Cosmolgy- Density of the Universe

In summary, assuming an average galaxy density of p=0.9 Mpc^-3 and a galaxy diameter of 30 kpc, in a Euclidean space and infinitely large and infinitely old universe, it can be concluded that no matter where one looks, a galaxy would be visible.
  • #1
EP
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Assume the universe has an average galaxy density of p=0.9 Mpc^-3. Each galaxy has a diameter of 30 kpc. How far would you see on average in any direction before your line of sight would hit a galaxy? Assume a Eucledian spcae and infinitely large and infinitely old universe.

Help get me started.
Thanks

My guess is the answer is that no matter where you look you'll see a galaxy under these conditions.
 
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  • #2
EP said:
Assume the universe has an average galaxy density of p=0.9 Mpc^-3. Each galaxy has a diameter of 30 kpc. How far would you see on average in any direction before your line of sight would hit a galaxy? Assume a Eucledian spcae and infinitely large and infinitely old universe.

Help get me started.
Thanks

My guess is the answer is that no matter where you look you'll see a galaxy under these conditions.
What units are are kpc and mpc?

AM
 
  • #3
Kiloparsec and Megaparsec
 

1. What is the density of the universe?

The density of the universe is the amount of matter and energy per unit volume in the entire observable universe. It is estimated to be approximately 9.9 x 10^-27 kg/m^3, which is extremely low and considered to be close to the critical density needed for the universe to be flat.

2. How is the density of the universe measured?

The density of the universe is measured by using a combination of different observational methods, such as measuring the cosmic microwave background radiation, the distribution and motion of galaxies, and the abundance of elements in the universe. These measurements allow scientists to estimate the total amount of matter and energy in the universe and calculate its density.

3. What is the relationship between the density of the universe and its expansion?

The density of the universe plays a crucial role in determining the rate of its expansion. According to the theory of general relativity, the density of the universe affects the curvature of spacetime, which in turn influences the expansion rate. A higher density would result in a slower expansion, while a lower density would lead to a faster expansion.

4. How does the density of the universe impact its fate?

The density of the universe has a significant impact on its ultimate fate. If the density is high enough, the universe will continue to expand for a certain period before eventually collapsing in a "big crunch." However, if the density is low, the expansion will continue indefinitely, resulting in a "heat death" scenario where the universe becomes cold and dark.

5. Is the density of the universe constant?

No, the density of the universe is not constant. It has changed over time as the universe has expanded and evolved. In the early universe, the density was much higher and has been decreasing as the universe expands. However, the total density of matter and energy in the universe remains constant, according to the law of conservation of mass and energy.

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