physics – Page 20 – National Radio Astronomy Observatory

How Did Erathosthenes Know when it was Noon in Alexandria When he Measured the Earth’s Circumference?

Hello Oscar, Eratosthenes actually measured the length of the shadow of a vertical pole in Alexandria when the Sun…

Yes, in fact emission from a cloud of gas which contains hydrogen atoms which are in excited states, called…

Question: It is said that light traveling from a star that is currently 10 billion light years from us…

Question: Does light wave disintegrates(i.e. its crest and troughs vanishes leaving a straight line) when it travels unhindered and…

Question: I read that radioactive decay rates for some elements show cyclic variations, possibly due to varying solar neutrino…

Question: Hi, I am trying to establish whether each star has a unique signature. I asked an astronomer locally…

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