The entire universe in blog form

Dec. 24 2014 7:15 AM

No, a Planetary Alignment on Jan. 4, 2015, Won’t Decrease Gravity

The very first nonsense I had to debunk in 2014 was a claim that on Jan. 4 of that year a planetary alignment would cause gravity to decrease, allowing you to float momentarily or fall more slowly if you jumped in the air at the right moment: “Zero G Day.” This exact same hoax has resurfaced this week in a couple of places, so I’ve decided to update the debunking to include some new links and repost it, hopefully to stem the tide of silliness at year’s end. It seems fitting that (hopefully) this is also the last debunking I’ll make in 2014. But who knows? There’s still a week left.

Something you’ll never hear me say: “Well, now I’ve heard it all.”


Long experience has taught me there is always a sillier claim. Always. And you’re hearing that from a guy who has debunked the ideas that the Maya calendar predicted the end of the world, that the “Supermoon” caused earthquakes, and that a magnetic pole flip of the Earth will cause superstorms (and another saying the Earth is already physically starting to flip over).

So what’s sillier than these? Well, we now have the claim that early next year—on Jan. 4, 2015 at 09:47 PST to be exact—due to the combined gravity of Jupiter and Pluto, you will be able to jump in the air and float for just a couple of seconds (or at least fall more slowly, depending on different “sources”).

It’s hard for me to overstate just how wrong this claim is. First off, this exact same hoax was pulled last year, in 2014, by a site called News Hound (now offline, apparently), and a lot of people fell for it. Here we are again, a year later, back at the same spot. This time the joke is being made by a “news” site called Daily Buzz Live (which didn’t even bother to change much of the wording of the original hoax). They even have a picture of a NASA tweet about the event:

fake NASA tweet

Photo from Daily Buzz Live

There’s only one problem: That picture is completely fake. NASA never tweeted it, and it was presumably made up wholesale for the article on Daily Buzz Live. Whoever did it was clever, adding the number of retweets and favorites, but it’s as fake as a $20 iPhone you can buy on the street in New York City.

After all, the physics of “Zero G Day” is wrong, the claim about Pluto and Jupiter is wrong, and—and this part is the real killer—it’s based on a joke made by an astronomer nearly 40 years ago!

Despite this, it’s spreading around Facebook (and Twitter) so much once again that I got a lot of people asking or telling me about it. That’s why I’m debunking this thing again.

So to get started, here’s the claim:

It has been revealed by the British astronomer Patrick Moore that, on the morning of January 4th 2014, an extraordinary astronomical event will occur. At exactly 9:47 am, the planet Pluto will pass directly behind Jupiter, in relation to the Earth. This rare alignment will mean that the combined gravitational force of the two planets would exert a stronger tidal pull, temporarily counteracting the Earth’s own gravity and making people weigh less. Moore calls this the Jovian-Plutonian Gravitational Effect.

Yeah, except this is all baloney. To be polite. OK, so why is this wrong?

Pluto and Jupiter, Sitting in a Tree …

First of all, the gravitational forces of the other planets in the solar system have essentially zero effect on you personally.

And we’re done. Full stop.

OK, fine, I’ll give some brief details. The planets are big objects with lots of gravity, but that only affects you if you’re close to them. Space, however, is big—that’s why we call it space—and planets are far away. This weakens their gravity on you hugely, reducing it to less than the impact of the flutter of a butterfly’s wing.

woman floating

Photo by Shutterstock/Jaimie Duplass

If you want the math, then here you go: Even if you add all of the planets together, they pull on you with a force less than 2 percent of that of the Moon! The Daily Buzz Live article mentions tides, too, but that’s even worse: The combined tidal force from the planets is far less, like 0.005 percent of the Moon’s! Simply put, the planets are just too far away to have any real effect on you. By the way, the Moon orbits the Earth on an ellipse, so its own gravity fluctuates far more than the combined strength of the planets every two weeks.

Note that you cannot float in the air every two weeks.

