Questions tagged [observable-universe]
The observable universe of a given observer encompasses the volume of space from which information - particles, radiation - could ever (past, present or future) reach that observer.
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Negative Horizon distance
Consider a flat universe, here, proper distance can be given by R-W Metric:
$$d_p (t_0) = c\int_{t_e}^{t_0}\frac{dt}{a(t)},$$ $t_e$ is the time when a photon is emitted from a distant galaxy, $t_0$ is ...
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Can the observable mass within the observable universe be estimated without using $G$?
The estimation of the baryonic mass of the observable universe can be done through its density parameter and the critical density, which depends on the gravitational constant $G$.
Is there a way to ...
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Horizon problem, what if our observable universe is roughly equal to the whole universe, especially in early times?
How do we know that at a time of 380.000 years, when CMB got free, the observable universe was not equal to the actual universe? Maybe they were roughly the same and couldn't that explain the horizon ...
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Does going to the other side of Milky Way galaxy mean seeing different observable universe?
What if there was a robot that got sent to the other side of the Milky Way by just traveling with a fusion engine and started orbiting a planet that has around Earth's gravity in order to avoid any ...
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If the observable universe had only one galaxy, how would people know the expansion of the universe?
Hubble measured high redshifted galaxies to discover the cosmic expansion. In a hypothetical universe where only one galaxy exists, would there still be observational evidence for the Big Bang theory? ...
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Can LISA observe BH beyond the observable universe?
Reading the paper "Astro2020 Science White Paper
Where are the Intermediate Mass Black Holes?", and the plot in Fig.1, page 5, it seems LISA can see IMBH beyond 100 Gpc...Since the ...
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Will cosmic microwave background become invisible in the future?
If my understanding of CMB and Hubble's Law is correct, then CMB photons emitted from more than ~14.4 Glyr during Recombination Epoch would not reach us. The reason is this would correspond to Hubble'...
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Why can't we see past the observable universe?
Why can't we see light from beyond the observable universe?
I've done a lot of research on this and all I've found is unsatisfactory answers and straight up nonsense.
Some claim that the universe &...
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What is the rough distribution for number of galaxies with a given mass in the observable universe?
Is there a rough formula for the fraction of galaxies in the observable universe with masses between M and M + dM? Or perhaps a graph that displays the same information? I've looked online but can't ...
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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?
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Does expanding universe length units also expand? [duplicate]
Information
I have read an explanation about the expanding universe which represents our universe as a metal plate that tends to expand simultaneously in all directions while being heated. One can ...
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How a star can move out from visible universe? [duplicate]
We see only stars whose light is not older than the age of universe. This is understood. If a star is too far away that currently we don't see it then possibly we will see it later, then the age of ...
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Hubble expansion across time dimension?
The expansion of the universe, as described by the Hubble's law, refers to the expansion of space itself. This expansion is observed in the three spatial dimensions (length, width, and height), rather ...
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Big Bang and where do we stand relative to it? [duplicate]
Maybe dumb question, not sure, but I would need some help here to understand.
https://theglobestalk.com/james-webb-telescope-see-back-in-time/
So according to physics we can look back in time ...
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Size of the observable universe and CMBR [duplicate]
Why can we detect the Microwave Background radiation (the earliest light that we can see) and not the light from stars beyond the observable universe? Should not the microwave radiation also be ...
