EGAD

Going offline

Today's weather: Rainy with a high of 62 F; a strong cold front will drop temperatures into the 20s-30s overnight.

Today's weather in Madrid: Fair, high of 86 F, falling to 54 F overnight.

Today's weather in Rehovot: Scattered clouds, high of 96 F, overnight low of 69 F.

Going offline in a moment, and apparently not a moment too soon. So long, suckers! Enjoy the winter.

Done at school

Having made my journal club talk, my responsibilities here are complete.

Title slide of the talk I gave today.

And with that, some last-minute shopping awaits. After which, there shall be packing, interspersed with yelling at the tele during the debates. Tally-ho.

Surveying the Conflict

In visiting Israel, the elephant in the room, the reason everybody keeps telling me to stay off the busses, is the low-level civil war they've had going for the past few years. The State Department's Bureau of Consular Affairs cheerfully declares that Americans should reconsider travel to Israel. But then again, and not to suggest that Powell thinks Americans are complete wussies or anything, they also warn that all travel to that big place called "abroad" might be considered risky.

I have generally been under the impression, and people who research this kind of thing more than I do seem to agree, that war is confusing and reliable facts hard to come by. Nevertheless, when it comes to the Palestinian-Israeli conflict, there seems to be no shortage of people both offering and arguing from what appear to be suprisingly complete, detailed statistics on the conflict. Clearly, we are talking about an amazingly well-documented war for one that the media largely ignores. In analyzing wars, as in cosmology, I tend not to trust those who claim to have a curious abundance of data.

What is clearly the case, almost any way one treats the numbers, is that as a non-Jew, non-Israeli, I am in somewhat to considerably greater danger from the Israeli Defence Force than I am from the Palestinian resistance, even if I stay out of Gaza (as I will).

On the topic of establishing who can be trusted, this database can come in handy. As the site says, the emphasis of the project is on cataloging articles as they come out, along with their provenance -- background information on the authors and publishers, so that they can be judged on their track records. My impression so far is that a depressingly large fraction of the extant literature is wholly unreliable. While this is true on all sides of the debate, I would particularly highlight out the pro-Zionist think tanks and some of the Arab state-run media outlets as the locus of two extremist poles of thought, each working out of its own fantasy world, totally incompatable with that of the other, not to mention the real world.

It's worth mentioning that our current president has an imaginary world of his own, too, and certain folks are starting to call him on it.

To close on a brighter note, it's good to see that some people are still advocating for a nonviolent approach to resolving the situation. A few thousand guerilla fighters will not stop and certainly cannot destroy an adversary like Israel. A million ordinary people resolved to flaunt the unjust restrictions placed upon them. however, has brought down much larger and better-entrenched systems of repression than this. If this basic fact is in the air, not all hope is lost.

I needed a book

Date: Wed, 29 Sep 2004 07:40:20 -0500 (CDT)
From: "P.E. Robinson" 
To: Michael Milligan 
Subject: Re: being cheap

You can borrow my copy if...

you can give me a quantitative answer to this:

are there more stars in the universe than grains of sand on the Earth?

One of my students asked me this, and I told him that I thought stars
would win...but I figured you have probably actually thought about this...

-p-

On Tue, 28 Sep 2004, Michael Milligan wrote:

> Hey folks!
>
> Being as it's expenseive and hard to find, and since you (hopefully)
> only take grad e+m once and always do the homework with other people
> anyway, I never bothered to acquire a copy of Jackson.
>
> Yet, as fate and my big mouth would have it, I've landed a line of
> research that would be made easier by having one handy for the next few
> months.  I.e., while I'm in Israel.
>
> Anyone feel like loaning me their copy for a while?  It'll be about as
> likely as I am to come back in good condition.
>
> Thanks,
> ...Milligan

Ah, a challenge. The best way to win a book. Or, as I've found, a good way to annoy students while teaching them about scientific notation. Naturally, if contrary to the usual wisdom, sand throws down.

Pity he had to add the "on the Earth" bit, because I was all ready to throw in the snarky point that there are vastly more grains of sand than stars. Figure an Earthlike, water-eroded planet contains around <N> grains. Well, it's got to be true that more than 1/<N> stars will harbor such a planet. Especially when we consider just how big that is.

The question Paul really asked, though, is how compares to what we'll call N_*, the number of stars contained in our local Hubble volume. NASA thinks this number is around 10²¹, although 2dF survey data suggest it's closer to 10²³; personally, I'm a little leery of the effect of cosmic variance on the 2dF sample, though -- that's rather a lot larger than previous estimates.

Giving the stars the benefit of the doubt, let's say a typical grain of sand occupies a cubic millimeter (they're generally a little smaller). That puts 10¹⁸ grains in a cubic kilometer.

Let's say a typical beach extends 100 m inland. I don't know how deep the sand generally is, but I'd imagine 10 m is a reasonable estimate. That gives a beach a cross-sectional area of about .001 km². A book and documentary by PBS suggests there are 1.6 million km of coastline on Earth; we'll call it 1 million since not all of that is sandy beach, for a total of 1000 cubic kilometers of beach sand, or about 10²¹ grains.

Already we're up to the lower value of N_*; to push <N> over the top, consider that continental shelves are also sandy, if submerged, and extend 1-10 km from the shore. So chalk up at least another two orders of magnitude for the ground-up rock.

Now, just to be mean, we'll throw in the deserts, where the real sand is hiding. There are at least four really big ones: the Sahara, the Gobi, the Austalian Outback, and our very own Chihuahan-Permian desert. Each is on the order of a thousand miles on a side (some more, some less), and in deep desert, I wouldn't be surprised if the sand goes down rather more than 10 m, perhaps to 100 m or so. A few times a million square kilometers times a reasonable fraction of 100 m comes out to 100,000 cubic kilometers of sand, as much or more as in all the planet's continental shelves, and at least as many as the most generous estimate of N_*.