Questions tagged [big-bang-theory]
Questions regarding the currently prevalent cosmological model for the origin of the universe.
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How did cosmic inflation even occur?
I wanted to ask this question that which inflation model shall i believe?
Following below will be MY UNDERSTANDING (MAY NOT BE CORRECT) OF IT:
I read "A Brief History of Time" and in chapter ...
6
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1answer
1k views
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 ...
9
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1answer
868 views
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 ...
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0answers
110 views
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 ...
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0answers
27 views
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 ...
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1answer
97 views
Because the Universe is expanding, what is it taking up?
It is my understanding that the universe is expanding and that matter takes up space. While the universe only contains small percent of matter, wouldn't expansion indicate that the universe is ...
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1answer
33 views
Can two neighboring galaxies move apart at steady speed?
While I was trying to understand the three models that obey Friedmann's two assumptions of a non-static universe, I came across a line that says and I quote "It (referring to Big Bang) starts at ...
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0answers
51 views
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 ...
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61 views
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 ...
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0answers
35 views
Expanded element (and molecule) abundance graph?
There is the "classical" nucleosynthesis timeline chart where the $\log ({\rm mass \,fraction})$ is plotted as a function of $\log(t)$ where $t$ is in seconds after the big bang, looking e.g....
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3answers
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Could liquid water have existed in open space 15 million years after the Big Bang?
Around 15 million years after the Big Bang, the ambient temperatures was about $24^\circ {\rm C}$, which is in a range where water could be liquid. Could liquid blobs of water be existent then?
PS: I ...
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1answer
69 views
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. ...
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0answers
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Early (high density) Universe's event horizon [duplicate]
Taking into consideration the big bang theory and the followed expansion of our Universe, was there a time when density of the Universe created an event horizon?
If so, then for how long and how is it ...
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0answers
62 views
Math for the "universe in a black hole" hypothesis?
There are various pop-science article entitled Are we living in a Black Hole? or Did A Black Hole Give Birth To Our Universe? which say things like
There’s a lot to like about the idea that there’s a ...
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0answers
52 views
Could the duration of some gamma ray bursts be information from outside our universe?
Could we be in a system where a large mass explodes dispersing matter in all directions until gravity pulls it together with matter from other explosions until the maximum mass limit is reached, ...
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0answers
58 views
in current models of the Big Bang, what happens to the products of baryon annihilation?
In current thinking about the Big Bang, the baryogenesis phase involves CP/CPT symmetry violation. There is an excess (says Wikipedia) of perhaps 1 in $10^{10}$ baryons over antibaryons, the majority ...
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77 views
Accuracy of the Inflation theory
In the Inflation theory, it said that the Inflationary epoch has happened $10^{-32} \,\mathrm{s}$ after the Big Bang, and I cannot find anything related to how this number was calculated and how ...
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1answer
60 views
Centre of the Universe [duplicate]
Why shouldn't the original singularity of the big bang happen to be the centre of the Universe? Assume that the universe is expanding isotropically with a constant speed.
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0answers
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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 ...
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1answer
97 views
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 ...
2
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1answer
285 views
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, ${\...
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2answers
153 views
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 ...
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2answers
147 views
What powered the Big Bang?
According to the first law of thermodynamics, law of conservation of energy states,
The total energy of an isolated system is constant; energy can be transformed from one form to another, but can be ...
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0answers
64 views
Was universe spawn from nothing? [duplicate]
Was universe spawn from nothing?
Until now, scientists figured out that the Big Bang happened from a tiny particle which was infinitely energy densed and having infinite mass. If that is the case ...
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1answer
286 views
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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1answer
349 views
Why is the Cosmic Microwave Background at the same distance no matter the direction we look?
I've read from different sources that:
The CMB is visible at a distance of 13.8 billion light years in all
directions from Earth, leading scientists to determine that this is
the true age of the ...
4
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2answers
666 views
What is meant by "vastness of space, which now filled a volume of a hundred million light years"?
I am reading the book Cosmic biology: How life could evolve on other worlds (citation below) and do not understand the meaning of the following paragraph from page 4 (emphasis mine):
It took 200,000 ...
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1answer
170 views
How can something infinitely big have expanded from an infinitely small?
Please help me reconcile what I see as contradicting theories:
The universe began with the Big Bang and expanded from an infinitesimally small point.
