia book recommendation combines science with biography and high drama.  It's the story of the discovery of oxygen, through the work of the sometimes friends, sometimes bitter rivals Joseph Priestley and Antoine Lavoisier.   A World on Fire: A Heretic, an Aristocrat, and the Race to Discover Oxygen is a fascinating read, both for the science and for the very different personalities of the two men involved.  Priestley was determined, serious, and a bit of a recluse; Lavoisier a pampered nobleman who was as often making the rounds of the social upper-crust in 18th century Paris as he was in his laboratory.  But despite their differences, their contributions were both essential -- and each of them ended up running afoul of the conventional powers-that-be, with tragic results.

The story of how their combined efforts led to a complete overturning of our understanding of that most ubiquitous of substances -- air -- will keep you engaged until the very last page.

[Note:  If you purchase this book by clicking on the image/link below, part of the proceeds will go to support Skeptophilia!]

Buzzing off

I have great respect for scientists, which I hope is obvious from the content of this blog.  Even so, there are times I read scientific research and say, "What the hell were they thinking?"

That was my first thought when I read a BBC News article claiming that playing dubstep music by Skrillex makes mosquitoes less likely to bite and mate.  If you don't know who Skrillex is, that's probably a good thing if you've got reasonably refined musical sensibilities.  I try to be tolerant of other people's musical tastes and acknowledge that what you like is a matter of opinion, but it is my considered judgment that Skrillex sounds like a robot having sex with a dial-up modem.

So apparently what they apparently did is to play Skrillex for some mosquitoes, and the mosquitoes apparently didn't feel like eating or mating, which I have to admit is kind of the effect it has on me.  "[T]he occurrence of blood feeding activity was lower when music was being played," the scientists write.  "Adults exposed to music copulated far less often than their counterparts kept in an environment where there was no music...  The observation that such music can delay host attack, reduce blood feeding, and disrupt mating provides new avenues for the development of music-based personal protective and control measures against Aedes-borne diseases."

[Image licensed under the Creative Commons, Aedes aegyptii, photograph taken by Muhammad Mahdi Karim]

When I finished reading the article, my first thought was that this was a typical sensationalized report on scientific research, where popular media completely misrepresents what the scientists did in order to get clicks.  Sadly, this is not the case.  The BBC News actually did a pretty good job of describing the research -- it's just that the research was kind of... um... terrible.

Here's a piece from the paper itself, which appeared in Acta Tropica last week and is entitled,
"The Electronic Song 'Scary Monsters and Nice Sprites' Reduces Host Attack and Mating Success in the Dengue Vector Aedes aegypti," by a team of researchers led by Hamady Dieng of the University of Malaysia:

Sound and its reception are crucial for reproduction, survival, and population maintenance of many animals.  In insects, low-frequency vibrations facilitate sexual interactions, whereas noise disrupts the perception of signals from conspecifics and hosts.   Despite evidence that mosquitoes respond to sound frequencies beyond fundamental ranges, including songs, and that males and females need to struggle to harmonize their flight tones, the behavioral impacts of music as control targets remain unexplored. In this study, we examined the effects of electronic music ("Scary Monsters and Nice Sprites" by Skrillex) on foraging, host attack, and sexual activities of the dengue vector Aedes aegypti.   Adults were presented with two sound environments (music-off or music-on).  Discrepancies in visitation, blood feeding, and copulation patterns were compared between environments with and without music.  Ae. aegypti females maintained in the music-off environment initiated host visits earlier than those in the music-on environment.  They visited the host significantly less often in the music-on than the music-off condition.

Which is pretty much what the BBC News article said.

What's wrong with this research is that it falls into what I would call "so what?" studies.  It's the kind of thing that even if the protocols and controls were appropriate, doesn't tell you very much.  Okay, Skrillex screws up mosquitoes.  Why?  They only did "music on" and "music off;" they didn't try different kinds of music, various pure tones, harmonics, combinations of sounds, and other sorts of sounds.  So the outcome really gives us very little information about what's actually going on, and why -- nor how this could be used to reduce the spread of mosquito-borne diseases.

Because frankly, if I had a choice of getting dengue fever and listening to Skrillex all day, I'd have to think about it.

So anyhow, I guess having a paper in a scientific journal doesn't necessarily guarantee that the research it describes isn't kind of silly.  And it also highlights the importance of going from the account in the popular media to the research itself before making a judgment.  Most of the time, if there's a problem or a misrepresentation, it's the popular media that's at fault.

But not always.  So if you want to repel mosquitoes, you might want to do your own experiments.  There must be a better way than subjecting yourself and everyone around you to dubstep.

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This week's Skeptophilia book recommendation combines science with biography and high drama.  It's the story of the discovery of oxygen, through the work of the sometimes friends, sometimes bitter rivals Joseph Priestley and Antoine Lavoisier.   A World on Fire: A Heretic, an Aristocrat, and the Race to Discover Oxygen is a fascinating read, both for the science and for the very different personalities of the two men involved.  Priestley was determined, serious, and a bit of a recluse; Lavoisier a pampered nobleman who was as often making the rounds of the social upper-crust in 18th century Paris as he was in his laboratory.  But despite their differences, their contributions were both essential -- and each of them ended up running afoul of the conventional powers-that-be, with tragic results.

