4 ms·
Basically, there are some knowns: The universe expands according to the fried,am equation. Different percentages of matter, energy give rise to different expan
by harshpotatoes 15y ago
Basically, there are some knowns:
The universe expands according to the fried,am equation.
Different percentages of matter, energy give rise to different expansion rates.
Expansion history of the universe is known via looking at supernova (which are equally bright at the source).
Knowing matter is mostly hydrogen/helium and energ is mostly photons allows us to calculate the density of matter/energy in the universe. These don't match the terms found from measuring supernova leading the differences to be called dark matter/dark energy.
Additionally, gravitational lensing is seen by objects which can't be seen. Meaning, they have mass, but don't appear to absorb/reflect light. Additional additionlly, similar effects are seen affecting the formation of galaxies: extra matter is needed to give the structure we see, but we apparently can't see that matter.
So it was originally dark because we knew nothing about it, but the name stuck once it appeared we could not see it.
It is definitely matter.
- po 15y agoIt is definitely matter. The whole point of the article that we're commenting on is that it might not be matter. The root problem is that the observed doesn't line up with the expected. Is the problem with the observed or with the expected? We don't know. You're assuming the problem is with the observed. This article is saying we can modify our expected values with a tweak to the model. We should name the phenomenon after the problem, not after one of the not-yet-proved-but-expected-to-be solutions.