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U-Haulin’ it and the Haul Hall of Fame

June 27, 2008 on 2:05 am | In Random Stuff | 9 Comments

Today is the day! My partner Jamie, myself, and our puppy Cordelia are making the move up to Portland, OR. This morning, we’re off to get the U-Haul, and we’ll be driving all weekend. Hopefully, we’ll arrive in Portland on Monday, and then we’ll find a place to live and some jobs.

Anyone want to hire an astrophysicist/writer/teacher/Halloweener? I’ve got a very fancy resume for you!

Although I only expect it to last about a week, I’m sad to report that this blog is going to have to go on a short hiatus while this happens. We’ll be back, better than ever, hopefully during the second week of July. In the meantime, the least I can do is offer you a link to the posts that you have decided are your favorites over the past five months since we started; these are the ones with the most views since we started. And I should thank the more than 16,000 unique people who’ve visited this website, downloading more than 40,000 pages! Without further ado, here are your Hall of Fame posts:

And I’ll see you again when I’m up in Oregon; best of luck to you all until then!

An open letter to the Future President

June 26, 2008 on 2:05 am | In Politics | 7 Comments

Whether it’s Obama, McCain, or somebody else, I think this is a necessary thing for science literacy everywhere. I’m not a big science policy person (my friend Brian is more into that), but this is important enough that I feel the need to say something. A copy of this letter is being sent to both the Obama and McCain camps:

To the future President of the United States:

I have been paying close attention to your presidential campaign, and I look forward to the reshaping of our nation that will begin in 2009 under your leadership. In particular, I am anticipating the creation of a more informed, educated society, where the nation is capable of making the best decisions possible on any given issue.

And yet, it is impossible for our people to be capable of that without the ability to distinguish valid information from invalid pseudoscience. It is for this reason that I recommend that when you take office, one of your first acts should be to install, as part of the president’s cabinet, a Presidential Science Advisor. It should be a person of science; that is, someone who has experience as a scientist, and is capable of gathering the relevant scientific information regarding a policy issue and presenting you with the information needed to both inform the public and also to make the best decision to ensure the health and welfare of the nation.

This is an extraordinarily difficult task, and although I find your positions on the issues to be far more scientifically accurate than the current administration’s, there are a number of issues where I have noticed that you do not appear to have the proper scientific information. One prominent issue is the connection between vaccines and autism. Although there is much public buzz surrounding this issue, the scientific facts show that there is no connection between rates of autism and vaccinations. However, it is unclear as to what exactly causes autism, and this is an important area to further investigate. It is not acceptable, for the public health and welfare of Americans, to allow the proliferation of the notion that it is in a parent’s best interest to not vaccinate their children. Contrariwise, there have been more cases of the measles reported to the CDC this year than any other year in this decade in the United States; measles had been officially eliminated from the United States in 2002, and its return coincides with the choice to not vaccinate children for personal or religious beliefs.

I would strongly recommend that you expand the powers of the Office of Science and Technology Policy, and to utilize the full power of the resources available to you to help create the informed, educated, healthy nation we all want to live in. I will be happy to do anything in my power to assist you in this endeavor.


Ethan R. Siegel, Ph.D.

Dark Matter in Our Solar System

June 25, 2008 on 2:05 am | In Dark Matter, Solar System | 78 Comments

Disclaimer: cutting-edge research ahead.

Sometimes I spend so much time on education and communication that I lose sight of an important fact: I’m a really good astrophysicist! So, for the last six months, I’ve been working on a project with a graduate student (hi, Xiaoying!) that I’ve been mentoring, and our work has finally come to fruition. Today, our paper entitled Dark Matter in the Solar System becomes publicly available. In it, we figure out how much dark matter there is at every place in our Solar System, and it’s pretty awesome!

Let’s give you the understandable version. First, in every big galaxy that we know of, including ours, there’s a big, diffuse halo of dark matter that surrounds and permeates all the stars and gas, looking something like this:

So we can model the halo, and figure out how much dark matter there should be where our Solar System is. And that’s what everyone else has done up until now when they’ve tried to figure out how much dark matter is in the Solar System. But our Sun and planets have been around for 4.5 billion years, moving around the galaxy for a long time:

Well, all this dark matter flies by the Sun, and flies off again. But here’s where our planets are actually important: occasionally, dark matter will fly by a planet, and the planet will steal some energy from the dark matter. We’ve done this for spacecrafts, using planets to both steal energy from them (which is how we get to the inner planets) and to give extra energy to them (which is how we get to the outer planets). The only thing we need to do this is gravity and a good initial aim. Here’s the Galileo spacecraft as an example:

So, how much dark matter experiences this lucky kind of interaction to bind it to the Solar System? Not most of it, that’s for sure. (In fact, we had to simulate over one trillion dark matter particles to find the answer!) But the final answer turns out to be a lot; about 1020 kilograms of dark matter is bound to the Solar System, or about 0.0018% of the mass of the Earth.

Not impressed? How about this little fact: the density of dark matter present at Earth is a factor of 16,000 times larger than the old, naive prediction that doesn’t take this into account! I can even show you, from our paper, where the dark matter is, relative to the old, naive expectation:

You see that first big spike on the left? That’s Mercury. The next two? Venus and Earth. (Mars is too little and too far away to show up.) Then the next big one is Jupiter, and if you look closely, you can see a little bump (that’s Saturn) and then another one (that’s Uranus and Neptune combined). Think people doing experiments looking for dark matter will pay attention to this? I hope so!

