How do scientists know the bones are really 68 million years old?Today's knowledge of fossil ages comes primarily from radiometric dating, also known as radioactive dating.

radiometric dating on fossils-5

To read the time on this radioactive clock, scientists use a device called a mass spectrometer to measure the number of parent and daughter atoms.

The ratio of parents to daughters can tell the researcher how old the specimen is.

Radiometric dating relies on the properties of isotopes.

These are chemical elements, like carbon or uranium, that are identical except for one key feature -- the number of neutrons in their nucleus.

Only hard parts, like bones and teeth, can become fossils.

But for some people, the discovery raised a different question.

How do we fit these few scattered artifacts and bones into a coherent history? Secular investigators start with the assumption that humans evolved from a common ancestor with the apes and then dispersed across the globe over millions of years.

Somehow, we need to work out the age of each find so it can be put in the correct place within the biblical framework of human history. Secular scientists have several dating methods at their disposal, which they claim support their views. Consequently, they have interpreted the evidence accordingly.

This means that isotopes with a short half-life won't work to date dinosaur bones.

The short half-life is only part of the problem when dating dinosaur bones -- researchers also have to find enough of the parent and daughter atoms to measure.

Once all the parents have become daughters, there's no more basis for comparison between the two isotopes.