Bad Astronomy
The entire universe in blog form

Jan. 17 2017 8:45 AM

Apollo Astronaut Gene Cernan Has Died at 82

Apollo 17 Cmdr. Gene Cernan has died.

Besides being a Naval aviator, a fighter pilot, and an engineer, he is best known as the last human to have stood on the surface of the Moon.


Like every other astronaut of the time, Cernan was quite the character, with a storied life. He had been an aviator for five years when, in 1963, NASA tapped him to be an astronaut. In 1966 he piloted Gemini 9A, the pre-Apollo mission for which he was part of the backup crew before the prime crew died in an airplane crash*. Gemini was a precursor to Apollo, a way for NASA to learn the skills needed for the mission to the Moon.

9A had a series of mishaps itself. Its primary mission was to rendezvous and dock with an uncrewed vehicle that was to be launched hours earlier, but that rocket failed during flight. A second uncrewed vehicle was launched successfully two weeks later, but on its first attempt, the rocket with Cernan and Thomas Stafford suffered a malfunction and didn’t launch. It finally went up two days later.

Things still went poorly. Once in orbit they found the rendezvous vehicle slowly spinning (and a shroud had failed to jettison, making docking impossible). Cernan’s extravehicular activity (EVA) was postponed until the mission’s third day. Even then he had serious problems with his suit, and the two-hour EVA exhausted him. They had to cut it short, but he was so overheated and tired there was real concern he wouldn’t be able to get back into the capsule. He did, of course, and NASA eased up the workload of future missions to prevent overtaxing the astronauts.

I cannot stress enough how difficult that Gemini 9A EVA situation was, and how hard Cernan pushed himself to get done what had to be done. I suggest reading the Wikipedia entry for the mission to get a flavor of it, and to let the word hero be fixed in your mind as you do.

Six years later, on Dec. 7, 1972, he commanded Apollo 17, and despite everything else he did to earn his mark in history, this will be forever why we remember him. You can read about its exploits in many places; I suggest you pick up a copy of my friend Andy Chaikin’s book A Man on the Moon, which, in my opinion, is the single best written history of the Apollo program. Cernan (along with co-author Don Davis) wrote about this as well in his book The Last Man on the Moon.

About that mission …

At 05:40 GMT on Dec. 14, 1972, a week after he left Earth and after completing three successful lunar EVAs with his fellow crew member Jack Schmitt, Cernan stood on the surface of the Moon, preparing to go back up the ladder and get back inside the Lunar Module. Just before he did, he said:

I'm on the surface; and, as I take man's last step from the surface, back home for some time to come—but we believe not too long into the future—I'd like to just (say) what I believe history will record: that America's challenge of today has forged man's destiny of tomorrow. And, as we leave the Moon at Taurus–Littrow, we leave as we came and, God willing, as we shall return, with peace and hope for all mankind. Godspeed the crew of Apollo 17.

He then climbed aboard the LM, and in that moment became the last human to stand on the Moon.

For now.

Cernan’s family released this statement upon his death:

Even at the age of 82, Gene was passionate about sharing his desire to see the continued human exploration of space and encouraged our nation's leaders and young people to not let him remain the last man to walk on the Moon.

Cernan himself did not wish himself to hold this place in history and pushed for NASA to go back to the Moon. All these years later we still haven’t, but that will not stand. China and India have both said they want to send people to the Moon, and Russia has made similar claims.

NASA has set its sights on Mars, but I still hope we go back to the Moon first, doing something similar to Gemini before Apollo: Use our more advanced technology to learn about how we can achieve human deep-space flight better, and most importantly, more sustainably. Apollo, as heroic and historic as it may have been, was, after all, a “flag and footprints” mission, designed to get there before the Soviets did. A race to the finish cannot be a long-term plan. We must commit to going back, and doing it to stay.

I remember the Apollo missions, barely. I was a child at the time. But I hope that within my lifetime I will see a wonderful thing: Another human stepping out of a lander and dropping down onto the surface, a puff of regolith dust arcing out ballistically from their boots in the airless environment.

And when this happens, we will update our references to Cmdr. Cernan, adding the words “… of the Apollo era” to his descriptor, “the last human to walk on the Moon.” At that moment he will become the last of the first, and, with our eyes open and our dedication firmly in place, there will never be another last.

