Isotope best dating very old rocks
Geologists have found annual layers in ice that are easily counted to multiple tens of thousands of years, and when combined with radio isotope dating, we find hundreds of thousands of years of ice layers.Using the known rate of change in radio-active elements (radiometric dating), some Earth rocks have been shown to be billions of years old, while the oldest solar system rocks are dated at 4.6 billion years.Here we will describe just two types of evidence for an old Earth and two types of evidence for an old universe; more types can be found under further reading.
Shorter than violet you would see the ultraviolet, that which gives us tans and sunburns, and then you would encounter much more dangerous X-ray radiation and finally deadly gamma rays.
Astronomers use the distance to galaxies and the speed of light to calculate that the light has been traveling for billions of years.
The expansion of the universe gives an age for the universe as a whole: 13.7 billion years old.
They led to the discovery that certain very heavy elements could decay into lighter elements – such as uranium decaying into lead.
Many independent measurements have established that the Earth and the universe are billions of years old.