Posts Tagged ‘Physics’

Wow, I thought the worry that the LHC might destroy the world was amusing, like most predictions of the end of the world. It turns out people have been sending actual death threats to LHC researchers.

The annoying part of this is that just a couple people (who Mark correctly identifies as crackpots) have managed to generate a storm of publicity. There are pieces in the Times, the other Times, and the Guardian to pick the first three I could find. The WorldNut Daily even ran a poll with… well… “interesting” responses.

What’s even more annoying is that this has happened before. (more…)

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Rocketboom is reporting that scientists have found a way to produce a Star Trek style warp drive. It’s a cute story, but it suffers from having more than one tooth fairy.

Let me explain.

The report appears to be based on this paper, by Richard Obousy and Gerald Cleaver from Baylor university. The idea of a warp drive is to produce a “bubble” of space that moves by distorting spacetime itself, and is therefore not subject to the cosmic speed limit of 300 million meters per second. What the authors have done is to construct a scenario where one could create such a bubble. The idea itself appears to be correct, and is actually quite creative.

For their idea to work, though, 4 things need to happen. First, spacetime needs to have more directions than the 3 space and 1 time dimensions that we currently enjoy, and that these extra dimensions be curled up in a little ball. This idea is far less crazy than it sounds at first. There are good reasons to think they might exist, and many experiments searching for them. That said, it’s still a long shot. (Sean, more or less arbitrarily, puts it at 11%, I think that’s pretty high). Still, basing an idea on a long shot has a long history, and a potential for huge payoffs. After all, the tooth fairy might exist, and she might be interested in your wonderful business plan for second-hand tooth distribution.

The problem is that they still need 3 more things to happen. They need, for technical reasons, the current acceleration of the universe to be due to these extra dimensions; something which is far from certain even if the dimensions do exists. They need a technology that can control the size of the dimensions. And finally, they need a way to generate the enormous amount of energy this would require – they estimate that this is about what would be obtained by converting the mass of Jupiter to energy. Each of those is asking for another tooth fairy. If the payoff is big enough, searching for one tooth fairy might be a very good idea. Looking for more than one that all have to be there…. Well, just don’t get your hopes up.

Note 1: I don’t mean to pick on the authors of this paper. They wrote a very nice paper as a fun exercise, and are certainly aware of everything I talked about here.

Note 2: I learned the “tooth fairy” method of evaluating ideas from Tom LeCompte, a physicist at Argonne National Laboratory.

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Destroying The Earth

In the break room for the theory group at SLAC, I once found a folder titled “Scientific Eschatology”. Eschatology being the study of end times, this presumably was an attempt to understand what our current theories tell us about how we could go splat.

It’s always fun to think about the ways the world might end. Phil Plait has an entire book about it coming out soon. There are a lot of exciting possibilities. The sun might die, a nearby star might go supernova, nuclear war might break out, fiery horsemen might come riding out of the sky, the center of the Milky Way could turn into a quasar after colliding with Andromeda. (In that last case, we would all feel fine.) Of course, some of these are more likely than others.

On way that it should probably not end is for a scientific experiment to tear a hole in the fabric of spacetime. It is, therefore, a relief that the Large Hadron Collider, soon to turn on in Geneva Switzerland, will not produce this result, as some have claimed. The paper linked goes into some detail, but the bottom line is quite simple. The LHC collides two beams of protons. The Earth is constantly being bombarded by cosmic rays, which at high energy are mostly protons. The energy in the collisions of cosmic rays with The Earth (generally the upper atmosphere) are often as high as the energy of the LHC, occasionally much higher. A little math, and one finds that if the LHC was going to destroy our planet, it would have been destroyed many billions of years ago, just after it was formed.


What I find strange about this is not that people think we could destroy the world with science. Of the ways the world might end that I’ve heard of (where world is defined as “humans”), the most likely seems to be nuclear war. The surprising bit is that people think we could out-do nature itself in terms of the scale of destruction. There are places in the universe where collisions much, much, much more powerful than anything we will ever produce on Earth occur regularly. We’ve gotten pretty good at making particle accelerators – the LHC is an incredible accomplishment – but we still have nothing on, say, quasars.

I was reminded of this by the appearance of a new paper on the arxiv rebutting yet another claim that black holes would eat The Earth. The fun never stops.

Oh, and the folder titled “Scientific Eschatology”? It was empty.

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