The Moon looks huge!!

June 24, 2008 on 4:13 pm | In Astronomy | 26 Comments

Have you ever seen the Moon shortly after it rises, and had it look huge to you? Maybe you’ve seen something like this:

Or maybe, if you don’t happen to be living by the Temple of Poseidon in Greece, it looks more like this:

And yet, when the Moon gets higher in the sky, it appears much smaller. Here’s the bizarre thing, though. When I photograph the Moon with a camera, it doesn’t appear any bigger at the horizon than anywhere else in the sky; on film, it looks to be the same size everywhere.

What’s going on? I think it’s pretty clear that your eyes are playing tricks on you, but how? The answer (from NASA) is that we still don’t know. Regardless of where the Moon is, it forms the same size image on your retina.

But there are two possible explanations, and they both have to do with the fact that seeing is relative. Why don’t you listen to both of them, and then tell me which one you like better:

1. We don’t know where the sky is. When we look at the horizon, we think of “the edge of the sky” as being farther away than when we look up. This is called the “flattened sky” model.

2. Trees and temples and whatever’s on the horizon looks like it converges to smaller and smaller sizes on the horizon, so that something that’s the same angular size looks bigger based on its surroundings. Here’s an example with train tracks; both yellow lines are the same size, even though the top one appears larger; this is called Ponzo’s illusion.

Finally, if you don’t like either of these explanations, there are other alternatives here from a retired professor, here from two psychologists, and some further explanation from a physicist.

My take? I think it has to do with the fact that we perceive things based on our surroundings. When the Moon is close to the horizon, we recognize that it’s much farther away to the objects that are seen relative to it, and yet is the same size as a tree or a temple. In the sky, all you have is clouds, if that. There’s nothing relative to compare it to, but at the horizon there is. If you want proof that it isn’t an atmospheric effect, look at the horizon Moon through your fingers like this, so you can’t see anything except the Moon:

and you’ll see that it appears to shrink! Neat, hmm?

Hippie Science and Melting Icecaps

June 23, 2008 on 8:49 am | In Life, Politics | 12 Comments

The more astute among you may have noticed that I haven’t been keeping up with the news the last few days. Your top stories are:

Why have I been delinquent? Because this past weekend I was away at the Telluride Bluegrass Festival, where some amazing sets were played by Ani DiFranco, Bela Fleck, Skaggs & Hornsby with Kentucky Thunder (probably my favorite set of the festival), Sam Bush, Arlo Guthrie, and many others.

It’s a well-known fact that hippies love music festivals, and one of the neat sustainability initiatives they had at the festival was no bottled water.

How does this work? You bring your own bottle, and they have a big booth dispensing drinkable, pressurized tap water into whatever container you like. It was really well-done. And on that booth was a sign with some facts about the bottled water industry, including the following two important ones:

  • 17 million barrels of oil are used to make the plastic for water bottles by the bottling industry every year.
  • Water kept in bottles is removed from the water cycle.

And I got to thinking about that second one. Water kept in bottles is removed from the water cycle. What does that mean? It means that it comes out of the environment’s ecosystem indefinitely, meaning this: we can use the bottled water industry to combat sea-level rising. Here’s how. You see, a barrel of crude oil contains a lot of different components, some goes towards producing gasoline, some towards plastics, and some towards oils like vaseline. Well, in the US, we use a lot of oil, namely, around 20 million barrels of oil per day. So about one day’s worth of plastics from crude oil is used by the bottled water industry. How much water is bottled per year? As of 2004, 41 billion gallons (154 billion liters) of bottled water in one year.

Well, instead of using this for selling and drinking, what if we used this to package the ice melting from Greenland and the Antarctic continent; could this offset global sea-level rising? Let’s find out! If the whole Greenland ice sheet melted, the sea level would rise by 7 meters, and if the whole Antarctic ice sheet melted, it would rise by 61 meters. More realistic estimates show that by 2100, the sea level will rise somewhere between 0.15 and 0.95 meters, with the average estimate of 0.5 meters. Well, about 2/3 of the Earth is water, and one liter is 1000 cubic centimeters. That means the volume of water on Earth of a rising sea is:

V = 2/3 * 4 * ŌÄ * r2 * h

r = 6.37 * 108 cm, the radius of the Earth

h = 50 cm, the amount of sea-level rise expected

V = 1.7 * 1020 cm3 of water, or 170,000,000,000,000,000 (170 quadrillion) liters of water.

Well, that’s a lot more water than we can bottle. But what if we devoted our plastics industry to doing just this? Well, we currently bottle 154 billion liters a year, but only use a day’s worth of oil to do it, and the US only uses 25% of the world’s oil.

So if we took all the world’s oil and used it to make bottled water, we could store about 1500 times as much water as we currently do, or about 230,000,000,000,000 liters per year. If we did that with all of the crude oil worldwide every day for the next century, and stored that water away, we could remove 23 quadrillion liters of water from the ecosystem, or enough to lower the sea level by 7 centimeters.

So the bottled water industry isn’t going to be able to save us from sea-level rising after all. Well, now you’ve seen the math worked out, and so now you know why. It was a nice idea; too bad it won’t work out. Back to the four R’s: reuse, reduce, recycle, rot!

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