The half-life of some radioisotopes is given in the table below: years.This means that if a rock contained 100 g of uranium-238 at the time the earth came into being, then at the present time the rock would contain only half that amount, ½ × 100 = 50 g, of uranium-238.
You, like other living systems, are an amazing energy transformer.
As you move your eyes to read these words, your body is busily converting chemical energy from your lunch into kinetic energy and thermal energy (heat). Some of them are eukaryotic (human), but many more of them are prokaryotic, thanks to the friendly bacteria of your gut, skin, and other body systems.
Similarly, we could determine how long we would have to wait in order for there to be only 75 grams of uranium-238 left in the rock.
Reading this off the graph, we see that the answer is about 0.18 × 10 We can determine the half-life of strontium-90 by inspecting the mass of strontium-90 remaining in the bone.
Did you know that your body is approximately 18% carbon?