The entire universe in blog form

April 17 2014 7:30 AM

Look! It’s a Car on Mars!

Right now, there are five spacecraft at or on Mars (and two more on the way). One of the spacecraft on the surface is of course the rover Curiosity, the plutonium-powered Mini Cooper–size mobile chemistry lab. One in orbit is the Mars Reconnaissance Orbiter, equipped with the fantabulous HiRSE camera, capable of seeing objects a half meter across on the Red Planet.

Hey! Curiosity is bigger than a half meter. A lot bigger. Can MRO see it?

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Why yes. Yes it can.

rover on Mars
Red rover red rover. Or blue, in this not-quite-true color image. Click to enaresenate.

Photo by NASA/JPL-Caltech/Univ. of Arizona

Can you find the rover in the picture? Hint: Follow the wheel tracks, which you can clearly see.

Holy wow. I love pictures like this. And there’s great value to them, too. Curiosity has cameras on the surface, several in fact, which map out the area in great detail. But we need an overview as well, just like it helps to have a map when you’re out driving. With eyes in the sky and on the ground we get both.

So what was Curiosity seeing at the time this photo was snapped from above? This:

Curiosity view of Mars
Mount Remarkable, a butte on Mars. Click to embiggen.

Compare that to the picture above.

Curiosity had stopped at a location called the Kimberley, which consists of quite a few interesting rock outcroppings. Centered in that shot is a five-meter high butte nicknamed Mount Remarkable (off to the left is the direction it was looking when it saw the still-unexplained light). The rover is still on its way to Mount Sharp, aka Aeolis Mons, its ultimate destination. It’s already covered several kilometers of the trip.

Amazing. I’ve had worse maps with me on trips, and here we are marking the exact location of a rover on another planet.

Science! I love this stuff.

Note: I totally stole the title of this post from Bobak Ferdowsi, who will forgive me or else I will shave the rest of his head.

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April 16 2014 11:42 AM

Watch and/or Hear Me Speak at You About Things

I did a couple of interviews recently that I figured I should let y’all know about.

First, I spoke with my pal Desiree Schell on her Science for the People podcast about the recent BICEP2 news about cosmic inflation, as well as the new Kuiper Belt Object that was found in the outskirts of the solar system (I wrote about both stories: here and here, respectively). Desiree also talked to Paul Bogard and my good friend Nicole Gugliucci about other astronomy things in that same interview.

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Second, I was in Australia in 2013 to give lots of talks and soak up Aussie culture (and as many Tim Tams and Minties as I cold get my hands on). The very first thing I did after arriving was talk to astronomers Katie Mack and Alan Duffy for their Pint in the Sky video podcast. They split it in to two parts; here’s Part the First:

and here’s Part B:

Basically, I shilled my nerd insult book 27 Nerd Disses: A Significant Quantity of Disrespect (also available on Amazon) that I co-wrote with Zach Weinersmith (and illustrated by Jess Fink) and generally was a smart-ass. But we also talked about other stuff, including how I wended my way down the torturous path to science communication, and what it means to be an astronomer.

These were all fun interviews, so thanks to Katie, Alan, and Desiree for inviting me on!

Also: I'll be in Edmonton, Alberta to give a free public talk about the Mars Curiosity rover called "Where Our Curiosity Has Taken Us" on May 3, sponsored by the Royal Astronomical Society of Canada. So take off to the Great White North, and I hope to see you there!

April 16 2014 7:30 AM

What Happens When You Throw a Peep Out an Airlock?

Peep
Holding your breath only makes it worse.

Photo by Phil Plait

Q: What would you hear if you tossed an Easter marshmallow candy out a spaceship’s airlock?
A: Not a peep.
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Peeps, the wildly popular sugary marshmallow treats, have little nutritional value and take up a lot of space for their mass, so I wouldn’t imagine they’d be a staple food for astronauts. But if some future space voyage stocked them for the astronauts, instead of eating them it might be a lot more fun to throw them out the airlock.

Why? Because this*:

Every year, the Texas A&M University throws the Physics and Engineering Festival, a weekendlong event with dozens of science demos, talks, and entertainment. I was invited to speak in the evening at the 2014 event and spent the day wandering the halls and grounds of the Mitchell Physics Building and Institute, enjoying myself immensely. It was so much fun to see students enthusiastically run their demos to the huge crowd of people who came from all over the Lone Star State.