Gene Cernan
Gene Cernan, 1934–2017.


*Correction, Jan. 17, 2017: I originally wrote that Cernan was the commander of Gemini 9A, but he was the pilot; Stafford was the commander.

Jan. 16 2017 8:45 AM

SpaceX Returns to Flight

Over the weekend—on Saturday—SpaceX launched a Falcon 9 into space, successfully completing its primary mission of deploying 10 Iridium communication satellites.

The secondary mission? To land the first stage booster on a drone ship in the Pacific. And that happened perfectly:


How cool is that? What happened is that after boosting the second stage toward orbit, the first stage flipped around, performed an engine burn to slow down, flipped again, deployed the steerable grid fins, then (after much shorter burns of the main engine and some help with cold jets for attitude control) landed smack dab in the center of the drone ship Just Read the Instructions (the barges are named after sentient ships in the science-fiction novels of Iain M. Banks).* This was the first successful landing of a booster in the Pacific Ocean; an earlier attempt in January 2016 came close, but one of the landing legs failed to lock, the booster fell over after the soft landing, and then exploded (and you want to click that link; the video is really something).

This mission was important, marking the return-to-flight status for SpaceX after an explosion during fueling of a Falcon 9 in September. SpaceX traced the cause of that to a liquid helium tank in the second stage.

As my colleague Eric Berger at Ars Technica writes, the helium tanks are mounted inside the liquid oxygen tanks; as the oxygen is used up during launch, helium is released to maintain pressure in the tank. However, the liner wrapping of the helium tanks under a carbon fiber coating appears to have buckled in the extreme cold environment, letting oxygen in between the coating and the tank itself. Liquid oxygen isn’t flammable, but when it contacted the much colder liquid helium tank, it froze and combusted, causing the explosion. To prevent this from happening again, they’re returning to their “flight proven configuration” of the tanks for now (an older setup with warmer helium), and in the future will change the fiber wrapping to prevent it from buckling.

Berger also has an interesting article about SpaceX’s finances; it lost quite a bit of money ($250+ million) in the 2015 accident where a rocket was lost on its way to the space station but still has ambitious plans for more than two dozen launches this year alone. That includes tests for the first crewed flight, and the first flight of the Falcon Heavy, its next-generation rocket that will be the most powerful rocket in the world … though Blue Origin has its goals of building some pretty big boosters as well.

This should be a pretty exciting year for space exploration. Let’s hope it all goes well. In the meantime, congratulations to SpaceX for getting the planet underneath them once again.

*Correction, Jan. 16, 2017: I originally had embedded the wrong video, it was from an earlier launch. Also, I said the carbon fiber wrapping had buckled, when it was the aluminum liner under the carbon fiber that buckled.

Jan. 13 2017 8:45 AM

Give Me Your Tired, Your Poor, Your Huddled High-Mass Stars …

Let me tell you something funny about that picture above.

Somewhere between 7,000 and 10,000 light-years away—estimates vary—lies the huge nebula NGC 3576. It’s very roughly 75 light-years across, making it one of the bigger star forming regions in the galaxy.

And that’s just the visible part of it. It appears to be part of a larger complex of dark, dense gas as well, which is pretty typical of such objects. But the part we do see is impressive enough: It has 10,000 times the mass of the Sun just in hot gas, and glows at a fierce 10 million times the brightness of the Sun as well. Many hundreds of stars are in the process of being born there, making it a fairly fecund stellar nursery.

Jan. 12 2017 8:45 AM

The Clouds of Andromeda

The image above is as baffling as it is gorgeous.

First, kudos go to my pal Rogelio Bernal Andreo, who took this magnificent shot. It shows the Andromeda galaxy, the closest big spiral galaxy to our own, and in fact the other big member of our neighborhood galaxy minicluster called the Local Group. At 2.5 million light-years away, it’s bright enough to see with the naked eye from moderately dark sites and shows quite a bit of detail even through small telescopes.


Rogelio’s image is unusual. First of all, it shows a huge area of the sky; Andromeda is several times the apparent size of the full Moon in the sky (see here for a comparison). Hold up your hand, and fold in your pinky and thumb; the width and length of your three middle fingers extended at arm’s length would be about the same area of sky as the photo.

