- Gravity is the force the prevents the Sun from expanding despite
the fact that it is a hot gas and keeps the Earth forever falling towards the
Sun in it's orbit and keeps all the people in this room in their seats. One way
to look at gravity is that it is an attractive force between objects with
- Electric Force is a force felt between charged particles
like electrons (e-) and protons (p+). There are both attractive and repulsive electrical
forces. Like charges repel, opposites attract. The Electrical Force
holds atoms and molecules together and is useful for all kinds of
nifty gadgets that have been built in the last 150 years.
Fun note: The electric force is what keeps you from falling through the
chair and floor and earth and being cooked in the center of the Earth.
You are suspended above your chair by the repulsive force of the protons
in your body against the protons in the chair.
- Nuclear Force. If you think about it for a minute, nuclei of
atoms which contain protons (positively charged) and neutrons (no charge) should
not be stable. All those ``like'' charged protons should be repelling one another and
fly right out of the nucleus. Since nuclei ARE stable, it can be inferred that
there is another force that is stronger than the electrical force which glues
those nuclei together. This is the Nuclear Force or the Strong force.
The Nuclear force would right now be binding EVERYTHING together except for
the fact that it acts over only very tiny distances.
For the ``heavy'' elements in the Periodic Table there are some that
have nuclei that spontaneously fall apart - these are the radioactive
The wild thing about this is that if you weigh the initial nucleus
and weigh the bits after the ``fission'' they don't add to the same total.
- The Missing Mass in the fission reaction has been converted into
energy via the only equation that 8 out of 10 Americans know:
This equation says that Mass and Energy are interchangable.
- The equation above as applied to this reaction (and also to chemical
where is the mass difference between the Uranium nucleus and the
fission product nuclei.
- This is a pretty efficient source of energy. Some fission reactions
release as much as ergs/gram of fissionable material. The problem
is, the Sun has only a tiny fraction of its composition in radioactive
THE ANSWER: NUCLEAR FUSION
There is a short string of similar reactions that go on in
any hot gas of hydrogen atoms. This is called the proton-proton cycle or the
The whole thing can be summarized with one net reaction:
- Now let's suppose the Sun is made of Hydrogen and it
is hot enough to run the P-P Chain. How long would its lifetime be
at as a nuclear-fusion powered object?
- This is the available energy from hydrogen fusion
- This is the lifetime of the Sun with fusion power:
- Looks pretty promising!
- Is Hydrogen Fusion for real or just another theory? It's
for real - don't forget Bikini Atoll.
- WHAT ARE THE REQUIREMENTS FOR A FUSION-POWERED SUN?
- Lots of protons - no problem, the Sun is made mostly of hydrogen.
Fri Feb 6 23:24:56 PST 1998