The Peep demo was one of the first I saw, and one that made me laugh the hardest. It’s funny, but it’s science!

So what did you just see? Peeps are basically spun sugar, starting as a liquid slurry which gets air whipped into it, and then is extruded by a machine into the familiar chick shape. When the sugar solidifies it’s full of little holes, like a sponge. It then gets spritzed with coloring to give it that healthy neon yellow (or in this case, blue) sheen.

peeps_354
We who are about to dye salute you.

Photo by Teresa Boardman

In the demo the Peep is placed on a rubbery surface, the glass bell jar is put over it, and the air pumped out. Air expands to fill whatever volume it is in, pushing on the walls of its container until the pressure is balanced. When the air outside the Peep is removed, the air in the little spongy holes expands to replace it. Because the Peep is soft, the material around the holes gets pushed by the air and expands as well, inflating the Peep overall. The tension in the material itself provides a force that keeps the air from expanding into the jar, so at some point the expansion stops when the forces balance.

However, that material is made of sugar molecules all stuck together in a crystalline state. When the Peep expands, the crystal structure is partially broken, and it stays expanded only because the air pressure inside the bubbles is holding it up, balanced by the tension in the sugar. Once the air is let back into the bell jar the air inside the bubbles contracts again, and the material collapses. That part made me laugh even more than the expansion.

Peep
See? I warned you.

Photo by Phil Plait

Although changed physically, nothing chemically has changed in the Peep, so they’re still edible. Well, by definition, I suppose. That part of the demo is clear enough, though I wonder how many Peeps physics grad student Leo Alcorn, who ran it, ate over the course of the weekend.

Atmospheric pressure here in Boulder, Colo., is about 18 percent less than at sea level, so I hope she avoided any trips to Colorado before she digested them all. Which makes me wonder … are Peeps in Colorado measurably bigger than ones sold elsewhere?

You’re welcome, Colorado parents and students who are looking for a last minute science fair idea.

*I know, I held my phone vertically and not horizontally, against the laws of nature and science and the 'Net. However, there were lots of little kids wandering around, and I figured it was better to orient the phone portrait mode so they wouldn't be included. Also: Tip o' the bell jar to Leo Alcorn, who was awesomely cool about all this.

April 15 2014 1:36 PM

Blood Moon: The Lunar Eclipse of April 2014

Did you watch the total lunar eclipse last night? Judging from my Twitter feed, a lot of people did! Chatter and pictures were flying around the ‘Net as the silvery full Moon slowly drifted into the Earth’s shadow and turned a lovely shade of orange.

I took the picture above at about 07:21 UTC (01:21 Mountain time, local for me), about 15 minutes after the total phase started. You can see the bright star Spica (the brightest star in the constellation of Virgo) just to the Moon’s lower right, and the much fainter star h Virginis just above and to the left of the Moon. It was fun to see fainter and fainter stars pop up as the Moon faded away, its bright glow no longer capable of washing them away.

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Over the course of an hour and a half I took some video using my camera (a Canon T41 with a 250 mm lens), so, for your eyes’ and brain’s pleasure, here it is:

I suggest making it big, if not full screen, and make sure you have the volume up for the first few seconds.

The coyotes really set the mood, didn’t they? Even though I was freezing my toes and fingers off, it was truly a wonderful and fun evening. I’ve seen a dozen or more total lunar eclipses, and I think my favorite part of this one was sharing my photos on Twitter in near real time. People all over the world were excited to see it, and that is a big part of why I do this.

eclipse
A little over half an hour into the eclipse, a longer exposure reveals details on the shadowed part of the Moon.

Photo by Phil Plait

Due to the complex and subtle dance of gravity and geometry, there will be three more total lunar eclipses visible to the United States over the next year and half: in October this year, and in April and September of 2015. While there won’t be any bright stars near the Moon for the eclipse in October, the planet Uranus will be only a degree away! That’ll make for some nice family portraits. And there’s also a partial solar eclipse two weeks later, on Oct. 23, 2014, too! That’ll be a treat. And if you live in Australia there’s a nice annular solar eclipse on April 29; this is when the Moon is slightly smaller than the Sun and leaves a ring of Sun around the dark Moon. There was one of these last year and there were some fantastic pictures and video. I hope we’ll get more.