The image is a composite of “natural” color imaging using red, green, and blue filters to mimic what we’d see with our eyes, together with a “luminance” or white-light image, taken with no filter. That adds detail and depth to the image; together astrophotographers call it an LRGB image.

But there’s more. He also took many hours worth of observations using a filter that lets through a very specific wavelength, or color, of light. This red light, called Hα (literally, “H alpha”) is emitted by warm hydrogen gas. Since hydrogen is so common throughout the Universe, an Hα filter is very useful; you can use it to accentuate nebulae and galaxies.

The red clouds in the image are hydrogen nebulae. They’re extremely faint; Rogelio had to work very hard to make them visible above the background light of the sky. In the photo their brightness has been magnified by a substantial amount, so the image isn’t “natural” in that sense; if Andromeda had been scaled on the same brightness range as the clouds, the galaxy would be vastly overexposed, a huge white blob blotting out everything around it.

So the image isn’t really what your eyes would see through a telescope but has been adjusted to show these two very different views simultaneously. Still, it’s beautiful for sure … and very odd.

The big question is, what are those clouds?

On his website (and in a follow-up on his Facebook page), Rogelio describes his observations, their history, and his research into the glowing clouds. He points out he loves chasing faint, diffuse clouds. Called galactic cirrus (or the fancier Integrated Flux Nebulae), these are generally very thin streamers of dust—grains of silicates or long carbon molecules—strewn throughout space inside our galaxy. They’re exceedingly faint, and difficult to image. But if the dust is warm, it can glow in infrared. So Rogelio checked professional observatory infrared images of that area in the sky, but the clouds seen in them don’t fit well to what he observed. That seems to rule out galactic cirrus.

However, he did see them, barely, in a pair of surveys that mapped the sky in Hα. He shows this on his page, and looking at them I’m confident these clouds are real, and consist of glowing hydrogen.

Rogelio also argues, and I agree, that the clouds aren’t physically associated with the Andromeda galaxy. At that distance those clouds would have to be huge, tens of thousands of light-years across, far too large to make any sense. We do see clouds of gas this big in the Universe, but generally speaking they don’t display the structure in the image. For example, that one above the galaxy near the top center shows a long, flat, bright edge. Features like that are common in smaller gas clouds a few light-years in size. You get them when an expanding (or rapidly moving) gas cloud hits material outside it. The gas piles up, forms a sharp edge, and gets denser and brighter. But something like that would be highly unusual, to say the very least, in a cloud of galactic size.

So clearly these are gas clouds inside our own Milky Way, and we’re looking through and past them to the much more distant Andromeda galaxy. But that’s still odd. Nebulae like that are usually heated up and lit by nearby massive stars. The stars emit ultraviolet light, which pumps energy into the gas, and it responds by glowing like a neon sign (literally). But I don’t see any stars close by that could do that.

So why are they glowing?

Given the lack of nearby luminous stars, my first guess was that they are colliding with lower density gas around them. That would explain the one cloud with the sharp edge, but the others are even more diffuse, so I’m not sure that explanation works for them.

I have another idea. Perhaps there’s enough ambient ultraviolet light from massive stars spread out in space that, combined, they can cause these clouds to softly glow. This would be a sort of background UV light, very faint, but enough to trigger the nebulae into emitting Hα light. While that’s a guess, it seems plausible … and I don’t see anything else that makes much sense.

Let me say here that I love this. Andromeda is one of the best studied objects in the entire sky, yet here are objects in the same field of view that have essentially escaped notice all this time. That’s understandable; Andromeda is so bright that faint clouds are ridiculously hard to see, but our technology and techniques are getting so good that the previously hidden is becoming revealed. And on top of that, it also took the dedication of someone like Rogelio to pursue this.

The next step, I should think, is to find a research astronomer who can take an interest in this and get even deeper images and take spectra of these clouds (to determine their chemical composition as well as motion, which can help nail down their distance). There are lots of fascinating questions to answer here. How common are these clouds? How old are they—are they recently cast off by dying stars, or primordial, dating back to when the galaxy was young? Are they everywhere in the sky, or do they tend to be clumped near the galactic plane? And to me, the most interesting question of all: What’s lighting them up?

They’re certainly lighting me up. I hope we can find out more about these elusive beasts soon.

