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Quantum Setback For Warp Drives
KentuckyFC writes "Warp drives were generally considered impossible by mainstream scientists until 1994 when the physicist Michael Alcubierre worked out how to build a faster-than-light drive using the principles of general relativity. His thinking was that while relativity prevents faster-than-light travel relative to the fabric of spacetime, it places no restriction on the speed at which regions of spacetime may move relative to each other. So a small bubble of spacetime containing a spacecraft could travel faster than the speed of light, at least in principle. But one unanswered question was what happens to the bubble when quantum mechanics is taken into account. Now, a team of physicists have worked it out, and it's bad news: the bubble becomes unstable at superluminal speeds, making warp drives impossible (probably)."
THANK YOU. Once upon a time we all knew that the gods made things fall to the ground. Then we knew that things have the falling nature, and the world was flat so things fell "down" no matter where you were. Then we knew that F=MA. Now we know that E=MC^2. What will supersede relativity? (QM is just too wacky, it has been said that if it doesn't confuse you, you don't understand it. I think that means it's a bad model, and we should just abandon particles. But whatever.)
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Quantum would be an atomically short distance...
IE: a "Quantum leap" is just an electron jumping to another valence level in an atom... it's not a very large distance =)
up 12 days, 22:30, 2 users, load averages: 993.20, 994.21, 994.56
*makes note to limit user processes...
That doesn't work. You can't transmit information faster than light; contrary to popular conception, quantum entanglement does not involve classical information transfer.
If you have one of a pair of dice, and the other is a thousand light-years away, one way to think of entanglement is to imagine that whatever number you roll is the number that shows up on the other die the next time it is rolled. Even if the two dice are linked, you can't control which number shows up, so you can't use the dice to communicate information.
No we don't, and no you couldn't. I suppose you're thinking of the EPR paradox? Very well. Let us say that I have a set of electrons in equal spin superpositions, and you, at some distant location, have their entangled counterparts. What's the protocol for communication?
Well, if I measure the spin of my electron 0 about the x axis, then in doing so I will also establish the spin of your electron 0 about that axis. The superposition on your electron has vanished without you touching it. Terrific, that's communication, right? I collapse your electrons in sequence, this one on the x axis, this one y, this one x, and so on, a binary code?
Well, no, it doesn't work like that. How can you tell if I've done anything at my end? By making measurements of your electrons? No - because that will collapse the superposition too. Let's say I measure electron 0's spin around the x axis to be positive. Immediately and instantaneously, faster than light across the universe, the superposition on your electron 0 collapses and I know it to be positive about the x axis.
But you don't know that. You might pick the y axis to measure, which is still a superposition. Or you might pick the x axis, and certainly you'll get a +, but you might have got that anyway. You can measure each electron only once - you change its state in doing so - so you can't do a series of tests, build up the statistics and find that on the y axis it's a 50/50 shot but on the x axis it's + every time. That's what you'd need to do in order to determine that I'd chosen the x axis. That's what you'd need in order to communicate faster than light. But since you only ever get one measurement, you get no information about what I did at the other end.
Real Daleks don't climb stairs - they level the building.
entropy dictates that that everything loses to heat. This heat is at such a low energy level eventually that it can't cause any increase in energy to anything at all around it. This is how a system winds down, eventually all the energy in the atom will get sapped off this way and then it will start breaking down. Eventually devolving into the quantum soup that makes up the subatomic particles. Eventually, those too will lose energy to the space around them until everything is the same indistinguishable quantum soup.
This is the cold death scenario, and the only thing that can stop it is space itself increasing the density of energy instead of forever decreasing it. It's the expansion of space that continually provides for this loss of energy.
so no, atoms aren't perpetual motion machines. Though, for practical reasons, unless you need the machine to be functioning billions of years from now, you can call it perpetual.
In mathematics, a probability of an event A is represented by a real number in the range from 0 to 1 and written as P(A), p(A) or Pr(A). An impossible event has a probability of 0, and a certain event has a probability of 1. However, the converses are not always true: probability 0 events are not always impossible, nor probability 1 events certain. The rather subtle distinction between "certain" and "probability 1" is treated at greater length in the article on "almost surely".
Finally had enough. Come see us over at https://soylentnews.org/
Also, 0 is not "nigh impossible" - it is the definition of impossible.
Not necessarily. It may be that there are an uncountable number of possible outcomes, and each individual outcome has a zero probability, but large sets of them collectively still have positive probability. At least, models exist where this makes sense...
I am the man with no sig!
I think he said this words were _after_ his accident.
He was slowly recovering, something that seemed impossible at the beginning.
actually, as you approach lightspeed, your mass become infinite.... that's why the warp shortcuts need to be created....
secondly... P=mv
momentum equals mass times velocity....
higher the mass, the higher the momentum, the more force it takes to change velocity (or stop the object)
personally i'd prefer to catch a 40MPH baseball than be on the tracks trying to catch a 40MPH freight train.....
That doesn't work either because Joe doesn't know if you have rolled the dice or not.
Entangled particles are like dice that are already rolling, and they stop rolling the moment that either particle is observed.
So you and Joe each have a dice that, say, always roll the same number as each other. You look at your dice to cause it to stop rolling, and see that it rolled a 6. Joe can look at his dice too, and will also see a 6, but he doesn't know if he was the one that caused the dice to stop, or whether it was you who stopped it.
You both see a 6, but no actual information was transferred.
The entanglement usually occurs to conserve some physical quantity, such as spin or momentum. So for the dice example, let's say that every pair of entangled dice must add up to 7.
The problem is that they can only become entangled while they're still in luminal communication range - so you have to roll all the dice before the ship leaves.
If neither of you looks at your dice, then the number rolled remains undefined. As soon as one of you looks at a given die, both it and it's twin instantly take on their respective values (or you spawn 6 universes identical in every way except for the values rolled, if you like the multi-universe theory.) But when you look at a die, all you see is a number. You know that the number on the previously entangled die must be 7-#, but you have no way to tell whether you looked first or your counterpart on the ship.