All Questions
Tagged with universe astrophysics
51
questions
2
votes
1
answer
76
views
Can glueballs and bosons survive indefinetely in space (forming structures)?
I have been recently interested in looking for possible structures (ranging from clumped structures like "stars" to diffuse clouds of gas or halos) made from standard model-particles other ...
- 2,462
0
votes
0
answers
84
views
Numerical solution for the Mukhanov-Sasaki equation with Bunch-Davies vacuum state
I have the Mukhanov-Sasaki equation in terms of $u_k$
\begin{align*}
u''_k(\tau)+\left(k^2-\frac{a''(\tau)}{a(\tau)}+f(\tau)\right)u_k(\tau)=0
\end{align*}
and also the initial condition from Bunch-...
1
vote
1
answer
54
views
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 ...
- 419
0
votes
2
answers
101
views
Could Dark Matter have negative pressure?
Is it possible for dark matter to have negative (but negligible) pressure? How small should it be to fit with observations? Dark matter pressure is actually known and measured?
- 495
4
votes
2
answers
948
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
2
votes
1
answer
76
views
Reversal of the psychological arrow of time on the contraction of the universe [closed]
In Brief History of Time, it says that the people living in a contracting phase (although unsuitable for living or even existence itself, but lets assume) would remember the future but not the past. ...
- 472
-4
votes
1
answer
139
views
Anyone please tell how flat universe have infinite Volume?
I'm not able to imagine how flat universe have infinite volume can anyone please tell?
- 1
-1
votes
1
answer
1k
views
Did gravity exist before the Big Bang?
Gravity is one of the biggest mysteries. It is the weakest of the 4 fundamental forces but we have no clue how it works. Einstein never was able to figure it out in his lifetime. There is evidence ...
- 129
1
vote
2
answers
866
views
Why do moving liquid metals generate a magnetic field?
The earth's magnetic field is generated due to the movement of liquid metals, but why not solid? Why is it that moving molten metals create a magnetic field, but when nothing of the sort happens when ...
- 257
0
votes
0
answers
125
views
Temperature of Closed Universe in future
This is a question from "Introduction to Modern Cosmology" by Andrew Liddle:
Suppose we live in a closed universe(k > 0), which will recollapse some time in the future. What will the ...
- 77
0
votes
4
answers
81
views
Homogenous Universe (Earthlike planets?)
The fact that the Universe is homogenous can lead to a conclusion that there are another earthlike planets, or planets like earth are considered as some differences that are allowed in the definition ...
0
votes
1
answer
175
views
Angular size of the largest region in causal contact at the moment of recombination
I want to calculate the angular size of the largest region in causal contact at the moment of recombination (z = 1100) to our universe, so we have: $H_0 = 68$ (km/s)/Mpc, $\Omega_{m,0} = 0.31$, $\...
- 55
1
vote
3
answers
537
views
Mean Gravitational 'Potential' Energy in Space
Imagine an arbitrary point in space. It is within the gravitational 'potential' of every mass (although billions of ly away) in the entire universe.
Since every mass adds a tiny fraction, what is ...
- 78
5
votes
1
answer
695
views
Could Alpha Centauri be made of anti-matter? [duplicate]
How can we tell if a star is made of matter or anti-matter? For example, is there any difference spectroscopically? Or could we tell from cosmic rays?
If half of the stars were made of matter and ...
0
votes
1
answer
105
views
A thought experiment related to the age of the universe
Okay,
So, this thought experiment starts with the movie, Interstellar. In which humans went through a wormhole to a system consisting of a Black Hole. They landed on a planet (I don't remember its ...
- 13