[讨论] 给有志于穿越的童鞋一点点理论支持

马丁

Desktop Big Bang Shows Time Travel May Be Possible After All (时空旅行至少在这个简易版的bigbang模型中可行)

来源：http://www.wired.com/wiredscience/2011/06/model-big-bang/

The first desktop model of the Big Bang reportedly showed why time travel doesn’t work. But a new look suggests time travel may be possible after all, at least on the lab bench.

Electrical engineers Igor Smolyaninov and Yu-Ju Hung of the University of Maryland announced in April that their model Big Bang — made from metamaterials that move light just as particles move through mathematical representations of space and time — suggested time travel’s impossibility.

Light couldn’t be steered in a circle, they said. Therefore particles couldn’t loop back to the space-time point where they began. So much for time travel.

But physicist Ulf Leonhardt of the University of St Andrews in Scotland disagrees. “They considered the wrong polarization,” he said. “Making a loop in space is perfectly possible in their model. Therefore, for this model, time travel is possible.”

The discrepancy comes down to the direction in which the light waves wiggle. Light can be considered as two fields, electric and magnetic. These lie at right angles to each other and to the direction in which light is traveling. In the model Big Bang, the electric field has to point upwards from the plane of the metamaterial, or the analogy to space-time falls apart.

According to Leonhardt, the equations used by Smolyaninov are valid when the magnetic field — not the electric field — points upwards. Make the necessary correction, and the barrier to creating time-like loops in the metamaterial disappears.

“That doesn’t mean that real time travel is possible,” he said. “But for this analog model, it is so.”

Smolyaninov stands by his original conclusion, noting that only certain kinds of light can propagate through the model Big Bang in the first place.

“You could create a different physical system, maybe [time travel] would be possible in another model,” he said. “But not in this one.”

马丁

Let's say it is possible to go back in time, but it shouldn't be possible to change anything. If you ...
minchi 发表于 2011-6-11 05:38

    Your presence in the past world itself is a change after all. There is not an ultimate rule that we cannot make anychanges to ourselves. OK, following your logic~~~Have you ever played a Möbius Strip game? An ant can start from the other side and arrive at the same end. Although splitted, it just forms a bigger and more twisted ring... We might not change the result but we may at least change the reason, together with the whole process.

马丁

We started from a physical experiment, and fell into logic trap o>_<o~

Do u mean that only if one finds a reasonable path leading to his future existence can time travel sound true? The matter does not extinct. Even if one kills his grands in the past, it is possible he comes out from another gene combination. We understand that 4+5=9, while 3 and 6 also makes 9~~~

^_^)Y