Blogs / Bad Astronomy

For some reason, people want to blame the Sun for global warming.

This, despite there being no evidence for it, and plenty of evidence against it.

The latest round was brought to my attention from DarkSyde, a science blogger at DailyKos. In an article he put up last night, he notes that an online mag called Daily Tech has a blogger who is claiming that last year was cooler than average… which contradicts a study by NASA’s Goddard Institute for Space Studies that shows that last year was among the hottest on record.

Which one is right? Duh. NASA. The Daily Tech columnist evidently confused a below-average January temperature for an entire year’s worth.

Oops.

He also quotes anecdotal data about places having cooler than normal weather. While he acknowledges this is only anecdotal data (though it’s his biggest paragraph in the story), he forgets that scientists have been saying for years now that global warming does not mean every place on Earth gets hotter. Some places get colder, much colder. The weather patterns changes, and arctic air can be brought down to areas on the planet that don’t usually get them.

Ironically, a few years ago global-warming deniers tried to frame the debate by changing the phrase "global warming" to "climate change", because it sounds less threatening. It’s ironic because it probably is a better term: the climate is changing. It’s getting hotter in some places, colder in others. Wetter in some places, drier in others. In some ways I wish it were as a simple as things warming up. It’s not.

We depend critically on huge areas of this planet being stable and capable of supporting crops. Ask a Kansas farmer what happens when it doesn’t snow all winter, or a citrus grower in California what happens when it gets unusually cold.

The Daily Tech article is very misleading — even plain old wrong — and that hurts the rational discourse on this topic… especially when garbage hounds like Matt Drudge pick up on it, as he did on his website today.

The comments on the Daily Tech article are full of errors, too: several people are saying it’s the Sun causing this climate change. That is utter baloney.

Let me make that clearer: BALONEY. I wrote about this extensively in my upcoming book, so I talked to quite a few solar astronomers about this very topic. In general the solar output varies very little over the course of a year, less than 1%. Over the whole sunspot cycle, though, it’s a little more complicated. The sunspots darken the Sun by about 1%, but they are surrounded by regions called faculae, which are actually brighter in the visible and ultraviolet. So when the Sun is its spottiest, it’s actually brighter than average by about 0.1%.

At most, this would raise the temperature of the Earth on average by 0.2 degrees Celsius (and it’s generally less), and we are measuring increases much larger than that (not to mention the trending just keeps going up, and doesn’t rise and fall with the sunspot cycle). People have also tried to tie global warming to sunspots by invoking cosmic rays; when sunspots are at a minimum the Sun’s magnetic field is weakest, and it lets subatomic particles from outer space into the solar system. This can seed clouds (so it’s claimed) and cool the Earth. Maybe, kinda, sorta. The evidence for this is incredibly weak, and it’s not taken very seriously yet.

People who try to tie global warming to the Sun are in for a losing fight, it seems, though in many cases this just makes them scream all the louder. But they have very very spotty (har har) evidence, and what they do have does not come close to explaining the rise in temperature we see on Earth.

The south pole of the Moon is pretty intriguing. There are craters there that are deep enough that sunlight never reaches the bottom, because the Sun is always very low in the sky.

This has inspired some scientists to wonder if there might be water ice there. Comet impacts on the Moon, for example, could distribute water all over the surface. UV light from the Sun would quickly destroy the water molecules, but not if the sunlight can’t reach it! So it’s speculated there might be ice located at the south pole, deep in the permanent lunar antarctic shadow. Different observations have looked for it, but nothing conclusive has been found. People are eager to find it because finding water on the Moon could make it a lot easier for future colonists; hauling water up there is pretty tough. Water is heavy.

To aid future explorers, NASA has released the highest resolution radar images of the lunar south pole yet obtained. From this, they have been able to determine the topology of the surface there; that is, get accurate heights and depths of crater walls and crater floors. From that, and knowing the Sun’s elevation over the pole, they have been able to make this totally awesome video [edited to add, link now fixed] showing what shadows and illumination look like there over the course of a lunar day, a little over 29 days long.

Cool, huh? Now play it again, and watch the craters near the bottom of the frame. See how the floors of some of them are dark all day long? That’s where the Sun don’t shine, as they say, and where there might — might — be ice. No one knows for sure if it’s there or not. But aided with maps like this, future missions planned that will make better maps, and, of course, human exploration of the lunar surface, we’ll find out.

We know of a handful of very massive stars in the galaxy. And by massive, I mean whoppers: some with 100 times the Sun’s mass. These are enormous stars that are millions of times brighter than the Sun and live very short lives, ending in titanic supernova explosions.

The problem is, how do they form?

Stars form from clouds of dust and gas. These are generally pretty cold, just a few degrees above absolute zero (-450 Fahrenheit, -273 Celsius). The Sun formed from just such a cloud, we think. It’s not hard to form lots of stars like the Sun from a typical cloud, but massive stars are tougher. Cold gas tends to fragment into smaller clumps, and these clumps can’t make really big stars. So how do the monster ones get their start?

New work just published by Mark Krumholz at Princeton and Christopher McKee at Berkeley indicates that the big stars get a helping hand from small ones.

