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Q & A: Are electrons like planets?

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Most recent answer: 02/24/2013
Q:
General Theory of relativity states that mass curves the space-time. All planets move in this curved space-time following geodesic path. Hence planets need not radiate while rotating around the sun. Quantum theory may not agree with all aspects of General Theory of relativity. But the gravitation is proved to be the effect of curvatures of space-time by mass and not due to force of gravity. Still why do quantum scientists often speak of “Gravitons” as force carrier. Rutherford’s experiment indicates that electrons revolve around nucleus in big circles. If we ignore this experiment whether it can be accepted that electrons revolve around the nucleus within space time curvature created by nucleus instead of accepting the quantum theory “Both location and momentum of particle can’t be measured accurately and simultaneously”.
- Balakrishna Nikam (age 54)
Bangalore Karnataka India
A:
First, we should clear up some points.

Although planets do follow geodesics, that doesn't prevent the orbiting system from radiating. The planet-sun system has a mass quadrupole moment which keeps changing in the rotation, so there's gravitational radiation. It's extremely weak.

Rutherford's experiments showed that the mass of atoms was mostly concentrated in a very small region, with charge equal to the atomic number- the nucleus. He absolutely did not show, nor is it true, that electrons orbit the nucleus as if they were planets. That was a guess people made in trying to figure out how to picture the atom. It was quickly realized that the guess was not workable because the electromagnetic radiation would cause the atom to collapse very quickly.

Over small regions of spacetime, away from unusually dense masses, you can describe gravity well as if it were a force in flat spacetime. In a quantum version of that, the carriers of that force would be a spin-2 particle, which is called a graviton. Why do people choose to even talk about a quantum version, when there are no realistic prospects of detecting these gravitons? One reason is that it turns out that having any non-quantum field, even general relativity's spacetime, leads to logical incompatibility with quantum mechanics. The classical-like field could be used to unravel the uncertainty relations, which are a necessary consequence of the structure of quantum mechanics. So we think someday a logically consistent union of gravity and quantum mechanics will be developed and it will include quantized waves in spacetime.

Mike W.

(published on 02/24/2013)

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