And specifically, the gravity from Pluto is weakest of them all. Pluto is a teeny tiny ice ball, far smaller than even our Moon … and at its closest it’s flippin’ 4 billion kilometers (2.5 billion miles) from Earth. That’s a long way. A car on the road half a kilometer away has more gravitational pull on you than Pluto does.

In fact, doing the math, I find that the Earth pulls on you about 200 trillion times harder than Pluto does. That's about the same ratio as the number of cells in your body to a single cell ... so this claim that you can float is like saying you can shed a single cell and fly away by flapping your arms.


It gets worse (amazingly). The article says Pluto will be “directly behind Jupiter” on Jan. 4, 2015. I checked: On that day they are on nearly opposite sides of the sky. They’re really far apart, about 145°. You couldn’t have picked a much worse date to claim Pluto was behind Jupiter.

So the physics of the claim is ridiculous. But the origin of the claims makes it even funnier.

man levitating

Photo by Shutterstock/simekesh

Fool Me Once, Shame on You

The article on Daily Buzz Live mentions that this claim came from Patrick Moore. He was a real astronomer in the U.K., an enormously popular radio and television science program presenter—he predated Carl Sagan and is still considered an icon of science in England.

The wonderful thing about all this is: Moore actually did make this claim! However, as points out, it was an April Fools' Day joke. Moore made this claim in 1976 on his radio program. To my complete unsurprise, apparently some folks called in to say they did feel the effect! This is called “priming,” where you tell people in advance that they’ll feel something due to some cause, and they will, even if the cause never happened. It’s used by ghost hunters and ghost tour guides quite a bit, to spook people before they actually enter a “haunted house,” guaranteeing they’ll feel chills as they walk from room to room. I’ve seen this myself first hand: People can convince themselves of amazing things that never actually happened.

Hope Floats

So there you go: It’s a repeat of a silly claim based on a joke in the first place.

I know a lot of people reading this right now are slapping their foreheads and wondering how people can be so stupid as to fall for this. I understand this reaction, but I don’t share it. Smart people fall for silly things all the time, and intelligence isn’t really the prime factor here.

ice cream float
OK, this time, yes.

Photo by Shutterstock/Glenn Price

Skepticism is. In general, schools don’t teach people how to analyze a claim, how to tell if something makes sense on the surface of it, or how to go about looking into the claim. I knew right away to do the math, and to see if Pluto and Jupiter really were aligned as the article says. But all too often, people don’t think carefully (or at all) about these claims, and simply spread them through social media. All it takes is literally the click of a “Share” button. Pseudoscience thrives via this virulence, whereas truth must take a harder path.

In fact, that’s why I bother debunking stuff like this. Sure, this is a silly claim, and probably harmless in practice. But not all of them are; I already mentioned the “Mayan Notpocalypse” from 2012, and I can tick off a dozen other doomsday or scary claims that spread due to a lack of skepticism. And of course there are real issues like global warming denial, anti-vaccination, and more, which live and breathe and spread due to a lack of skepticism in the public.

In my original post about this in January 2014, I said, “This particular bit of fluff will dry up and float away in a day or two, but those others are here to stay for a long time.” I was wrong, and I should’ve known that something like this would resurface again in a year; it’s like the “Mars as big as the Moon” nonsense that comes back year after year.

Still, my hope is that every time we take a moment to inject a bit of (polite) skepticism into people’s everyday lives, it makes the world a slightly better place to be.

If enough of us do it often enough, we can change “slightly” to “magnificently.”

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Dec. 23 2014 7:15 AM

Follow-Up: Celebrities, Science, and Anti-Science  

Late last week, I posted an article about Mayim Bialik and the issues of celebrities promoting science—specifically, including her in a picture of four other actresses who hold degrees or have published in scientific fields. In general, I like it when actors/writers/famous people take a shine to science. They’re in the public eye, and if they promote science, then that’s a Good Thing.