Jan. 11 2017 10:53 AM

Talk Nerdy: Anti-Science, Trump, and Why I Hope Science Will Help Save the World

Funny how things work out.

I had already drafted an article about an interview I did over the weekend with my friend Cara Santa Maria for her Talk Nerdy podcast. We spent a lot of time talking about critical thinking, science, and Donald Trump.


And then, as I was editing that article, a whole passel of revelations came out about Trump. By now you’ve probably heard about the intelligence reports reporting ties between Russia and Trump's campaign to manipulate the presidential election.

Almost lost in all the noise over that was that Trump had a meeting with Robert F. Kennedy Jr., purportedly asking him to be on a panel on the safety of vaccines. I have written about RFK Jr.’s crackpot anti-vaccine stance many times (see, in order, this article, then the follow-up, and then a third one). His views are wrong, anti-scientific, and downright dangerous.

All of which makes this interview all that much more timely and, if I may say so, important. Please give it a listen.

Cara had me on her podcast back in 2015, and asked me to be on again because she happened to see my name in the credits of the movie Arrival, and wanted to know what my involvement was (spoiler: I made some minor comments on the script before it was finalized). The first half of the podcast is about that as well as the influence of science in movies and TV.

But then we spent quite a bit of time talking about Trump and his predilection for anti-science. As an easy example, his incoming Vice President Mike Pence and Cabinet picks Rick Perry and Ben Carson are all young-Earth creationists. Trump’s nominees are all basically the worst people a rational person would pick for those positions.

And while you might argue that someone being a creationist doesn’t disqualify them from being secretary of energy, for example, it does show Trump’s egregious propensity to actively seek out people who deny science for positions of power. The meeting with RFK Jr. just confirms that.

So. The big question is, is there hope?

Yes, I think there is. And it may come from an unlikely direction.

Cara ends every podcast asking her guest two questions: What is your biggest fear for the future, and what is your biggest hope?

My answer this time was similar to the last time I was on her show: climate change and science, respectively. But I generalized it a bit this time.

Certainly climate change on its own is terrifying; I’ve written many times how it’s the single greatest threat we as a species face right now, and how denying it is a threat to our national security. But it’s more than that. The denial of human-induced climate change is just one symptom of the much larger suppression and active antagonism toward science, especially with the incoming Trump administration.

Yet I still have hope. Why? Because there are tens of millions, hundreds of millions, of Americans who are still reality-based. The majority of us understand that climate change is human-caused and a real threat. That means science can still prevail over politics and personal ideology.

In his farewell speech Tuesday night, President Obama said this:

Politics is a battle of ideas; in the course of a healthy debate, we’ll prioritize different goals, and the different means of reaching them. But without some common baseline of facts; without a willingness to admit new information, and concede that your opponent is making a fair point, and that science and reason matter, we’ll keep talking past each other, making common ground and compromise impossible.

Science is a critical piece of that common ground. We need people to be more comfortable with science, which means exposing more of them to it. Even more importantly they need to understand scientific thinking: being critical of sources, data, and conclusions; questioning the process all along the way; and looking for personal biases that might lead to incorrect conclusions.

And that’s why I answered Cara’s last question the way I did. One way to get people to see science is to get it into all aspects of modern culture. Two of the biggest influences on society are TV and movies, and that’s why I’m so happy to see science and scientists being portrayed better in those media. It may seem fatuous, but I contend that it’s an excellent place to start. Like it or not, people, especially younger ones, consume a lot of entertainment. If we show them stories where scientists are just like them, where science is important, where it’s fun, where it can help, where it can save us all, then we still have a chance here.

We have a long, long way to go, and the next two to four years will be trying indeed. But we can do this. Make your voice heard, and make it a voice for science. As long as there are people who would tear down the fabric of reality, there will be those of us who will give their all to defend it.

Jan. 10 2017 8:45 AM

My God. It’s Full of Black Holes.

The image above doesn’t look like much at a glance, does it?

Look again. What you’re seeing are thousands of black holes. Thousands.


That image is a part of the Chandra Deep Field South, the result of a series of very long exposures of one small section of the sky using the space-based Chandra X-Ray Observatory. Astronomers combined images taken over the 18-year period from 1999 to 2016, creating a stacked image that’s the equivalent of a single 7,016,500 second exposure. That’s more than 81 days.

