Modern scientific consensus puts the age of the earth at about 4.5 billion years old ± 0.1 billion years. This was estimated by literally finding the oldest piece of rock we know and dating it using radiometric dating.

For the curious, this is how radiometric dating works.

Some people argue that the earth is young (< a million years old). So, I'll like to use this opportunity to call on vooks to explain how that time frame was arrived upon.

How does radiometric works, first?

Uh uh . . .

Of course, whatever explanation he has to give will include the necessity of a supernatural entity.

this, of course, is against the philosophy of science and thus, his argument is dead on arrival since this is the science section.

tempem:
How does radiometric works, first?

Geologists discovered that radioactive materials decay into other
elements at a very predictable rate.

Some materials decay quickly, while others can take millions or even billions of years to fully decay. Ernest Rutherford and Frederick Soddy, working at McGill University, determined that half of any isotope of a radioactive element decays into another isotope at a set rate.


For example, if you have a set amount of Thorium-232, half of it will decay over a
billion years, and then half of that amount will decay in another billion years. This is the source of the term “half life”.


By measuring the half lives of radioactive isotopes, geologists were
able to build a measurement ladder that let them accurately
calculate the age of geologic formations, including the Earth. They
used the decay of uranium into various isotopes of lead.

By measuring the amount of three different isotopes of lead (Pb-206,
Pb-207, and Pb-208 or Pb-204), geologists can calculate how
much Uranium was originally in a sample of material.


If the Solar System formed from a common pool of matter, with
uniformly distributed Pb isotopes, then all objects from that pool of
matter should show similar amounts of the isotopes.

Also, over time, the amounts of Pb-206 and Pb-207 will change because as
these isotopes are end-products of uranium decay. This makes the
amount of lead and uranium change. The higher the uranium-to-
lead ratio of a rock, the more the Pb-206/Pb-204 and Pb-207/
Pb-204 values will change with time.

Now, supposing that the source of the Solar system was also uniformly distributed with uranium isotopes, then you can draw a data line showing a lead-
to-uranium plot and, from the slope of the line, the amount of time
which has passed since the pool of matter became separated into
individual objects can be computed.

Bertram Boltwood applied this method of dating to 26 different
samples of rocks, and discovered that they had been formed
between 92 and 570 million years old , and further refinements to
the technique gave ages between 250 million to 1.3 billion years.
Geologists set about exploring the Earth, seeking the oldest rock
formations on the planet.

The oldest surface rock is found in
Canada, Australia and Africa, with ages ranging from 2.5 to 3.8
billion years. The very oldest rock was discovered in Canada in
1999, and estimated to be just over 4 billion years old.

Read more here http://www.universetoday.com/75805/how-old-is-the-earth/