Sunday, April 27, 2008

Speak of the devil

I was back at the Lick Observatory this evening, with another UCM field trip group.

Like last time, we all got to look through the 36 in Lick refractor (that's the Shane reflector above).

Unlike last time, Saturn was up. Can you guess what that means?

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Friday, April 25, 2008

If I was emperor...

Here's what I'd do first. I'd come to your home, right after dinner, take you by the hand, drag you outside, and make you look at Saturn through a telescope, so you can see the rings.

Partly because I know you'll really dig it. I have to yet to meet anyone who didn't.

But mostly because I love watching people's reactions when they see it for the first time. About three weeks ago I took some of my ecology students on a field trip to Yosemite, and I took my little Edmund Scientific Astroscan (love it!). About 9:30 I set it up on the hood of an SUV (on a towel, so it wouldn't scratch the paint) and gave the interested a brief tour of the sky. We started and ended at Saturn. One of the guys had never looked through a telescope before. I'm not saying that to knock on him--most people haven't. I'm saying it because it was freakin' awesome to get to be the one to show him this stuff for the first time, and especially freakin' awesome to start with Saturn.

Then a couple of weeks ago we had some friends over and as we were walking them to the car at the end of the evening we all stopped to have a naked-eye gander at the moon. Somebody asked if any planets were up so I pointed out Saturn right by Regulus, and then I said, "Look, just wait two minutes. You've got to see this." I keep Shaft, my Orion XT6 Dobsonian reflector, parked against the wall in our pointlessly immense* entryway for just this purpose, and about 90 seconds later one of our friends was getting her first ever look at Saturn. She literally squealed with delight.

* I'm convinced that the houses in this addition have big entryways just to stick it to people from the coast. It's about a third the area of our entire apartment in Berkeley and it serves no purpose other than to ostentatiously show off the fact we have tons and tons of space.

Look, seriously, if you haven't seen it you just have to. It's mandatory. Most space stuff you can see pretty well with binoculars, like the Orion Nebula and the moons of Jupiter, but you'll need higher magnification to grab Saturn's rings and that means a telescope. In the Bad Old Days decent telescopes were usually prohibitively expensive, but not anymore. Orion's StarBlast has gotten uniformly great reviews (here and here for starters; Sky & Telescope and Astronomy both loved it but their reviews are behind paywalls) and it is under $180, so unless you're reading this from a library computer you've got the juice. A new Edmund Astroscan is just under $200, damn near indestructible, and will last forever.

It works well for kids, too, and it's tough enough you won't freak about that. If you need something bigger--something you might need more than one hand to carry outside, say--I got Shaft on sale for under $250 and it looks like a freakin' howitzer.

Back to task: Saturn. Look now, and save me some work in the future.

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Thursday, April 10, 2008

More glittering gems from my outbox: finishing the dissertation

I don't update this thing very often, but I'm on e-mail all the time, and the profound wisdom and sparkling wit just comes jetting out of me like one of those lava fountains in Iceland. So I'm going geothermal here.

A recent correspondent asked me about dissertation stuff, and this is part of my response:


....The most honest and useful advice I ever heard about dissertations came from Darren. I wrote to ask him what finishing was really like (this was when I was still a few months out). Tragically I've lost his original reply, but the gist was, "Eventually you will realize that you can't finish by treating the dissertation like a day job. It is a godforsaken monster that will continue to ruin your life until finally you've had enough and you just decide to kill it. After that, you may put in impossible hours and push yourself right to your limits, but you will finish. It's the only way I know to do it." [Darren, if you have the original thing you sent, please feel free to resend it or post it as a comment. UPDATE: Darren just posted it in a comment, below, and as I suspected it's much better than my paraphrase.]

That was certainly true in my case. The only thing that finally made me face finishing was my committee's insistence that I needed to get it done that semester. And even then I spent the first half of the spring of 2007 treating the diss. like a day job. It wasn't really until the final month and a half that I went into overdrive, literally staying up past my bedtime every night and gradually letting every other concern in my life slide. It sucked, bigtime. And after I filed I didn't look at the diss. at all for about three months. But I did get it done and filed.

It might be possible to just decide, "Okay, I'm going to finish my dissertation now," no matter where in the process you are, but I doubt it and I wouldn't recommend it even if it is possible. I think it's more like trying to climb Everest when there's a storm coming. There is some point up the side of the mountain when you are close enough to the summit to make a dash for it. There's no point in starting the dash until you're that close; otherwise you'll just exhaust yourself and possibly die of exposure. So for now just keep grinding away, a little here and a little there, until you are (a) sick to death of it and (b) close enough to make a run on the summit.

