The entire universe in blog form

Sept. 4 2014 7:30 AM

Our Place in the Universe: Welcome to Laniakea

When I was a kid, playing with my fellow nerdlings, we used to try to come up with the most specific address we could for ourselves—including the whole Universe. It would go something like this: “Phil Plait, 123 Main St., Springfield, Virginia, United States of America, Earth, Solar System, Orion Spiral Arm, Milky Way Galaxy, Local Group, Virgo Supercluster, Universe.”

It looks like we can now add another locality, squeezed in between the last two: Laniakea (la-NEE-uh-KAY-uh I think is pretty close to how you pronounce it), a galactic supercluster. The folks involved put together a video explaining it, which may help before I launch into my own discussion of it:

(A second video with a slightly different take is on

So, let me back up a sec. The address locations I mention above are obvious enough up to the solar system. The Sun is located in what’s called the Orion arm in our spiral-armed Milky Way galaxy, which itself is part of a collection of a few dozen galaxies called the Local Group (we’re the biggest, along with the Andromeda galaxy). This ragtag group is on the outskirts of much bigger cluster of galaxies, called the Virgo Cluster, which has more than 1,000 galaxies in it and is several million light years across.

That in turn is part of an even more ridiculously huge structure called the Virgo Supercluster, which contains several clusters (including, perhaps confusingly, the Virgo Cluster; these get their names from their locations in the sky). Superclusters are among the largest scale structure in the Universe, spanning over a hundred million light years.

Mapping our local supercluster is rather difficult. First, it doesn’t really have a defined edge like a solid planet; it just kinda fades out with distance, until the next supercluster comes along. Also, you need to get the three dimensional location of the galaxies around us, which also presents difficulties.


However, work done by a team led by astronomer Brent Tully has done just that. The team used radio telescopes to observe thousands of galaxies in the local Universe. As the Universe itself expands, it carries these galaxies away from us, and their radio waves (as well as all light they emit) loses energy—this is very similar to the more familiar Doppler shift. Astronomers call this loss of energy “redshift,” and the farther away a galaxy is, the higher the redshift is.

But if galaxies are clumped together closely in space they’ll orbit each other, or at least their mutual gravity will affect their motion. This in turn affects the redshift for each galaxy on top of the cosmic expansion. We know pretty well how the Universe is expanding on local scales, so if you subtract that part away, what’s left is the local motion of the galaxies. That can be used to map how gravity of other nearby galaxies is affecting them. This let them make a map of the density and movement of galaxies in space.

That, finally, means they could map where all these galaxies are in the Universe. They found that the Virgo Supercluster, our old home, is actually part of a bigger structure they named Laniakea, which apparently is Hawaiian for “immense heaven.” No arguments here!* Laniakea is about 500 million light years across, a staggering size, and contains the mass of 100 quadrillion Suns—100 million billion times the mass of our star. That’s a lot of mass.

Laniakea border
Your local supercluster. Each white dot is a galaxy; red regions have lots of galaxies, dark blue regions are voids with few. The white lines represent flow streams, along which galaxies are moving toward the center of mass of Laniakea. The blue dot to the right is our location, near the edge of the supercluster.

Illustration by SDvision interactive visualization software by DP at CEA/Saclay, France.

The border of Laniakea isn’t well-defined, but the astronomers decided how to get a sense of it: its gravity. Put a galaxy near Laniakea; if it falls toward the supercluster then it’s inside the border; if it falls away toward some other supercluster than it’s outside. As definitions go it’s not so bad. It’s not the be-all-end-all; as another astronomer points out in the Nature news article, it doesn’t tell you what the eventual fate of the supercluster is (which depends on its mass and size). Like most definitions, it depends on the question you’re trying to answer. In this case, it’s more of a guideline than a definition, and I’m OK with that.

Astronomy is both ennobling and humbling. It tells us our place in the Universe, which can make you feel small … but don’t forget that we’re a part of that Universe, and the fact that we can figure this stuff out at all makes us very big indeed.

*I’ve also seen it translated as “immeasurable heaven” which means more or less the same thing colloquially, but also has an ironic ring to it, given that measuring it is exactly what we’re doing.

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Sept. 3 2014 3:18 PM

Sunrise on a Blue Planet

Sometimes, you just need to be reminded that our planet is a beautiful place to be.