So yeah, it’s a deep image. The entire Deep Field image covers roughly the area of the full Moon on the sky using multiple pointings of the telescope. The center of the field has the most observations and is therefore the most sensitive; the image above shows that inner portion of it.

Everything you see in that image is a source of high-energy X-rays—a form of light like the kind we see but with far, far higher energy. Each dot represents the X-rays from an entire galaxy, some more than 12 billion light-years away! The light we see from those most distant galaxies left them when the Universe itself was only a little more than 1 billion years old.

Only very powerful astronomical objects can generate strong X-ray emission, and the X-rays from the galaxies in the Deep Field are coming from one or both of two very luminous sources: high-mass X-ray binary stars and supermassive black holes.

high mass X-ray binary art
Artist depiction of a high-mass star losing material to a companion black hole.


The binaries are pretty cool. Many very massive stars are born in pairs, which orbit each other. After a short time, one of them can explode as a supernova, and its core collapses to become an ultra-compact neutron star or a black hole. This compact object can feed off material from the “normal” star; as that stuff falls down into the tiny companion’s ferocious gravity, it can heat up to millions of degrees and emit X-rays.

One important part is that these binary systems are young. These stars are so massive they use up their nuclear fuel in the blink of a cosmic eye, perhaps a few million years. That’s critical, because these stars are born in gigantic gas clouds that form lots of stars. By adding up all the X-ray emission we see from high-mass binaries, we can calculate how many there are in a galaxy, and from that extrapolate how many stars are being born in total. That tells us a lot about the conditions in galaxies, and in really distant galaxies we can then see what they were like when they were very young.

Our galaxy was very young once, but we only see it now, after it’s more than 10 billion years old. By looking at distant galaxies we can better understand how our own was formed.

But that’s only half the story. In the center of every big galaxy today we think there lurks a supermassive black hole, a beast with millions or even billions of times the mass of the Sun. That’s still small compared with the host galaxy (the Milky Way has a mass of hundreds of billions of times the Sun), but that supermassive black hole is important. We’ve found that the mass of the central supermassive black hole in the galaxy is correlated with galactic characteristics like the total mass, luminosity (how much energy it emits), and rotation. These are hard to measure directly in distant galaxies, so by looking at their central black holes we can learn more about the galaxies themselves.

The Milky Way’s black hole isn’t currently feeding, so it’s relatively quiet. But in other galaxies the black holes are eating, and when they do that, matter piles up in a disk and can reach temperatures of millions of degrees due to friction and other forces. That’s hot enough to blast out X-rays, which is why we can see them in the Chandra image.

black hole
Artwork: A disk of material around a black hole heats up and emits X-rays, as well as a beam of energy due to twisted magnetic fields.


That’s why this deep observation is so important! By examining the X-rays from each source we learn a lot about the galaxy that emits them, far more than simply how much X-ray light they’re blasting out.

Remarkably, astronomers were able to see X-rays from galaxies more than 12.5 billion light-years away, the farthest ever reliably detected. Also, they did not see X-rays from galaxies even a bit farther than that (about 12.6 billion light-years), suggesting either those sources are too faint, or that it was around that time (1.2 billion years after the birth of the Universe) that these sources started turning on, or that they are so obscured by dust in the host galaxy we can’t see them.

The scientists estimate that roughly 70 percent of the objects in that image are supermassive black holes, and in the whole image there are about 5,000 sources. Imagine: Thousands of black holes in just that one tiny part of the sky! Extrapolating to the whole sky, astronomers estimate there must be more than 1 billion supermassive black holes out in the deep Universe that Chandra could see. A billion.

That’s a lot of black holes. And it’s actually only a tiny percentage of what’s out there; there are hundreds of billions or even trillions of galaxies in the Universe. Each may have its own central black hole, but we just don’t see them (because they’re quiet, or feeding but still too faint to see at large distances).

And that’s just the supermassive black holes. Ones with lower mass, formed when stars explode, probably number in the many millions per galaxy. Extrapolating that means there are quadrillions of black holes in the visible Universe. More.