But this can come at a cost, when the promoter in question may hold some anti-scientific beliefs. When they promote those as well, what to do? As I wrote at the time, what I try to do is applaud them when they’re right and point it out when they’re wrong.


For the specific case of Bialik, this gets more complicated. She holds a degree in neuroscience, and is an enthusiastic supporter of getting more girls into science, technology, and math. That’s great!

But she also supports a lot of what I would call anti-science. Her statements have made it clear she holds some anti-vaccination beliefs and promotes homeopathy, two stances I am very, very strongly against.

In the end, I felt the good outweighed the bad, though, and said so.

A lot of people agreed, a lot disagreed. Keith Kloor, for example, wrote an interesting piece on his Discover magazine blog Collide-a-Scape, pretty much agreeing with my premise (though he doesn’t really talk specifically about Bialik; he applies it to Dr. Oz).

My good friend Steve Novella wrote a typically thoughtful and smart piece as well. He also agreed with my premise in general—we need to take these promotions of science on a case-by-case basis—but disagreed with my stance about Bialik. He thinks her anti-science stance tips the balance, and we shouldn’t hold her up as a role model:

In the specific case of Mayim Bialik I have to disagree with Phil. I think the bad outweighs the good. Just the mere fact of an actor who is a neuroscientist is not that big a deal. Her views on vaccines and medicine in general, however, are extremely pernicious. In fact, her credentials as a scientist are a negative in this case because they mostly serve to lend weight to her antivaccine views. I would not promote her in any way, and I certainly would not do anything that could possibly lend the imprimatur of legitimacy to her views.

I’ll admit I hadn’t considered that her credentials could be used by anti-vaxxers and the like to promote their incorrect (and dangerous) beliefs, and that gave me pause. Thinking that through, I have to say that does sway me; if she were promoting something like astrology, I’d probably just roll my eyes a bit and carry on. But these medical health issues are serious, and I’ve been very vocal for a very long time about vaccines and homeopathy.

Because of that, I’ll be clear: I’ve changed my mind; given the opportunity again, I’d say using her as a science role model is not a net benefit. I’d have left her off the picture.

Mind you, I’m talking about this one case where someone promoting science and/or rationality may have beliefs or opinions that bump up against the evidence*. There are many others, and both Steve and Kloor bring them up (including Bill Maher, Bill Nye, Richard Dawkins, and more). I’m not surprised. The main thrust of my article is that we all have things we believe that may not hold up to scrutiny.

There’s a line attributed to Penn Jillette: “Everybody’s got a gris-gris.” Putting people up on a pedestal without reflection is a bad idea; feet of clay tend to crumble. Where we draw the line is an interesting and fruitful topic of discussion, and I imagine for many it will be a subjective judgment call.

I will, however, disagree with Steve on one thing. I do think that an actor with an advanced science degree is remarkable, and it is reason to praise them (all other things being equal). Like it or not, a lot of people listen to celebrities (the word is a cognate of “celebrate”, after all), so when some of them are clearly pro-science, I’m happy to support them.

On a case-by-case basis, of course.

Correction (Dec. 23, 2014): Keith Kloor's blog is on Discover magazine's blog, not Discovery as originally written.

* Update (Dec. 23, 2014 at 17:30 UTC): I rephrased this sentence to make it clear I was not talking specifically about the same issues as with Bialik; i.e. anti-vax and homeopathy.

Dec. 22 2014 1:34 PM

Twinkle Twinkle Little Star, an Astrophysically Correct Book and Song Are Now What You Are

This is so fun: my friends Zach Weinersmith of SMBC and Henry Reich from Minute Physics have written an astronomically corrected version of the song “Twinkle Twinkle Little Star” for kids!

They also put together a totally adorable short video with Henry singing the song:


They have all kinds of e-versions available, and you can pre-order a physical copy, too. The drawings are by children’s book illustrator Chris Jones, so this really is top-notch stuff.