The story of how their combined efforts led to a complete overturning of our understanding of that most ubiquitous of substances -- air -- will keep you engaged until the very last page.

[Note:  If you purchase this book by clicking on the image/link below, part of the proceeds will go to support Skeptophilia!]

Chasing Goldilocks

Given my fascination with the possibilities of life in other star systems, I was thrilled to read two papers that came out last week detailing our efforts to narrow down where to look.

After all, that's the problem, isn't it?  There are billions of stars in our galaxy alone, and it's impossible to study all of them with any kind of thoroughness.  It seems pretty certain that most stars have some kind of planetary system, but trying to find Earth-like planets is another thing entirely.  Most of the exoplanets that have been identified are gas giants, and a good many of those are very close to their parent star (and so are extremely hot).  The reason these were identified first is not necessarily because they're more common; being more massive, and (for the close-in ones) having a stronger gravitational pull on their stars because of their proximity, makes them easier to see by both of the common methods used -- occlusion (seeing them pass in front of their stars) and Doppler spectroscopy (massive planets cause a wobble in the position of their stars as they orbit).

But there's no reason to believe that Earth-sized planets are uncommon, and indeed, we're now finding that they're plentiful.  The trick, of course, is not only locating one that's the right size, but one in the "Goldilocks zone" -- the distance from the star that is neither too hot nor too cold, but just right.  (Since we're concentrating on "life as we know it, Jim," we're most interested in planets where water can be in liquid form during at least part of its orbit.)

[Image licensed under the Creative Commons ESO/L. Calçada, Artist’s impression of the exoplanet Tau Bootis b, CC BY 4.0]

The first paper, called "Habitable Zones and How to Predict Them," by a team led by Ramses M. Ramirez of the Tokyo Institute of Technology, takes a purely practical approach of not only estimating habitability based upon a planet's size and distance from its star, but looks at composition -- quantity of water, presence of carbonate and silicate minerals, percentage of the atmosphere that is carbon dioxide or methane (both greenhouse gases that considerably raise the heat-trapping ability of the air), and the presence of tectonic activity.  The authors conclude with a cautionary note, however, about not concluding too much based upon partial evidence:

[W]e should be careful about using our Earth to extrapolate about life on other planets, particularly those around other stars.  The future of habitability studies will require first principles approaches where the temporal, spatial, geological, astronomical, atmospheric, and biological aspects of a planet’s evolution are dynamically coupled.  This, together with improved observations, is the key to making more informed assessments.  In turn, only through better observations can we improve such theoretical models.

The second paper, published last week in Astrophysical Journal Letters, describes a study by a team of astronomers from Cornell University, Lehigh University, and Vanderbilt University, in which TESS -- the Transiting Exoplanet Survey Satellite -- will examine 400,000 stars considered good candidates for hosting planets in the habitable zone.

"Life could exist on all sorts of worlds, but the kind we know can support life is our own, so it makes sense to first look for Earth-like planets," said Cornell astronomer Lisa Kaltenegger, who was the study's lead author.  "This catalog is important for TESS because anyone working with the data wants to know around which stars we can find the closest Earth-analogs."

Even the scientists who study this stuff on a daily basis recognize what a leap forward this is.  TESS has already identified over 1,800 stars that have planets up to 1.4 times the mass of the Earth -- considered an upper limit for habitability -- and 408 for which TESS could recognize a planet as small as, or a little smaller than, the Earth from one transit alone.

"I have 408 new favorite stars," Kaltenegger said.  "It is amazing that I don't have to pick just one; I now get to search hundreds of stars."

Unlike the old look-everywhere-and-hope-for-the-best approach, this study starts out by examining the most likely candidates, making the hopes for positive results much stronger.  "We don't know how many planets TESS will find around the hundreds of stars in our catalog or whether they will be habitable," Kaltenegger said, "but the odds are in our favor.  Some studies indicate that there are many rocky planets in the habitable zone of cool stars, like the ones in our catalog.  We're excited to see what worlds we'll find."

So am I.  It's long been my dearest hope to have unequivocal proof of extraterrestrial life in my lifetime.  (Intelligent life would be even better, but I'm trying to keep a modest goal, here.)  The idea that we are now devoting significant time and effort into locating good candidates for hosting life is tremendously exciting.  While it's still not likely that we'll find neighbors to talk to, at least knowing they're out there is cool enough for now.

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

This week's Skeptophilia book recommendation combines science with biography and high drama.  It's the story of the discovery of oxygen, through the work of the sometimes friends, sometimes bitter rivals Joseph Priestley and Antoine Lavoisier.   A World on Fire: A Heretic, an Aristocrat, and the Race to Discover Oxygen is a fascinating read, both for the science and for the very different personalities of the two men involved.  Priestley was determined, serious, and a bit of a recluse; Lavoisier a pampered nobleman who was as often making the rounds of the social upper-crust in 18th century Paris as he was in his laboratory.  But despite their differences, their contributions were both essential -- and each of them ended up running afoul of the conventional powers-that-be, with tragic results.

