Do we need Dark Matter or are we just time blind

  • #26
Chalnoth
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I'm not seeing this yet. Are you saying that gravitational time dilation can't possibly flatten the curve, or are you saying that significant gravitational time dilation is ruled out?
I'm saying that adding a bunch of mass to the center will result in a steeper rotation curve, not a shallower one.
 
  • #27
Vanadium 50
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  • #29
Apologies for my absence from the discussions and thank you for your interest in the ideas. I accept that time dilation is too small to have any practical affect on astronomical measurements.

However, I still think that the concept of viewing an event from a different time frame is one which should always be considered.



As a frivolous example, imagine driving your car slowly up to a brick wall until you just touched it. If the event was recorded using time lapse photography, the resulting video might show that it was perfectly safe to drive into a brick wall at 100mph.



During the big bang, the entire mass/energy of the universe was concentrated in a tiny “pinprick”.

The gravitational forces in this pinprick must have been enormous and the time dilation appreciable.

Hence the velocity and hence violence of the initial expansion may not have been as great as we now think when viewing it in our time frame.



Hence, perhaps the universe did not expand faster than light speed, perhaps the expansion was not violent enough to produce significant gravitational waves and according to the particles involved, the universe is older than 13.7 billion years.
 
  • #30
PeterDonis
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The gravitational forces in this pinprick must have been enormous and the time dilation appreciable.
No, they weren't. The spacetime curvature in the pinprick was enormous (because the density of stress-energy was enormous), but that spacetime curvature showed up as very rapid expansion, not as "gravitational forces". And there was no gravitational time dilation because the density was the same everywhere, so the spacetime curvature at a given instant of time was the same everywhere.

Hence the velocity and hence violence of the initial expansion may not have been as great as we now think when viewing it in our time frame.

Hence, perhaps the universe did not expand faster than light speed, perhaps the expansion was not violent enough to produce significant gravitational waves and according to the particles involved, the universe is older than 13.7 billion years.
These speculations are incorrect, because they are based on a mistaken premise. See above.
 
  • #31
Chronos
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The baryon mass fraction of the universe has been measured with great precision by a number of studies [Planck, WMAP, BAO] which rules out any significant unaccounted contributions from black holes. For further discussion see https://ned.ipac.caltech.edu/level5/Peebles2/P5_2.html
 

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