Thursday, August 31, 2006

Quick Links

First, everyone watch this. Then tell people you know to watch it. Everyone should see that.

On a far less serious note, I'm now writing this blog using, Google's online kick in the balls to Microsoft (which, as a kick in the balls, connects it to my first link). If I make spelling errors, you should report them at, since the software is beta. It isn't my fault anymore :-P

Tuesday, August 29, 2006

APOD Shuffle

Random thoughts inspired by NASA's Astronomy Picture of the Day (APOD):

  • Orion Nebula: This picture shows how the Orion Nebula looked 1500 years ago. Or, well, at least how it would look if we could see in infrared. But, really, it's only 1500 years on average. Stuff in the front of the picture sent that light out more recently than stuff in the back. The whole sky works that way. We see Proxima Centauri as it was a mere 4 years ago, while we see the Andromeda Galaxy as it was about 2.5 million years ago. If we somehow constructed a map of where the stars are right now and how bright they are, it would look different than the sky we're used to. Not only would some stars be missing and some new stars be added, but everything is also moving relative to one another. Those things that we see as they were 2.5 million years ago likely are quite a ways away from where we see them, for example.

  • Horsehead-shaped nebula: This beautiful image of a horse's head (not to be confused with the Horsehead Nebula) is also a great example of the strange and interesting phenomenon called pareidolia. Humans are pattern-seeking creatures, so when we look at things, we try to assign them to categories. We look at this nebula, and we see a horse's head. We look at a hill on Mars,and we see a face (and some continue to do so even when a second photo shows that the resemblance in the first photo was coincidental). And, of course, some people look at a grilled cheese sandwich, see a shape that looks vaguely like a human female, and assume it's the Virgin Mary.

  • Lagoon Nebula: Why couldn't whoever runs the APOD at NASA take the 5 minutes to make those two pictures line up (mouse over the picture to see what I mean)? Sigh. Still beautiful.

  • 3D galaxy: It's amazing to me that that's a photo; strangely, it looks too real to me for me to immediately accept that it's really a photo. It's the kind of shot you might create for Star Trek credits or something. That galaxy is about 50 million light years away, but remember: the front edge isn't quite as far away (and therefore not as far in the past) as the back edge. However, compared to the total distance, the 30 thousand light year diameter of the galaxy is almost nothing.

Monday, August 28, 2006

Mapping Human Knowledge

A couple years ago, when the company I work for ramped up work on our homework system, my boss jokingly gave me the task of "mapping human knowledge" to create our topic list. We pawned much of the effort off to the authors working on our authoring projects in an attempt to make things easier, but that turned into a colossal mess.

Tonight, I finished collapsing that mess into a canonical list of chemistry topics.


Sunday, August 27, 2006

Memorizing Very Exact Mnemonics Jeopardizes Science's Updatable Nature

"My very excellent mother just served us nothing. That is not nearly as yummy as nice pie. Darn astronomers stealing Pluto from our solar system."

That was what my sister sent me when she heard Pluto had been demoted from planethood. And, of course, she wasn't alone; many people were upset to "lose" Pluto.

Of course, we didn't "lose" Pluto. It's still out there, orbiting the Sun. You can even call it a planet if you want. All that happened is that the International Astronomical Union, for the first time, defined what a planet actually is, and that definition doesn't apply to Pluto.

Why did they do it? They tried not to. In October, 2005, they were set to define a planet as "Any object in orbit around the Sun with a diameter greater than 2000 km." That was a fancy way of saying, "A planet is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto," since at the time they thought Pluto was bigger than all of the "potential planets" that have been discovered in recent years. Of course, that definition wasn't very precise, because the Moon (the one that orbits Earth) also orbits the Sun (if we lived on the Moon, we'd probably think of Earth as another planet sharing our orbit), and, with a diameter of 3500 km, it has no trouble squeaking in.

But then we got a good measurement of Xena. Xena, also known as 2003 UB313, is a ball of ice and rock orbiting the Sun in an orbit similar to Pluto's. Earlier this year, NASA pointed the Hubble space telescope at Xena, and found something interesting. Xena has a diameter somewhere between 2300 km and 2500 km. Pluto has a diameter between 2280 km and 2330 km. Xena is right around the same size as Pluto, and quite possibly bigger.

So why did the IAU eliminate Pluto from their definition of planet? Because they're scientists, and scientists have to deal with the real world, not with how they wish things worked. For the word planet to have any scientific meaning, we have to be able to rationally decide if some object is or isn't a planet. In order to do that, there have to be some sort of measurable criteria. Try as they might, the IAU couldn't come up with a definition that seemed important enough for what we've always meant by "planet," but still included Pluto.

But that's the great thing about science. As we find new information, we continuously tweak our explanations to match the data. As time goes by, and we get more information, we refine our predictions and explanations to make sure they still hold up. We constantly update what we think we know to match what we observe.

This is what allows us to make progress. This is why I'm able to write a blog on a computer that communicates through the rest of the world through the air, rather than writing letters that take months to cross the ocean. This is why we now have bathrooms in our houses, rather than in the yard. This is why babies dying at birth is a rare event now, rather than the norm.

And that's why now we know that we have eight planets in our solar system, plus at least three dwarf planets. That's the thing people seem to be missing. We didn't lose Pluto. We gained 3 dwarf planets (besides Pluto, one was formerly an asteroid, and the other was formerly one of those things that we didn't have a name for before). We gained slightly better understanding of the solar system in which we live.