When I first saw it I thought I saw a mistake in it, but I was wrong. I point it out so others don’t misunderstand it the way I did. The lyric is about a pulsar: “Out away from Earth your drift, this is known from your redshift.” I mistook this line to say we know its distance from its redshift, but that only works for very distant galaxies, not pulsars, which are inside our own galaxy. But I misunderstood; they’re saying we know it’s moving away from Earth by its redshift, and that’s technically correct. So there.

Anyway, this has come out just in time for the holidays. Go buy it, and turn more kids into little science pedants!

Dec. 22 2014 7:15 AM

So a Galaxy Walks Into a Bar ...

Adam Block is one of my favorite astrophotographers. Now, he has a bit of an unfair advantage: the 0.81-meter Schulman Telescope at the top of a mountain in Arizona at his disposal. He’s also really good at finding interesting but lesser-known objects and has a serious knack for creating incredible images of them.

I’ve featured his images many, many times on this blog, but I think this may be the very best I’ve ever seen: the spiral galaxy NGC 1398.

Dec. 21 2014 7:00 AM

Today the Sun Stands Still

Today is the real reason for the season: It’s the winter solstice! If you’re a purist, then raise your glass at 23:03 UTC (18:03 Eastern U.S. time), because that's the moment the solstice occurs.

There are a lot of ways to look at this, but they all boil down to the Earth’s axis being tilted with respect to its orbit. You’ve seen this with classroom globes; they’re tipped by about 23.5°. As it orbits the Sun, the North Pole of the Earth’s axis is always pointed pretty close to Polaris in the sky, which means that sometimes the axis is tipped toward the Sun, sometimes away. When it’s tipped as far from the Sun as it can be, that’s the moment of the winter solstice.


Illustration by Tfr000 on Wikipedia, Creative Commons License. In this animation, the winter solstice occurs when the Earth is to the far left part of its orbit, and the northern axis points away from the Sun.

Of course, when the northern pole is tipped away the Sun, the southern pole is tipped toward it, so it’s summer down there. In that sense, it’s better to call today the “December solstice” rather than “winter solstice.” Nearly 900 million people live south of the equator, so it’s probably a good idea to keep them in mind when we name things.

But for us in the north, today is the day the Sun stands still (the literal meaning of “solstice”). What does that mean? If you go outside every day at local midday (literally, halfway between sunrise and sunset) and note the position of the Sun in the sky, it changes during the year. It’s lower in the winter and higher in the summer.

Sun's path
The Sun’s path across the stars during the year, seen at midday.

Illustration by Phil Plait

Today is the day it gets as low as it can at midday—that’s why it “stands still”; it’s dipped as low as it can go and has stopped its decline. It’s the shortest day and longest night of the year. If you go out tomorrow it will be a wee bit higher at midday, and the day will be a tad longer.

The change is slow at first, then speeds up, accelerating the most at the vernal equinox in March. On that day, the days are lengthening as quickly as they can, usually by a couple of minutes or so per day. Then, at the June solstice, the Sun is as high in the sky as it can get, days are at their maximum length, and the Sun stands still once again. It reverses course, and starts getting lower every day at midday until late December.

Lather, rinse, repeat. Unless you're in the Southern Hemisphere, where this is all upside-down, so for you austral folks: repeat, rinse, lather. 

And this is why we have seasons: In the summer the Sun gets higher in the sky, heating us more efficiently, and the day is longer, so there's more time to warm up. In the winter it's lower, and the days are shorter, so it gets cold. 

Some people call today the first day of winter, but I prefer to think of it as midwinter’s day. After all, today the Sun starts getting higher in the sky, so why say that’s the first day of winter? Weather is regional, anyway, so trying to tag a definition of when winter starts is pretty silly.

Instead, use today to think about astronomy, cycles, the motion of the Earth, the patterns of the sky, and the amazing nature of our Universe.

Or, honestly, why not every day?

Dec. 20 2014 7:30 AM

Detecting an Exoplanet … Without a Telescope

Years ago, when the first transiting exoplanet (HD 209458b) was found, I was startled to realize that it could be easily detected using a small, inexpensive telescope.