The universe is infinite.
How can something ...
13
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1answer
4k views
At the Big Bang, when everything was close together, why did it not "collide", violating Planck length or Pauli Exclusion Principle?
How could so much matter, or "all" in fact, have been concentrated in a smaller universe without being in the actual same place? Why did this not result in undercutting the Planck Length or ...
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0answers
89 views
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 ...
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1answer
78 views
Types of Multiverses [closed]
Can anyone recommend me books or other online resources on the concept of the Multiverse, it types, and about higher mathematical dimensions of space-time. I have been interested in such topics for a ...
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1answer
100 views
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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0answers
51 views
How is the big bang a plausible theory? [duplicate]
In the Big Bang Theory, it is said that it started with a small speck of matter, yet we have an unimaginable mass of expanding universe which is assumed as immeasurable. If the theory of "Matter ...
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0answers
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Is there a place where one can see the beginning of the universe? [duplicate]
If the night sky Is dark because we’re seeing the world as it was a long time ago, when there wasn’t much to see, is there a place on the universe where we can see the universe at the beginning of ...
6
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1answer
175 views
Why is the Cosmic Microwave Background evidence of for a hotter, denser early Universe?
In his book Gravitation and cosmology, Steven Weinberg says that CMB makes it "difficult to doubt that the universe has evolved from a hotter, denser early stage".
In my understanding, the ...
2
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1answer
115 views
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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2answers
292 views
Is Olbers' Paradox Nonsense? [closed]
Ok, this is a bold question, I know. But, let me explain: After first hearing about Olbers' paradox, I found that something seemed 'off' about it, so I looked into the subject as much as my skills (...
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0answers
36 views
Must all galaxies in a galaxy cluster have the same expansion rate?
If we observe a distant galaxies cluster where all galaxies travel with the same speed away from us, except for one galaxy whose speed is significantly lower than of the neighboring galaxies. Does ...
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1answer
91 views
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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2answers
235 views
Are there only a set number of atoms in the whole universe?
As per the title, are there only a set number of atoms in the universe? Or does the universe make more atoms, and if so, how does it work?
I'm a high school student that just had a question during ...
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1answer
118 views
Understanding The Fluctuations In The CMB Maps
If I'm understanding this correctly the fluctuations in CMB are a result of the "last scatter" of photons when electrons joined together with nuclei that before this formed plasma. CMB is among other ...
8
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1answer
188 views
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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2answers
641 views
If space is negative energy and matter is positive energy then does that mean the universe is finite?
I was reading a book by Stephen Hawking, it was written that universe is made up of 2 ingredients,i.e., space and energy and space was the negative energy, so they add up to 0. But since space is ...
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1answer
225 views
What does it mean for space to expand?
In this YT video Michelle Thaller says The Big Bang wasn’t an explosion but an expansion and as such there's no empty center where the explosion would've been.
To explain expansion she uses the ...
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6answers
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Why do galaxies collide?
If the universe is expanding outward, what is the processes for one galaxy to get off track enough to collide with another?
Say, the Andromeda Galaxy and the Milky Way.
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1answer
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Have we measured or found evidence of a detectable origin point of the big bang? [duplicate]
Based on reading the wiki page of the big bang, a simple question with a probably not a simple answer came to mind.
The statement on the wikipedia page was.
Since Georges Lemaître first noted in ...
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Is it possible for 'pre-big bang' empty space to have the property of being able to spawn matter and/or energy into existence? [closed]
.. and if so, wouldn't this also mean that during this event, time would be created as a collateral, as a canvas for this property to manifest?
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Expansion of space - how do we end up with an unobservable region?
I've just been answering a question on this issue,in physics SE,and realised that my answer conceals a point I don't myself understand.
I understand that
The expansion of metric isn't affected by ...
4
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1answer
218 views
How much helium has been created since the Big Bang?
When I try to find figures for the amount of helium today and just after the Big Bang, I get similar figures. I was expecting that all of the stars since then would have created more helium. Is the ...
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0answers
50 views
How did the Big Bang occured if before that there was no time? [duplicate]
I am thinking, that if the Big Bang created time, it implies that before the Big Bang there was no time (correct me if I am wrong).
My question is that, if there was no time before the Big Bang, how ...