Earth from space.
Dawn, over the one planet we call home, seen from the International Space Station.

Photo by NASA

Or, a beautiful place to be above. Imagine seeing more than a dozen of these views every day ...

Sept. 3 2014 9:45 AM

Refacing the Face on Mars

I got a good chuckle out of a video Slate just posted over on the video section of the site*: a deconstruction of the “Face” on Mars.

Heh. I hadn’t thought about the Face in some time; it’s been a while since anyone’s really talked about it. Despite being one of the silliest examples of pseudoscience in history, a few years ago it was Big News; I even had a popular public talk I gave lambasting it. Mostly the idea was promoted by Richard Hoagland, about whom I’ve pretty much said everything there needs to be said.

angry slippers
You'd be yelling too if someone stuck their stinky feet into you every day.

Photo by Phil Plait

As the video lays out, the picture of the Face was first taken by the Viking 1 spacecraft in the 1970s, and it really does look like a face … just like low-resolution images of just about anything resemble faces. Even some hi-res ones.

But then better space probes were sent to the Red Planet, better images were taken at higher magnification and different lighting angles, and the Face disappeared in a puff of logic.

For a while you’d still get a glimpse of it in magazines and newspapers, and I’d get the odd invite to give my public talk. Eventually, though, that went away.

It’s the fate of most pseudoscience, actually, to fade away as tastes change (or if the promulgators dumbly put an expiration date on their nonsense [cough cough 2012 Maya apocalypse cough]). You’d think that might mean eventually debunkers go out of business as well.

Mars face

Photo by NASA/JPL/University of Arizona

Oh, you naive thing, you. A debunker’s work will never end, because there will never be an end of bunk to debunk! Ignoring big mainstream stuff like creationism, global warming denial, and anti-vaxxers, there will still always be nonsense like UFOs, astrology, ghost hunters, life in meteorites, and so on. A lot of the time it’s just silly, but sometimes—far too often—people die because of belief in nonsense. They really do.

It’s OK to chuckle over stuff like the Face on Mars. But remember, it’s not always so benign. And even believing in minor silliness means you’re giving up a precious bit of reality. There’s a vast, amazing, real Universe around you in every direction. Take a look at it! You’ll have enough wonder to last a thousand lifetimes.

*You did know Slate has a video section, right? Lots of really good stuff there.

Sept. 3 2014 7:30 AM


Have you had your “holy wow!” moment for the day? No? Then let me help you. Presenting the Andromeda galaxy. And oh boy, is it a presentation!

Sept. 2 2014 11:30 AM

New Observations Confirm Greenland, Antarctica Losing Land Ice Rapidly

A new study just published shows that—using more accurate measurements than ever before—Greenland and Antarctica are together losing ice at incredible rates: Together, over 500 (±107) cubic kilometers of ice are melting from them every year.

That means 450 billion tons of ice are lost every year, melted away into the oceans. That’s staggering.

Tim Radford at the Guardian has the story. In a nutshell, the European CryoSat-2 satellite measures the height of the ice over the two land masses. As they lose ice, the height drops, and that change is seen by the satellite.

This loss is of course due to global warming; we’ve known for some time that land masses at both poles are melting away their ice, but these new measurements confirm the bad news, and give more accurate numbers. They also found that West Antarctica—the focus of much concern lately—is losing ice three times faster now than it was in the time period from 2003–2009. That’s astonishing. Note that they did find a mild increase in ice in eastern Antarctica, which was known before as well, but it’s not nearly enough to compensate for the huge losses elsewhere (in other words, beware of The Usual Suspects trying to use this to say land ice is increasing).

I can’t help but mention that I saw this news literally the day after an atrocious Mail Online article also reported on satellite imagery of the North Pole but then grossly misinterpreted it to make the claim that Arctic sea ice is recovering from the record loss in 2012. As I pointed out yesterday, that claim is just so much fertilizer. The contrast between the Mail reporting and that of the Guardian can’t be more different. The latter is trustworthy, the former … less so.

Be careful where you get your news about anything, of course, and especially when it’s about scientific issues that have become political ones. It seems that a lot of venues out there are going to great lengths to keep people in the dark about global warming. I will do what I can to shine a light on them.

Tip o’ the snow plow to Dana Nuccitelli.

