How old is the earth?
That should be easy to calculate from any number of processes. And it is. The problem is that the different processes give different answers. Here’s basically how to do it. Let’s say there is a process (radioactive decay) that converts one substance (call it A)into another (call it B). All we need to know is the rate of conversion and the amount of substance B created by the process. We can observe the current rate of conversion and assume that has been constant over time. We can assume that all of substance B currently in existence was the product of the conversion. Divide the quantity by the rate and you get the time. Simple, no?
What’s that you say? How do we know that all of B came from the conversion process? I told you. We assume it. Now what? How do we know there was no change in the conversion rate over the years? We assume it. For short periods of time that is not a bad assumption. What? You want to know how we can be sure the rate did not change over millions of years? What kind of radical trouble maker are you anyway? What part of ASSUME do you not understand?
Besides, the earth must be billions and billions of years old in order for evolution to have created the current array of humans and livestock form the primordial rocks. No intelligent person doubts the extreme age of the earth. Anybody who thinks the earth is young must be some kind of nut.
More to come . . .