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Chapter 26: Problem 4

What does it mean when astronomers say that we live in an expanding universe? What is actually expanding?

Short Answer

Expert verified
When astronomers say that the universe is expanding, it means that the space between galaxies is getting larger, resulting in galaxies moving away from each other. Therefore, the 'expansion' refers to the increasing distances between galaxies rather than the galaxies themselves moving away from a fixed point. Ultimately, it's the cosmic space that's expanding.

Step by step solution

01

Understand the Theory of Expanding Universe

The theory of an expanding universe originates from observations and interpretations of the redshift of distant galaxies. This redshift is understood as a Doppler effect, indicating that these galaxies are moving away from us, hence proposing that the universe is expanding.
02

Grasp the Concept of 'Expanding'

When astronomers say the universe is expanding, it does not mean that the galaxies are flying away from a central point in space, but rather space itself between the galaxies is expanding. Hence, in effect, galaxies are moving further away from each other.
03

Understanding What is Expanding

What is actually expanding is the space between the galaxies. This means that the universe doesn't have a center point from which everything is moving away, instead all space is expanding and has been since the Big Bang, creating more distance between cosmic bodies.

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