13.7 billion years is a common estimate for the age of the universe. As far as I know this number is calculated using observations of red shifted galaxies. We see that the universe is expanding and simply extrapolate backwards to determine that matter comes to a singularity at T-13.7 billion years. But I wonder if this simple calculation from the "outside" point of view truly represents the proper time a given particle would experience. According to general relativity, time slows down for a particle in a gravity well. For example clocks on GPS satellites run faster than ground based clocks and this effect must be compensated for. Wouldn't this effect be significant in the early dense universe? It occurs to me that the proper time experienced by a particle might be significantly more than 13.7 billion years. Perhaps it even approaches infinity as the universe becomes infinitely dense. Indeed this might change that status of the Big Bang from an actual event to an asymptotic limit.

I am merely an amateur throwing stones here. I would be grateful for expert information on this.

For the particle itself, time just runs as fast or as quickly (whatever you like) as always, as well in a gravity well as outside of it.

Relativity only tells us that for someone outside of the gravity well looking in, it will appear that the clock for that particle is ticking more slowly than this person's own clock.

So your "time slows down" only happens for outside observers and not for the observed.

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Optimism does not change the laws of physics. (T'Pol)
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Martin ( http://www.geocities.com/DrMartinV )

That is, in fact, exactly what it is. The "calculation" you referred to is a calculation of proper time. So when cosmologists report an age of the universe, that "age" is in fact the proper time measured by a clock moving in free fall from the bang to us.

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