When objects stick together, they interact with a certain strength — the binding energy. The concept applies widely:

• in the nuclei of atoms, protons and neutrons overcome their normal repulsion and cohere via strong interactions, with typical energies of millions of electron-volts (eV);
• electrons orbiting the atomic nucleus are held by the electromagnetic attraction of the oppositely-charged protons, with energies of a few eV or so;
• atoms bind to each other to make molecules, again through aspects of their electrical charges, but with (usually) weaker residual forces;
• moving up many orders of magnitude, discrete bodies such as asteroids, planets, or stars hold themselves together via gravitational binding energy;
• pairs of stars in binary systems, and thousands of stars in globular clusters, orbit their common center of mass again held by gravitational forces; galaxies cluster together similarly.

Binding energy considerations provide good mental tools to understand countless phenomena:

Why do solids melt or decompose at particular temperatures?

It happens when thermal energies exceed the binding energy of the molecules.

Why do Saturn and Jupiter (and Uranus, etc.) have rings?

When small bodies get too close to a large mass (within the "Roche Limit") tidal forces exceed the gravitational self-binding and the little masses are torn apart.

Why do nuclear bombs release so much destructive energy compared to chemical explosives?

The binding energies of the nuclei are millions of times greater.

Why do globular clusters or galaxies tend to evolve over time to have black holes at their centers?

When several stars coincidentally pass near each other, sometimes the gravitational interactions will kick one star away rapidly, leaving the others more tightly bound together; the process, repeated over millions of years, tends to produce high-density central cores, which then collapse into black holes.

Why are extraordinarily powerful nanotechnology "mechanical explosives" (e.g., as described in Neal Stephenson's Diamond Age sf novel) implausible?

Any hypothetical nanotech components (rotors, spokes, etc.) would have to be held together by intermolecular forces, and cannot have binding energies beyond those of ordinary molecules — so the tiny mechanical explosives would fall apart if one tried to store more than usual chemical energies in them. They thus might be equivalent to normal explosives, but not significantly more powerful.

The concept of binding energy could also be metaphorically applied to nonphysical entities ... ecological systems ... groups of people ... technological webs ... interacting societies ... networks of ideas ....

Monday, June 14, 1999 at 19:21:07 (EDT) = 1999-06-14

TopicScience

(correlates: OnDuals, NegativeHelp, CoherentInterference, ...)