Transiting exoplanets are planets that orbit other stars, and from Earth we just so happen to see their orbit edge-on. That means the planet passes in front of its parent star (that’s the transit bit), blocking a fraction of its light. A tiny fraction, usually far less than 1 percent. But if the star is bright, this dip in brightness can be spotted in small telescopes. I remember doing the calculations and finding that a 30 cm telescope could detect HD 209458b in a single night’s observations. Tough, but possible.


That meant an amateur astronomer could detect exoplanets! What didn’t occur to me at the time is that you don’t necessarily need a telescope to do so.

David Schneider, an editor at IEEE Spectrum, has described a setup using a digital camera and 300mm telephoto lens that has allowed him to detect the transit of the exoplanet HD 189733b, a so-called hot Jupiter, a massive planet orbiting very close to its star. The transit depth is about 2.6 percent, and his data look pretty good to me. He based his work on an amateur astronomer (vmsguy on the Cloudy Nights forum) who has also posted data that look pretty convincing.

Basically, the idea is to take several exposures over the course of the transit, taking care to make sure you get pictures taken before and after the transit. That’s your baseline. Using software to align the images and examine the stars (both vmsguy and Schneider used IRIS, which is Windows only, but other packages exist), you measure the brightness of the star over time to see the transit.

Not that it’s that easy! In reality you do relative photometry: You measure the brightness of many stars at the same time, so that a passing cloud doesn’t dim your star and make you think you’ve found an exoplanet. You also have to take other calibrations (like darks and flats), and apply them carefully. But it’s not impossible, and in fact sounds like fun.

Mind you, Schneider went all-in, even to the point of building his own gear to track the stars, but if you have a telescope you can always just use the motor drive that does that for you. The point is, you can detect exoplanets using just a camera, a good long lens, and a solid mount!

That’s amazing. I’ve been thinking of trying this sometime using my own 20 cm ‘scope; a lot of exoplanets are within range. But I’m still figuring out how to take astrophotographs, and believe me, I know how addicting this can be. I used to do this for a living, and if I get the software and start observing, I’ll be down the rabbit hole pretty quickly!

But in some ways, that’s the point. If you have the time and resources, it’s pretty amazing what you can do. You can even observe alien worlds.

Tip o’ the lens cap to James Walker.

Dec. 19 2014 2:15 PM

The Horsehead and the Flame

Well folks, looks like I have your next desktop wallpaper for you: a Spitzer Space Telescope image of the incredible Flame Nebula, a star-forming gas cloud hanging off Orion’s belt:

Dec. 19 2014 7:15 AM

Science, Celebrities, and the Perils of Promotion

Update (Dec. 23, 2014): After considering some comments and thoughtful disagreements to the article below, I changed my opinion about the relative good-versus-bad merit of using Bialik as a role model for science. My overall thoughts are the same—celebrities endorsing science is a good thing in general, but we must have a care about them. I wrote a followup article explaining all this, so please read that before commenting here.

Promoting science can be tricky. In general it’s fun and rewarding. I have a passion for science, and I wear it happily for all to see.


But there are minefields afoot. Of course there are people who deny science, and they will let the vitriol flow if you happen to stick a toe into their territory. There’s also the issue of diversity, including topics like women in science as well as people of different backgrounds, color, beliefs, and so on. I’m all for promoting more inclusion in science: the more the merrier! Reality is, and should be, for everyone.

But how to do this, how to actually promote these ideas, can get interesting.

scientists actresses
Actresses, scientists.

Graphic by Elise Andrew

A while back I was skimming my Twitter stream, and saw that my friend Christina Ochoa had retweeted a fun graphic created by Elise Andrew of I F’ing Love Science:

The picture is titled “Actresses with a passion for science” and shows five such women: Hedy Lamarr, Lisa Kudrow, Mayim Bialik, Natalie Portman, and Danica McKellar. I know how important it is to have good role models for kids and how girls need more support in getting into STEM (science, technology, engineering, and math) fields. Like it or not, actors and other famous people bear weight, so showing famous actresses who love STEM in my opinion is a pretty good thing.

