In 1935,
when both quantum mechanics and Albert Einstein’s general theory of relativity
were young, a little-known Soviet physicist named Matvei Bronstein, just 28
himself, made the first detailed study of the problem of reconciling the two in
a quantum theory of gravity. This “possible theory of the world as a whole,” as
Bronstein called it, would supplant Einstein’s classical description of
gravity, which casts it as curves in the space-time continuum, and rewrite it in
the same quantum language as the rest of physics.
Bronstein figured out how to describe gravity in terms of quantized particles, now called gravitons, but only when the force of gravity is weak — that is (in general relativity), when the space-time fabric is so weakly curved that it can be approximated as flat. When gravity is strong, “the situation is quite different,” he wrote. “Without a deep revision of classical notions, it seems hardly possible to extend the quantum theory of gravity also to this domain.”
His words
were prophetic. Eighty-three years later, physicists are still trying to
understand how space-time curvature emerges on macroscopic scales from a more
fundamental, presumably quantum picture of gravity; it’s arguably the deepest
question in physics. Perhaps, given the chance, the whip-smart Bronstein might
have helped to speed things along. Aside from quantum gravity, he contributed
to astrophysics and cosmology, semiconductor theory, and quantum
electrodynamics, and he also wrote several science books for children, before
being caught up in Stalin’s Great Purge and executed in 1938, at the age of 31.
The Soviet
theoretical physicist Matvei Petrovich Bronstein (1906-1938), a pioneer of
quantum gravity research whose work remains largely unknown in the west.
The search
for the full theory of quantum gravity has been stymied by the fact that
gravity’s quantum properties never seem to manifest in actual experience.
Physicists never get to see how Einstein’s description of the smooth space-time
continuum, or Bronstein’s quantum approximation of it when it’s weakly curved,
goes wrong.
The
problem is gravity’s extreme weakness. Whereas the quantized particles that
convey the strong, weak and electromagnetic forces are so powerful that they
tightly bind matter into atoms, and can be studied in tabletop experiments,
gravitons are individually so weak that laboratories have no hope of detecting
them. To detect a graviton with high probability, a particle detector would
have to be so huge and massive that it would collapse into a black hole. This
weakness is why it takes an astronomical accumulation of mass to
gravitationally influence other massive bodies, and why we only see gravity
writ large.
Not only
that, but the universe appears to be governed by a kind of cosmic censorship:
Regions of extreme gravity — where space-time curves so sharply that Einstein’s
equations malfunction and the true, quantum nature of gravity and space-time
must be revealed — always hide behind the horizons of black holes.
“Even a few years ago it was a generic consensus that, most likely, it’s not even conceivably possible to measure quantization of the gravitational field in any way,” said Igor Pikovski, a theoretical physicist at Harvard University.
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2 Comments
I don't know, that the theory of Newton still a joke, or a misunderstanding of the physics, but Newton has had no information enough about the cosmos. It was 350 years ago! But, right now, we know the space well. And have to know, there are no gravity over the Kàrmàn-line, what is 100kms/70mls! What we are talking about??
ReplyDeleteSo...what was the trick referred to in the title???
ReplyDelete