Remember: Look up! There are always amazing things to see.

April 15 2014 7:30 AM

Cassini May Have Witnessed the Birth of a New Saturn Moon!

Saturn
Discovery image of the new moon, seen as a clump of material just outside Saturn's main ring. Click to encronosenate.

Photo by NASA/JPL/Space Science Institute

Just when I think Saturn can’t surprise me any more: The Cassini spacecraft may have taken the birth pictures of a new moon! It may have also spotted its demise. Or maybe part of its demise. Also, it may be twins.

OK, let me explain.

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The potential moon (nicknamed Peggy) is tiny, probably only about a kilometer (0.6 miles) across—really a moonlet—and is invisible in the Cassini pictures. However, its presence is betrayed by an odd clumping of material at the very edge of Saturn’s A ring, the outermost of Saturn’s main rings.

It was discovered by accident in an image taken on April 15, 2013—one year ago today. The picture above shows the main rings, the thin F ring outside them, and the irregularly shaped moon Prometheus (the actual target of the shot) in the center just inside the F ring. If you look carefully you can see a blob on the edge of the A ring. Here’s a close-up, with the clump indicated:

That’s clearly not a discrete object; it’s about 10 kilometers (6 miles) wide and 1,200 kilometers (740 miles) long, but this is what you would expect if a small object were located near the edge of the ring—and why astronomers think there's most likely a moonlet there. It would have feeble gravity, but enough to affect the ice particles in the ring, creating the long, trailing clump.

Saturn's new moon
Zooming in on the new moon's clump.

Photo by NASA/JPL/Space Science Institute

Once they knew it was there, the astronomers were able to calculate an orbit for it, and then go back and look for it in older Cassini images. They found the clump in more than 100 such pictures! But in most cases it’s so faint and difficult to see that it was completely overlooked before. It appears brighter at certain viewing angles, which is why it was so obvious in the discovery image. The earliest it was seen was in May 2012, but before then Cassini was not in a good orbit to detect the clump, so there’s no way to really know how old it is.

But then things get weirder. In images taken before January 2013 there’s only a single object, but in later images, just around the time the object was discovered, a second one appeared! They’re obviously related, but it’s not clear whether the main object broke up due to a collision with something else, or whether Saturn’s tides (the change in the force of gravity over distance) pulled it apart. It may also be due to some other mechanism entirely.

I dug up another of the images showing the clumps, taken on June 22, 2013:

clumps
The two elongated clumps are indicated; they are just outside the main ring. Click to embiggen.

Photo by NASA/JPL/Space Science Institute

I’ve indicated their locations; you can just see a gap between them and the main A ring. Once I knew what to look for they were obvious, but I can see why they could’ve been missed before. They’re hard to spot. I’ll note that in other images they found what may be a third object as well, but it’s difficult to know what its relationship is to the other two (if any).

And we’re still not done. Not long after the discovery image, Object 2 disappeared! Due to complex interactions with the ring particles, an object the size of the small moon can migrate outward, away from Saturn, over time. Once it leaves the rings it would become essentially invisible. An alternate explanation is that it disintegrated; if its orbit was a bit eccentric, a bit stretched, compared to the particles in the rings it would have been continually bombarded by them, and could have been obliterated.

Still, it was there, at least for a while. And the other object may have survived as well.

So I suppose congratulations are in order for Saturn on its possible new moon … but it’s funny. Saturn is the Roman name for the Greek god Cronus (or Cronos), who was known for eating all his children to prevent them from overthrowing him (when you get down to it, a lot of the ancient myths are really, really horrid). But now we find out the opposite is true! The smaller moons may have been birthed by Saturn (or at least, its rings) and moved out before they could get eaten.

Science! I’ll take it over myth any day.

