Blogs / Bad Astronomy

Update (5/7/08): The image I had posted originally was distorted due to the wrong picture being made available to the press (like me!). I got a nice email from Joerg Dietrich, one of the astronomers who took the data, with a link to the correct image. I have updated both the image and the link. Sorry, and enjoy!

We’ve known for a long time that most of the Universe is invisible. 72.1% of it is dark energy, about which we know very little. 23.3% of it is dark matter, which was only recently tagged for real and for sure; we still don’t know what particles make it up, but we’re on the verge of finding out.

Normal matter — us — makes up just 4.6% of the Universe’s energy and mass budget. But here we are! At least, here we mostly are: actually, we only see roughly half of the normal matter in the Universe. Stars, galaxies, and warm-to-middling gas aren’t too hard to spot in general, but they only make up about half of what we expect to see of normal matter.

Where’s the other half?

Let’s turn the wayback machine to about 13.6 billion years or so ago. The Big Bang is old news at this point, but the first stars have yet to be born. Matter and energy are mixed everywhere, but some of it is different. What we now call dark matter is starting to clump together through gravity, forming long sheets and filaments far bigger than any galaxy we see today. This forms a grid, a framework, upon which normal matter starts to fall. Eventually, galaxies and clusters of galaxies and clusters of clusters of galaxies will form along these cosmic skeletons.

Fast forward to today. Bang! We see galaxies everywhere… well, not exactly everywhere. We see them lying in those long sheets and filaments, showing us where the dark matter structures are, like dew drops on a spider’s web.

But that’s just the stars and galaxies, remember? It’s only half. Where’s the other normal matter?

The hypothesis is was that it would be in the form of very hot gas strung out along those filaments as well. Hunting for it would be hard: it would be very diffuse, making it dim, and very hot, meaning it would only emit at short wavelengths, like extreme ultraviolet or X-rays.

Hey, we have telescopes that can see those!

And now we have (and more pictures can be found here). Astronomers upped the odds of finding the gas by looking around galaxy clusters, where it would be denser, and also doing something clever: looking near clusters that are near each other in the sky due to perspective. One would actually be farther away than the other, but peering very nearly along the angle separating them they would look like they’re right next to each other. Since we’d be looking along a long thin cylinder of gas, that would make it appear brighter than if we saw it through its side.

The picture above shows the galaxy clusters Abell 222 and 223, both about 2.5 billion light years away. The visible light image just shows them as clumps of points, but remember: each dot is a massive galaxy like our own! The technicolor bit is from the XMM-Newton orbiting X-ray observatory, and shows the hot gas. Since these are separate clusters, they should be detached from each other. But instead, they’re connected by a gas bridge of ten-million-degree plasma. That’s the missing stuff! That’s made up of baryons; particles like protons and neutrons, atomic nuclei and the like. Look around you: everything you see is made of baryons (and leptons, which include electrons), so this gas is your kin.

It’s a bit more rarified, though: there are only about 30 baryons per cubic meter in this bridge. Good thing it’s big (about 4 million light years wide) and we’re looking down its length! But then, that’s why so much of this stuff is missing. It’s really hard to detect.

According to the models, there is enough stuff in this bridge to extrapolate the existence of the rest of the missing normal matter. Of course, we only have a data set of one, which is a bit rocky, but I suspect more of these will be found now that we know they’re out there.

And may I add, phew! It’s always nice when half the stuff you can’t find finally turns up.

When the Space Shuttle Columbia disintegrated over Texas in 2003, it was a disaster and tragedy for many obvious reasons. One news item that was lost — literally — amidst the wreckage was that some scientific experiments being done were also destroyed.

However, there is a somewhat happier ending for at least one of them. An experiment done on board Columbia was testing certain physical properties of xenon gas. The data were recorded on a hard dive, and it was assumed the drive burned up or was destroyed upon impact along with most everything else from the mission.

However, the hard drive was recovered. Not only that, but the data on the drive were recovered as well! And now, years after the accident, the scientists were able to publish their results, which is rather nice to hear.

I’m not happy with NASA’s direction of late in sacrificing science for ill-advised missions, and I was never happy about the science capabilities of the Shuttle or the space station. But it’s nice to see, in one small way, that some of what science was being done was able to be saved.

When I was at CERN in April, one other visitor with our entourage was Chris Morris. He’s practically unknown in the US — which is a crime, I assure you — but is very well-known in the UK for his incredibly funny, clever, and risque satricial comedy shows like "Brass Eye" and "The Day Today".

He is also a science junkie, and while we were all at the Large Hadron Collider he chatted with Brian Cox about what the LHC will do. The CERN podcast of the interview is now online.

Chris is a very intelligent and funny guy, and the interview may come as a bit of a shock to some fans of his since he really is earnest about the science. But lemme tell ya, Gia showed me some of the "Brass Eye" episodes, and I have to get a copy. Wow. Let me just say, it will never ever ever ever be broadcast in the US. But I laughed until I cried. YouTube has some samples… but most are very much NSFW. Check ‘em out, and see how smart people can love science and be really funny, too.

I pointed out recently about the anti-intellectual gasbag that is Tennessee Republican John Duncan, saying that using experts to help make policy decision is "elitist", like that’s a bad thing.