Sept. 2 2014 7:30 AM

Mystery No More: The Sliding Stones of Death Valley

Oh how I love nature and science! The former sets up mysteries that baffle us, and then the latter equips us with tools with which to solve them.

When I was a kid, one of the coolest mysteries going was the moving stones of Racetrack Playa. This is a dry lake bed in Death Valley, California, where large rocks are embedded in the dried mud. However, many of the rocks have clearly been moving; there are long tracks behind them in the caked, baked mud pushed up like rails along the tracks’ sides.

What could be moving these stones? No one knew. They would sit for years, then suddenly be found to have moved many meters. Could wind push them? Maybe ice formed after rain, forming rafts that floated the rocks up. Speculation abounded, and I remember watching TV shows about the rocks, and reading about them in sketchy “Mysteries of the Paranormal” type books when I was a wee lad.

Now, however, this enduring mystery has been solved. And I mean, solved. Like, we know what’s causing this. A team of scientists and engineers were able to capture the motion on camera, finally revealing the mechanism behind this bizarre behavior.

It was wind. And rain, and ice. But not quite the way it was thought before. Here’s a video describing it, from one of the scientists, Scripps paleo-oceanographer Richard Norris:

In a nutshell, the playa is very dry, getting only a few centimeters of rain per year. In the winter, when it does rain, the slightly tilted playa gets accumulations of water a few centimeters thick at one end. It gets cold enough for the water to freeze on top. When the Sun comes out, the ice begins to melt, forming large chunks called rafts. The wind blows these rafts (which are typically a few millimeters thick), which then hit the rocks and push on them. The ground is softened by the water, so the rocks can move more easily ... and then they do.

The team set up a weather station, time-lapse cameras, and 15 rocks with GPS units embedded in them. With this equipment, they were able to capture and record the motion. The rocks move at slow speeds, perhaps a few meters per minute, but that was enough to get caught on camera. Here’s one (indicated by the red arrow; in the background are two stationary rocks indicated by blue arrows) in action:

rock moving
The movement of one of the Racetrack Playa rocks over the course of about 14 seconds. The lighter rippled material is open water; the darker smooth patches are ice.

This also explains why sometimes several rocks show not only parallel trails, but also apparent simultaneous changes in direction; the sheets of ice were blown by the wind, and when the wind blew from a different direction, the ice sheets responded.

Wind alone couldn’t do it, and the ice wasn’t acting as a buoyancy agent, either. It was basically sheer muscle power, surprisingly, given how fragile you might think that ice was. I think that’s one of the reasons no one seriously considered this as an explanation before.

multiple rocks
Tracks left by multiple rock are parallel, apparently making the same angled turns at the same time.

I love this. It makes me ridiculously happy to see this. There’s so much wonderfulness to it! A mystery that’s lasted for decades, no explanations that ever seemed to completely work, then a devoted and dedicated effort was mounted … as had previous ones, but this one got a big stroke of luck, catching this movement on several occasions when the events might not happen for a decade at a time.

At this point I have to disagree with my friend Zach Weiner, who put together a compilation of his Saturday Morning Breakfast Cereal comics into a book called Science: Ruining Everything Since 1543.

Science! It doesn’t ruin anything.* It reveals the amazing, subtle, wondrous, and simply cool mechanisms that make the natural world what it is: endlessly fun.

*At least, nothing that doesn’t deserve to be ruined. Also: I’m in that book, and you should buy multiple copies, because in the end I still think Zach’s the bee’s knees.

Sept. 1 2014 7:30 AM

No, You Can’t Claim Arctic Ice Is “Recovering”

Sigh. Here we go again.

The Daily Mail and Mail Online are to scientific accuracy what a sledgehammer is to an egg. Especially when it comes to global warming.

David Rose is oftentimes the wielder of that sledgehammer. He’s written error-laden climate articles in the past, like saying that global warming has stopped (no, it hasn’t), that the world is cooling (no, it really really isn’t), and that the Intergovernmental Panel on Climate Change had to hold a crisis meeting because Rose’s articles have caused such a fuss (that meeting never happened, which Rose had been told several times, but he still made the claim). Other examples abound.

This time, in Sunday’s Mail Online he writes that Arctic sea ice, which hit a major record low in 2012, “has expanded for the second year in succession.”