April 14 2014 2:28 PM

Science Ranch 2014: A Few Spots Left

There are only a few spaces left at Science Ranch 2014, a weeklong science-based vacation with me, June 22-28, at the Waunita Hot Springs Ranch in the Rocky Mountains near Gunnison, Colo. In addition to your humble host, we’ll have a geologist and an ecologist with us all week as well. There’ll be science talks, stargazing, nature hikes, horseback riding, rafting, great food, and special programs just for kids. We’ll also be taking a day to visit the staggeringly dramatic Black Canyon, which seriously has to be seen to be believed (check out this photo, for example).

My wife and I both love science, and when we go on vacation we always want to learn more about the natural history of where we travel … that’s why we started Science Getaways. We bring along professional scientists to tell us about what we’re seeing and to answer your questions, and I bring my 8” Celestron telescope so we can view the heavens. The dark skies at Wuanita should provide fantastic views (weather permitting, but summers in Colorado are almost always quite lovely and clear). You’ll have a great time, and you’ll learn something, too.

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It’s a vacation with your brain.

April 14 2014 11:09 AM

No, Scientists Have NOT Found Life in a Meteorite. Again.

Hey, look! This again. An article claiming scientists have found microscopic life in a meteorite. I’ve been getting emails from folks (mostly via Facebook) asking whether this is real.

OK, let’s put this in context: For as long as humans have looked at the stars, we’ve wondered if there is life in space. Once science and technology caught up with our imagination we started using radio telescopes to listen for alien signals, we built giant telescopes on space and on the ground to search for other planets, and spent billions of dollars sending missions to Mars to looks for signs that there was once water flowing there, and even just the potential for life.

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So if scientists found actual microbes—living bacteria, as claimed in this case—inside a meteorite that fell from space, I think it might make somewhat bigger news than being reported on some random news-like website you saw linked from Facebook.

And I say "news-like" website because the site in question, World News Daily, is satirical. It has articles with headlines like, “Former Pope Warns of Vatican Alien Agenda” and “Arctic Penguins Now Extinct” (think about it…).

And if the site is being serious, then its scholarly levels make the Daily Mail look like the New York Times.

The article itself is a clever mix of reality and outright crackpottery. It mentions real scientists, like Peter Brown, who is in fact a meteoriticist. The meteorite discussed in the article is claimed to come from a fireball that occurred on March 18, 2014 over southern Ontario; a real event (though, to my knowledge, no meteorites from it have yet been found).

The article also mentions Charles Bolden, the NASA administrator. The quote has a, um, key tell in it:

The general director of NASA, Charles F. Bolden, saluted the discovery and praised the canadian university for it’s exceptional contribution to the world’s astrological knowledge.

Emphasis mine. But I hope you see the point (not to mention the two grammatical errors).

meteorites
Separated at Earth? The claimed Ontarian rock (left), and one found a few years ago in Antarctica (right). Hmmm.

Photo from World News Daily and the University of Toronto/Ray Jayawardhana

Also, on a hunch, I did a reverse image search on Google using the picture of the meteorite shown in the article. It turns out to be one found in Antarctica a few years back. That’s a bit of a walk from Ontario.

So yeah, to be clear: This article is 100 percent bovine excrement, fertilizer, baloney, nonsense, hokum, and fish-wrappery.

Got it?

I can understand it spreading, though, especially on social media. It only takes one person to post about it (either missing the signs it was satire and taking it seriously, or sharing it as a joke) to get things started. People tend not to read past headlines—did you see the NPR April Fools’ Day joke that proved this?—or in general they just skim an article like this. And even if they do a quick check of the facts by, say, looking up the Ontario fireball event or the names of the scientists, they’ll find they’re real (though I suspect the number of people who would go that far is negligible).

Making it worse is that actual scientists have been making similar claims about life in meteorites lately, all of which have been utterly wrong (see Related Posts below for more about them). Those claims were just plain old bad science, but people half-remember them, and so it's no surprise to me that a joke article can wind up getting taken seriously.

Remember folks, put stuff in context! If the news is this big, you would’ve heard about it sooner and in a more reliable venue. And even that doesn’t make it true; you have to do a little work, dig a little deeper, to get to the truth.

Before hitting that button to send something to all your friends, remember: If you care enough to share, you should care enough to beware.

