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Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

Do worm holes allow all times to exist simultaneously?

Well..Not really. It depends whose clock you are talking about. For observers outside black holes, time is unique up to the usual definitions provided by special relativity. If you were falling into certain types of rotating black holes, some theoreticians say that you could travel in time, but still there would be no 'simultaneity' of all times. There may be one place where this could happen. According to quantum gravity theory, at the so-called Planck Scale about 10^20 times smaller than an atomic nucleus, spacetime may cease to exist as the kind of mathematical entity we have come to regard it. Mathematicians call it a manifold, and it has the characteristic that about each point in spacetime, there is a well-defined neighborhood of other points whose distances are less than a certain arbitrarily small value. These points define the neighborhood of a point. But, if quantum spacetime consists of quantum black holes and other exotic topology-changing events, the neighborhood of every point could contain innumerable worm hole 'mouths' whose end points are at any arbitrary distance from the original point. The concept of a 'neighborhood' defined in terms of a specific distance, breaks down completely, and spacetime ceases to behave like a mathematical manifold. Under these conditions, all kinds of causality-violating events can occur freely, and in some sense time ceases to be a useful parameter to organize these events. many unrelated events could happen simultaneously within the Planck scale of physics.

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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.