Bad Astronomy Blog
People love a good “David versus Goliath” story, especially when David is an outsider, a lone voice against a big government agency that he’s accusing of being incompetent and wasting money.
The problem with that narrative is that sometimes David is wrong.
Nathan Myhrvold is a billionaire, the former Chief Technology Officer at Microsoft, and holds a PhD in physics. He has a scientific background, obviously, and recently became interested in the search for Near-Earth Asteroids, the kind that get close enough to our home planet to be a threat.
After doing some of his own research, he thinks that a team of scientists at NASA/JPL and Caltech have made serious errors in measuring the properties of asteroids. And he’s gone farther than that: He’s accused them of making “colossal error[s]”, and made hints of fraud.
That’s an extremely serious accusation. It’s also, in my opinion, grossly wrong (NASA also issued a response backing up the scientists). After considering his research, I have concluded that the team is not in error, Myhrvold is.
The team of scientists is working on a potential NASA mission called NEOCam — the Near-Earth Object Camera — to map out the locations, orbits, and physical characteristics of Near-Earth asteroids as way to systematically determine what threat they pose to our fair planet. To do this, the scientists need to understand how their telescope operates; that is, if it sees an asteroid, how do you convert that brightness measured to a diameter? The size of the asteroid is a critical factor; without that it’s very difficult to understand much else about it. Over time, the team has published several papers showing how they make this calculation, using methods used before for earlier satellites, including NEOWISE, the predecessor of NEOCam.
Myhrvold, wanting to explore this topic himself, set about trying to replicate their results on his own. What he found, though, was that his numbers for asteroid diameters disagreed with the results from the team of scientists, sometimes by a huge margin.
One of them was wrong. Which one?
Myhrvold contacted the team, including Amy Mainzer, the NEOCam principal investigator, who has a long history of publishing scientific papers in the asteroid discipline, in order to discuss his ideas. [Full disclosure: I have known Amy for many years, and consider her a friend. I talked with her about Myhrvold’s claims and she was very helpful in pointing out references and explaining some of the physics and mathematics involved.]
At this point, the accounts diverge. Myhrvold says the team was not cooperative about their work, and gave him “cryptic” answers to his questions.
Mainzer told me a very different story. She said she worked with Myhrvold multiple times, trying to show him where some of his ideas were either incorrect or not applicable to the work they were doing, but he remained defiant. She pointed out specific errors, but despite that the errors remain his work.
The errors she mentioned are various, including his confusing diameter with radius in his calculations, and using a model that incorrectly determines diameters. For his part he says their model doesn’t include some basic physics, and that some of their numbers are suspicious.
So what’s going on? Other articles cover some of the basic claims (see Further Reading at the end of this article) but I want to take on some of the science claims.
The Light and the Heat
Myhrvold claims the physical model of asteroids the team uses doesn’t work, and that they ignore “basic physics.” Now, setting aside the rather bizarre idea that an entire team of professional scientists at JPL and Caltech might not understand undergraduate level physics, his claim that their model doesn’t work is simply wrong. Worse, it’s his own model that falls short.
The basic goal here is to determine the diameters of asteroids. How do you do that? The idea behind NEOCam is that it will use very sensitive detectors to measure the amount of infrared light the asteroids emit. Anything warm emits infrared light, and the amount of light an asteroid gives off depends in part on its size. By measuring different colors of infrared, complicating factors (like reflectivity) can be accounted for, and the diameter found.
To make sure they’re doing it right, the NEOCam team looked at asteroids for which the diameters are previously known (that part’s important). There are quite a few with accurately measured diameters; for example, some have been pinged with radar, which yields very good results for asteroids that get near the Earth. Others have had their sizes measured using occultations: Sometimes an asteroid will pass directly in front of a star, blocking its light as seen from Earth. Knowing the velocity at which the asteroid moves around the Sun together with the length of time it blocks the star gives you its size.
NEOWISE (the earlier satellite) observed these asteroids. The team then used the known diameters to create a model (a mathematical equation) of how the light is emitted. That way, they can then observe other asteroids with unknown diameters and use their brightness to measure their sizes. This is the model they’re using for NEOCam.
This is the model Myhrvold claims is wrong. However, the asteroid diameters found by the NEOWISE team agree very well with previous satellite measurements. NEOWISE looked at many of the same asteroids as an earlier mission called IRAS — a couple of thousand of the same asteroids — and found that the diameters calculated for those asteroids matched the measurements using IRAS to about ten percent. Not only that, measurements using a Japanese satellite called Akari also yielded similar results, and all three agree well with the radar and occultation measurements.
That’s a very good indication the NEOCam team is doing things right.
Despite this, Myhrvold disagrees. He says the team is ignoring basic physics, and the diameters they are getting are wrong.
Myhrvold has written a paper with his results, and when I read it became clear to me that this accusation is based on a false premise. He is trying to calculate asteroid diameters starting with basic physics (from the ground up, so to speak), while the NEOCam team is doing it empirically, based on observations (so, from the top down). In the latter case the physics is built in to the way the model is generated.
Here’s an analogy: Imagine a quarterback trying to throw a football into a receiver’s hands. An accomplished quarterback has thrown the ball thousands of times, and already knows by feel and muscle memory how to throw the ball, giving it the right speed, direction, and spin to complete the pass.
What Myhrvold is trying to do is start with the physics of motion, trigonometry, momentum transfer, air drag, and so on and then telling the quarterback how to throw the ball.
But the physics is built in to the quarterback’s experience. The passer doesn’t need to calculate all the physics to complete the pass. If we humans had to do the calculus every time we wanted to move, we’d be frozen stiff. So Myhrvold’s accusation that the NEOCam’s team ignores basic physics is incorrect.
Worse, Myhrvold’s model is wrong. He published his results in his paper, and the numbers he gets are way off. For example, in Figure 21, he uses his model to calculate the diameter of the asteroid 295 Theresia. The known diameter of that asteroid is about 28 km. Myhrvold gets a diameter of 660 km, over 20 times too big (if he were correct, it would be the second largest asteroid known)! Other examples with similar erroneous diameters can be found. It’s worth noting that other groups have used the NEOWISE data to compute their own models and have had no problems.
Let me be clear here: If you are accusing scientists of messing up the single most important thing they’re trying to measure — an asteroid’s diameter — you’d better get that right yourself. Myhrvold didn’t.
There’s more. For example, Mainzer told me that he confused radius for diameter in several places in his work—which she pointed out—but those errors remained even as he updated his paper. She also told me he based some of his numbers on an old paper about IRAS that had a systematic error in it, one that overestimates the sizes of asteroids.
Despite his own errors, he is accusing the NEOCam team of being wrong.
But it gets worse.
Cut and Paste
Myhrvold wrote what’s called a “white paper”, an overview of the situation as he sees it using simpler language. In it, he notes that some of the diameters for asteroids the NEOCam team calculated are exactly the same as found by earlier mission. Like, exactly, to several decimal places. Because the chances of this are essentially zero, Myhrvold speculates that the NEOCam team may have had a bug in their code that copied the diameters from the earlier results and propagated it to subsequent results.
