Re: How old are atoms?

From: Sbharris[atsign] (
Date: 03/25/05

Date: 24 Mar 2005 20:48:22 -0800

>>I know they can be smashed and crushed by humans and that some of
degrade from unstable to more stable isotopes and that the sun turns H
He but...

How long do atoms generally live?

Are some of the ones around now orignals created at the beginning or
they all been transformed by stars or some other routine process? <<


I think you're trying to ask how old atoms are. That depends on the
atom. Nearly all atoms of deuterium are 13.5 billion years old, having
been made in the big bang and been around since then. Makes you admire
that bottle of heavy water. Probably a lot of light hydrogen atoms are
that old also, but it's hard to tell which ones.

Most of the heavier atoms are thought to have been formed in supernovas
which blew up in our region of space 5 to 10 billion years ago, and
scattered the dust cloud from which our solar system formed. So they're
round about that age. All older than 4.6 billion years (the age of our
solar system) but not as old as the big bang. From the patters of
elements, there were apparently at the very least, dozens of such stars
which contributed to our solar dust cloud. So the mix of ages of stable
atoms is quite wide. All we can say is that they're probably all
younger than our galaxy, but older than our solar system.

Some stable atoms are younger than our solar system and the earth
(which are about the same age-- 4.6 billion years). Probably most
helium from the ground is made of retired alpha particles from U and
Th, so it's younger than the Earth. Still millions to billions of years
old, though.

Most radioactive elements are also younger than the Earth, and are
products of decays have have happened since the Earth formed. Important
exceptions are uranium and thorium, which are extremely long-lived, and
date back to the supernovas previous referenced.