Eli5 if time is relative and gets effected by gravity how could we possibly determine the age of our universe?

Question

Eli5 if time is relative and gets effected by gravity how could we possibly determine the age of our universe?

In: 843

Answer 1

I would think the scientist take all that into account in their calculations. It is mind boggling to me.

Is it wrong to apply black holes to the big bang?

Like , the more mass condensed will warp spaceTime, slowing it down.

So at just after the big bang, so much mass is in so little space that time is almost zero. And as it expands and spreads , time( as in not drastically affected by mass), ramps up to one second per second as a default?

So the big bang IS the beginning of time at Zero, as we know it.