Or, he goes further: He speculates that maybe this is due to fraud.
Yes, fraud, as in knowingly faking these numbers. This is a stunningly serious accusation. But there’s a much simpler explanation about the duplicate numbers. I asked Mainzer about this specifically. She told me the numbers are the same because they are copied, but it’s not due to fraud. The mathematical model they use does indeed calculate the diameter, as well as several other important variables that are initially unknown (for example, how reflective the asteroid is in visible light and infrared light). However, if the diameter has already been accurately measured in other ways (radar, occultations or from previous satellite measurements), they can use that number to better calculate the other variables.
This technique is discussed in a paper published in 2011. Myhrvold acknowledges that but then says this is never mentioned in subsequent papers. If true, that would make it seem like the team, in those subsequent papers, is claiming the diameters were calculated using their model, and were not actually from previous measurements. Hence his suspicion of fraud; in fact in his white paper he goes on at length about this. However, as just one example, in this subsequent paper by the team (in section 3, first paragraph), they clearly reference the first paper describing the method they use, including using measured diameters if available to better nail down the other variables.
In other words, Myhrvold is wrong. They do in fact discuss how they got the diameters in later papers. He may have simply missed this in the later paper. But either way he should have been more diligent in discussing this with the NEOCam team, especially given the seriousness of his accusations.
If you mention fraud, even as a possibility, you’d better have solid data to back it up. From what I’ve seen, Myhrvold’s claims don’t even come close.
There’s one final thing, and it’s important: Myhrvold’s paper has not yet been peer reviewed. This is a critical step in the scientific process: Other scientists look over the paper and make sure it has the proper methodology, it doesn’t have errors, it’s relevant, and more. They make suggestions to the author, who then rewrites the paper (or redoes the research if necessary), and resubmits it. If the reviewers approve, it gets published in a journal.
The peer review process is absolutely necessary to vet work from start to finish, but Myhrvold’s paper has not yet gone through this process. It may not be foolproof, but it’s at least likely to catch errors that are hard for the author to see (like his own erroneous asteroid diameter calculations). An outsider’s opinion can sometimes be valuable.
Despite that, he issued a press release, which is unconventional to say the least. This is sometimes done when a team wants the general community to contribute and comment, but that’s not what Myhrvold is doing. He’s using it as a platform to make accusations that have not been thoroughly checked. It lends a bad smell to what he’s done.
I know this is a complicated issue, but it’s an important one. Questioning results is fine, if it’s done in good faith and by someone who is well-versed in the subject. Myhrvold has cast himself as the outsider with a unique perspective, as David. But in this case, there’s a reason Goliath is, well, Goliath. The NEOCam team has the data, they’ve been open about their methods, and everything they’ve done is online and available for scrutiny.
I’ll be very curious to know what happens once Myhrvold’s paper is peer reviewed. I hope he’ll be as public about it then as he has been up to now.
Because this topic is complex, here are few links to other articles about this to help you parse it all:
- The New York Times article (which is sympathetic to Myhrvold’s claims)
- An article critical of Myhrvold in the Washington Post
- The NASA response
- A neutral synopsis at Inverse
- A neutral synopsis at Science (the comments are interesting too)
- An occultation astronomer opinion critical of Myhrvold on the Minor Planet Mailing List
- A member of the NEOCam team also posted to MPML with a critical look at the claims
I’ve said it before, and no doubt I’ll have many opportunities to say it again: If you like big, splashy, gorgeous astronomical photos, it’s hard to beat a ridiculously magnificent grand design spiral galaxy.
And if you like ridiculously magnificent grand design spiral galaxies, it’s hard to beat Messier 81, especially when it’s displayed in all its glory in a mosaic created by astrophotographer Robert Gendler:
See? Told you.
M81 is a spiral galaxy about 12 million light years away, making it close as far as astronomers are concerned. It’s actually close enough that it can be spotted in binoculars, and I’ve seen the spiral arms myself through a small telescope. It’s the biggest galaxy in what’s called the M81 group, a collection of a couple of dozen other galaxies including the dazzling and weird M82.
The image above is a combination of observations taken using Hubble Space Telescope and the huge 8.2-meter Subaru telescope, as well as data taken by Gendler himself and his collaborator, Roberto Colombari. The detail is amazing, and the overall image very lush.
M81 has two major spiral arms, with various spurs and smaller arms sticking off and in between the major ones. The young, hot, massive stars color the arms blue, and also light up the gas clouds from which they’re born, which glow a lovely reddish-pink. You can also see the feathery lanes of cosmic dust threading through the arms, the opaque clouds of carbon and silicates blocking the light behind them, following the overall spiral pattern.
… at least, most of them do. When I was perusing the high-res version of this image (and holy yikes you want to as well) I noticed a handful of dust lanes that were not curved at all, instead streaking straight across the right hand side of the galaxy. Here’s a close-up with the contrast enhanced so you can see them better:
OOooooo, a mystery! What are those?
I had a suspicion, but wanted to check. I typed “m81 galaxy dark stripes” into Google and immediately hit pay dirt: I found a journal paper from 1979 entitled, “The Enigmatic Dark Lines Crossing M81”.
The author, Nigel Henbest, notes the exact dark lines I saw, and shows that they are most likely “high latitude galactic cirrus”, clouds of dust that exist high above our Milky Way galaxy’s disk. This material is very faint, generally seen in silhouette against brighter sources — like, say, a nice bright background galaxy — but has also recently been found to shine feebly due to reflecting the combined light of stars in our own galaxy!
Gendler noted that you can see some of this “integrated flux nebula” in his image at the upper right. You might need to stretch the contrast to see it. And don’t confuse that for the splotch of stars directly above M 81; that’s actually a companion satellite galaxy to M81 called Holmberg IX.
There’s more to see in this photo as well, including multihued stars in our own galaxy, and a lot of far more distant background galaxies, many that are over a billion light years away. How about that? In this image you can see stars and dust in our galaxy, a pair of more distant galaxies, and dozens of galaxies that may be much like the Milky Way and M81, but shrunk to mere smudges by the perspective of their terrible distance.
I do love a good astronomical photograph. There’s always so much to see and discover in them!
In early 2012 a mystery literally erupted on Mars. Well, above it.
Amateur astronomers viewing the Red Planet from Earth noticed weird features on the limb of the planet (the edge as seen from Earth) in March and April 2012. They appeared to be clouds or plumes of some sort, but they were huge, and several hundred kilometers above the surface of Mars. No cloud has ever been seen that high, nor is there any obvious way to make one or get one there.
The features were definitely real; others have been seen (including with Hubble). Lots of ideas were considered—volcanic plumes, aurora, and so on (though Martian war machines were ruled out fairly quickly)—but nothing quite fit.
Now though, astronomers analyzing data from the Mars Express orbiter may have found a solution. Mars got hit by a solar storm.
Mind you, this isn’t conclusive, but it’s promising. Here’s what’s what.
A solar storm is when the Sun throws a magnetic tantrum, blasting off huge clouds of subatomic particles. These events carry a great deal of energy, and their own magnetic field. If they hit the Earth and interact with our magnetic field they can cause aurorae, blackouts, and other issues.
