<span>This
is because astronomers have discovered that
the Crab Nebula is 6500 light years from earth. This means it takes 6500 earth years
for light to get from the Crab Nebula to
earth. Therefore, if we are able to observe the
Crab Nebula and beyond it then it means that earth has been in existence for 6500 years and
over. </span>
