Clocks may be used to estimate how long a process has been taking place.All clocks (including radiometric ones) require the use of at least three assumptions.As time passes, the amount of helium in the atmosphere increases.Scientists have estimated the amount of uranium in the earth's crustal rocks.Therefore scientists must make a guess with regard to what they believe the original conditions might have been.The shorter the time involved, the more likely that a specific process has been constant, and unaltered by external influences.
A "clock" is any geophysical or astronomical process that is changing at a constant rate.
If we assume a growth rate of one tree ring per year, then the oldest trees are between 4,500 and 4,767 years old.
The fact that these trees are still alive and growing older means that we don't yet know how old they will get before they die.
The gravitational pull between the Earth and Moon causes the Earths oceans to have tides.
The tidal friction between the Earths terrestrial surface and the water moving over it causes energy to be added to the Moon.
The following clocks point to a young earth, solar system, and universe.