Physics Forums » Cosmology
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Cosmology is the origin, evolution, structure and eventual fate of the universe. Join in the expert discussion on topics revolving around cosmology. Ask questions, share your views, and get opinion from fellow cosmology enthusiasts.
Physics Forums » Cosmology
2d ago
Dr. Smethurst summarizes the latest results of the DESI collaboration. What I found especially interesting is that the current value of the Hubble constant that they obtained from baryon acoustic oscillations is in good agreement with the value obtained from Lamda-CDM using Planck data...
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Physics Forums » Cosmology
2d ago
Is there a Big Crunch in an infinity, Newtonian, symmetrical universe, e.g. an infinity grid, with stars in its nodes, due to the gravitational attraction?
One can argue that every net force is 0, so there isn't one.
But I think there is an another argument, that leads to a Big Crunch, that...
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Physics Forums » Cosmology
5d ago
It is said that the universe is made up of approximately 4.9% ordinary matter, 26.8% dark matter and 69.3% dark energy. Why isn't ordinary energy included in this "pie"? I suppose it is included within ordinary matter, but could it be calculated what % are particles with mass and what % is pure...
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Physics Forums » Cosmology
1w ago
I don't understand the discovery of "accelerating expansion" in 1998 (hence the postulate of dark energy, etc..), because Hubble's old law already described exponentially accelerating expansion in 1929, right ..read more
Physics Forums » Cosmology
1w ago
Dr. Becky Smethurst provides a summary of the latest analysis of JWST data by Freedman et al., indicating that there's no statistically significant discrepancy between the value of the Hubble constant thus obtained and the value obtained from Lambda-CDM using Planck data ..read more
Physics Forums » Cosmology
2w ago
Hi I'm a medical doctor, this is just a hobby my uncle got me interested in as a kid. If the universe is acceleration and galaxies are moving further apart, we assume the universe as a whole is expanding as a result. It's also projected to my understanding that eventually the universe will...
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Physics Forums » Cosmology
2w ago
I found this paper (https://arxiv.org/pdf/hep-th/0211160.pdf) which argues against the possibility of a decay from a metastable vacuum to a true vacuum state. However, this is the first time I've read this. Is it then impossible that a vacuum decay from a false vacuum may occur (even in...
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Physics Forums » Cosmology
2w ago
I'm studying the freeze-out moment of different particles and I have few questions that I can't find answer about the Wimp particles.
First of all, the freeze-out temperature of the wimp particles is around 0.4-40gev much higher than 1 mev for the neutrinos.
Thus, that means that the freeze-out...
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Physics Forums » Cosmology
2w ago
Hi, I was thinking about the claim that for instance Sagittarius A* (Sgr A*) black hole is a at 26996±29 light years from the Earth from a GR point of view.
Assuming a FLRW model for the Universe, maybe the above meaning is that at a given cosmological time ##t## (the "present" time) the...
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Physics Forums » Cosmology
2w ago
Dear all!
I'm not a scientist, but I'm thinking about something, I'm curious, is it possible to believe that our universe is in a vacuum, the stars are moving away a not because of the dark energy but becouse it behave like a luffbaloon in a vacoom. Sorry for noob questions ..read more