1

Good afternoon.

I'm doing research for a possible hard science fiction project and was looking up information on dark matter. Wikipedia--hardly an authoritative source, I know--mentions that the evidence for dark matter stems from an observation where galaxies were rotating around each other faster than what should be possible given visually observable mass.

Has there been an experiment or anything to try to explain the faster-than-expected rotation via Special Relativity? I mean, we're sitting inside of a gravity well looking at galaxies very far away, wouldn't the perception of time be different since we're sitting in a different gravitational field?

I'm absolutely not a physicist--just a layman asking a question to people who might have a better idea than me. Thanks.

Teeeeeeeeeeeeeeeeeeeeeeeeeeeej
  • 111
  • 5
    Did you meant to ask about general relativity rather than special relativity? Either way, it's taken into account, it doesn't solve the discrepancies that we see, though. – pfnuesel Jan 19 '16 at 20:14
  • I guess I did. Not really sure what terms I should be using to google the topic, maybe that's why I wasn't seeing any information. – Teeeeeeeeeeeeeeeeeeeeeeeeeeeej Jan 19 '16 at 20:25
  • 2
    Galaxies, apart from the regions around the black holes at their centers, are non-relativistic objects. Our sun, for instance, is moving around its galactic orbit at approx. 230km/s, i.e. less than 0.1% of the speed of light. The missing mass in galaxies would either behave according to Newtonian gravity, or we need a completely new theory of gravity at large distances, altogether, which leaves us with two alternative hypotheses, one is cold dark matter particles, the other would be some form of modified Newtonian gravity and its relativistic extension. Most physicists are betting on CDM. – CuriousOne Jan 19 '16 at 20:45
  • 1
    The rotation curve problem is just one of the pieces of evidence that point to dark matter. – ProfRob Jan 20 '16 at 00:21
  • 1
    @CuriousOne The rotation curve problem alone does not lead to the idea of cold, dark, non-baryonic matter. The missing mass required could be in any non-luminous form. Other pieces of evidence (and the lack of plausible baryonic contributors) point to it being CDM. – ProfRob Jan 20 '16 at 00:25
  • @RobJeffries: Of course I wasn't implying that one could compress the entire evidence in a three sentence comment. The crux of the (dark) matter is that there is plenty of unexplained gravity in the universe and the most direct evidence is actually in form of missing Newtonian mass. Astronomers have been combing the sky for decades for baryonic matter that could fill this accounting discrepancy and they didn't find it. Even if we knew nothing about GR, this problem would persist, but we also know that GR doesn't solve it, either. – CuriousOne Jan 20 '16 at 02:43

0 Answers0