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Seti@HOME Cracked By Aliens?
Chris L. Mason
writes "The Seti@HOME website appears to have been cracked. The front page has been replaced by a picture of ALF (from the really bad comedy.) However, the perpetrators have been somewhat polite about it. A comment in the new html tells where the original page has been backed up. " Might be fixed by the time you read this, but it really happened. The story was submitted by a number of slashdot readers almost immediately. Thanks.
The whole question of "If the speed of light is constant, how come it slows down in things like lenses" stems from the fact that the explanation of refraction given in high school textbooks is much simpler than what is actually going on.
If I remember correctly (it's been a while), what happens when light passes through a transparent medium (like glass or water) is that it interacts with the electrons in the material so as to be briefly absorbed and then re-emitted in the same direction (I may be mangling this - like I said, it's been a while). This kind of interaction is logical when you think about it - a photon is a packet of coupled electric and magnetic fields, while matter is made up of charged particles (electrons and atomic nuclei [small enough to look like points to most photons]).
The net effect of photons being absorbed and re-emitted is that the propagation of the light wave seems to slow down in the material. In actuality, the photons are still travelling at the speed of light in vacuum - they're just not travelling very far before interacting with the matter they're travelling through.
It turns out that a very small fraction of the photons do manage to travel through the material without interacting with anything (though this drops off very sharply with distance). Someone built a device a few years ago that used this effect to take "x-rays" of peoples' hands with visible light (detecting these "ballistic" photons only; their pattern naturally varied depending on how absorbing the materials they passed through were, and was sharp because the photons hadn't scattered off of anything). Check back issues of Scientific American (or possibly Discover) for the reference.
Recent speculation about the speed of light in vacuum not being constant stems from completely different observations, probably celestial.
If you look at the source of the page, you can see the following:
//---! original index.html is backed up as index.html.old !---//
(took out greater-than and less-than signs)
Looks like the crackers were just having a little bit of fun. I found it kind of amusing. If the page is gone, at any time later, im gonna mirror it at http://high.amvalue.com/~edgy/seti in case anyone misses it.
Unfortunatly, not. If you site gets cracked, you can't assume anything on the machine is safe-you need to wipe it, reinstall, apply every patch that you can find, and then grovel over a backup of the hacked site to see if you find a new hole. It's an enormous PITA.
It may be funny to the joker who decided to post it, and it does seem harmless, but the sysadmin who runs that machine has just found himself with a minium 48 hour job-and then, of course explaining to the boss-no, the Primary Investigator, what the hell happened, and why he didn't stop it.
(The PI is the guy who got the grant. They are not noted for thier sense of humor-or proportion)
Ceci n'est pas une sig.