This claim is a humdinger, and typical denial double-speak. It’s technically true, but also really wrong. It’s like examining someone who has a 106° fever and saying it’s really made their skin glow. But what do you expect from an article that has this breathless headline:

Myth of arctic meltdown: Stunning satellite images show summer ice cap is thicker and covers 1.7million square kilometres MORE than 2 years ago...despite Al Gore's prediction it would be ICE-FREE by now

“Myth of arctic meltdown” is enough to tell you just how slanted and wrong the conclusions of this article will be … and the inclusion of Al Gore’s name brings it home. Mentioning Gore is at best a distraction, red meat to the deniers. Gore isn’t a climate scientist, and as we well know actual climate scientists overwhelmingly agree that the world is warming. One of the outcomes of this is the decline of Arctic sea ice.

Briefly: Arctic sea ice reaches a minimum in late September every year. The overall trend for the amount of ice at that time is decreasing; in other words, there is less ice all the time. Some years there is more than others, some less. But the trend is down, down, down.

In 2012, a mix of unusual causes created conditions where the minimum reached a record low, far below normal. The next year, in 2013, the ice didn’t reach quite so low a minimum extent, and this year looks very much the same as 2013. But saying the ice is “recovering” is, to put it delicately, what comes out the south end of a north-facing bull. You can’t compare two years with a record low the year before that was due to unusual circumstances; you have to look at the average over time.

Of course, if you do, your claims that global warming isn’t real melt away.

Yearly ice extent.
Arctic ice extent for 2012–2014, with the average for 1981–2010 in black.

Graph by NSIDC

The black line is the average for 1981–2010. The gray region shows the ±2 standard deviation extent for that average; statistically speaking it’s an expected range of extent (it’s actually more subtle than that, but that’s enough to understand what’s going on here). The dashed line shows the 2012 ice extent, and is clearly very low, well outside the expected range. The brown line is 2013, and the light green line is this year, 2014, up to late August. Notice 2014 follows the year before pretty closely.

Note also they are well below average, near the bottom of the expected range. If you look at any recent year’s ice it’s below average; you have to go back to 2001 to find an ice extent near the average.

So the claim that the ice is “recovering” is made based on the wrong comparison. Compare the past two years to the overall trend and they fit in pretty well with overall decline.

Also, that “recovery” claim cannot be made with only two data points. Two years is not a trend. There have been many times ice has gone up over a year or two in the Arctic, only to drop once again over the long run.

ice extent anomaly
Sea ice anomaly, showing annual ice extent versus an average value.

Graph by NSIDC

That’s also from NSIDC, and it shows the ice extent for August of every year from 1979 to 2013. Yes, in 2013 it goes up, but note: 1) There are several times it jumps up for a year or so, but 2) the overall trend is down. Looking at two data points in a row and ignoring everything else is incredibly misleading at best. David Appell at Quark Soup shows this very clearly as well.

There’s plenty more to debunk about Rose’s article, but this shows that his central premise is dead wrong. You absolutely cannot say Arctic ice is recovering, and in fact everything we know—like rising temperatures, and how the Arctic is more sensitive to warming than the rest of the world on average, and the obvious long-term trend—is that we are still losing Arctic sea ice at an alarming rate.

And don’t believe the tired malarkey you might hear about Antarctic sea ice increasing; that has nothing to do with any of this, and is hugely offset by the tremendous land ice loss every year anyway.

What makes this even more aggravating is that there’s nothing new here. This claim of Arctic ice recovering was made last year, and it was just as wrong then as it is now. It’s shameful. Global warming is real, it’s a huge problem, and it’s our own damn fault. There’s still time to fix this, though that breathing room is getting slimmer all the time … and it’s not helping when media give air to deniers.

Correction, Sept. 1, 2014: In the original version explaining the first graph, I wrote "temperature" when I meant "extent." My apologies for any confusion.

Aug. 31 2014 8:00 AM

Time-Lapse: The ESO Observatories

The northern part of Chile is a forbidding and remote desert. Called the Atacama, it is one of the driest places on Earth, and also reaches high elevations; in some places the desert floor is 4,000 meters above sea level … and that’s not counting the numerous mountains and volcanoes that stretch even higher.

All of this is why the Atacama is home to some of the finest astronomical telescopes observatories on the planet. The clear air lets through a lot of light, visible light as well as other flavors invisible to the eye, and the landscape is dotted with bizarrely shaped observatory buildings and arrays of dishes pointing skyward.