So I retweeted the picture, adding “Love this” to it.

Then things got interesting.

Within minutes I started seeing responses about Dr. Bialik. Yes, “doctor”; she has a Ph.D. in neuroscience. The thing is, she also holds a number of beliefs with which I and many others disagree, some of them very strongly. For example, she’s a spokeswoman for a group called Holistic Moms—they support homeopathy, a provably worthless and arguably dangerous bit of “alternative medicine.” They are also strongly anti-vaccination, and Bialik herself supports anti-vaxxers (she has stated she has not vaccinated her own children, a position I am strongly opposed to).

I knew all this when I retweeted the picture. I’ll admit, I hesitated before doing so, specifically because of this. Is promoting this picture also promoting anti-science beliefs? Looking at the responses on Twitter, a lot of people think so. I see their point, but I also don’t think this is quite so black-and-white.

I do strongly disagree with many of Bialik’s beliefs. But I also know that she is a high-profile actress, starring in The Big Bang Theory where she plays a scientist. Her character, Amy Farrah Fowler, is a biologist and is commonly seen doing work in the lab and talking about her research with her friends. I’m quite fond of her character; she’s a passionate scientist, a decent person, a dork, emotional, analytical, and has trouble being objective when assessing her relationship with her significant other. I know a lot of people like that. I am people like that.

On top of that, Bialik has promoted science herself. For example, I urge you to take a few minutes and watch this delightful video where she does a great job talking up science:

Clearly, she can be a positive role model for science. However, we must have a care. The same people who might be inspired by her pro-science message might look into her more and find that she holds some less-supported beliefs, some that are anti-science.

So is using her in that montage of pictures a good thing or a bad thing? I would argue it’s neither, but the good outweighs the bad. The facts are that she is a scientist, she is an actress, and the picture was about actresses who are scientists. In point of fact, celebrities can be influential, and it’s a good thing that people see science supported by celebrity.

But of course we should also be careful not to put celebrities on too high a pedestal. Yes, Bialik has beliefs unsupported by science. But so does everyone. I imagine if we dig into the histories of the other four women shown in the picture we’ll find all sorts of things that go against the foundations of science, just as you would if you examined anybody’s thoughts. I have met my fair share of scientists who believe in one thing or another without evidence, or despite it. Heck, you can find Nobel scientists who fall into that category, ones who have supported clear crackpottery.

I’ll note I’ve dealt with this before when I was at an event with a Miss Utah; though she and I would disagree strongly on a number of topics, she was also an outspoken promoter of STEM, which is why she was there. And I was glad she was there, doing what she did. Think of it this way: If you knew of someone who did a great job taking down psychics, but also thought global warming was a hoax, would you then stop praising them for their work against psychics? It’s not an either-or thing; I would hope you would continue to praise them where appropriate but also take them to task where needed, too.

While you might dismiss those ideas and think less of the person holding them, that doesn’t necessarily subtract from their contributions to science. In this case, Bialik has done a lot to raise awareness of science and women’s contributions to it. Celebrating her (and the other four actresses) for that is great, and that was the sole purpose of the picture, and it’s appropriate to praise her there.

That doesn’t mean I am forgiving of Bialik’s beliefs at all. And in fact her presence in the picture has brought attention to them, which I think is also a good thing. A lot of folks agree with her when it comes to health issues, and that’s a big problem in this country; I’ve been clear about that for years.

That’s what I meant about this not being black-and-white. We’re all shades of gray, and if you really only want to praise people who are absolutely the perfect icons of science in every way, well, good luck finding them. You’ll be looking a long time.

As for me, I will continue to support science the best I can, and also support women in science. That’s the bigger picture here, and one we should all bear in mind.

Note: The friend I mentioned above, Christina Ochoa, is part of a group of actresses (also friends of mine) who love science. They call themselves Scirens and you should follow them on Twitter. They're good people, and I’m pleased to help support their efforts.


