All Questions
Tagged with big-bang-theory cosmology
38
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Big bang cosmology [closed]
What is the main evidence that the Big Bang is real. Why can we know that the big bang exists. In a short summary,
the evidence? In your owns words?
- 227
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0
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97
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Why is it assumed that the universe started out with a size equal to the Planck length?
What if the Planck length is the distance between particles when the universe was very small .
For a spherical ball of 10^ 78 protons that would give the universe a radius of 10^26 X 10^-35 = 10^-9 ...
user50623
17
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1
answer
3k
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Why do cosmologists assume that inflation began shortly after the Big Bang, rather than at the exact start?
Somehow, I have never come across an explanation of why cosmologists claim that the alleged inflation of the very early universe occurred not at the Big Bang, but very shortly afterwards (~10^-36 to ...
- 5,307
1
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1
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Could inhomogeneities or topological defects break the fundamental symmetries of the Universe?
I have heard that some types of inhomogeneities and topological defects in cosmology have been proposed to be able to break fundamental symmetries of nature such as the Poincaré, Lorentz, ...
- 1,017
3
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333
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Redshift distance proportionality at high Z and need for "mighty mouse" galaxies?
Allegedly supported by some evidence from the new James Webb space telescope physicist Eric Lerner has written an article that have garnered some attention. He writes that:
"Put another way, the ...
- 457
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2
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241
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Expansion rate of an infinite universe at the Big Bang
If the universe is infinitely large, then any two arbitrarily distant points must have been arbitrarily close together at some earlier point in time. Doesn't that mean that the expansion rate of the ...
- 123
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1
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109
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Does the Cosmic microwave background (CMB) have an amplitude? Does it vary, like the 'temperature' (wavel./freq.) and the polarization?
Somehow, I have never read about this or thought about, until now...
Does the number of photons from the CMB hitting us from all directions vary at all?
- 5,307
2
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1
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147
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Strange plot in Max Tegmark book, Our Mathematical Universe
In Max Tegmark's book, Our Mathematical Universe, we can find (in chapter 5, figure 5.3) the following (horrible and poor quality) plot that is supposed to highlight the extreme sensitivity of the ...
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1
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Why was the Cosmic Microwave Background (CMB) released at a blackbody temperature of 3000K rather than 30,000K?
If the ionization (or reionization, or Recombination) energy of atomic hydrogen is 13.6 EV, which corresponds to a black body temperature of 30,000K, why did the CMB not begin to appear then?
Why did ...
- 5,307
9
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1
answer
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Why isn't the CMB blurred by the blackbodies emitted in the time after atoms first formed?
I am confused about why the light released from the moment when gas first formed was so dominant in comparison to the light released afterwards. Why isn't the CMB in interference with a series of ...
- 91
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140
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How did the Universe climb out of its own Big Bang black hole?
The Big Bang started as a singularity. That means small. All the matter in the universe was in a volume smaller than its own Schwarzchild radius. The universe was inside a black hole.
At present, the ...
- 1,121
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How can scientists deduce the number of types of neutrinos, or 'effective number', from Planck satellite data?
Is it related to the way they deduce the Hubble constant from Planck data?
Would more types of oscillating and mixing neutrinos mean faster or slower expansion of the universe?
Would a fourth mass ...
- 5,307
2
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0
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77
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How do we know or predict which particles were present before Big Bang Nucleosynthesis occurred?
I'm reading Carroll and Ostlie's "An Introduction to Modern Astrophysics". In the BBN section, they describe that the universe contains a mixture of photons, electron-positron pairs, and ...
- 1,111
8
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1
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187
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What is the history of the average pressure, density, and temperature of the matter in the universe over time?
This question is inspired by this more specific question where Cerelic wanted to know if conditions were suitable for liquid water to exist during an epoch when the characteristic temperature of the ...
- 3,944
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111
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Shouldn't the estimate of the universe's age be higher, not lower, after the attractive strength of gravity is taken into account?
From 'Fundamentals: Ten Keys to Reality', by Frank Wilczek :
"Running the movie of cosmic history backward in our minds, we found the galaxies all coming together to meet at a definite time. ...
- 5,307
4
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101
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From what distances do the atoms in you come from?
If the atoms of a human come from stars, comets, nebulas and magnetrons, then what is the greatest distance that two atoms of a human can possibly have been away from each other previously? Perhaps ...
- 4,268
3
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180
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Question on the singularity theorem
I have just started studying Cosmology and we have been asked to prove that in an expanding FRW Universe which obeys the strong energy condition: $$\rho + 3P >0$$
Then there must exist a Big Bang ...
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2
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1
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854
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What is the 'scale factor' equation for a dark-matter dominated universe?
