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Author Topic: Can light waves from the sun pass through the earth?  (Read 953 times)

Offline thedoc

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Nadia Adam  asked the Naked Scientists:
   Hello, I have a question, can light waves (electromagnetic waves) from sun reach to the core of the earth or even pass through it to the other side of the earth? Thanks i hope you will answer.

 
What do you think?
« Last Edit: 26/01/2016 09:50:03 by _system »


 

Offline Colin2B

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Re: Can light waves from the sun pass through the earth?
« Reply #1 on: 26/01/2016 12:43:21 »
Nadia Adam  asked the Naked Scientists:
   Hello, I have a question, can light waves (electromagnetic waves) from sun reach to the core of the earth or even pass through it to the other side of the earth? Thanks i hope you will answer.

 
What do you think?
Light won't, it will be absorbed or reflected at the suface.
Radio waves - another form of electromagnetic radiation - can penetrate the surface, but is unlikely to go very deep.
 

Offline evan_au

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Re: Can light waves from the sun pass through the earth?
« Reply #2 on: 26/01/2016 17:59:37 »
Quote from: Nadia Adam
can light waves (electromagnetic waves) from sun pass through (the Earth) to the other side of the earth?
The Sun generates some outbursts of incredibly low-frequency radio waves due to solar flare activity, with periods of a second or more. And a periodic oscillation in the orientation of the overall magnetic field with a period of 22 years. Both of these have wavelengths much larger than the Earth (the 22-year cycle is far larger than the solar system), and so they will pass by the Earth without being absorbed or deflected.

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can light waves (electromagnetic waves) from sun reach to the core of the earth?
We can categorize electromagnetic waves as follows:
  • Very short wavelengths from the Sun (X-Rays) are absorbed by the atmosphere, as is most ultraviolet.
  • Ultraviolet, visible and infra-red are absorbed by the top millimeters of soil, or 100 meters of ocean.
  • Microwaves will be blocked by the ocean, or any moisture in the soil (although in deserts, some frequencies can penetrate the sand to reach bedrock).
  • Radio waves are blocked by the conductivity of the ocean and the ground (antenna design calls this the "ground plane").
  • Very Low Frequency radio waves find the ground and the ionosphere conductive on the scale of a wavelength, although frequencies around 50Hz are used to communicate with submerged submarines a fraction of a wavelength underwater (using the skin effect).
  • Frequencies with wavelengths of 1000km or more could conceivably penetrate the Earth's crust and mantle to a depth of a wavelength. However, they would be blocked by the extremely conductive iron core of the Earth, so they wouldn't reach the exact center of the Earth.
  • As mentioned above, wavelengths far greater than the diameter of the Earth will pass straight around the Earth unobstructed. But these wavelengths would not be detectable with an antenna that could fit into the core of the Earth.

There is another sense in which electromagnetic disturbances from the Sun could affect the core of the Earth - with a Coronal Mass Ejection. In this case, a burst of ionized gas is blasted out in the direction of the Earth, carrying with it part of the Sun's magnetic field that was present when the CME was released. When this CME strikes Earth's magnetosphere (a day or two later), variations in Earth's magnetic field can be observed, over periods of a minute or more. These variations in magnetic field are certainly detectable at the surface of the Earth, and may well be detectable at the core of the Earth (if we could get a sensitive compass down there without being demagnetized).

But the CME is "cheating", since these do not travel as electromagnetic radiation from the Sun (which would arrive in 8 minutes), but are local electromagnetic effects generated in the vicinity of the Earth by the interaction of the CME's magnetic field with Earth's magnetic field and magnetosphere (which takes days to arrive).
 

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Re: Can light waves from the sun pass through the earth?
« Reply #2 on: 26/01/2016 17:59:37 »

 

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