Mars doesn’t have a strong magnetic field, but it’s there; it’s only a couple of percent as strong as Earth’s, mostly due to magnetized rocks left over from when Mars did have an actively generated field (which has since shut down). And, in fact, the magnetic field is known to be a bit stronger over the region where the mystery plumes were seen.
A Mars plume spotted on March 20, 2012. Photo by W. Jaeschke.
Mars Express has been orbiting the planet since 2003, and is equipped with an instrument called ASPERA-3 that studies the interaction of particles from the Sun with the Martian magnetic field, and another one called MARSIS that uses radar to study the atmosphere and look for water under the surface. Looking over the data, scientists found that there were large space weather events around the same time both plumes were seen.
They did not see any obvious effects of this in the Martian ionosphere, the high altitude layer of the atmosphere where the molecules are stripped of electrons and become ionized. This is where you’d expect to see the biggest effect, so that’s a little odd, but it’s also known that the ionosphere in that region of Mars is “disturbed” due to the magnetic field there, so it’s hard to identify anything that would make it even more jinky.
Interestingly, Hubble observed a plume like this in 1997, and it turns out there was also a solar storm that might have hit Mars just before that observation was made. It’s not certain, but it’s compelling.
So what causes the plume? We know that the Martian atmosphere is being slowly stripped away by the solar wind, the more or less continuous stream of subatomic particles blowing off the Sun. Although the details are complex, and not fully understood, what may be happening here is that a storm from the Sun accelerates that process, compressing the Martian magnetic field, exposing the upper atmosphere to the direct effects of the storm. This allows more of the atmosphere to leak into space than usual, which we see as the plumes.
Mind you, this is still fairly conjectural; the evidence is indirect and circumstantial, but it does fit the idea that the storms caused the air over Mars to be extra leaky. Storms like this are rare, and detailed observations of Mars from Earth aren’t done around the clock, so they can miss the effects. Even orbiters around Mars itself may be in the wrong place at the wrong time to catch the effects.
The only way to know for sure is to catch one in the act. The best witness for that would be orbiters on the spot, but even observers from Earth can be crucial. Like seeing asteroid impacts on Jupiter, the more people we have observing Mars the better.
It makes sense to me. It’s easy to believe that in the early years of the 21st century that world would be watched keenly and closely; across that gulf of space, intellects vast and warm and sympathetic would regard Mars with curious eyes, and slowly and surely draw their plans to understand it.
The Universe lights up when you look at it with different eyes. And, in a very real sense, I mean that literally.
Our galaxy, the Milky Way, is more than just a few hundred billion stars. It’s also loaded with gas and dust, the raw materials from which stars are made. And stars are being made: roughly two to four times the Sun’s mass worth of stars are born every year in our galaxy. Usually that means lots of little stars like red dwarfs, but sometimes it means a truly massive star dozens of times heftier than the Sun. But on average, a handful are born every year.
They form in nebulae, clouds of gas and dust, under a variety of circumstances. There are huge cold clouds of dust out there called molecular clouds, and these are key sites of star birth. They can have regions inside them, knots or clumps they’re usually called, where the density of material is pretty high, big enough that gravity is a player. This material can draw itself together, and stars condense out of the resulting collapse.
That material has to be cold, or else its internal heat can prevent the collapse. So, ironically, one of the best places to look for stars about to be born is inside the coldest places in the galaxy.
The image above shows one such place: a ribbon of brutally cold dust and gas, only about 15°C above absolute zero! The image was taken by the ESA Herschel observatory, which is sensitive to light in the far infrared, way way outside what our eyes can see. This sort of light is emitted by very cold objects, such as clouds undergoing collapse.
The ribbon of material, called LDN 914 (or G82.65-2.00 depending on what astronomical catalog you like) is about 50 light years long and has about 800 times the mass of the Sun in total, plenty of raw material to make stars. Come back in a few million years, and this will look quite different, lit up by the fierce intensity of dozens of newborn stars.
When I saw this image I thought it looked familiar. It turns out I was mistaken; I was thinking of a different ribbon of star-forming nebula I wrote about back in 2013. But that got me wondering what this object looked like in visible light. I had a suspicion I knew, but I wanted to make sure.
I dug around the ‘net, but didn’t find anything at first. Then, on an astronomy forum for astrophotographers, I saw a post by Werner Mehl. He had taken a very deep exposure of the sky in the constellation of Cygnus, and in his shot was a ribbon of dark material he was having difficulty identifying. Here’s his photo:
Gorgeous, isn’t it? I grabbed his picture, rotated and resized it, and bingo! It’s a perfect match to LDN 914. I contacted Mehl to ask his permission to use it, and also let him know the name of his find (if you’re curious, LDN stands for Lynds Dark Nebulae, a catalog of such objects first published in 1962).
But perhaps you’ve noticed something weird: In Mehl’s photo, LDN 914 is dark, but in the Herschel image it’s bright. What’s going on?
In visible light, that cold dust is extremely opaque. It’s very efficient at blocking light from the stars behind it, and so Mehl’s image shows it as black, with very few stars in it (those are certainly foreground stars, closer to us than the nebula and so unblocked by it).
But anything above a temperature of absolute zero emits light, and what kind of light depends mostly on its temperature. The Sun is very hot, and glows in visible light. A red dwarf is cooler, and emits mostly red or infrared light. Cold dust clouds glow in the far infrared, where Herschel can see them.
And that’s what I meant at the top of this post. When you look at the Universe with different eyes, it literally lights up.
My favorite examples of this are when visible and far infrared images are overlaid; you can really see how something dark in visible light glows brilliantly in longer wavelengths. The best ones I’ve seen are the Cat’s Paw Nebula, IC 5156, and this, M78 in Orion:
The blue part of the image is visible light, and has very dark dust lanes running through it. The orange is from APEX, which sees light with submillimeter wavelengths, where cold dust glows. I love how they fit together like puzzle pieces. Amazing. And truly lovely.
See how beautiful something can be when you widen your perspective a little bit? If there’s a life lesson there, feel free to take it.
Post script: And oh yes, the reason LDN 914 looked familiar to me? I was able to crack that one pretty easily.
I love a good coincidence. Especially a series of them. To wit:
Last week I wrote an article about a massively viral optical illusion photo of a brick wall—if you haven’t seen it yet, I won’t spoil it; just go to my post and be amazed.
The very next post I put up after that had images taken by the Dawn spacecraft of the protoplanet Ceres, showing the cratered surface.
The funny thing is I got a few emails and tweets from people saying they were seeing the craters not as depressions in the surface, but as domes popping up out of it.
I had to chuckle about that. That’s another illusion I know very well, usually called the crater illusion. It was a funny (if minor) coincidence that people saw it in the post following a post about an illusion. It was funnier to me because in the brick wall post, I actually (and also coincidentally) linked to one of my favorite examples of the crater illusion, where dunes in the north African desert look like holes in the ground.
The icing on the coincidental cake? The very next day, the European Space Agency posted a photo of the Rub al Khali desert in the Arabian Peninsula, showing this same illusion, also featuring sand dunes!
