All Questions
Tagged with cosmology estimation
42
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Is there an estimate for how many monopoles would be produced in the very early universe?
The question really hits it with this one. I haven't really found some good numbers other than the whole “It'd be so many (per Hubble vol) to recollapse the universe”. I don't know if that comes of as ...
- 207k
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How far apart are galaxies on average? If galaxies were the size of peas, how many would be in a cubic meter?
The actual number:
How far apart are galaxies on average?
An attempt to visualize such a thing:
If galaxies were the size of peas, how many would be in a cubic meter?
- 1,421
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4
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Accelerating Expansion of Universe - Why Not Caused by Radiation?
As I understand it, dark matter and dark energy are used as an 'explanation' for how universe expansion is accelerating; because without it gravity would be expected to cause a long term shrinking.
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What fraction of the universe's energy is contained in photons?
From each point in the universe, the light of billions of stars, galaxies, supernovae etc. can be detected. So there seems to be a lot of energy/momentum "in flight".
Is it possible to ...
- 6,404
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Size of the universe 13 billion years ago
When wee look at the sky in opposite directions, we can see early galaxies that were formed about 13 billion years ago. At that time, the distance between two such galaxies at the opposite ends of the ...
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What was the size of the observable universe at the matter-dominated era and its mass density?
For instance, at the scale factor $a=0.5$ and matter dominated era, what was the size of the observable universe and matter density?
- 207k
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What is the expansion of space of one megaparsec in one year?
suppose we know Hubble's constant. In a hypothetical scenario an astronomer finds and confirms Hubble's law for a galaxy 1 mega parsec away.
Next year, how much distance will the hypothetical ...
- 207k
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Why are departures from flat spacetime geometry small on scales smaller than the Hubble radius?
In Chapter 5 of Baumann's cosmology book where he discusses structure formation starting from Newtonian perturbation theory, Baumann mentions at the beginning that
Newtonian gravity is a good ...
- 207k
4
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2
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What paper can I cite for the estimated number of atoms in the observable universe to be lower than $10^{82}$?
The title contains the whole question. I am a logician in theoretical computer science and want to use the estimated number of atoms in the observable universe to show what a ridiculous amount of ...
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If all the black holes in the Universe were combined into one supermassive black hole, what would its diameter be?
I am curious to know if anyone has ever sat down and calculated what the diameter of a black hole would be, in kilometers, if it were to contain all the mass of all the black holes that are currently ...
- 207k
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Does the Casimir effect give the correct value for Dark Energy?
My understanding is that the Casimir Effect is caused by vacuum energy. Quantum mechanics (QED) predicts vacuum energy, but gets the value grossly wrong, by a factor of $10^{120}$. On the other hand, ...
- 207k
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What was the density of the universe when it was only the size of our solar system?
What was the density of the universe when it was only the size of our solar system? Did it approach neutron star density? Is it physically correct to even ask such a question?
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Could gravitational waves be cosmologicaly 'redshifted'? [duplicate]
Is it posible that gravitational waves detected here on Earth could be cosmologicaly 'redshifted'? So, at emission they had higher frequency then after reaching Earth?
- 207k
15
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Is CMB slowing down all moving objects in the universe?
1/
Object moving relative to the CMB frame of reference will see the CMB blue shifted where it is heading and red shifted where it came from.
Correct?
2/
The blue photons ahead should have more ...
- 133k
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How fast is the edge of the observable universe expanding from the Earth?
If the universe is expanding at 73 kilometers per second per megaparsec, what is the fastest expansion speed that we can observe from Earth? I'm assuming that's the edge of the observable universe ...
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