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P H V SIC 5 OF THE IMPOSSIBLE
ANTIGRAVITY AND ANTI-UNIVERSES
Using Dirac's theory, we can now answer a host of questions: What is
the antimatter counterpart of gravity? Do anti-universes exist?
As we discussed, antiparticles have the opposite charge of ordinary
matter. But particles that have no charge at all (such as the photon, a
particle of light, or the graviton, which is a particle of gravity) can be
their own antiparticle. We see that gravitation is its own antimatter; in
other words, gravity and antigravity are the same thing. Hence antimatter should fall down under gravity, not up. (This is universally believed by physicists, but it has actually never been demonstrated in the
laboratory.)
Dirac's theory also answers the deep questions: Why does nature
allow for antimatter? Does that mean anti-universes exist?
In some science fiction tales, the protagonist discovers a new
Earth-like planet in outer space. In fact, the new planet seems identical to Earth in every way, except everything is made of antimatter. We
have antimatter twins on this planet, with anti-children, who live in
anti-cities. Since the laws of anti-chemistry are the same as the laws of
chemistry, except charges are reversed, people living in such a world
would never know they were made of antimatter. (Physicists call this
the charge-reversed or C-reversed universe, since all charges are reversed in this anti-universe, but everything else remains the same.)
In other science fiction stories scientists discover a twin of the
Earth in outer space, except that it is a Looking Glass universe, where
everything is left-right reversed. Everyone's heart is on the right side
and most people are left-handed. They live out their lives never knowing that they live in a left-right reversed Looking Glass universe.
(Physicists call such a Looking Glass universe a parity-reversed or
P-reversed universe.)
Can such antimatter and parity-reversed universes really exist?
Physicists take questions about twin universes very seriously, since
Newton's and Einstein's equations remain the same when we simply
flip the charges on all our subatomic particles or reverse the left-right
P H V SIC 5 OF THE IMPOSSIBLE
ANTIGRAVITY AND ANTI-UNIVERSES
Using Dirac's theory, we can now answer a host of questions: What is
the antimatter counterpart of gravity? Do anti-universes exist?
As we discussed, antiparticles have the opposite charge of ordinary
matter. But particles that have no charge at all (such as the photon, a
particle of light, or the graviton, which is a particle of gravity) can be
their own antiparticle. We see that gravitation is its own antimatter; in
other words, gravity and antigravity are the same thing. Hence antimatter should fall down under gravity, not up. (This is universally believed by physicists, but it has actually never been demonstrated in the
laboratory.)
Dirac's theory also answers the deep questions: Why does nature
allow for antimatter? Does that mean anti-universes exist?
In some science fiction tales, the protagonist discovers a new
Earth-like planet in outer space. In fact, the new planet seems identical to Earth in every way, except everything is made of antimatter. We
have antimatter twins on this planet, with anti-children, who live in
anti-cities. Since the laws of anti-chemistry are the same as the laws of
chemistry, except charges are reversed, people living in such a world
would never know they were made of antimatter. (Physicists call this
the charge-reversed or C-reversed universe, since all charges are reversed in this anti-universe, but everything else remains the same.)
In other science fiction stories scientists discover a twin of the
Earth in outer space, except that it is a Looking Glass universe, where
everything is left-right reversed. Everyone's heart is on the right side
and most people are left-handed. They live out their lives never knowing that they live in a left-right reversed Looking Glass universe.
(Physicists call such a Looking Glass universe a parity-reversed or
P-reversed universe.)
Can such antimatter and parity-reversed universes really exist?
Physicists take questions about twin universes very seriously, since
Newton's and Einstein's equations remain the same when we simply
flip the charges on all our subatomic particles or reverse the left-right