New answers tagged cosmology
20
votes
Why is WR124 not brighter?
It's 7.7 times the absolute temperature of the Sun and if it is 12 times the radius.
The luminosity will therefore be $(7.7)^4\times 12^2 = 515000$ times that of the Sun.
Close enough, given you haven'...
- 141k
18
votes
What would evidence of stars and galaxies significantly older than 13.8 billion years old look like? In what parts of space has it not been found?
Assuming the cosmological principle still holds, then we might expect that your own galaxy and those around us should contain evidence of stars/objects older than 13.8 billion years old.
These might ...
- 141k
3
votes
How long has it been since dark energy started to reverse our slowdown and accelerate the expansion of the universe? 4 billion years ago? 4.5? 5?
If we consider that the universe is Euclidean and that the radiation density to be negligible compared to that of matter and dark energy, the instant when the expansion shifted from deceleration to ...
- 1,720
9
votes
How long has it been since dark energy started to reverse our slowdown and accelerate the expansion of the universe? 4 billion years ago? 4.5? 5?
It is likely that you or your sources are conflating two different events.
Dark energy begins to comprise the majority of the Universe's energy density about 4 billion years ago.
The expansion of the ...
- 4,261
1
vote
Gravitational-wave Angle?
Gravitational waves, far from their sources are (in General Relativity) transverse. That is, the stretching and compressing of space always takes place at right angles to the direction of wave ...
- 141k
5
votes
Why can't dark energy be considered a 5th fundamental force?
Dark energy's influence on cosmic expansion isn't a new force. It's just gravity. Calling dark energy a force in the context of cosmology would be like calling the Sun a force in the context of the ...
- 4,261
8
votes
Accepted
Why can't dark energy be considered a 5th fundamental force?
Dark Energy is a scalar field, whereas forces are vector interactions
As far as we know, we are sure that dark energy, or more accurately, the expansion of space-time, is a scalar quantity. That is, ...
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0
votes
Understanding The Turnover Point of Angular Diameter Distance
While the angular diameter turnover is often explained in terms of the expansion of the universe, the more direct physical cause is that gravitational lensing by the universe's homogeneous mass ...
- 4,261
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