I figure I might as well cut & paste my 'clocks' post here:
CLOCKS
Visit any limestone cave. Stalactites grow at a rate of about 1mm per 10 years. So a 10 meter stalactite has been growing about 100,000 years. And close examination of cross sections shows the year by year layering (where rainfall is seasonal). These stalactites can be found all over the world. The ages are corroborated by radiometric carbon dating.
Tree rings are clocks. The oldest living tree goes back about 4800 years. But wood from dead trees can contain records of volcanic events, thus extending the record back much farther.
Originally developed for climate science, the method is now an invaluable tool for archaeologists, who can track up to 13,000 years of history using tree ring chronologies for over 4,000 sites on six continents.
The ages are corroborated by radiometric carbon dating (establishing age by measuring ratios of radioactive vs stable isotopes).
Seasonal snowfall on glaciers accumulates to form countable layers. Greenland ice sheet layers can be counted back about 110,000 years. The ages are corroborated by radiometric dating. Other glaciers go back as far as 700,000 years, but on those the older data is mostly radiometric dating.
Salt flows from rocks into lakes and the ocean. If no salt left the ocean, that would give an age of 50 million to 70 million years. However, various geologic processes cause salt to leave the ocean at about the rate it's entering, so 50 million to 70 million years becomes a minimum estimate of the age of the earth.
Layering of sedimentary rocks - such as in the Grand Canyon - forms a series of clocks. These layers correspond to different stages in the evolution of life on the planet. The layers can be dated by positional order (bottom layer formed first), sedimentation rate, age of fossils found in the layer, and of course, radiometric dating. There are five main isotope pairs used for dating sedimentary rocks as well as the 'fissile track' method; you can read about it all here:
https://australian.museum/learn/minerals/shaping-earth/radioactive-dating/
Then there's all the fossils of extinct animals found in the rock layers. They're not exactly a clock, but they are an indicator of the vast amounts of time over which evolution occurs.
Of course outer space offers many clocks. Accumulation of craters on airless bodies like the Moon forms a clock. Shells of glowing gas left over from novas and supernovas form clocks (the Lambda Orionis Ring is about 1 million years old). The redshift of light from galaxies billions of light years away form clocks. The Hubble expansion of the universe forms a clock. The frequency shift of big bang radiation to form the cosmic microwave background is a clock.
No one clock is perfect, but they all corroborate each other pretty well, and they ALL give life FAR MORE than 6000 years to evolve.
If you argue "God hid those dinosaur bones (and all the isotopes used for dating) in the rocks" I can't disprove it. If you argue "God built all those layers into the glaciers and into stalactites, made the nova remnants appear millions of years old, etc." I can't disprove it. But you've got to ask yourself, why would God put all these inter-corroborating clocks all over the Earth and all thru the galaxy if they were all false???