I read some books on writing when I was trying to write my diss--possibly more displacement activity--but none of them were worth a damn. The book that I wish I'd had then but only discovered recently is Steven Pressfield's The War of Art, which I cannot recommend highly enough. It's shelved in the Self-Help section at the bookstore, which strikes me as perverse. It's not really that. It's more like a personal philosophy on how to think about your work and all the things that keep you from getting it done....


I do recommend The War of Art, to everyone. Jarrod put me onto it. It's a short read, but pithy, and decidedly non-lame. I put it up there with Paul Graham's essays in terms of great writing about how to do useful stuff in the real world.

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Wednesday, April 09, 2008

Why we can see unimaginably distant galaxies from Earth, but not the moon landers

Recent Correspondent: We know where the guys langed on the Sea of Tranquility (and the other missions too of course, not just 11), and though small, they left behind a lander and moon rover etc. So, I assume with a big enough telescope (and we have some monsters) we could just hunt around a bit, and actually *see* where we landed - right?

Me: Sorry, it's a good thought, but the landers and so on that we left behind are waaay too small to be seen by any telescope on earth or in orbit.

Recent Correspondent: I must say I am surprised. We have these scopes that appear to be able to see tiny little planets in other galaxies. I know that is a big object, but it is a shit load further away. I figured the size vs distance would be on the side of the lander...

When I replied, I was just repeating what I've read lots of places. I've never seen anyone actually demonstrate that it's true. So I am endeavoring to do so now. There are a couple of things to clear up here. The first is the discovery of extrasolar planets around other stars, and the second is whether size vs. distance is on the side of the moon landers, or the unimaginably distant galaxies.

Part 1: Extrasolar planets

We have not seen tiny little planets in other galaxies. There is a literally vast confusion of scale here. The most distant extrasolar planet discovered to date, OGLE-2005-BLG-390Lb, is only 21,000 light years away. On one hand, that is a hell of a long way away. Our ancestors were hunting down the last mainland mammoths when light from that planet's primary was barely halfway here. On the other hand, it's nothing. The Milky Way is estimated to be about 100,000 light years across, so OGLE-2005-BLG-390Lb is only a fifth of the way across our own galaxy. The closest major galaxy to the Milky Way--excluding our dwarf satellite galaxies, like the Magellanic Clouds--is the Andromeda galaxy, which is 2.5 million light years away. It is the most distant object that you can see with the naked eye, which is pretty cool, because the photons that fall into your unaugmented retina left Andromeda when our ancestors were banging rocks and dreaming of taming fire. But it is more than 100 times as distant as OGLE-2005-BLG-390Lb.

It gets worse. Nobody from Earth has seen OGLE-2005-BLG-390Lb. We only know it's there because of gravitational microlensing. The most distant planet we've actually seen is 2M1207b, if it actually is a planet and not some kind of dwarf star, and it's only 173 light years away.

In other news, the "hot Jupiter" that orbits HD 189733 has methane and water in its atmosphere. Here's how we know that. The planet above is not extrasolar; it's wholly terrestrial in origin.

So to sum up, all of the extrasolar planets we've found are in our own galaxy, and pretty close even on a galactic scale, and we've only directly imaged one of them, and the one we've imaged may be more of a failed star than a planet.

Part 2: Which is smaller, the Eagle or a smudge in the HUDF?

The Apollo Lunar Modules are about 14 feet in diameter, with a maximum landing gear spread of about 30 feet. At its closest approach, the moon is 225,000 miles away, or about 1.19 billion feet. So the ratio of size to distance is 1:40 million even if we use the landing gear spread, and 1:80 million if we use the vehicle itself.

The Apollo 17 lander was actually photographed from lunar orbit, but that's a distance of about 69 miles, not 225,000 miles. And it shows up as a single pixel, plus a pixel of shadow. You can see that photo, along with tons of cool zoomable moon landing site photos, here.

Although there are galaxies somewhat larger and much smaller than the Milky Way, let's say for the sake of argument that most galaxies are about 100,000 light years across. The most distant galaxies ever imaged, in the Hubble Ultra Deep Field (shown above), are about 13 billion light years away. Which yields a ratio of size to distance of only 1:130,000, or about 300 times bigger than the moon landers to observers on Earth or in Earth orbit.

Which is why we can see galaxies on the other side of the universe from Earth, but not our own moon landers. The galaxies are indeed shitloads further away, but they are also many, many shitloads larger.

Feel free to poke holes in my math or logic.

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