All Questions
352
questions
1
vote
2
answers
106
views
In spacetime time is a coordinate. Does it mean there is a single objective timeline for the Universe?
If every event can be defined with x, y, z, t coordinates - does it mean all events with the same t are composing the whole Universe at the moment t?
0
votes
0
answers
26
views
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 ...
2
votes
2
answers
414
views
What is the cardinality of intervals in space, and what is the cardinality of intervals in spacetime?
The interval $|(0, 1)| = |\mathbb{R}|$. I naively thought that one could treat intervals in space in kind, i.e., that the cardinality of any interval in space has the cardinality of the continuum. You'...
- 23
1
vote
1
answer
102
views
If spacetime is discrete, would we observe continuous models to show non-rounding and non-truncation errors?
Typically, the ground truth is taken to be the continuous model. Numerical simulations are taken to be the approximation. These simulations deviate from the continuous model due to both a constant ...
- 870
1
vote
1
answer
67
views
Does the universe have an infinite volume? [duplicate]
The implications of a spatially infinite universe is profound, but so are the implications of a finite universe. What we know about this issue?
- 11
0
votes
2
answers
47
views
Is this the Format of the Observable Universe?
The way I have it is: the Observable Universe looks as follows. In some ball, all the galaxy clusters exist, then in a bigger concentric ball the dark ages exist (no galaxies), then on the surface of ...
- 61
0
votes
1
answer
46
views
Average Time since the Big Bang
Can we define an average time for the entire universe relative to the Big Bang and call this the universal time since the beginning of the universe? (time, averaged relative to all possible reference ...
- 613
0
votes
1
answer
122
views
Cosmological principle: can there be a center of the universe "outside" the universe?
I've been watching youtube videos about the cosmological principle. I understand that the expansion of the universe is not concentric (around a specific point in space). The balloon example helped me ...
- 3
-1
votes
2
answers
74
views
The speed of expansion of space in big freeze
In the case of big freeze, space expansion will be accelerating and there appears to be a lot of different phenomena occurring. However, in the case of big rip, the expansion is super-accelerating so ...
- 13
2
votes
1
answer
100
views
Topological phase transitions for the whole universe...?
Physicist Grigory Volovik has put forward some ideas about the universe undergoing a topological phase transition (especially in the early stages of the universe). He published a book called "The ...
- 2,462
0
votes
0
answers
44
views
Effects of anisotropy and non-homogeneity in the universe's symmetries...?
I was reading Philip W Anderson's essay "More is Different" (https://www.tkm.kit.edu/downloads/TKM1_2011_more_is_different_PWA.pdf) and at some point he links the isotropy and homogeneity of ...
- 2,462
0
votes
0
answers
51
views
Was Big Bang the "START" of time? [duplicate]
I know that this question has been repeated a lot. But I still don't understand this concept.
Big bang created matter and space but how could it possibly create time?
If Big bang didn't create time ...
- 77
4
votes
2
answers
950
views
Could it be possible that the Universe is expanding in some areas while contracting in other areas?
I am wondering if could it be possible that the Universe is expanding in some areas while contracting in other areas.
I have wondered if perhaps as one area of the Universe is squeezed inward by some ...
- 478
1
vote
1
answer
81
views
What if the universe was not uniform...?
In this popular science article, they say that if our universe resulted to be non-uniform (that is highly anisotropic and inhomogeneous) then the fundamental laws of physics could change from place to ...
- 2,462
-1
votes
2
answers
83
views
Can a physical object escape the universe? [duplicate]
Can a particle, like an electronic or photon, leave the universe? If the photon for instance travels out toward the edges of the universe, assuming it is flat, will it encounter an invisible wall, or ...
- 13