OK, wow, that was an awful aphorism. How about this: Before you share, use a skeptical glare.

Yeah, that’s worse. Whatever. All I ask is that you hesitate a moment before sharing a story like this one so you can think it over. Does it make sense? Is there another place I can look for more info (cough cough)? Is there a chance this is a joke/hoax/fake/wrong?

If you do that, then you’re well on your way to making the world a more real place. And I thank you for it.

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April 14 2014 7:30 AM

Watch the SpaceX Launch Live Today at 20:58 UTC

Today (Monday, April 14, 2014), SpaceX is scheduled to launch a modified Falcon 9 rocket on a resupply mission to the International Space Station. The launch is scheduled for 20:58 UTC (4:58 p.m. EDT), and you can watch it live on NASA TV or Ustream (I prefer the latter; there’s less lag in the video stream).

This third mission for SpaceX to the ISS has some interesting stuff going on. I think the most exciting is the Optical Payload for Lasercomm Science, or OPALS. Spacecraft currently communicate with the ground via radio transmissions, the signal encoded with information much the way as how a radio in your car works. OPALS will use an optical light laser for this instead, which is a big leap forward if it works. Lasers take very little power, and the shorter wavelength of optical light means a lot more info can be encoded into the beam. This test will beam a video taken on ISS along with other information down to the ground.

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When I was a kid, I read all of science-fiction author Larry Niven's stuff, and his ships communicated using lasers (they played key roles in several stories, too). When I got older I realized how many advantages there were to using lasers instead of radio, and now it's becoming a reality. Score another one for sci-fi.

Two other payloads include a suite of hi-def cameras that will take video of Earth (to test which designs work best in space) and a nifty package (called Veggie) that will allow the astronauts to grow vegetable plants in space using LED lights.

But there’s still another cool thing: SpaceX will be testing the hardware needed to have the first stage of the Falcon 9 rocket land itself for reuse. This is an idea they’ve been testing with their Grasshopper series of test flights, using landing legs stowed on the side of the booster. After the stage separation (and the second stage lofts the Dragon capsule up into space), the booster will execute a burn to slow down, and the legs will deploy during the burn. This will all happen over the Atlantic Ocean, so it’s not an actual full-up landing burn; it’ll be a splashdown! But it’ll test many of the needed systems for an eventual and literal landing. SpaceX says the odds of this being a completely successful test are low, but it’s worth giving it a shot.

Once the Dragon capsule is in orbit it’ll rendezvous with ISS and berth on April 16. If there is a delay in launch, the next possible launch date is April 18. Various hardware issues on the Dragon and ISS have delayed the original scheduled launch, but engineers have decided it’s a go for today.

SpaceFlightNow will have fairly up-to-date messages loading on its site for more information. I’ll be watching and live-tweeting as well, of course. Watching a rocket launch is always fun, so I hope you’ll join in.

April 13 2014 7:30 AM

Jenny McCarthy: “I’m Not ‘Anti-Vaccine’”

Jenny McCarthy
Which Jenny McCarthy should we believe?

Photo by DFree / Shutterstock

Jenny McCarthy is claiming she is not anti-vaccine.

Here’s the problem with that claim: Yes, she is. That’s patently obvious due to essentially everything she’s been saying about vaccines for years. Yet in an op-ed in the Chicago Sun-Times on April 12, 2014, she tries to ignore all that, and wipe the record clean.

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In case you think I may be misquoting her, here is the first line of that op-ed: “I am not ‘anti-vaccine.’”

So, there you go.

She says she’s never told anyone not to get vaccinated. Assuming that's true, great! But that’s hardly the entry-level position for being anti-vax. For example, you can say things that are grossly incorrect about them that would scare parents into not vaccinating their children. That would fit the moniker “anti-vax,” I’d think.

So, for example, saying vaccines have toxins in them—as she has said for years, and as she reiterates in her op-ed—is a clear sign of being anti-vax. After all, if someone tells you you’re putting toxins in your body, that sounds awful, doesn’t it? Doesn’t that make you want to stop doing whatever it is that’s putting them inside you?

