<p>Hubble discovered that he could measure the approximate distance to some galaxies by observing a type of variable star. The absolute brightness of these stars is known, so by measuring their apparent brightness Hubble could find how far away a galaxy was. </p>

<p>It was also discovered that most galaxies were "red-shifted", which was interpreted as meaning that the other galaxies were moving away from the Milkyway. Hubble plotted a scatter graph with distance on one axis and speed on the other, and noted that the more distant galaxies were moving faster, and the relationship was approximately a straight line. This meant that all galaxies were moving away from all other galaxies. </p>

<p>This expansion could be predicted by general relativity, which allowed for  the space between galaxies to expand. It also suggests that the galaxies were closer together in the past, suggesting that the early universe was hot and dense.</p>

<p>The Milkyway does not have a special position in this expansion, all galaxies are moving away from each other. There is no implication that the Milkyway is central to the universe.</p>

CC BY-SA 3.0
2016-12-18T13:23:32.687Z
2016-12-18T13:23:32.687Z
James K
<p>How did Edwin Hubble determine the Universe was expanding?</p>

<p>Was he looking in a particular direction?</p>

<p>And where does this Galaxy sit in the expansion.</p>

CC BY-SA 3.0
2016-12-18T01:37:22.993Z
Before you ask a question on Stack Exchange, try to see if you can find the answer yourself.  A quick Google search could have brought you to this page:  https://en.wikipedia.org/wiki/Metric_expansion_of_space
Phiteros
CC BY-SA 3.0
2016-12-18T02:55:10.887Z
@Phiteros  I am sure that a layperson looking at the title alone of the link you provided, would not see the connection between the question being asked and any possible answers that could be ascertained from the content of said link.
LaserYeti
CC BY-SA 3.0
2016-12-18T03:15:26.720Z
Google Hubble's law.   Wikipedia's page is long, here's two shorter ones.   http://starchild.gsfc.nasa.gov/docs/StarChild/questions/redshift.html  and  http://www.infoplease.com/encyclopedia/science/hubble-law-discovery-explanation-red-shift.html   He looked in several directions.   The first link shows a chart with about 20 distant galaxies.  He wouldn't have been able to reach a conclusion without looking in many different directions.
userLTK
<solar-system>
Understanding the theory of an expanding Universe
user15211
# Understanding the theory of an expanding Universe

(Asked by: username_0 on 2016-12-18)

How did Edwin Hubble determine the Universe was expanding?

Was he looking in a particular direction?

And where does this Galaxy sit in the expansion.

**Tags:** solar-system

> **Comments:**
> **username_1**: Before you ask a question on Stack Exchange, try to see if you can find the answer yourself.  A quick Google search could have brought you to this page:  https://en.wikipedia.org/wiki/Metric_expansion_of_space  
> **username_2**: @username_1  I am sure that a layperson looking at the title alone of the link you provided, would not see the connection between the question being asked and any possible answers that could be ascertained from the content of said link.  
> **username_3**: Google Hubble's law.   Wikipedia's page is long, here's two shorter ones.   http://starchild.gsfc.nasa.gov/docs/StarChild/questions/redshift.html  and  http://www.infoplease.com/encyclopedia/science/hubble-law-discovery-explanation-red-shift.html   He looked in several directions.   The first link shows a chart with about 20 distant galaxies.  He wouldn't have been able to reach a conclusion without looking in many different directions.  

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## 1 answers

### Answer by username_4 on 2016-12-18. Score: 2

Hubble discovered that he could measure the approximate distance to some galaxies by observing a type of variable star. The absolute brightness of these stars is known, so by measuring their apparent brightness Hubble could find how far away a galaxy was.

It was also discovered that most galaxies were "red-shifted", which was interpreted as meaning that the other galaxies were moving away from the Milkyway. Hubble plotted a scatter graph with distance on one axis and speed on the other, and noted that the more distant galaxies were moving faster, and the relationship was approximately a straight line. This meant that all galaxies were moving away from all other galaxies.

This expansion could be predicted by general relativity, which allowed for the space between galaxies to expand. It also suggests that the galaxies were closer together in the past, suggesting that the early universe was hot and dense.

The Milkyway does not have a special position in this expansion, all galaxies are moving away from each other. There is no implication that the Milkyway is central to the universe.


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