The photo at the top of this post shows a part of the (much larger) image, taken by the Sentinel-2A satellite in December 2015. To me, the illusion that the dunes are actually pits in the surface is very strong. Does it look that way to you?
The reason for this is that we evolved to interpret scenes assuming the light is coming from above, like sunlight. When we see a photo, our brains assume the sunlight is coming down from the top of the picture. Something popping up out of the surface (like a sand dune) would be illuminated by that source of light, with the upper part of it (the part nearer the top of the photo) bright and the lower part shadowed.
But in the Sentinel photo, the lower parts of the dunes are bright, and the upper parts dark. That’s because the sunlight is coming from more or less the bottom part of the photo. But our brains have a hard time with that, assume the light is coming from above, and think the dunes must actually be pits. To our addled brains, something with its brighter part toward the bottom must be depressions in the surface, not something popping up out of it. So we see the dunes as pits.
Don’t believe me? I flipped the image over. Take a look:
Now that the light looks like it's coming from the top of the image, do they look like dunes to you? They do to me!
I played with the images for a while and found the illusion to be stronger when I shrank it down quite a bit; if I zoomed in on the dunes I saw them as dunes, and not pits. That was odd. I suspect the wavy lines of dunes give clues to my brain that the lighting doesn’t make sense if they’re pits (especially where the dunes make tight Z-shaped jogs in the lines). Those clues are too small to resolve when the image is smaller, so the illusion is stronger.
As always, while fun, there’s an underlying message here too: Your brain is lying to you. All the time. It does not see the world for what it is, but instead interprets it through a vast number of filters and preconceptions.
What you see is not what you get. It’s a pretty important lesson to remember.
In 1994, Jupiter was pummeled by the repeated impacts of the comet Shoemaker-Levy 9. The comet had been caught by the planet’s gravity earlier, torn apart by the tidal force during a close pass, and then each chunk slammed into Jupiter’s upper atmosphere and exploded, one by one, over the course of a week.
These impacts were easily seen from Earth (I saw the dark dust clouds peppering the cloud tops of Jupiter myself through a 15 cm telescope!), the first time any body other than Earth had been unambiguously seen to be hit by a comet or asteroid.
Since that time, five more impacts have been seen: in 2009, June 2010, August 2010, 2012, and 2016. In each case, the events were caught accidentally by amateur astronomers when they were taking video of Jupiter!
This raises the question: How often is Jupiter actually hit by an object big enough to make a flash visible from Earth?
At a workshop held earlier in May to encourage amateur astronomers to observe the planet in support of the upcoming arrival of the Juno mission to Jupiter, astronomers announced they have an estimated answer: Jupiter gets visibly hit by six to seven chunks of cosmic debris every year.
Yegads. That’s a lot!
They determined that number not just by the times amateurs have seen impacts on Jupiter, but also by how much they didn’t. If you happen to look at Jupiter and see an impact, you can’t know if you were just lucky; you have to observe the planet for a long time to see just how much it gets hit. In this case, observations from about 60 amateurs totaling more than 56 days of video were analyzed to look for impacts. None were seen, but that provides a valuable baseline for the impacts that were caught by accident by other amateurs.
While this is an estimate (and has not been through the peer-review process), it jibes with the numbers I was coming up with based on the impacts we’ve seen; on the order of once per year (meaning one to 10 times). And that’s only the impacts we can see; we miss half because they hit the far side of Jupiter, facing away from Earth, plus some when they occur within a few weeks of the time Jupiter is behind the Sun as seen from Earth.
Clearly, what we need here is a bigger team of astronomers across the Earth observing Jupiter, so we cover it as much as possible. The folks at the Juno workshop are working on that, as well as improving software that will allow analysis of video taken.
Why video? Well, it gives better time coverage of the planet—a single exposure is generally less than a second (Jupiter is bright through a telescope!), and a video can run for a long time. Also, Earth’s atmosphere boils and seethes, blurring out small details in astronomical targets. Video frames can be very short exposures, helping minimize that blur. Plus, one part of Jupiter might be relatively unaffected in one frame, while a different part of the planet looks better in a different frame. Sections of different video frames can be cropped out and reassembled to create a single, high-resolution shot of the planet. This is a relatively standard technique used by amateurs these days, and was how those more recent impacts were discovered.
As for the science, that part is pretty interesting. The impacts we see (with the exception of Shoemaker-Levy 9) are from pretty small asteroids, probably just a few dozen meters across. Jupiter’s ridiculously strong gravity pulls them in so hard that they are moving five times faster than impacts on Earth on average, making them 25 times brighter (energy released goes as the square of the impact velocity). In that case, even a smaller body can make a bright flash.
Asteroids that small are impossible to see directly from Earth because Jupiter is so far away. So the impacts on Jupiter give us an indirect way to figure out how many such objects are out there. Also, we don’t see too many impacts on other objects (pretty much just the Moon), so the more we see the more we can understand these events. I’m all for that.
As an aside, astronomy is one of the very few fields of science where amateurs* can make valuable contributions. Big professional telescopes are oversubscribed, and can’t afford the time to sit and stare at Jupiter for nights on end. In cases like this (and in many, many others) people with their own ‘scopes really fill a big gap in our understanding.
As someone who considers himself both an amateur and a professional astronomer, I love this. Science should be for everyone, whether you just want to learn more about it, enjoy it yourself, or participate in it directly. Astronomy is a fantastic way to do all of these things.
*Like so many other things in astronomy, there’s no good definition of what an “amateur” is. Someone who isn’t paid? Someone who does it as a hobby, or once a year when they haul a ‘scope out to look at the Moon, or who has done it for so long they know the sky like the back of their hand and write their own software to analyze their observations and create gorgeous images or scientific data? Yes.
Macabre? Sure. But my sense of humor runs dark sometimes, and I love science fiction, so this (very) short animation (very) briefly depicting a bunch of ways hapless space explorers can undergo Death in Space cracked me up.
I could nitpick the science — you won’t explode if you crack your helmet, but it won’t exactly be fun either — but that’s not really in the spirit of the thing. And that’s coming from a guy who literally wrote the book on this subject.
Tip o’ the spacesuit helmet to io9.
The other day I was puttering around in the house a couple of hours after sunset, and happened to glance out an open window. There, shining over the horizon in the east like a glowering eye, was an intensely bright red-orange “star”. I stopped for a moment, surprised, then realized what was going on: The star was a planet, specifically Mars, and it’s nearing opposition.
If you have a telescope, know someone who does, or live near an astronomy club (click here to find out!) or observatory, now’s the best time all year to see the Red Planet. It’s up all night and about as close as it can get to Earth. On May 30, it’ll be just a hair over 75 million km away, which as planets go is pretty close.
No, Mars won’t be as big as the Moon in the sky! Mars is only about 6,800 km across, about half the width of Earth, and from 75 million km away it looks pretty small. Still, it’ll be close enough that with a decent ‘scope you’ll see surface features. Maybe not as nice as that Hubble Space Telescope picture at the top of this post, but it’s pretty amazing to be able to see detail on the planet with your own eyes. If you get a chance to use a telescope over the next few weeks and observe Mars, take it!