The Friedmann equations can be solved exactly in presence of a perfect fluid with equation of state
$${\displaystyle p=w\rho c^{2}} \qquad p=w\rho c^2$$
where ${\displaystyle p}$ is the pressure, ${\...
- 5,307
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2
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290
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Why can't we point the centre of the universe from inflation graph we see?
This question is not about whether it makes sense to have a centre of the universe or not instead, it's about the inflation graph we used to see while describing the Big Bang. From the inflation graph ...
- 1,007
4
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1
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731
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What happened before, Big Bang or inflation?
I always thought that the cosmic inflation happened after the big bang (10-36 sec) and lasted for a very tiny fraction of time).
Now, I recently came across a couple of articles (links below) claiming ...
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126
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Does the cosmological principle apply to the entire universe?
Some cosmological models assume that the universe is isotropic and homogeneous and that is also flat and infinite. If the universe is infinite now it was infinite immediately after the big bang. If ...
- 91
-3
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1
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297
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Is our universe a singularity?
According to the Big Bang theory our universe used to be a lot smaller in size.
It actually used to be so small that in the beginning it used to be a singularity.
And the universe started to expand ...
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2
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1
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186
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Did Einstein supported Big Bang Theory cosmological model?
Einstein made many predictions, including gravitational waves and the possibility of black holes.
Relativity is taken into consideration for the Big Bang model, so did Einstein agree with it or did ...
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208
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What reference frame do age-of-the-universe calculations assume?
I'm thinking, in particular, about general relativity. When we speak, for example, of neutrino decoupling, what do we mean when we say this happened in the first second after the Big Bang? Do we mean ...
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256
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How do we know so many details about Big Bang, but we do not know if Universe is finite/infinite?
I understand that this question may be too vague, but I am confused about the following:
On one hand we know a lot of "details" about Big Bang, like really precise details, evolution of universe, age ...
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1
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201
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Is it possible that the Universe is expanding due to additional Big Bang events?
Is it theoretically possible that the Universe is expanding due to additional Big Bang events that have occurred at the same location that the original Big Bang occurred at?
Perhaps there has been an ...
user23327
0
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1
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144
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Fundamental axioms in LCDM
What are the axioms (if any) behind the LCDM model of cosmology?
NB: axioms, not postulates (e.g., inflation)
user19333
2
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0
answers
54
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How the observed deuterium abundance constrains big bang nucleosynthesis?
I know deuterium can be used as a good tracer to constrain the big bang nucleosynthesis. But can anyone tell me the in details how this is actually done?
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368
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How does inflation justify the nonexistence of magnetic monopoles?
It is said that inflation justifies that magnetic monopoles don't exist. Can anyone explain how inflation theory explains the non existence of magnetic monopoles?
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208
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How Good Are the Upper Limits on Heavy Elements?
There are between 90 and 254 stable nuclei all the way up to element number 82. In discussions and graphs about big bang nucleosynthesis nothing above lithium is even mentioned. It's a pretty safe bet ...
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31
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1
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Why didn't the Big Bang produce heavier elements?
Shortly after the Big Bang, temperatures cooled from the Planck temperature. Once temperatures lowered to 116 gigakelvins, nucleosynthesis took place and helium, lithium and trace amounts of other ...
- 8,135
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1
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230
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How can we use hypervelocity stars to determine the origins of the Universe?
I was reading this article finding evidence of Universe's origin, which describes that in 1 trillion years we may lose the ability to determine how the universe was created.
The answer seems to be ...
- 231
2
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1
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509
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Future redshifting and effect on the 'pitch' of CMB radiation
After discovering this question exploring the sound of a blackbody, I started wondering about the sound of the Cosmic Microwave Background radiation from the Big Bang, specifically what the current ...
- 123
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2
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368
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How is it possible that the CMB approaches the earth from all directions?
I presume that the photons from the CMB approach the earth from all directions, otherwise we couldn't detect them with a picture where it is present everywhere in the universe with a tiny anisotropy.
...
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2
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293
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Is mass+energy conserved when a new universe forms inside a black hole?
My understanding is that there are credible theories out there in which the formation of a singularity in a black hole also represents the beginning of a new universe via a big bang. We can't see the ...
- 369
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2
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833
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Time dilation at the Big Bang [duplicate]
At the time the Big Bang happened the matter had enormous density. According the GR (I may be wrong here) such density dilates time.
If so, could it be that the time periods just after Big Bang which ...
- 1,265
4
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1
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182
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Formation of Cosmic Microwave Background
It is said that the cosmic microwave radiation (CMB) was formed when the universe was 379,000 years old. How is this calculated?
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238
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Might the universe be really small yet seem infinite from spherical reflections? [closed]
if a single source of light quite small, was placed somewhere inside a completely reflective sphere, quite large, what would the reflections look like from the light source's point of view within that ...
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