But now Hillary Clinton has jumped on this make-us-all-dumber bandwagon. Sean basically nails it.

Mrs. Clinton’s campaign has been going increasingly off-the-rails lately, between her lying, her pandering (such as on this ridiculous gas holiday issue), and her attacks on Obama that are undeserved and unwarranted. It’s really become obvious to me that she is still in this race due to ego, and hardly anything else. I think the Hillary Clinton of several months ago would have made a good President — and I think that if push came to shove she’d still do pretty well, and certainly better than McCain (but then, I think a ficus would do better than McCain) — but it’s nonsensical garbage like this that pushes me toward Obama.

Let me make this clear: people are generally experts in a field for a reason. They’ve studied it. They’ve experienced it. They’ve done research, published papers, looked at the results, tried to interpret them, made predictions, done further experiments. They learn from what they experience.

That’s why they’re experts.

So when she uses the (oft-cited by Republicans) "elitist" card, then what she’s saying to me is "experience counts for nothing". Which is pretty darned funny and ironic, given that’s that how she terms the struggle between her and Obama for the Democratic nod.

Plus, it’s just stupid. Experience should count, and it must count. The last thing we need is yet another know-nothing Administration that ignores all the advice being given and all the reality taking place around it.

Chalk this one up to hard-to-believe: a substitute teacher in Florida lost his job in part because of a magic trick.

As reported by Channel 10 in Tampa, Jim Piculas did a magic trick where he makes a toothpick disappear and reappear. What happened next? The principal called him up to the office and told him he was being accused of — wait for it, wait for it — wizardry.

Yes, you read that correctly.

Now, to be fair, this looks like an excuse on the part of the principal or other Powers That Be to get rid of Piculas, whom they accuse of breaking other rules (accusations, Piculas claims, he never heard previously). But let’s be clear: they were still using wizardry (wizardry!) as an excuse to ditch the guy.

Teh stoopid! It hurts!

At first I was having a hard time thinking this story was true, but then realized it happened in Florida. I’m surprised they didn’t burn him.

And someone better tell Randi. They might have to nuke his whole house from orbit. It’s the only way to be sure.

The ways the Universe can deal out death are as numerous as they are terrifying. Asteroid impacts, nearby stars exploding, wandering black holes… I spent a year or so thinking of nearly every method of cosmic catastrophe I could while writing Death from the Skies!^*.

I wrote a whole chapter on what dangers lurk in our own Milky Way galaxy, and I was surprised to find out the Sun’s orbit around the center of the galaxy is a potential problem. The galaxy is flat, like a CD (in fact, the proportion is right if you stack about 4 CDs together). The Sun does not orbit the center of the galaxy in a nice, flat plane, like planets do around the Sun. Instead, it bobs up and down like a cork in water, making about four cycles for every one time it orbits the galaxy (which takes about 200 or so million years).

In my research, I came across the idea that when the Sun is at the apex of its bobbing, towards galactic north, it’s about 100 light years above the galactic plane. That’s far enough up that the magnetic fields of the galaxy are weaker, and it’s these fields that protect the Sun (and the planets, meaning us) from intergalactic cosmic rays, subatomic particles that zip around space between galaxies. When the Sun is up high, these cosmic rays can strike us, and we have to endure this particulate rain for millions of years. The radiation can do bad things, like damage the ozone layer or induce genetic mutations.

When researchers plotted the times of the Sun’s most northerly excursions (which happen every 64 or so million years), they lined up in time with many mass extinctions on Earth. Uh oh.

The good news is that this only happens at one part of the Sun’s orbit, so while we’re deep in the plane of the galaxy we’re protected and safe.

Or, actually, things get worse.

A new result has just been announced that says that when the Sun is in the thick of the Milky Way’s plane, tides from the galaxy can induce comets from the outer solar system to plunge down toward the Sun, meaning many will hit the Earth and potentially cause mass extinctions.

Well, nuts.

According to the new study, this happens every 35 - 40 million years, which is not too far off from the calculations in the older study. Since the Sun moves up and down in the plane, it actually plunges through the mid-plane twice each cycle. If it reaches its apex every 64 million years, then it should pass through the mid-plane every 32 million years, which is reasonably close to what the second study says.

So as if it’s not bad enough that we get irradiated at the top of the orbit, we get pummeled by comets twice as often!

Bummer.

So sure, having trillion ton chunks of rock and ice rain down every few 30 million years is bad and all, but that’s not the worst part! Horrifyingly, this news came too late for me to include in the book!

We have to keep our perspective on these things, after all.

During the live video chat on Sunday, I was asked a good question: why don’t nebulae, gas clouds in space, dissipate? What holds them together?

Here’s my answer:

The basic answer is: gravity. The clouds aren’t like clouds on Earth, or balloons filled with air; nebulae are immense objects with vast amounts of mass. Their own gravity holds them together, and can even cause them to collapse and form stars. And wouldn’t you know it, this goes against claims made by creationists that stars can’t form from gas clouds, so I included that as well in the video.

The images in the video, if you’re curious, are of the Orion Nebula (seen here too), very young stars forming in the Orion Nebula, and an artist’s drawing of a young planetary system still forming.