So what’s going on? Mars and Earth both orbit the Sun like two cars going around a racetrack at different speeds; the Earth is on the inside track and moves a little faster. When Earth passes Mars on the inside curve, they’re as close together as they can be. When that happens, from Earth, we see Mars on the opposite side of the sky from the Sun — hence the term opposition. Because of that it rises when the Sun sets, and is up all night. It’s a twofer: Mars is as close as it gets, and it’s up at a convenient time to see it.
Things do get a bit complicated in the details. For example, Mars is on a fairly elliptical orbit that takes it as far as about 250 million km from the Sun and as close as 207 million km. That means some oppositions are better than others; the closest approach can range from 100 million to as little as 57 million kilometers from Earth. That means this one is fair to middlin’.
Because of its elliptical path, it also means opposition and perigee (the time it’s closest to Earth) don’t fall on the same day; opposition is May 22, over the weekend, but perigee is a week later.
Still and all, it’ll be bright and pretty for the next few weeks, so you don’t have to rush out and see it only on May 30! Any time through June and even July will be cool.
And if you want to impress people with your knowledge of Mars as you observe it at a star party, then may I suggest watching my episode of Crash Course Astronomy about the planet? Take notes if you want; there’s no test. The only goal is to understand the Universe around you better, and appreciate it a little more.
I hope you’re sitting down for this shocker: Cramer is a global warming denier. And to be clear, he’s not just a denier. He’s a crackpot.
First, watch this video put together by the folks here at Slate to get an overview of this guy’s view on science:
Trump’s grave misunderstanding of the difference between weather and climate doesn’t surprise me; he’s a buffoon when it comes to such topics (case in point: he said global warming is a hoax manufactured by the Chinese). Given his history, his choice of a crackpot for energy advisor isn’t terribly surprising.
Cramer has a long record of climate change denial (apropos of nothing, over his career Cramer has received more than a half million bucks in funding from the fossil fuel industry, more than twice as much as any other industry). That’s also not surprising given that North Dakota is one of the largest producers of oil and coal in the nation. The burning of excess natural gas fracked in the state is so intense it’s easily visible to satellites in space. Given all that, Cramer denying climate change is de rigeur.
It’s the degree (so to speak) to which he denies it that’s staggering. He’s part of the tiny, tiny head-in-the-sand deniers who won’t even acknowledge the planet’s heating up. That line in the video where he says, “We know the globe is cooling; number one we know that” is from 2012, just a few years ago. We’ve known since long before then the planet is heating up, and the past few years the warming has gone into overdrive; each of the past seven months have been the hottest of those months globally. To actually say out loud that the Earth is cooling would make Orwell blush.
But he wasn’t done; he also added, “… the idea that CO2 is somehow causing global warming is on its face fraudulent.”
Holy. Baloney. He’s not just denying global warming, he’s denying a link between carbon dioxide and the planet’s increasing temperature. For the record, carbon dioxide being a greenhouse gas has been a matter of scientific fact since 1896.
The conservative party really is conservative. When it comes to science, Trump and Cramer want to wind the clock back to the nineteenth century. At least.
Cramer has made it clear that if Trump gets elected, he’ll be no friend to the environment, rolling back regulations and reversing the Clean Power Plan. Trump himself has said he’ll back out of (or “renegotiate”) the Paris climate treaty, a claim he makes based on 100 percent utter nonsense.
It couldn’t be more clear: If Trump does indeed take the White House our planet is, basically, screwed.
So, there you go. Nothing about this is at all surprising from the candidate who put away the dog whistle years ago, bringing out into the open the contempt he has for women, people of color, Muslims, gays, decorum, facts, and science. This is what the modern GOP hath wrought, and come November, hopefully they’ll reap what they’ve sown.
In April 2015, I wrote about a new expansion pack for the ridiculously popular game Cards Against Humanity. The new pack was the brainchild of Zach Weinersmith, who asked me to help come up with some of the funny science-based questions and answers to the party game.
That was an easy decision on my part, but it was made even easier because the CAH folks decided to take all the money—yes, all of it—that was made from the science pack and create a full-ride scholarship for young women attending college for a STEM (science, technology, engineering, and math) degree. This is a fantastic cause and something that can really help address the imbalance between men and women in STEM.
The call went out for video submissions, and more than 1,000 young women applied. The panel of 60 professional women in STEM went through them, and they have announced a winner: Sona Dadhania, a freshman at the University of Pennsylvania! She wants to study nanotechnology, and she put together this video as her submission:
Nice! She’s a freshman now, so CAH will pay for her tuition for the next three years (a sum of about $150,000). You can read more about her in an article on Philly.com. As for how she reacted to the news, well, see for yourself:
Yes, that may have choked me up just a little. I’m so happy for her, and proud of my friends for what they’ve done here.
But they’re not done here! The pack has so far raised more than $880,000—yes, you read that correctly—to help women get a STEM degree. That means there’s plenty left over for more scholarships, and applications for Round 2 will be opened this fall. Stay tuned.
Congratulations, Sona! Go make the world a better, cooler, and smarter place. And, y’know, just throwing this out there: The science pack is available at the CAH online store. If you already bought one, then thanks. Look what you helped do!
Tip o’ the Erlenmeyer flask to my friend Kim Arcand.
A new image of the protoplanet Ceres from the Dawn spacecraft caught my attention recently. It shows the western rim of a crater called Azacca (named after the Haitian god of agriculture; Ceres was the Roman goddess of agriculture). Only a portion of the 50-kilometer-wide crater is shown, but there’s a number of interesting features lurking there.
The most obvious is the small crater right on the rim. It’s younger than Azacca; it overlays the rim, so the impact that formed it must have happened after Azacca was already there. It’s fresher looking, with a sharp rim, though it has smaller craters inside which implies it’s not exactly young. It’s been around long enough to collect some later impacts of its own.
The bright streaks along the young crater’s rim caught my eye. Once a crater is made, material along the walls can slide down into it, revealing material that was once under the surface. In this case, those brighter streaks are tantalizing. Are we seeing the same sort of bright material that has captured the imagination of so many people since Dawn first approached Ceres back in January of 2015?
The most likely culprit for these bright features is salt. Maybe magnesium sulfate, a common mineral. We know Ceres has a lot of water ice in it, which may have been a subsurface ocean, a mantle of water, early in its history. Salts would have dissolved in it, sticking around even today, long after the undersurface water froze. If so, some sort of process may still be bringing it to the surface to create the bright features we see now.
Look around that crater. See all the bright spots? Here’s a closer view:
Each pixel in the original (1024 x 1024) image is about 35 meters on the surface, and many of those spots are 2 — 10 pixels across, so 70 to 350 meters in width. At least some look like small impact craters. It’s likely there’s ice just under the surface, excavated when small asteroids impact Ceres.
Interestingly, I found an image of Azacca itself that also shows small white spots in it. I’d expect a large impact would vaporize the ice underneath the crater, yet there are those spots. Is ice from deeper within Ceres coming up through cracks/vents in the crust? There are much larger cracks in the floor of Azacca, possibly due to pressure underneath the crater pushing the floor up (though cracks in the surface have many different sources). Hmmmm.