Yet as doctors say, dosage makes the poison. The amount of, say, formaldehyde in a typical vaccination is much less than you’d get eating an apple. The same can be shown for the other ingredients claimed to be toxins in vaccines as well. The truth is vaccines contain far too small a dose of any of these things to cause any of the problems McCarthy and other anti-vaxxers claim exist.

Also, botulinum is the single most lethal toxin known to humans. Yet McCarthy has enthusiastically praised injecting this toxin into her face. How can anyone possibly say that and also say vaccines have dangerous levels of toxins in them with a straight face?

Which brings us to autism. McCarthy is still claiming that there is a link between vaccines and autism. However that is simply not true. Again and again and again and again this has been shown. McCarthy asks us to talk to families of people who have children with autism. That's certainly a good place to start, but it's the first step to an answer, not the last. Anecdotes are not data. We know people are subject to dozens of different biases that lead them down the wrong path when trying to determine cause and effect. That’s why medical studies are done so carefully, to make sure we aren’t fooling ourselves. And the studies clearly show no connection between vaccines and autism.

And finally, let’s take a step back and look at the claim that she’s not anti-vax itself. Jeffrey Kluger is a science writer for Time magazine. He interviewed McCarthy in 2009 about this issue, and she mentions that interview in her op-ed piece. Kluger disagrees vehemently with what she wrote in the op-ed, to say the very least.

I can see why. Here is what she writes in the op-ed:

“People have the misconception that we want to eliminate vaccines,” I told Time magazine science editor Jeffrey Kluger in 2009. “Please understand that we are not an anti-vaccine group. We are demanding safe vaccines. We want to reduce the schedule and reduce the toxins.”

But Kluger points out that she left the last line out of that quotation. Here’s the whole thing:

People have the misconception that we want to eliminate vaccines. Please understand that we are not an antivaccine group. We are demanding safe vaccines. We want to reduce the schedule and reduce the toxins. If you ask a parent of an autistic child if they want the measles or the autism, we will stand in line for the f--king measles.

Huh. That last line rather changes the tone of her position considerably, wouldn’t you agree? That’s a difficult stance to square with someone who is not anti-vaccine. As Kluger points out, her entire premise is false; since vaccines don’t cause autism, no one has to make the choice between measles (and other preventable, dangerous diseases) and autism.

Kluger finishes with this:

Jenny, as outbreaks of measles, mumps and whooping cough continue to appear in the U.S.—most the result of parents refusing to vaccinate their children because of the scare stories passed around by anti-vaxxers like you—it’s just too late to play cute with the things you’ve said. You are either floridly, loudly, uninformedly antivaccine or you are the most grievously misunderstood celebrity of the modern era. Science almost always prefers the simple answer, because that’s the one that’s usually correct. Your quote trail is far too long—and you have been far too wrong—for the truth not to be obvious.

He’s right. She has gone on and on and on and on and on and on about it. She can claim all she wants that she’s not anti-vax, but her own words show her to be wrong.

Anti-vax is as anti-vax does. And she does.

April 12 2014 7:30 AM

Don’t Miss the Lunar Eclipse on April 14–15!

Do you live in North America, South America, Australia, or eastern Asia? Then you get to see a lunar eclipse on the night of April 14–15! And while North America is the best place to watch—we’ll get to see the whole event—the real action doesn’t begin until 05:58 UTC on the April 15, which is just before 02:00 EDT, so it’s a bit late. You might just want to stay up for it, though.

A lunar eclipse is when the Moon slips into the shadow of the Earth and gets dark. Unlike a solar eclipse (where the Moon blocks the Sun) a lunar eclipse lasts for hours and is perfectly safe to observe without protection. In fact, I find using binoculars is best!

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How does this work? The Sun lights up the Earth (big duh there), and anything that’s illuminated casts a shadow. Normally the Earth’s shadow just goes off into space, but sometimes the geometry works out that the Moon passes into it. The Moon has to be opposite the Sun in the sky for that to happen, so lunar eclipses only happen when the Moon is full.  

geometry of an eclipse
Schematic showing the geometry of a lunar eclipse. not to scale (duh).

