News says that we have finally observed "gravitational waves", one of GR's predictions. I've read about some other predictions of GR like how gravity affects the flow of time, gravitational lensing and so on. But these predicted phenomenons have all been observed and been proven to exist.

I'm wondering if there are other predictions of GR that for the time being have not been proven by experiment?

  • $\begingroup$ You could probably turn the question around and ask what we know empirically about solutions of general relativity and the answer is: almost nothing. There is preciously little observational evidence for the behavior of strongly gravitating system beyond the overall energy and angular momentum loss due to gravitational waves. LIGO is the first experiment that gives us precise data about the strong field case during the merger of compact objects, which is its true importance. The existence of gravitational waves was almost guaranteed, but how compact objects merge, that we have to learn. $\endgroup$ – CuriousOne Feb 14 '16 at 22:23

From the top of my head, there are both wormhole and white hole solutions to Einstein's equations that have not been experimentally observed

  • $\begingroup$ But these aren't predictions in the same sense as gravitational waves. Wormholes and such are things that might potentially exist given the right circumstances, while one would expect waves to be emitted in any big event such as the famous black hole merger. In other words, if we never detect a wormhole that means there's no wormholes, if we never detect a gravitational wave that's a problem. $\endgroup$ – Javier Feb 14 '16 at 23:39
  • $\begingroup$ @Javier i disagree completely. They are predictions. What could be discussed is whether there are some initial conditions that could lead to the realization of this solutions. And also, if we never detect a wormhole that does certainly NOT mean there are no wormholes. It just means we have not found a wormhole $\endgroup$ – Yossarian Feb 14 '16 at 23:46
  • $\begingroup$ @DmitryhandmetheKalashnikov It seems that a reasonable definition for "prediction" is something that a theory says should occur. As far as I know, general relativity doesn't say wormholes should occur, so they wouldn't be a prediction. Maybe you disagree with this definition, but I suspect this is standard usage. $\endgroup$ – JLA Feb 15 '16 at 0:21
  • $\begingroup$ @JLA I don't disagree with your definition, but I also think that the "should" in "should happen" is somewhat subjective. For some historical hindsight you can check this wiki page en.wikipedia.org/wiki/… where for example you can see how Einstein believed at some point that black holes couldn't form. Who is to say that white holes will not become standard someday? I wouldnt be so rush in ruling them out from the prediction category. $\endgroup$ – Yossarian Feb 15 '16 at 1:06
  • $\begingroup$ @DmitryhandmetheKalashnikov You can disagree all you like, but it's nonsense to claim that all possible solutions to a set of equations constitute predicted physical situations by a theory using these equations. That's the same as saying that "Newton's Laws predict a ball balancing on top of a solid half-ball to spontaneously start moving" (see Norton's dome). That's just wrong. $\endgroup$ – Danu Feb 16 '16 at 17:31

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