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Space time slow zones

  1. Feb 3, 2016 #1
    ok, sorry if i sound daft, but this one has been keeping me awake and i need a better physics brain to tell me why this is b'locks

    So, there was a recent study in aus that said Aliens don't exist, or rather that we can't find any evidence, because the conditions for life to evolve require, essentially, long periods of stability in which the evolving organisms regulate the atmosphere to be conducive to further evolution, and the odds of this are really long. i don't think that's the case.however. this got me thinking.

    Space and time are both sides of the same coin right. the curvature of space time is dependent on the mass of the objects in the firmament. is that right? the greater the density of matter in a particular area then the greater the time dilation?

    so areas that have more mass, like the central zones of galaxies, would have more curvature, both specifically on planets in that area and also generally in the whole zone, hence time would, for any being living there, be experienced at a different rate, more mass more speed or less mass less speed? is that right?

    perhaps because we exist in a particular 'zone' or 'band' or area of space time density what we are able to perceive is limited by that density, i.e. we can't perceive the faster or slower zones and they can't perceive us. consider a fly, it experiences time so fast that as we try to swat it it can easily dodge cos we are lumbering super slow giants to them. perhaps alien cultures are happening, either so fast or so slow relative to ourselves that we simply can't experience them. bonkers? possibly. what do you think?
  2. jcsd
  3. Feb 3, 2016 #2


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    Hi graemecr,

    Gravitational time dilation is a tiny effect. There's really not much more to say here.
    To get a dilation factor equivalent to something like two times slower passage of time than somewhere far away from any mass concentrations, you'd need to get very close to an event horizon of a black hole. Anywhere else and you're looking at best at something in the vein of a few hours, maybe days of difference per year of elapsed time.
  4. Feb 3, 2016 #3
    interesting thank you.

    So, how close? Because at the centre of the Milky way there is a supergiant one and in the region around that there are literally billions of stars in close proximity - could they be affected. Also, just to be sure, you're saying that the mass that causes dilation would need to be very localised and concentrated and that having equal mass over a larger area - say the inner belt of stars around that black hole would not cause an effect?
  5. Feb 3, 2016 #4


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    The super massive BH at the center of our galaxy is ~4.3 million times more massive than our Sun. This gives it a event horizon radius of 1.27e7 km. For an object orbiting it to show a time dilation factor of 1/2 as mentioned earlier, it would have to orbit at a distance of 2.54e7 km. To give you an idea of how close that is, Mercury orbits the sun at a distance of 5.79e8 km or better than 20 times further away. A clock orbiting the BH at the same distance as Mercury orbits the Sun would only show a dilation factor of 0.9834 ( run slow by ~1 min per hr.)
  6. Feb 3, 2016 #5
    Perhaps you are also mixing up perception of the passage of time with a comparison of the passage of time. Just because time appears to pass extremely slow while waiting in front of a microwave oven in comparison, it really doesn't. Same with the fly and the human. However, someone living on a planet as close to a black hole as described above (if they could actually survive living in such an environment) still perceives time as happening one second at a time just like you perceive it now. However, an independent observer would notice your time as running at half the speed of the poor stretched out alien's living too close to a BH. Hope I have this right everyone?
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