(Solved) how do scientists measure the distance between things in space?

juliejusu

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11 years ago

how do scientists measure the distance between things in space?

I read somewhere that they first used parallax which makes sense but now they use radar signals. I read that radar signals travel at the speed of light and they send a powerful one out to rebound off of a planet and time how long it takes to return. If a planet was say 10 lightyears away, wouldnt it take the radar signal that long to be returned back to the original source if its traveling at lightspeed? Please help me understand this its very interesting!

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lflmk

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11 years ago

I don't know of us using radar for anything further than the Moon. Parallax can be used for most of the nearby galaxy, Cepheid variables and type Ia supernova for nearby galaxies, and Doppler (red) shift for further objects.

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rjlene

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11 years ago

This verified answer contains over 180 words.

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lf1206

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11 years ago

I agree with the ladies above. One thing worth mentioning that they did not note is that the three methods overlap and agree with each other on the overlap within their respective allowable error bands. For example, there are Cepheid variables within distant galaxies that can also be evaluated using redshift. The numbers agree. Within our own galaxy, parallax is limited to stars that are pretty close by. But the Cepheid variables within our galaxy provide a rational picture of the galactic structure that makes sense for both measurement techniques.

This is important when you have folks questioning the data.

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