# Tag Info

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There is no problem with gravity. We have general relativity to describe it in full, and it works as far as we can tell. The "problem" in the movie, as I understand it, was that it was infeasible to evacuate everyone from Earth. It takes an enormous amount of energy to get even a small amount of mass out of Earth's gravity well. The movie called for some ...

4

Is Nash's equation interesting? That is a matter of taste, but objectively I can say that his equations have (independently) interested physicists in the recent past. The equation of motion in your question originates from an action with higher-derivatives and without the usual Einstein-Hilbert action: $$S = \int d^4 x \sqrt{-g}\left[2 ... 4 The large scale structure of the universe can be described with general relativity. Whether the structure of general relativity can be described with quantum mechanics is an unsolved problem. Many people certainly think so and have spent a considerable amount of effort on trying to formulate such a description. For the second part of your question, I would ... 3 You need to distinguish between the virtual gravitons that appear in a quantum field theory calculation of a gravitational interaction and real gravitons that form a gravitational wave. The sort of experiment you're describing requires the emission of real graviton i.e. the emission of a gravitational wave. The trouble is that the coupling constant for the ... 3 Anything is possible with enough persistence. The probability of correctly learning quantum physics and relativity without any help or feedback from a professor, or even watching a blackboard presentation, is nonzero. But the chances of giving up or arriving at misconceptions are a lot higher. To learn any subject, you must focus on it. You won't learn to ... 1 I think I found a coordinate transformation that shines more light on this. Instead of looking for a conical singularity in g_{tt} alone I must look at conical singularities in any part of the metric (apart from g_{rr}) First of all the metric can be expressed in terms of r_\pm and Wick rotated t\to it_E such that$$ ds_{E}^2 = \frac{ ...

1

There is a tiny bit more going on than the otherwise excellent answer by zeldrege suggests. Imagine that you wish to probe an unspecified object to examine its structure. If we use light to look at the structure of an object, we need to have its wavelength smaller than the size of the details we wish to look at. Probing an object that has a (linear) size ...

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