<p align="right">Last Update: <font color="#4f81bd">January 07, 2025</font></p>
## BIG IDEAS
- Cosmic Microwave Background (CMB) Analysis helps scientists infer the geometry and size of the universe.
- The redshift of light from distance galaxies is used to measure velocities relative to Earth.
- By comparing the observed brightness of supernovae with their intrinsic brightness, astronomers can calculate their distances.
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### Scale of the Universe
The scale of the universe is monumentally difficult to picture. The latest estimates are that in the known universe there are over 2 trillion [[galaxies]].
### Techniques
> The technique makes use of a familiar property of any sort of wave motion, known as the [[Module 4 Doppler Effect|Doppler effect]]. $^1$
> The time between crests is just the [[Wavelength|wavelength]] divided by the speed of the wave, so a wave sent out by a source moving away from us will appear to have a longer wavelength than if the source were at rest. $^1$
### Hubble's Law
According to Hubble's Law, the farther away a galaxy is, the faster it appears to be receding from us, which indicates the universe's expansion. By measuring the redshift and using the known rate of expansion ([[Hubble constant]]), cosmologists can estimate the distance to faraway galaxies.
### Slide Deck
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### Related Topics
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[[Home|Home]] | [[The Universe]] | [[The Big Bang|The Big Bang Theory]] | [[Solar System]] | [[Galaxies]] | [[Star Clusters]] | [[Superclusters]] | [[Black Holes]]
### Footnote
[1]: Weinberg, S. (1993). _The first three minutes: A modern view of the origin of the universe_. Basic Books. p. 15.