Why are standard candles important to astronomers trying to measure the Hubble constant?
When Edwin Hubble first proposed his idea of universal expansion, it was based on the observation that the farther a galaxy was from the Earth, the faster it was moving away from us. When Hubble plotted the distances,
In other words the velocity at which galaxies are receding from us increases with distance at a constant rate. We can express this mathematically as;
Where A standard candle is a light source for which we know the absolute magnitude. By comparing the absolute magnitude, Hubble used Cepheid variable stars for his standard candle. Cepheid variables are stars that change their brightness over regular time intervals. This period of brightening and dimming is directly correlated with the absolute magnitude of the star.
Cepheid variables are also incredibly bright, making them observable in other galaxies.
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The inverse square law of light can be used to calculate the distance of distant galaxies from Earth, and when combined with the observed redshift of the galaxy, this distance can be used to calculate the expansion rate of the universe, which is captured in the Hubble constant. Standard candles are crucial to astronomers trying to measure the Hubble constant because they provide a consistent and known luminosity.
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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.
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.
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.
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.
- Wavelengths of light from a distant galaxy are found to be 0.44% longer than the corresponding wavelengths measured in a terrestrial laboratory. What is the speed that the wave is approaching?
- How many shapes of galaxies exist?
- Does the density of the universe change over time?
- How long does it take the sun's energy to get to earth?
- If nothing can travel faster than light then how fast did the universe expand during the big bang?

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