The European Southern Observatory commissioned some of the best astrophotographers in the world to travel to Atacama and capture the ethereal and literally unearthly beauty of the desert … and one of the results is this wonderful time-lapse video called “The ESO Observatories: Atacama Transitions and Landscapes under the Southern Sky” taken by friend-of-the-BA-blog Christoph Malin. Watch.

There’s a lot to see, but I think my favorite is at 6:45, when a bright fireball lights up the sky (that’s the still at the top of this article); you can actually see different colors in the meteor streak, most likely due to different elements burning off it as it plunged into our atmosphere from space.

Right after that, you can watch as the multiple dishes of the ALMA array dance in synchronized perfection, moving in unison to capture faint millimeter waves trickling down from distant cosmic sources.

Also, starting at about 9:50, the buildings housing the magnificent four-part Very Large Telescope come into view, each an 8.2 meter behemoth. At first it’s quite normal appearing, but then the powerful laser erupts from one building, a science-fictional beam that is used to aid the telescope in removing distortion from the ocean of air above our heads. As you can imagine, they have to be careful and coordinate with the local air traffic authorities; such a device wouldn’t be a good mix with an airplane flying into the beam.

Finally, I want to point out a phenomenon that is both subtle and astonishing: At 10:20, with the Milky Way’s companion galaxies the Magellanic Clouds hanging on the left and a mountaintop silhouetted in the center, you can see faint, colorful bands of light moving in from the right side of the frame. This is almost certainly airglow, caused by atoms and molecules nearly 100 kilometers above the ground giving up the energy they absorbed from the Sun during the day. This commonly is red and green, as seen in the video.

The ripples in them are amazing. There is wind in the air, even so high off the ground. If it blows steadily across the air below it, ripples can form in the boundary layer (they can also be caused by atmospheric disturbances like thunderstorms, too). These are called gravity waves (the Earth’s gravity fights with buoyancy, and the result is the oscillation of the air, moving it up and down like a cork in water). It’s similar to the phenomenon of ship wave clouds, which happen much closer to the ground.

As usual, there’s far more going on over our heads than we appreciate. Sometimes, it’s when we train our cameras to the sky—and allow them to play with time and space and brightness and color—that we can truly see the exquisite machinery of the heavens.

A laser beams out of one of the VLT observatory buildings.

Photo by ESO

Aug. 30 2014 11:57 AM

Two Days Previously

Heh. What was the view like two days before the video I posted this morning?



That's the Orbital Sciences Corporation's Cygnus resupply ship (the Janice Voss) at the end of the space station's Canadarm 2, then leaving in a hurry in this time-lapse video taken on Aug. 15, 2014. The resupply ship brought well over a ton of supplies to the astronauts, and had been reloaded with trash. It was unberthed by the remotely controlled arm (operated by Alex Gerst on the ISS), then commanded to head off. Two days later, it burned up re-entering Earth's atmosphere.

Watching this video I noticed a peculiar thing: It appears to go up, away from the Earth, instead of down toward it. I suspect this is at least partly due to the pictures being taken with a wide-angle lens, which distorts the image; for example, the Earth isn't nearly that curved when seen from ISS. However, the ship didn't burn up until two days later, so it's likely it wasn't sent immediately into a de-orbiting path, so it may have just moved ahead of ISS for a while before dropping down. Things like this can be difficult to track down, so I'll see what I can do to get more info. 

In the meantime, the video is mesmerizing, isn't it?

Aug. 30 2014 7:30 AM

Swan Dive

Cygnus reentry
The Cygnus resupply vessel burning up upon re-entry to Earth's atmosphere on Aug. 17, 2014. Click to enmeteorenate.

Photo by NASA

A couple of weeks ago I posted a dramatic picture (above) of the Orbital Sciences Cygnus resupply ship, the Janice Voss, burning up on re-entry after a successful mission to the International Space Station.

Yesterday, astronaut Reid Wiseman posted an incredible Vine video of the event. Watch this!

Wow. I mean seriously, wow. That’s video of a spaceship burning up as seen from above by astronauts on a space station orbiting the Earth.

People keep complaining that we don’t have flying cars. Those people are silly. The future: We are in you.