Holy cow. The good news is they’re far away, and don’t pose any sort of threat to us. And in reality, instead of being scared, you should be thankful: Galaxies and black holes form together, so the Milky Way being here the way it is today is due to its central supermassive black hole. And massive stars exploding seed the Universe with heavy elements like iron, calcium, and other ingredients necessary for life to form. They may leave behind a black hole after the supernova, but they also made it possible for us to be here at all.

It’s a weird Universe indeed where we owe our existence to these cosmic devourers. But, literally, that’s where we are. And that’s why I love this Chandra image and research so much. It tells us so much about ourselves and how we came to be.

Jan. 9 2017 8:45 AM

A Distant View of Home

When I saw the image above, the hair on the back of my neck stood up. Recognize them? Those are the Earth and Moon, as seen from Mars.

That image was taken by the phenomenal HiRISE camera on board the Mars Reconnaissance Orbiter, which was more than 200 million kilometers from Earth at the time. It’s actually a composite of a few separate images, processed to show the relative size and position of our planet and its moon.


HiRISE normally points down to take amazing images of the surface of Mars; it can resolve objects less than a meter across! But it sometimes is pointed at Earth to take calibration images; Earth has known characteristics like color and reflectance that make it a nice test subject for the camera. The image above is composed of ones taken in near-infrared, red, and blue/green, and that’s displayed as red, green, and blue here. Vegetation is highly reflective in near IR, so continents look red; Australia is in the center and Southeast Asia to the upper left. Antarctica is the bright white patch to the lower left.

Also, the contrast has been changed; the Earth is on average more than three times as reflective as the Moon. At the contrast scale Earth is displayed at, the Moon would be almost black, so the brightness of the Moon image has been increased. In this image, you can clearly see features on the Moon, the darker basaltic scars from ancient giant impacts.

Mars and Earth posiitons
The physical locations of Mars, Earth, and the Sun when the image was taken: From Mars, Earth appeared half-lit.

Sky Safari planetarium app

This image was taken on Nov. 20, 2016. At the time, the Earth, Sun, and Mars made an isosceles triangle, with Mars at the narrow angle. From Mars, Earth appeared half-lit, at “first quarter,” if you will. From Earth, the Moon was at third quarter, half lit by the Sun and approaching its new phase. That puts the Moon on the far side of Earth as seen from Mars, about 300,000 kilometers farther away. But that’s a drop in the 200 million kilometer bucket, so for all intents and purposes they’re at the same distance. This means the scale of this is right; the Moon is ¼ the size of Earth.

It’s amazing to think that’s home, that we can see our planet and its attendant satellite from so far away. We’ve seen it from farther, of course, including the famous Voyager 1 Pale Blue Dot image (the Moon is invisible in that one), and others taken by the Cassini spacecraft orbiting Saturn and MESSENGER at Mercury (though that last one, I think, was from closer). But in this case, it’s the tantalizing detail that makes it so eerie; there’s just enough there to remind us of home, but not quite enough to make it easy.

Would you have known that was Australia without it having been pointed out? I’m not sure I would have.

It makes me think that there will come a day, perhaps not too long in the future, when we will have an image like this, but it won’t be of the Earth and Moon, or any planet in our solar system. It’ll be an exoplanet, an alien world orbiting an alien star. When that happens, will we see fuzzy continents, pixelated oceans, or a blobby moon?

Jan. 6 2017 8:45 AM

That’s No Ordinary Taco. It’s a SPACE Taco.

People ask me a lot of questions. One of the most common, understandably, is, “Would you like to go to space?”

My answer is always the same: “I’d like to be in space, but I don’t want to go to space.” The difference being the idea of strapping myself into a chair on top of a 50-meter-high stack of explosives isn’t my idea of fun.


But my answer is a bit of a cheat anyway. Honestly, I don’t even want to be in space. I’d love to soar over Saturn’s rings, orbit low over an asteroid, or dive the cliffs of Miranda … but to do so I’d have to be in free fall, and that—to say the least—doesn’t appeal to me. I have a pretty weak stomach, and I know that being in microgravity* would probably mean me throwing up everything I ever ate ever.

I wish it weren’t true. Weightlessness looks like an awful lot of fun, and it makes everything more interesting. Sleeping, working, everything is different when you’re in free fall.