As my friend Emily Lakdawalla wrote on her blog at The Planetary Society, the key to understanding the surface of Ceres is to understand what lies beneath. There are plenty of clues! With Dawn continuing to map this weird little world in high resolution, the evidence will continue to come in. I hope planetary scientists can make sense of the place. I do love a mystery, but I also love it when it’s solved. There are always more to take its place.
I love optical illusions, especially ones that really twist your brain around. I saw one recently that really had me going for a minute. And it’s not so much the illusion itself that really gets me, but my own brain’s reaction to it.
The photo is above. I saw it on a Facebook post from this week, though it’s been around since at least 2014.* It shows a brick wall, seen at a shallow angle, with somewhat large gaps between the bricks. The bricks are red, and it appears that there’s a small gray rock stuck in between them just above center.
So what’s the illusion? I couldn’t see it at all, even after a good 30 seconds of staring at it. I was starting to suspect there was no illusion, and it’s a gag to fool people, when I read the comments and realized what I was missing.
If you still haven’t seen it, then what follows below will spoil it for you. If you don’t want to know then don’t read any further until you’ve figured out the illusion!
OK, fairly warned be thee says I.
The illusion is that it’s a cigar stuck in the wall. It’s actually sticking out at a 90° angle, but the shot is taken so that the body of the cigar is aligned with a horizontal gap in the bricks. Together with the cigar being dark, it just looks like the cigar is the gap in the bricks, and the ash at the end is a rock stuck in the gap.
This should help: I blurred the bricks, so the cigar stands out more clearly:
How about that! Pretty cool.
Now here’s the part I love: Scroll back up to the original picture. When I look at it, I can’t not see the cigar! Once you’ve seen it, it cannot be unseen.
I find that fascinating. I’m pretty good with illusions, but I really couldn’t see the cigar until I got a hint. Now, no matter what I do, my brain won’t see it as anything but a cigar. I sent the image to my editor, and the exact same thing happened to her; looking over the comments on the Facebook post that seems to be the case with a lot of people.
Interesting. So why is that? I couldn’t see it at first because for me, the visual cues were so subtle. The dark cigar, the blending with the crack, and so on. Worse, my brain interpreted the ash as a small piece of rock or mortar, and stubbornly refused to budge from that notion until the visual cues were overwhelming!
But once I did see it for what it was, the visual clues were easily visible, and importantly I then knew they were there. It’s much harder to ignore what you see than notice something you don’t see. I guess that sounds almost like a tautology, but when it comes to illusions it’s quite true.
And I imagine that this must be a head-scratcher for people who see the cigar right away. I’m sure they have a very hard time understanding how easy it is for most people to miss the incredibly obvious stogie sticking right out of the wall.
A lot of people dismiss this illusion; the comments show a lot of folks basically saying, “meh.” But I think they’re missing the bigger point. Obviously, quite a few people are fooled by the photo, and it’s quite easy to be so. The lesson here is that we miss obvious things right in front of our noses all the time, and it’s not until someone points them out to us that we finally notice.
Ironically, people dismissing the illusion are doing the exact same thing. There’s a bigger point here about biases, perception, and entrenched opinions, and they’re skipping right over it. I hope that some of them read this, and see what they’ve missed.
More illusions to destroy your brain:
- The Blue and the Green (simply the greatest illusion of all time)
- Are These Lines Moving or Is It a Spinning Square?
- Rotating Rings
- Viral Illusion Will—and Should—Have You Doubting Your Eyes
- The Dragon That Follows Your Gaze
- OK Go: The Writing’s on the Wall
- Illusions of Dune
- This Illusion Will Drive You Mad (one of my favorites!)
- Square Circle Spiral
- How Many Circles Do You See?
Tip o’ the Necker cube to Fark (note: it’s Fark, which I love, but generally has, um, NSFW and sometimes fairly juvenile comments).
*I’m having a hard time tracing this back to the person who originally took it; the reverse image search yielded a lot of Spanish-speaking websites, but none that I found actually gave credit to the photographer of it. If anyone knows who took it, please email me!
When you look at the image above, you may be reminded of a cell undergoing mitosis. Certainly, even if you knew it was an astronomical object, you’d be excused if you missed the idea that it’s actually one of the most catastrophic events in the Universe: a supernova.
The violence of a supernova is almost too huge to overstate. When a star explodes (an entire star! Exploding!), the energies involved crush our human perspective into dust. The core of the star collapses, and the outer layers—an octillion tons of vaporized star-matter—are hurled outward at a significant fraction of the speed of light. This debris covers millions of kilometers in seconds, billions in hours, detonated by a blast that’s equivalent to the entire lifetime’s supply of energy from a star ignited all at once.
We have observed literally thousands of these events, but, even for the closest, the fantastic speeds of their motions are dwarfed by their distance from us, seemingly frozen in time when you see their images.
Only, that is, if you aren’t patient. In a single image that motion is invisible, but wait a few years, and even the chilling remoteness of a galactic supernova cannot erase the motion of its debris.
And we do have the sharp eyes and glacial endurance of telescopes. In the case of the image above, the Chandra X-ray Observatory (together with radio observations from the Very Large Array in New Mexico) observed a supernova remnant over the course of several years, and when those images are put together in an animation, the expansion of the vast cloud of matter is visible. Behold!
Let that animation repeat a few times; the motion is most apparent in the outer blue ring, the glow from electrons heated to 10 million degrees Celsius by the exploded star’s shock wave. The debris itself is turbulent, bubbling away from the center, and its motion too can be seen over the decade and a half of observations.
As the animation plays, let this thought run through your brain: These observations indicate that in some places in the cloud, the debris is expanding at a numbing 5,000 kilometers per second. In the time it takes you read this paragraph, the gas will have traveled comfortably farther than the diameter of the Earth.
The star that gave up its life for these observations lies between 6,000 and 9,000 light-years from us—60,000 to 90,000 trillion kilometers—and when its light reached Earth in 1572, it was bright enough to outshine every other star in the sky, and even be visible during broad daylight. Astronomer Tycho Brahe was captivated by it, documenting his detailed observations made before telescopes were commonly used to peer into the sky. Had he been able to see its motion, he may have guessed what it was.
To me, this is thrilling. Astronomical objects are so distant and so vast that change in them seems impossible; it feels as if they will appear now as they always have, and always will. But the Universe changes at its own pace, and that evolution is perceivable by humans due to our own curiosity and sense of exploration. Despite its appearance over the puny duration of a human life span, the cosmos is neither eternal nor static. But we only notice if we’re paying attention.
Every now and again, a photograph from a spacecraft stops me dead in my tracks. The shot above is one such image, taken by the wonderful Lunar Reconnaissance Orbiter.
It shows sunrise on the western part of the rim of Jackson Crater, on the far side of the Moon. Jackson is a relatively young crater about 70 km across, with a well-defined rim that extends around it like a single, long rampart bent into a battered circle.
