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Alien Solar System Much Like Ours
MrGort writes "Wired News reports that British astronomers say they found the first sun-like star with a giant gas planet in an orbit similar to Jupiter's, which leaves plenty of room for worlds like Earth and Mars. This system is a quick 90 light years away. The similar solar system to ours means that this gas giant could attract most of the debris, allowing smaller planets closer to the sun to develop like ours did!"
You know, this reminds me of the setup of a book by John Varley, called "The Ophiuchi Hotline". It starts off with us learning that humanity started receiving transmissions from space, in the direction of the Ophiuchus constellation. We started receiving it about 400 years prior, and have been decoding peices of it ever since. Of the amount that can be decoded and translated, we've learned about medicine, space travel, computers, etc. All kinds of amazing technology. No one knows who is sending it, or why.
But a repeating message has appeared, taking up more and more of the transmission. Our hero is summoned to a meeting where he learns that some of this repeating message has ben translated.
In summary, it reads: "Payment for service is overdue. Please remit immediately, or severe consequences will result."
The book plays out from this premise.
Let's hope we never have to deal with intergalactic IP issues.
"It's overkill, of course. But you can never have too much overkill." - Anonymous Slashdot Coward
>beyond any technology we have or have even dreamed of
We've dreamed of some pretty impressive things. For example, the Alcubierre drive (http://www.wikipedia.org/wiki/Alcubierre_drive). It has some [facetious]minor engineering problems like requiring negative energy density and more total energy than exists in the universe[/facetious], but it's a warp drive that satisfies the equations of general relativity. Faster than light, and physically legal.
Off topic, did the headline of this story strike anyone else as being like a headline from The Onion?
There is no such thing as a perfectly rigid body. Everything else follows from this.
Stick Men
No. Relativistic contraction happens only in the direction of motion. The stick would "thin", not shrink.
If you shoved it "towards" Europa, for instance, then the stick would shrink slightly, but, if you're jiggling the stick back and forth, the stick would be shrinking, expanding, shrinking, expanding as you stop and start the motion. It's even worse than that as you're attempting to move a massively elongated object, so you get displacement waves rather than motion.
Plus the fraction that we're talking about here is REALLY small. Look it up - just look up Lorentz contraction somewhere, and use a value of, I don't know, v = 1 m/s (which is still fast). It's ungodly small - somewhere in the vicinity of 1 part in 1 billion.
It's not an easy question to answer - there are quite a few complications involved - but it suffices to say that nothing weird happens. The stick would take a long time to move (at least the characteristic period of the object - speed of sound*length) and if you tried to shove it harder, you'd just distort the stick (bend/break, etc.) and send a wave down the stick, thus moving YOUR end, but not moving the entire object!
I mean, let's work it out - let's assume that it's a billion meters long, so moving it at 1 m/s shrinks it by 1 meter. Let's also say that the speed of sound in the material is 1000 m/s, so it takes a million seconds for a "push" from one end to move to the other end. In order for you to actually see any real Lorentz contraction (from the whole stick), the entire thing has to be moving at 1 m/s, not just the end - Lorentz contraction comes from the fact that a reference frame moving with the stick must measure the speed of light the same as you do, and the 'fractional' contraction is due to the fact that the frame at the very far end of the stick is the same frame as the initial end of the stick.
So, in order for you to see the billion-meter long stick shrink by 1 meter, you'd have to wait a million seconds. And by then your end would have moved one million meters, and if you measured the length of the stick while it was moving at 1 m/s, you'd get 999,999,999 meters. It wouldn't be a sudden jump - it'd smoothly decrease in size as more and more of the stick begins moving. Then, when you try to stop it, it'd take a million seconds for the stick to stop, and the stick would smoothly stretch back out to 1 billion meters.
But, in the end, it still would've moved a million meters. It's only during the motion that you see anything weird happen.
So if you grab it before the whole thing starts moving, then the total contraction would only be due to however much of the stick is actually in motion.
Photons have no rest mass. You do. Figure out how to get rid of your rest mass, and you can travel at the speed of light...
The limitation on faster than light travel can be thought of as a requirement to preserve causality, if all reference frames (freely-falling ones, if you like) are regarded as equally good. Thus FTL travel would violate causality in the standard picture of relativity. But perhaps someone will show that a preferred frame exists. Even so, all alternative models I'm aware of which allow for a preferred frame (e.g. bimetric gravity) require causal behavior to stay within the "light cone."
It's true that Alcubierre's warp drive spacetime doesn't have any causality violation or other funny business going on locally (which is all relativity refers to), however, as has already been noted above, the warp drive requires matter with a negative energy density. Such matter can be defined mathematically but is physically meaningless. FYI, Alcubierre himself regards the solution as an interesting toy but not something to be taken seriously from a physical standpoint.
Wormholes also require negative energy. See above. Various people keep working to push the requirements so you need less negative-energy-matter. I say if you need any at all, the whole thing makes no sense.