All Questions
Tagged with electromagnetic-radiation estimation
34
questions
139
votes
2
answers
71k
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How many photons are received per bit transmitted from Voyager 1?
As of 2024, according to https://voyager.jpl.nasa.gov/ , Voyager 1 is around one light·day away from Earth and still in radio contact. When Voyager 1 sends messages to Earth, roughly how many photons ...
- 145
0
votes
1
answer
100
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How many photons pass through us every second?
I just read this answer https://physics.stackexchange.com/a/229374, which says that, when a magnet rotates, photons are emitted with wavelength $λ=c/f$, where $f$ is the frequency of rotation. And ...
- 59.6k
6
votes
4
answers
2k
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Accelerating Expansion of Universe - Why Not Caused by Radiation?
As I understand it, dark matter and dark energy are used as an 'explanation' for how universe expansion is accelerating; because without it gravity would be expected to cause a long term shrinking.
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- 1,002
0
votes
2
answers
65
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Are these levels of RF radiation harmful?
I live on the top floor of a building that has four 5G antennas on the roof. The house is curved, and from my viewpoint, I can partially see one of the antennas pointing towards me. Curious about the ...
- 41.1k
15
votes
4
answers
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If microwave ovens run at 2.4 GHz, what is the long-term effect on living tissue of exposure to this frequency, but with a thousand times less energy?
Very low power electromagnetic waves with a frequency of 2.4 GHz can't cook anything. That's obvious, despite the heating effect such radiation has on water.
However, what if such an object containing ...
- 2,352
21
votes
4
answers
9k
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Can lasers lift objects?
I have been fascinated by a very intriguing question - Can lasers push objects up?
Let's say we have a $1000~\text{mW}$ laser and we would like to lift an object of weight $100~\text{g}$.
By ...
- 133k
10
votes
1
answer
1k
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What fraction of the universe's energy is contained in photons?
From each point in the universe, the light of billions of stars, galaxies, supernovae etc. can be detected. So there seems to be a lot of energy/momentum "in flight".
Is it possible to ...
- 6,404
2
votes
3
answers
247
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How much watts per square meter does Phobos receive from Mars?
Being so close to Mars, Phobos should receive a non-negligible amount of irradiance from Mars. Be it from reflected sunlight, Mars' emitted infrared radiation, or other factors. I have no idea how to ...
CommunityBot
- 1
1
vote
0
answers
48
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How much radiation on the surface of the moon during a Coronal Mass Ejection (CME)?
I'm writing a book set on the moon. A Coronal Mass Ejection (CME) as large as the Carrington Event hits it. Three astronauts are caught out during an EVA. They will cover their rover in regolith to ...
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12
votes
2
answers
5k
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From how far away could Earth's telescopes detect Earth-like radio signals?
The Earth has been broadcasting human generated radio signals for about 100 years now. If a nearby civilization were broadcasting similar radio signals, could we detect them with our own radio ...
- 207k
6
votes
0
answers
76
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Does 5G affect your physics experiment?
Our institution wants to lease a nearby roof for a 5G mast. Has anyone experienced the installation and operation of telecoms infrastructure - particularly 5G - significantly affecting physics ...
- 207k
0
votes
0
answers
233
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How much UVA and UVB is blocked by shadow or being indoors?
I could not find a clear answer online so I though to try this forum instead.
I did find answers on how different types of glass can block different degrees of UVA and UVB. But I was wondering, if I ...
- 207k
2
votes
5
answers
2k
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Theoretically, could radio waves carry enough energy to destroy bacteria or viruses by resonance?
I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
- 6,314
2
votes
1
answer
188
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Can extraterrestials detect our messages?
We transmitted several messages to the space and listening to space for signs of intelligent life for years (SETI).
Assuming they have at least the same technology we have, could they detect these ...
- 207k
1
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2
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109
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On which speed the relic microwave background radiation becomes dangerous for the people on space ship?
If we travel with speed close to the speed of light, the light waves becomes shorter and their energy increases (because we flight through much more light for the same time).
So, even background ...
- 40.1k