What it's for

Posted by DickT on February 05, 2003 at 13:31:26:

In Reply to: What's it for? posted by Heliothrope on February 05, 2003 at 12:25:47:

Heliotrope,

Superstring theory is still a possible candidate for the theory that unites gravitation with the rest of quantum theory. At the very least it is a way station on the road to a theory that does that.

You can build up atoms from Hydrogen to Iron because each atom has a lower binding energy than the one before it and a higher binding energy than the one after it. So a natural process that wants to go from higher energy to lower can execute that construction. Nature won't go the other direction by itself because it is "uphill" energywise.

Binding energy is the difference between the mass energy (e = mc^2) of the atomic nucleus and the total mass energies of the protons and neutrons that comprise it. It is the energy required to hold all those hadrons together in one nucleus.

The curve of binding energy starts out high at the Hydrogen end of the elements and decreases in steps to iron, the minimum. Even higher binding energies occur at the uranium end of the list, making fission an energetically favored possibiity. The binding energy drops as you go from uranium to lighter elements until, once again, you reach iron. Iron has been called the ash element, to build on it or to split it requires more energy than you get by doing the operation.
Regards,
Dick

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