# Relative and absolute dating for kids

*23-Oct-2017 10:34*

If the traveling clock experiences amount of time and the stationary clock experiences amount of time, then (which you’ll notice is always less than t) where v is the speed of the traveling clock and c is the speed of light.The ratio between these two times is called “gamma”, , which is a useful piece of math to be aware of.Now admittedly, there are examples of things either trapped in black holes or screaming across the universe at near the speed of light, but the good news for us (on both counts) is that such stuff is rare.The only things that move anywhere close to the speed of light is light itself (no surprise) and occasionally individual particles of matter.Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Physicist: One of the most profound insights ever made by peoplekind is that time is relative. The existentially terrifying answer is: there is no such thing as a “correct clock”.

Considering that our best estimates for the age of the universe are only accurate to within 20 million years or so (0.1% relative error), a few dozen millennia here and there doesn’t make any difference.

There are two ways to get clocks to disagree: the twin paradox and gravitational time dilation.

The twin paradox a bizarre consequence of the difference between ordinary geometry and spacetime geometry.

If you want to figure out the total dilation between, say, the surface of the Earth and a point “infinitely far away” (far enough away that Earth can be ignored), then you use the speed something would be falling if it fell from deep space: the escape velocity.

By and large, the effect from the twin paradox is smaller than the effect from gravity, because if something is traveling faster than the local escape velocity, then it escapes.So the velocity you plug into gamma for the twin paradox (the physical velocity) is lower than the velocity you’d plug in for gravitational dilation (the escape velocity).