# Electron in Earth Orbit: Does it Emit Radiation?

• yogi
In summary, the question is whether an electron in circular Earth orbit emits radiation and if so, why doesn't it spiral inwards? According to classical behavior, the electron would emit Larmor radiation at a tiny rate due to its high radial quantum number. The equivalence principle does not hold for radiation by electric charges, but references suggest that an electron in freefall will radiate and that an observer comoving in the frame will not see the radiation. This suggests that the radiation is due to a global property rather than identifiable local physics. Further investigation is needed to determine if a charged capacitor in orbit would emit radio frequency signals.
yogi
Does an electron in circular Earth orbit emit radiation?

A good question, similar to the question: "Does an electron 'sitting' on a laboratory bench emit radiation as by the equivalence principle it is accelerating upwards at an acceleration g?"

If the answer to the orbiting scenario is 'yes', then the electron might be expected to spiral inwards to conserve energy; however where does the energy of radiation of an emitting supported electron on a lab bench come from?

Garth

Last edited:
yogi: Yes. An e in Earth orbit behaves classically because its radial quantum number is so high. It would emit what is called Larmor radiation at the rate:
P=2e^2 R^2 \omega^2/3c^2. (This is in Gaussian units.)
You can put numbers into see that this radiated power is tiny.

Garth: The EP does not hold for radiation by electric charges.
There is another post about that today.

Meir Achuz said:
Garth: The EP does not hold for radiation by electric charges.
There is another post about that today.
Why not? It would seem logical to expect that all physical processes within this universe's space-time would be subject to the the geometric effects and principles of GR.

There has been dicsussion on this subject on these Forums some time ago.

Garth

Seems the references cited in the other thread support the notion that 1) an electron in freefall will radiate, and 2) an observer comoving in the freefalling frame does not see the radiation? So unless there is some identifiable local physics that tell the electron in free fall when and how to radiate - the radiation must be due to a global property. If we place a charged spherical capacitor in orbit we should expect to detect radio frequence signals? - what about a charged parallel plate capacitor?

## 1. What is an electron in Earth orbit?

An electron in Earth orbit is a negatively charged subatomic particle that is continuously moving around the Earth in a specific path or orbit due to the Earth's gravitational pull.

## 2. Does an electron in Earth orbit emit radiation?

Yes, an electron in Earth orbit does emit radiation. This is because as the electron moves in its orbit, it experiences acceleration and according to Maxwell's equation, accelerating charges emit electromagnetic radiation.

## 3. What type of radiation does an electron in Earth orbit emit?

An electron in Earth orbit emits electromagnetic radiation, specifically in the form of photons with different wavelengths depending on the energy of the electron. This radiation falls in the range of radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

## 4. Is the radiation emitted by an electron in Earth orbit harmful?

The radiation emitted by an electron in Earth orbit can be harmful in large quantities, such as in the case of high energy electrons in Earth's Van Allen radiation belts. However, the amount of radiation emitted by a single electron in Earth orbit is extremely small and not harmful to humans.

## 5. Can the radiation emitted by an electron in Earth orbit be used for any practical purposes?

Yes, the radiation emitted by an electron in Earth orbit has been used for practical purposes in various technologies such as communication, navigation, and medical imaging. For example, radio waves emitted by electrons in Earth orbit are used in radio broadcasting, while X-rays emitted by high energy electrons are used in medical imaging techniques such as X-ray radiography and computed tomography (CT) scans.

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