Because the rim rises up from the terrain around it, it’s the first to be lit by the rays of the rising Sun. The Moon spins once every 27 days or so, so sunrise takes 27 times longer than it does on Earth. Here on Earth the Sun takes about two minutes to clear the horizon, so on the Moon it takes roughly an hour.*
What a view that must be! And what magnificent scenery it illuminates. On the Moon, with no atmosphere, there’s no reddish-pink hue to the sky. It’s black all the time, even during the day. When the Sun rises, it must be like a light switch being thrown. Still, the low angle will illuminate the level ground less than something angled up, tilted such that it’s flatter to the incoming rays. So the inside wall of the rim is lit well, the lunar terrain outside the rim still appears somewhat dim, and the inside of the crater is cloaked in inky blackness.
The combination of stark lighting, soft lighting, and no lighting at all is entrancing. The moon is always a beautiful object to see, but it’s the shadows that add to the poetry of the composition. There’s mystery and intrigue in the shadows’ edges.
Another reason this image is so striking is that most LRO shots are “nadir angle,” looking straight down at the surface below the spacecraft. This one was taken at an oblique angle, the better to see contours and shadows (a zoomable map of Jackson using LRO nadir images shows just how different it looks in full sunlight and peering straight down at it). Between its unusual angle and the striking lighting, this image has quickly become one of my favorites from a mission that has provided so many stunning photographs of our cosmic companion.
*Ignoring atmospheric effects (on Earth) and latitude, which can actually change the length of sunset significantly. There’s no air on the Moon, but latitude effects can make the sunrise last for many hours or more near the poles.
[N.B. If this article sounds familiar, it should. This has been happening so frequently I just copied the post for March and updated it.]
October. November. December. January. February. March. And now April.
For the sixth seventh month in a row, we’ve had a month that has broken the global high temperature record. And not just broken it, but shattered it, blasting through it like the previous record wasn’t even there.
According to NASA’s Goddard Institute for Space Studies, March April 2016 was the hottest March April on record, going back 136 years. It was a staggering 1.28°C 1.11°C above average across the planet.* The previous March April record, from 2010, was 0.92° 0.87° above average. This year took a huge jump over that.
Welcome to the new normal, and our new world.
As you can see from the map above, much of this incredible heat spike is located in the extreme northern latitudes. That is not good; it’s this region that’s most fragile to heating. Temperatures soaring to 7° or more above normal means more ice melting, a longer melting season, loss of thinner ice, loss of longer-term ice, and most alarmingly the dumping of billions of tons of fresh water into the saltier ocean which can and will disrupt the Earth’s ability to move that heat around.
What’s going on? El Niño might be the obvious culprit, but in fact it’s only contributing a small amount of overall warming to the globe, probably around 0.1° C or so. That’s not nearly enough to account for this. It’s almost certain that even without El Niño we’d be experiencing record heat.
Most likely there is a confluence of events going on to produce this huge spike in temperature—latent heat in the Pacific waters, wind patterns distributing it, and more.
And underlying it all, stoking the fire, is us. Humans. Climate scientists—experts who have devoted their lives to studying and understanding how this all works—agree to an extraordinary degree that humans are responsible for the heating of our planet.
That’s why we’re seeing so many records lately; El Niño might produce a spike, but that spike is sitting on top of an upward trend, the physical manifestation of human induced global warming, driven mostly by our dumping 40 billion tons of carbon dioxide into the air every year.
Until our politicians recognize that this is a threat, and a very serious one, things are unlikely to change much. And the way I see it, the only way to get our politicians to recognize that is to change the politicians we have in office.
That’s a new world we need, and one I sincerely hope we make happen.
*GISS uses the temperatures from 1951–1980 to calculate the average. The Japanese Meteorological Agency uses 1981–2010, which gives different anomaly numbers, but the trend remains the same. Realistically, the range GISS uses is better; by 1981 global warming was already causing average temperatures to rise.
Seventy million light-years from Earth lies the somewhat odd galaxy NGC 1332. It falls somewhere in between the two main galaxy types of elliptical and spiral; it’s disk shaped but lacks obvious spiral arms and is quite elongated.
Like all big galaxies, though, it has a black hole in its very center. And not just any black hole, but a supermassive black hole. Current astronomical thinking is that these monsters form at the same time as the galaxy, and affect each other’s growth. Gas pours down to the center from the growing galaxy, feeding the black hole, and the black hole also emits a ferocious wind that can curtail the birth of stars in the galaxy.
When we look at a galaxy now, billions of years later, we see correlations between the mass of the black hole and the behavior of the galaxy. Because of that, knowing the mass of the black hole is important in understanding how galaxies are born, age, and evolve.
But how do you measure the mass of a black hole?
Isaac Newton helps us here. Objects near the black hole orbit it, and the speed at which they move (together with their distance from it) reveals the strength of the gravity of the black hole. That in turn—as Newton pointed out 400 years ago—depends on the mass doing the pulling.
It’s not that simple, of course! But it can be done, and has been done. A camera I worked on for Hubble, called STIS, was designed in part to be able to make these kinds of measurements.
For NGC 1332, various methods have been used, including measuring the velocities of stars near the center of the galaxy (and therefore close to the black hole) and looking at hot gas surrounding the galaxy. These methods have some issues, though, and can have large uncertainties.
A new telescope has come online recently, though, and has something to say about the matter. ALMA, the Atacama Large Millimeter/submillimeter Array, is a collection of large and very sensitive telescopes that detect light well outside the energy our eyes can see—between infrared and radio waves. Very cold gas and dust emit light in this range, and that’s where ALMA comes into the game.
Many black holes have huge, swirling disks of dust around them. These can be several hundred light years across, the whole thing moving around the supermassive black hole at high speed. Even though they’re big, from 70 million light-years away they look small and hard to see. ALMA, though, has terrific vision, able to resolve the disk down to just a dozen or so light-years from the central black hole.
That’s important. More than about 75 light-years out from the black hole, the gravity of the stars in the central region of the galaxy start to dominate; an estimated 10 billion stars exist within the central 750 light-years. So the closer you are to the black hole, the less an effect the stars have over the hole.
Measuring the disk rotation speed depends on measuring the Doppler effect: The part of the disk rotating around the black hole and heading toward us gets its light blueshifted (the wavelength gets compressed) while the side heading away from us is redshifted (the wavelengths get longer). ALMA can measure these shifts all along the disk, thereby measuring its velocity at different distances from the black hole.
By carefully modeling the gravitational effects of stars and the black hole and applying them to their observations, astronomers using ALMA have determined that the black hole has a mass of—I hope you’re sitting down—660 million times the mass of the Sun.
That’s a lot of hole.
As supermassive black holes go, that’s pretty supermassive-y. Quite a few have been found that are even bigger, but 660 million solar masses is pretty big. The Milky Way’s central black hole has a mass of only (!) about 4 million times the mass of the Sun, for comparison. So the one in NGC 1332 is a lot heftier than ours.
The good news is that this mass jibes with what’s been found for that galaxy using the other, independent methods. That gives us confidence the answer is correct. And the uncertainty in the ALMA measurements is pretty good, only about ±10 percent, better than most other measurements.
And it means we have yet another tool in our kit to measure the masses of these monsters. To put this in context, the ALMA observations aren’t a groundbreaking discovery, but they’re something just as important: a new way to probe distant cosmic objects. ALMA can perform similar observations on other galaxies, building up a census of black hole masses, which can be combined with all our other knowledge to help us better understand the lives of galaxies.
