Sorry if my question is not really clear, but indeed it is not clear in my mind neither. But maybe some of you can help. Time is not absolute and can be affected by the gravitational potential. Now the question is: do concepts like the age of the Universe, time between different cosmic epochs etc, depend on the position of the observer with respect to a gravitational field? If yes, how much things would change if we were observers, e.g., close to a black hole or in absence of gravity?

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    $\begingroup$ The difference in rate of time caused by Earth's gravity is smaller than the error bars on most (if not all) cosmological time estimates. It does affect however for example measurements of pulsars, so in such cases the gravitational time dilation must be and is taken into account. $\endgroup$ – tuomas Jun 22 '20 at 11:48
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    $\begingroup$ @tuomas I would write an answer. $\endgroup$ – ProfRob Jun 22 '20 at 12:21
  • $\begingroup$ @tuomas I see, thanks.. what about an observer far from any (local) gravitational field, e.g., a void? $\endgroup$ – user19333 Jun 22 '20 at 12:27
  • $\begingroup$ From en.wikipedia.org/wiki/Gravitational_time_dilation a clock on Earth's surface loses about 2.19 seconds per century due to the Earth's gravity. $\endgroup$ – PM 2Ring Jun 22 '20 at 15:03
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    $\begingroup$ @PM2Ring From this answer it seems that on Earth time is -0.7 ppb (parts per billion) slower due to Earth's own gravity well and rotational speed, (agrees with your value) but if you take into account that the Earth sits in the Sun's gravitational well and orbits it at about 29 km/sec, the effect is -15.5 ppb! Only slightly related: Parker Solar Probe passing extremely close to the Sun; what relativistic effects will it experience and how large will they be? $\endgroup$ – uhoh Jun 22 '20 at 22:57

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