This was driven home to me when I saw this video put out by the European Space Agency. It came out last year, but I missed it then; happily it’s making the rounds in Facebook again so I stumbled on it. It features one of my favorite astronauts, the Italian spacefarer Sam Cristoforetti, in the International Space Station doing something most of us would take for granted: making a taco.

It’s way different when you’re making … a SPACE TACO.

That’s so cool! I found it fascinating how, no matter how carefully she places the in-progress taco in front of her to float, it always drifts away. Part of that is due to air currents inside the station, but I suspect some of it is that it’s almost impossible to impart zero momentum to it; no matter how carefully you place it, you’ll always bump it or give it a tiny force, and that will make it move away.

She’s pretty good about capturing runaway food bits, too; catching what looks like a bean at 1:22, though she misses one that escapes a couple of seconds later. I hope she cleaned that up before it caused any problems (which should be fine as long as it isn’t ruffled).

My wife is an excellent cook, and one of my favorite meals she makes is fajitas from scratch. It’s always tempting to put too much filling in them because it’s all so good, but that leads to it plopping out the back end when you bite into it (we have a house rule that when that happens, the other person is within rights to yell out, “Rookie error!”). So I was cringing a bit as Cristoforetti made her taco, thinking it might eject glop into the station when she bit into it. It helped that she folded it in half, and also that she didn’t overstuff it, but still it made me think more about this. In space, the filling could stick farther out the back end of the taco without falling off because there’s no force pulling it down, overcoming its own internal cohesion.

While it does lead to fun physics thought experiments, eating in space is weird. But I guess I’ll never know first hand. Still, I—and my tummy—are OK with that.

* Sometimes you’ll hear people say there’s no gravity in space, but that’s not true; the Earth’s gravity on the astronauts in low Earth orbit is about 90 percent the strength we feel on Earth. But they’re moving around the Earth, moving sideways at the same rate they fall toward the Earth, so they fall continuously without ever hitting. That’s why I prefer the term free fall. Microgravity works too because there are still very small forces due to tides and other circumstances, and they really are roughly a millionth as strong as Earth’s gravity. Zero gravity is usually a close enough description, if a wee bit imprecise. I discuss all this in my episode of Crash Course Astronomy on gravity:

Jan. 5 2017 8:45 AM

New Study Confirms Sea Surface Temperatures Are Warming Faster Than Previously Thought

In 2015, scientists from the National Oceanographic and Atmospheric Administration published a paper that angered a lot of climate science deniers.* In it, the researchers found that some historic measurements of sea surface temperatures were off by a bit and needed to be corrected. Sounds innocuous enough, doesn’t it?

The thing is, when the researchers applied the correction, the so-called global warming pause disappeared. Poof. Gone.


For deniers, this was a red-alert situation. The slowdown in global warming was their go-to cry, their hammer they could wield to claim climate scientists were wrong about warming. If the proposed corrections were real, they lose a big weapon.

Fast-forward to Wednesday: A new paper published by a different group of researchers studies the same problem in a different way. What they found confirms the suppositions in the earlier paper: Some ocean temperature measurements were indeed off by a bit, and when corrected, show that the hiatus in warming never existed. In fact, the planet has been warming pretty consistently right through the latter half of the 20th century to today.

Deniers will not be happy about this.

The earlier 2015 paper, titled “Possible Artifacts of Data Biases in the Recent Global Surface Warming Hiatus,” discussed the methods used to measure planetary temperatures, including sea surface temperatures. They found that some older measurements were likely slightly off due to the way they were gathered.

In a nutshell, the problem is that sea surface temperatures are measured in numerous ways. Historically, a big method is to directly sample ocean water using ships. This is problematic, though, because different ships use different methods, and sample water from different depths. Worse, it’s common to measure the water scooped up by intakes that feed it to the engine room to cool the engines. Ships tend to be warmer than the surrounding ocean, of course, so the measurements done this way are biased to be too warm. The ocean water is actually about 0.1°C cooler than what’s measured.

Not only that, but only some ships bring the water in through the engine room. Others throw a bucket over the side and scoop up water. So you have to be careful and adjust for the difference.