The story of how their combined efforts led to a complete overturning of our understanding of that most ubiquitous of substances -- air -- will keep you engaged until the very last page.

[Note:  If you purchase this book by clicking on the image/link below, part of the proceeds will go to support Skeptophilia!]

Ghost galaxies

I love a mystery.

I think part of it is that a truly unsolved question is a blow to our complacent attitude that we know all we need to know about the universe.  It's all too easy to walk around thinking we understand everything around us, to be fooled into the misapprehension that the cosmos is simple and obvious.

Anyone with a science background already has a significant dent in this notion, but it runs far deeper than that.  I think the hardest punch to my own certainty came when I started looking into the concepts of dark matter and dark energy, something like thirty years ago.  The presence of dark matter was first discovered back in the 1970s by Vera Rubin, Kent Ford and Ken Freeman, when they found that the rotational speed of every galaxy they looked at was impossible given the amount of visible matter present.  The discovery of dark energy came from a different source -- data from telescopes studying the cosmic microwave background radiation found that the universe was expanding at a far greater rate than it "should" have been given the measured mass/energy we knew about.  As peculiar as it sounds, the expansion could be explained if there was an invisible sort of energy -- later christened "dark energy" -- that exerted a repulsive force.

What I haven't told you is that by the most recent measurements, dark energy comprises 68% of the total mass/energy density in the observable universe, and dark matter 27%.  If you're wondering if that means what you think it means, you're right.

Ordinary ("baryonic") matter only makes up 5% of the mass and energy of the universe.

Worse still, that 95% has thus far been undetectable except by indirect measurements -- a bit like seeing the footprint of the bear but not the bear itself.  Every attempt to observe either dark matter or dark energy directly has been an abject failure.  So although there is speculation about the nature of this ubiquitous stuff, at present what we know for certain about it is exactly zero, other than the fact that it exists.

Of course, some people even doubt the latter bit, and remind us of the "aether" -- a substance proposed in the 19th century to explain peculiarities about the propagation of light.  Like dark matter and dark energy, the aether resisted all attempts to elucidate its nature.  We now know why that is -- it doesn't exist.  It took a clever experiment by Albert A. Michelson and Edward W. Morley to show that its existence was impossible, and no less than Albert Einstein to explain how light could propagate in the absence of a medium.  I've heard more than one scientist compare dark matter and dark energy to the aether -- and suggest that we're still waiting for this century's Einstein to blow us all away with an elegant explanation of the data we have, with no need for mysterious undetectable substances permeating the universe.

Messier 51, the Whirlpool Galaxy [Image is in the Public Domain, courtesy of NASA/JPL]

But at the moment, we're still stuck with them, and the bizarre observations keep rolling in to further deepen the mystery.  Just last week, a study was published in Astrophysical Journal Letters about some highly peculiar galaxies that seem to be entirely devoid of dark matter.  Called ultradiffuse galaxies, they are as large as an ordinary galaxy, but have such a low matter density that you can see right through them.  Measurements of rotational rates and matter distributions support the conjecture that they have the characteristics they do because -- for some unknown reason -- they have almost no dark matter at all.

"I spent an hour just staring at the Hubble image," said Pieter van Dokkum of Yale University, who was part of the study that discovered ultradiffuse galaxies.  "It's so rare, particularly these days after so many years of Hubble, that you get an image of something and you say, 'I've never seen that before.'  This thing is astonishing: a gigantic blob that you can look through.  It's so sparse that you see all of the galaxies behind it."

"We hope to next find out how common these galaxies are and whether they exist in other areas of the universe," said the paper's lead author Shany Danieli, also of Yale.  "We want to find more evidence that will help us understand how the properties of these galaxies work with our current theories.  Our hope is that this will take us one step further in understanding one of the biggest mysteries in our universe — the nature of dark matter."

Which is certainly a laudable goal.  The idea that the lion's share of the stuff of the universe has up till now resisted every attempt to learn about its characteristics is frustrating, to say the least.  But it does fascinate me, despite the frustration.  It illustrates to me how much more we have to learn about the universe we live in, and that when it comes to our understanding of science, we're still at the starting line.  Perhaps Socrates put it best when he said, "The more I know, the more I realize how little I know."

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This week's Skeptophilia book recommendation combines science with biography and high drama.  It's the story of the discovery of oxygen, through the work of the sometimes friends, sometimes bitter rivals Joseph Priestley and Antoine Lavoisier.   A World on Fire: A Heretic, an Aristocrat, and the Race to Discover Oxygen is a fascinating read, both for the science and for the very different personalities of the two men involved.  Priestley was determined, serious, and a bit of a recluse; Lavoisier a pampered nobleman who was as often making the rounds of the social upper-crust in 18th century Paris as he was in his laboratory.  But despite their differences, their contributions were both essential -- and each of them ended up running afoul of the conventional powers-that-be, with tragic results.

The story of how their combined efforts led to a complete overturning of our understanding of that most ubiquitous of substances -- air -- will keep you engaged until the very last page.

[Note:  If you purchase this book by clicking on the image/link below, part of the proceeds will go to support Skeptophilia!]