Tip o’ the calculator to Joel Parker for the link to the video.

Dec. 18 2014 11:30 AM


I love photos of the Earth taken from space; our deserts, oceans, islands, volcanoes, farmland, forests …  all of it.

But there’s something special about seeing something recognizable, even iconic, from space. Perhaps we’re used to seeing such things on maps, but a photo of it adds the dimension of reality.


I’m not sure. But no matter why, it’s hard to deny this is just straight-up cool:

I’ve spent a lot of time on this peninsula; family vacations when I was younger, visiting friends when I was older, watching the odd rocket launch or three. My folks lived there for many years, so seeing this from space reminds me of combing beaches for shark teeth when my daughter was little, getting sunburned like an idiot despite slathering on lotion, sweating maniacally in March.

At night, from space, the outline of Florida makes it so obvious (like Italy; perhaps peninsulae are easier to recognize). The lights of the city are both lovely to see and appalling to seriously consider; the light pollution is overwhelming, ironically drowning out everything in the night sky except for the few brightest objects … like the International Space Station passing overhead, from where this photo was taken.

Our technology has made it possible to go up and look down, but much harder to stay down and look up. If there is some sort of allegorical conclusion to be drawn here, well, I’ll leave it for you to consider.

Dec. 18 2014 7:15 AM

Scientists Discover 38 Percent of the Earth

OK, so the title is a little tongue-in-cheek, but it's sorta true: Mineralogists have finally found naturally occurring samples of what may be the most common mineral on Earth: what’s called silicate perovskite, or (Mg,Fe)SiO­3.

They’ve also officially given it a name now too: bridgmanite. Percy Williams Bridgman won the Nobel in 1946 for studying high-pressure minerals … and that’s a clue to why this mineral was so hard to identify.*


Bridgmanite can only exist under conditions of high temperatures (at least 2,100 C) and pressure (240,000 times the sea level atmospheric pressure—a crushing 240 metric tons per square centimeter!). It’s thought to be abundant in the Earth’s lower mantle—a region 660 to 2,900 kilometers beneath Earth’s surface. The molten rock in the mantle is fluid, moving incredibly slowly inside our planet. Any bridgmanite in the mantle brought up toward the surface slowly breaks down under the cooler and lower pressure conditions, which is why it’s remained elusive, even though the mineral may make up as much as 90 percent of that part of the mantle (and therefore more than a third of the entire planet).

Layers in the Earth. 1) Inner core, 2) outer core, 3) lower mantle (the layer in question), 4) upper mantle, 5) lithosphere, 6) crust.

Drawing by Mats Halldin

The scientific break came in the form of a meteorite, called Tenham. Long ago, two asteroids collided, and the impact created high temperatures and pressures. Bridgmanite formed, and the piece cooled too rapidly for the mineral to decompose. In 1879 the rock fell to Earth in Australia, where it was found and eventually determined to have different kinds of high-pressure minerals in it. Bridgmanite exists in it in very small grains, typically only about 1 micron wide (a human hair is typically 100 microns in width), but it’s there. It was announced earlier this year, but the scientists just published their paper about it in November.

This is quite a boon! It’s difficult to reproduce the conditions in the deep Earth, and even if you can it’s even harder to study what you get. In this case, it’s like we got a sample of the Earth’s lower mantle for free. It’s also a nifty crossover between different disciplines: meteoritics, high-pressure physics, mineralogy, just to name some.

And also, it’s just amazing. We live on a ball of rock and metal 12,740 km across, with a staggering 1 trillion cubic kilometers of material in it, the vast vast majority of which we can never directly see. I wasn’t even aware that we didn’t actually know for sure what made up over a third of our own planet.

Science! Astronomy may be my passion and my love, but sometimes it’s good to remember that science also tells you, literally, what’s going on right underneath your feet.

Correction, Dec. 18, 2014: This post originally misstated when Bridgman won the Nobel. It was in 1946, not 1964.