Drawing by Shutterstock/fluidworkshop

The Earth actually casts two shadows; a wide, fuzzy one called the penumbra and a narrower, darker one called the umbra nested inside the penumbra. If the Sun were a point source in the sky (a little dot) there would only be one dark shadow, but because the Sun has a finite extent (that is, we see it as a disk) the geometry is a little more complicated. If you could see the shadows in the sky, the penumbra would be a big circle about five times wider than the Moon, and the umbra would be a circle inside it about half that size.

ayiomamitis_lunareclipse_umbra
By taking several exposures during a partial lunar eclipse in 2008, Anthony Ayiomamitis was able to create a mosiac showing the Earth's umbra cast into the sky.

Photo by Anthony Ayiomamitis, used by permission

It helps to think of it from the Moon’s viewpoint. If you were standing there, looking back at the Earth and Sun, you’d see the Earth (barely; you’re seeing it’s night side) sliding slowly over the face of the Sun. At the moment the edge of the dark Earth starts to block the sun, you’re entering the penumbra. It’s getting darker, but most of the Sun is still unblocked, so it’s not getting very much darker. About an hour later the Earth completely blocks the Sun, and you’ve entered the umbra. The Earth is much bigger than the Sun from your point of view (about four times larger) so the Sun stays blocked for a while. Finally, the Sun peeks out the other side of the Earth; you’ve left the umbra and are in the penumbra again, and things start getting brighter.

lunar eclipse seen from the moon
A lunar eclipse ... seen from the Moon! This was taken by the Japanese Moon probe Kayuga in 2009 and shows the Earth eclipsing the Sun.

Photo by JAXA/NHK

What does this mean for us here on Earth? We’ll see the Moon enter the penumbra at 04:53 UTC April 15, or 00:53 EDT (53 minutes after midnight). Again, it’s no big deal, and you’d hardly notice. But the Moon’s edge enters the darker umbra at 05:58 UTC (01:58 EDT) and over the course of a few minutes you’ll see that part of the Moon get dark. Over the next hour or so more of the Moon will fall into the Earth’s darker shadow, and at 07:06 UTC (03:06 EDT) the entire Moon will be dark. It’ll stay that way for the next hour and 18 minutes, until it starts to move out of the umbra at 08:24 UTC (04:24 EDT), and will start to be illuminated by the Sun again. The umbral eclipse ends at 09:33 UTC (05:33 EDT).

Here’s a diagram that may help:

lunar eclipse timeline
How the eclipse will play out; the description is in the text below. Click to embiggen.

Diagram by Fred Espenak/NASA (modified for clarity by Phil Plait)

The Moon moves from right to left in the diagram. The positions are labeled. P1 is when it moves into the penumbra, U1 is when it moves into the umbra, U2 is when it’s fully immersed, U3 is when it starts to leave the umbra, U4 is when it’s out of the umbra, and P4 when the Moon leaves the penumbra, and the eclipse ends. The times are listed in the lower right in UTC. Subtract four hours for Eastern U.S. time, and so on.

Sometimes when the Moon is fully immersed in the Earth’s shadow it can turn an eerie blood red due to the way the Earth’s atmosphere scatters light—it’s the same reason the Sun can look redder at sunrise and sunset.

Want to hear something poetic? If you were standing on the Moon during the deepest times of the eclipse, from your view you’re seeing all the sunrises and sunsets on earth at that moment.

When someone tells you science is cold and emotionless, tell them that.

The only problem with this eclipse is the timing; it happens late Monday night/early Tuesday morning for most of the U.S. But don’t let that stop you! If you have clear skies you really should go out and look. And if you have a camera, please take some pictures! With a little planning you can get some amazing shots like the ones I’ve scattered through this post (see Related Posts below for many more). Check out this incredible time-lapse animation made by Jeffrey Sullivan of a lunar eclipse in 2011:

Observing the Moon with a telescope or binoculars during an eclipse is a wonderful thing, but if you only have your eyes, that’s fine too. It’s fun to go out every few minutes between U1 and U2 and watch the Moon get eaten by the Earth’s arcing shadow.

I hope you have clear skies and good viewing for this event! And if you don’t, never fear: There’s another one in October, then a third in April 2015, and a fourth in September 2015 too. You’ll have plenty of chances to see this lovely astronomical bit of geometrical alignment over the next year and a half.

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