When the researchers applied a correction to the data to account for the measurement offset, they found that the rate at which the ocean surfaces were warming was faster than previously determined. When this was combined with data from land and air temperatures, it showed the whole planet was warming faster, too (oceans cover more than 70 percent of the Earth’s surface, and so strongly affect the overall measured temperature).

sea surface temperatures
Three datasets showing sea surface temperatures: The old NOAA data (blue), U.K. Hadley Centre data (purple), and the new NOAA data (red). Independent measurements using buoys, floats, and satellites show that the new NOAA dataset is the most accurate. It also shows the most warming.

Hausfather et al.

While it had previously looked like global warming had slowed, this correction shows it hasn’t; when they compared the rate of warming to that in the past few decades, they found it was equal; the warming was occurring at the same rate it had since the second half of the 20th century.

This is the part that, politically, hit like a bomb. For many years, deniers have been claiming that global warming has stopped, or at least drastically slowed, since 1998. This supposed plateau in temperature has been used to make a lot of hay by the anti-science brigade, from fossil fuel–funded “think tanks” to fossil fuel–funded politicians.

Given that denial is practically a party plank of the GOP, this caused quite a stir.  In reaction to the release of the research showing the pause never happened, Rep. Lamar Smith, R-Texas, chairman of the House Committee on Science, Space, and Technology, attacked the NOAA. He started a fishing expedition to try to impede any research it did on climate change, including issuing subpoenas for all emails and data from NOAA scientists, and went as far as accusing scientists of “altering” their data, when really what they were doing was calibrating them, making their data more accurate.

Smith’s McCarthy-esque political shenanigans are ongoing and will no doubt continue. He has shown no signs of abating. And moreover, he’s dead wrong about all this.

The new paper just published will no doubt enflame him. In it, a group of scientists investigated the claims of the earlier paper. They compared the various methods of measuring sea surface temperatures as a way to independently check the historical record. What they found is that the supposition of the first paper was correct: Some measurements were a bit off, and when a correction is applied, the global warming slowdown disappears.

Zeke Hausfather, the lead researcher, made a short video explaining what they did:

In the new paper, the researchers looked at newer ways to measure water temperature, including buoys that actually sit in the water, robotic ocean probes called Argo floats, and satellite data. These provide far more accurate data and provide a nice, homogeneous sample.

Isolating these methods and using them to compare to the older data, they found the same bias as found in the earlier paper, confirming them. And when they correct for them, again they find the oceans are warming steadily. The “hiatus” was never real. That’s why I tend to call it the “faux pause.”

This is a very big deal. Remember, Rep. Smith is accusing NOAA scientists of falsifying data! That is just about the highest crime you can accuse a scientist of doing.

And in fact, the opposite is true: These scientists are trying their damnedest to make sure their work is as accurate as humanly possible. They have devoted their lives to this field of study, and they are critically aware of how important this work is, and what its implications are.

Global warming is one of if not the biggest existential threats to humanity. These new results show that—once again—the overwhelming consensus of climate scientists is right. The planet is heating up. And we also know why: It’s our fault. We burn fossil fuels, adding carbon dioxide to the air, trapping warmth, and heating things up. This is having profound effects on our environment, effects we already see.

Despite this, I expect to hear more denial from Congress, from the incoming president, and from state governments as well. This denial will have a profound effect as well. It’s more than just the appallingly shuttering parts of NASA and the attacks on the NOAA. It means years more of inaction toward fixing the problem, and many years more of actively exacerbating it.

There is still hope, though. You can take action. It helps; as we just saw with Congress backing down (for now at least) its gutting of the Office of Congressional Ethics, phone calls work. Make your voice heard.

*Correction, Jan. 5, 2017: This post originally misidentified the National Oceanic and Atmospheric Administration as the National Oceanographic and Atmospheric Administration.

Jan. 4 2017 8:45 AM

The Snows of … Hawaii?

I’ve been fortunate enough to visit the big island of Hawaii a few times; it’s a fantastically beautiful place and an amazing science destination. There’s a seahorse farm, astronomical observatories, volcanoes, and an eclectic selection of environments, from forbidding lava flows to dry forests to lush tropics.

The edges of the island are at sea level (duh), but the highest point, the peak of Mauna Kea, stretches to 4,200 meters (2.6 miles) above. That brings a lot change in temperature, as you might expect. I watched the sun set from Mauna Kea while I shivered even when wearing a parka; I had gotten used to 35° C humid days.

Still, perhaps the last thing you might expect to see in Hawaii is snow.