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What distance method did Edwin Hubble use to determine the distance to local galaxies?   

Answer 1

Edwin Hubble measured speed of galaxies moving away from using red-shift method and then calculated their distance using Hubble's constant.

When we first blow a balloon a little bit and mark a few dots on it, and then blow it again, let's say at a uniform speed, one will notice that the dots are also moving apart.

After Edwin Hubble discovered in 1929 that galaxies seemed to be moving away from us, it was clear that the universe was also expanding in light of the example above.

When a light source moves away from an observer, Christian Doppler observed earlier in the 19th century that the spectral lines shift toward lower frequency. This shift was found to be proportionate to the object's velocity.

Hubble found that using this the velocity of a galaxy could be expressed mathematically as #v = H*d#, where #v# is the galaxy's radial outward velocity, #d# is the galaxy's distance from Earth, and #H# is the constant of proportionality called the Hubble's constant. Hubble's constant could be easily calculated by measuring red-shift in neighbouring galaxies, whose distance could be calculated using parallax system.

Therefore, one could determine the distance between galaxies by measuring the red-shift at a distance.

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Answer 2

Olivia Aldridge

Edwin Hubble calculated the distance to nearby galaxies by looking at Cepheid variable stars.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.