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Kamil Szot
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Here http://curious.astro.cornell.edu/question.php?number=278 I see the following:
Do I understand right that mentioning slower time passage at the bottom of the tower here is slightly inappropriate? Red-shifting of the light here is totally accounted for by photons loosing some energy crawling up against gravity (or space near the bottom of the tower being stretched by gravity).
Gravitational time dilatation would be visible if you blinked light up the tower exactly each second and the observer at the top would register blinks slightly more spaced out. Am I right?
This is a special case of a more general phenomenon known as the "gravitational redshift" which describes how gravity's effect on spacetime changes the wavelength of light moving through that spacetime. The classic example of the gravitational redshift has been observed on the earth; if you shine a light up to a tower and measure its wavelength when it is received as compared to its wavelength when emitted, you find that the wavelength has increased, and this is due to the fact that the gravitational field of the Earth is stronger the closer you get to its surface, causing time to pass slower - or, if you like, to be "stretched" - near the surface and thereby affecting the frequency and hence the wavelength of the light.
Do I understand right that mentioning slower time passage at the bottom of the tower here is slightly inappropriate? Red-shifting of the light here is totally accounted for by photons loosing some energy crawling up against gravity (or space near the bottom of the tower being stretched by gravity).
Gravitational time dilatation would be visible if you blinked light up the tower exactly each second and the observer at the top would register blinks slightly more spaced out. Am I right?
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