Let's ignore extraterrestrial visitors on Earth because I don't want to discuss twin paradox, we should be focusing on life inhabiting on another planet instead.

Here on Earth we can do carbon dating because of plant and animal eat them even indirectly, it contains trace of C14, radioactive isotope produced as byproduct from the bombardment of cosmic ray or underground unclear testing etc. The alien sample should be exchanging C14 unless it dies and we know how to apply the known half-life of C14 to calculate their current approximate biological age, but does it hold true to other life in the universe as well?

Let's ignore extraterrestrial visitors on Earth because I don't want to discuss twin paradox, we should be focusing on life inhabiting on another planet instead.

Here on Earth we can do carbon dating because of plant and animal eat them even indirectly, it contains trace of C14, radioactive isotope produced as byproduct from the bombardment of cosmic ray, underground nuclear testing, etc. The alien sample should be exchanging C14 unless it dies and we know how to apply the known half-life of C14 to calculate their current approximate biological age, but does it hold true to other life in the universe as well?

Let's ignore extraterrestrial visitors on Earth because I don't want to discuss twin paradox,we should focus on life on another planet instead.

Here on earth we can do carbon dating because of plant and animal eat them even indirectly too, it contains trace of C14, radioactive isotope from cosmic ray or underground unclear testing etc. The sample should be exchanging C14 unless it dies and we know how to apply the known half-life of C14 to calculate their current approximate biological age, but does it hold true to other life in the universe as well?

Let's ignore extraterrestrial visitors on Earth because I don't want to discuss twin paradox, we should be focusing on life inhabiting on another planet instead.

Here on Earth we can do carbon dating because of plant and animal eat them even indirectly, it contains trace of C14, radioactive isotope produced as byproduct from the bombardment of cosmic ray or underground unclear testing etc. The alien sample should be exchanging C14 unless it dies and we know how to apply the known half-life of C14 to calculate their current approximate biological age, but does it hold true to other life in the universe as well?