Imagine a giant cloud of gas, a light year or so across and containing a couple of hundred times the Sun’s mass. It’s cold inside, and the gas starts to collapse here and there under its own gravity. Small stars like the Sun start to form. When they do, they heat up the environment around them. This heat input suppresses the further fragmentation of the cloud, allowing it to collapse more than it would otherwise. So if a big star starts to form, there is a constant supply of gas to feed it, letting it grow larger. If the smaller stars weren’t there, the insides of the cloud would fragment and cut off the supply of mass to the nascent massive star.

This may sound a little contradictory: a warmed up gas expands, right? Well, usually, but we’re not talking about a major heating here. The sun-like stars raise the temperature of the cloud just a few degrees. That’s enough to stop the fragmentation, but not enough to counteract the cloud’s own gravity causing it to collapse. Note to creationists: when you talk about all gas expanding, and therefore stars cannot form, you look a little silly. You might want to look into some actual science once in a while.

Anyway, this new model explains something that has been seen but not well understood: massive stars only seem to form in clusters. The vast majority of truly huge stars we see are members of clusters, indicating that there is something in the cluster environment they need to get so big. It looks like Krumholz and McKee have found it: there have to be other stars around to help them grow.

Of course, this work is just beginning. There are lots and lots of things that can affect star formation, and they have only modeled a few. But this is an excellent start in solving one of the bigger — literally! — mysteries in star formation science today.

What the heck is dark matter?

We know it’s real: many, many independent observations indicate that the majority of matter in the Universe does not give off light that we can detect, but we can detect the effects of dark matter very clearly.

We also know it’s not made of normal matter, like anything made up of electrons, neutrons, or protons. The effects we see would be very different if it were, so it must be made up of some kind of exotic matter we don’t have experience with, yet.

A leading contender for this stuff are WIMPs, or Weakly Interacting Massive Particles. It’s a bit of a generic term for a class of subatomic particles that don’t interact well with normal matter. They can pass right through you — actually zillions of them can — without having any effect on you whatsoever.

That’s not to say that WIMPs don’t interact at all. It’s just that they affect us weakly. According to theory, every now and again a single WIMP will ping off an atomic nucleus of normal matter, making it resonate like a hammer hitting a bell. It’s possible to detect that effect, and from that deduce the mass of the particles. That in turn will tell physicists a lot about the particle itself.

So lots of folks are looking for just that ringing. Caltech has an experiment running called Cryogenic Dark Matter Search, or CDMS. Deep underneath northwest Minnesota, 2400 feet (730 meters) down, is a laboratory that contains cryogenically cooled detectors, kept to within a hair’s-breadth of absolute zero. Billions of WIMPs pass through the detector every second, but it’s likely that only one or two per year will actually smack into a nucleus and shake it up.

New results just announced indicate that the mass of any purported WIMPs must be less than 100 times the mass of the proton. How do they know? Because they have been looking long enough that if any WIMP more massive than 100 times a proton existed, they’d have detected it by now. They haven’t, so the mass must be less than that.

It sounds like a negative result, but that can still be pretty useful. In this case, it’s consistent with theory, which poses the most likely WIMP mass at about 40 times the mass of a proton. As the experiments continue to run, and the detectors get better, they’ll be able to nail things down to that mass range as well.

If and when they find their WIMP interactions, it’ll be a HUGE day for astronomy. It’s a little frustrating to know that dark matter is out there, to see it affecting whole galaxies and clusters of galaxies, but not know what the heck it is!

I bet that inside of a decade (probably sooner) we’ll have either detected WIMPs, or ruled them out as a contender for dark matter. I’m not sure which I’d prefer. It would be incredible to have a new particle in our repertoire, especially since its existence would have been predicted by astronomy and not from the standard model of subatomic particles. It would also be fascinating to find out that there is something out there even weirder than WIMPs, which are plenty weird enough.

And while you’re thinking on that, chew on this: it’s only been in the past few decades that the very biggest thing of all — the Universe — has been tied to the smallest things of all — subatomic particles. The very small and the very big are connected in a fundamental way, and it’s only been through science that we’ve perceived that connection.

Some people like to say that science can’t answer questions like why are we here, and what the Universe is all about. I think those people are wrong. By peeking behind the Universe’s curtain, we’re learning more about it every day. Big questions deserve big answers, and science is up to the task.

In 2006, I attended the science fiction/fantasy/comic book convention Dragon*Con, along with 30,000 of my closest friends.

It was a blast.

So I applied to be a guest at D*C 2008, and they accepted me! Woohah!

D*C really is vastly ginormously huge, with an expected attendance this year of 40,000. Yes, 4×10⁴ fans. The guest list is already awesome, even this early: Adam Baldwin (JAYNE! from FIREFLY!), James Randi, James Hong (Lo Pan from Big Trouble in Little China, the best movie ever made, ever), and lots more to come. Pamela Gay and Fraser Cain will be there too, and there’s a whole thread on skepticism.

Hawesome. Totally and completely. So if you’re in Atlanta at the end of August, you should go. But get tickets now! They go fast, and the hotels (four of them) are probably already booked. Yes, it’s that ginormous.

I am writing a short article for a kids magazine about Hubble and other astronomical telescopes (I’ll have a link later when it’s published). I needed to find some images for the article, including pictures of the telescopes in question.

I was searching for a picture of some telescopes, and found this one for the European Space Agency’s ISO observatory:

What are we trying to teach kids here? Potential caption: "Astronomers use the ISO observatory to detect and destroy incoming alien fleets."

Of course, the US can’t let Europe do this on their own. Just look at this artist’s illustration of NASA’s James Webb Space Telescope!

Red alert!