Galaxies are in many ways the building blocks of the Universe, and we happen to live in one, so I’m all for understanding them better. Everything we learn in this way is a piece of the puzzle and adds to the picture we build of the Universe.
I’m all for that, too.
Wow! What a great example of von Kármán vortices!
This image, taken by Landsat 8 on May 3, 2016, shows a layer of stratocumulus clouds over the southern Indian Ocean. Poking above the layer is Mawson peak, a stratovolcano (lots of stratos in this shot) on Heard Island, one of a chain of volcanic islands near Antarctica.
The wind is blowing to the east near the island, which creates a wiggling tail of air downstream from the island as it flows around. As that tail “flaps”, the vortices are spawned, which then flow along with the wind. As I’ve written before:Imagine you have a cylinder (a pencil, or a bucket, or a concrete pylon) that you place in flowing water. It’s an obstacle, and the water will flow around it. However, near the cylinder’s surface the water slows, piling up a bit. The water farther from the cylinder is moving faster. This causes eddies (vortices) to form, curls in the water. This kind of motion is a bit unstable, and can cause a slight force, pushing the water perpendicular to the direction of flow. But the water all around the flow pushes back, causing a sort of oscillation, like a pendulum swinging. The result is a series of vortices forming and flowing downstream, one on each side of the obstruction, alternating in pattern. An animation, in this case, is worth way more than a thousand words: See how the fluid wiggles like a tadpole tail downstream? Eventually those vortices dissipate, losing coherence due to turbulence and drag. This process from start to finish is called “vortex shedding”, which just sounds intrinsically cool.
I love stuff like this, but what makes this even more fun is that in the Landsat 8 image, you can see the winds take an abrupt left turn, suddenly blowing north. That’s not easy to see in the clouds themselves, but it’s pretty obvious when you look at the chain of vortices, which make a sudden change in direction.
I found this picture (via @NASAEarth) on NASA’s terrific Earth Observatory Image of the Day site, one of my favorite places on the ‘net. They also mention that you can use the NASA WorldView page to zoom in and out of this shot, putting in in the greater context of flows around the southern continent. Amazing.
If you’re a US citizen, your tax dollars have already paid for all this, so go play. And if you’re not American, please allow us to let you use this for free. If I may speak for NASA, it’s honestly our pleasure to share our wonderful planet with you.
On the occasion of the recent revealing of the James Webb Space Telescope’s completed golden mirror array, I wrote a post describing the mirror(s) and how they got their golden atom-thin sheen.
Apropos of that, a couple of pretty nifty videos were recently released. Right now, JWST is in the big “clean room” at Goddard Space Flight Center, a huge warehouse-like room that is kept almost entirely free of dust and other particulates that might muck up the optical works. There are a couple of webcams installed there (called “Webb cams”, because of course), and they were online when the entire mirror assembly was moved from the horizontal to vertical position. The result is pretty cool, especially when you consider just how big this assembly is: Remember, it’s 6.5 meters across!
I think my favorite part is at the 30-second mark when all the engineers in the bunny suits pose for a snapshot in front of it.
Here it is from another angle. The color is a bit distorted since it’s through a window, but the gold mirrors are still really something.
The reason the mirror was moved into this position is for the next very, very big step in the assembly: Installing the detectors behind the array. As I wrote before, the telescope is set up so that the big primary array collects the light from astronomical sources, reflects it up to a smaller secondary mirror, which in turn reflects that light down through a hole in the primary down into the instruments behind it. Those instruments include cameras and spectroscopes that will capture and dissect the light from distant galaxies, exploding stars, planets around other stars, Kuiper Belt Objects in our own solar system, and much, much more.
Launch is planned for 2018, so there’s still plenty of time for assembly. I’m glad to see, after so many years, this whole thing finally coming together.
I’ve always been something of a map dork. I remember sitting in the back of the car on long rides as a kid, poring over the foldout maps, the US map, and the key map my folks had under the passenger’s seat. It was so much fun to look at the roads, the landmarks, the cities and places I had never heard of before… It’s easy to see now why so many great stories start with finding a secret map.
Sometimes it goes the other way, though: Our stories inspire maps. Eleanor Lutz is an artist who has a self-professed love of medieval maps. She created an amazing and really quite beautiful map of Mars in that historical style. A portion is shown above; but you really should see and peruse the bigger version. It’s lovely. I’ll note she has prints of the map for sale, too.
She titled it “Here Be Robots”, which I love. As many people have pointed out, Mars is the only planet we know of inhabited entirely by robots. She has the landing sites of a few of them labeled, too.
I love the layout and flow of the map; it does have that medieval style, but with a modern take — it’s Mars, after all, and it’s real. This map is based on observations made by humans from Earth over the centuries, and then the details filled in by a score of probes sent there in the past half-century.
There’s a story for you: The exploration of an alien world, close by but still terribly distant, full of wonder and bizarre terrain and things we still don’t understand. And apropos of the style of the map, Mars is like a monster guarding the bridge; half the missions sent there have resulted in failure.
Like Scylla and Charybdis, Mars is a dangerous stretch of water, apt to eat unwary travelers. If there were ever a warning to put on a map like this, “Here Be Dragons” would be appropriate.
And yet we pushed through, and we have sent spacecraft there successfully, one after another. Unlike those old fables that promote the fear of the unknown, when we keep our eyes open, our heads high, and our brains fully on alert, we can push through the ignorance and turn terra incognita into Mars cognita.
Lutz has more of her artwork at her blog, Tabletop Whale, and on Deviantart. Seriously, watch this animated graphic of human fetal development. Amazing!
Look, I know you like science: You’re reading my blog (QED). And I’m guessing you like gorgeous tropical beaches, amazing food, incredible scenery, active volcanoes, and being around other science-minded people.
So let me gently remind you that there are slots still available for Science Luau 2016, a trip to the Big Island of Hawaii with bonus added SCIENCE! My wife and I are doing this through our company Science Getaways, where we start with vacations you’d want to go on anyway and then add tons of science to them.
Our agenda for Science Luau 2016 includes swimming with manta rays, visiting a native Hawaiian dry forest filled with endangered wiliwili trees, and touring the active Kilauea volcano … after sunset you can see the sulfurous plume illuminated from below by the glowing red-hot lava in the Halema'uma'u crater.
Sometimes, along the highway lined with jagged volcanic rocks laid down by eruptions decades ago, you can see families of goats walking along eating the sparse invasive grass, too. You know how I feel about that.
There'll be plenty of down time, too, where you an just sit back and enjoy the tropical island. I'll be packing my solar telescope, so we'll be doing some Sun observing (seeing towering prominences and winding filaments on the Sun is pretty common). And, of course, since my wife and I are running the show, I'll be there the whole time if you want to ask questions about astronomy or just sit on the ocean's edge and talk about the Universe.
This will be a fantastic trip, with the extra advantage of being with other science enthusiasts; we’ve found that many people who meet on these trips become lifelong friends. It’s really quite lovely.
So come join us! Who wouldn’t want to experience science in paradise?