According to the current cosmological theories, it's the model that explains the early life of the universe, starting from a rapid expansion of hot and dense matter.

learn more… | top users | synonyms

5
votes
4answers
286 views

Could there have been two “Big Bangs”?

A couple of years ago, I remember seeing a documentary on the big bang theory. The theory presented was that to explain the cosmic microwave background radiation, there needed to have been two big ...
0
votes
1answer
85 views

Big Bang Quarks Travelling at Light Speed [closed]

When I think of an explosion it lasts a fraction of second. When the entire mass of the universe explodes how much time passes before the perfect sphere slows from traveling at/near the speed of light ...
5
votes
1answer
124 views

The naive idea of the big bang

Many people think that according to big bang cosmology, first there was empty space, then there was an explosion in the middle of the emptiness, and now all the galaxies are flying away from that ...
-4
votes
0answers
40 views

Could Dark Matter Exist Prior to the Big Bang? [closed]

Recent discoveries that the universe is accelerating in its expansion has made me consider the possibility that dark matter might have existed prior to the time the universe sprang into existence, ...
18
votes
4answers
744 views

Interpretation of a singular metric

I'm interested to find out if we can say anything useful about spacetime at the singularity in the FLRW metric that occurs at $t = 0$. If I understand correctly, the FLRW spacetime is a combination ...
3
votes
1answer
1k views

Obtaining a copy of Hawking's Ph.D thesis - Properties of Expanding Universes

Due to its popularity, I am interested to know the 4 chapter titles and topics covered in S.W. Hawking Ph.D, Properties of Expanding Universes. I also ask this because that thesis is hardly available. ...
9
votes
6answers
6k views

Why was the universe in a extraordinarily low-entropy state right after the big bang?

Let me start by saying that I have no scientific background whatsoever. I am very interested in science though and I'm currently enjoying Brian Greene's The Fabric of the Cosmos. I'm at chapter 7 and ...
1
vote
3answers
101 views

Observing a point 13.82b ly away, 1b years ago

I understand that we can observe far away galaxies to get an idea how the universe looked like in the past. Assuming the universe is 13.82b years old, would it be correct to say that if we looked at ...
10
votes
3answers
483 views

Age of the universe versus absolute time [duplicate]

In Wikipedia, the age of the universe is defined as the "time elapsed since the Big Bang" while "time" links to "the cosmological time parameter of comoving coordinates" which itself links to "the ...
3
votes
1answer
79 views

Why is the gravitational constant.. constant? [duplicate]

Many scientists have now come to the conclusion that a big bang might not explain the 'start' of the universe and are coming up with alternatives. Could it be that gravity is dependent on the ...
2
votes
0answers
53 views

Where does all the energy in the universe come from? [duplicate]

The principle of conservation of energy says that all energy in a system will remain the same. It can just be transformed. The universe contains a huge amount of energy, but where did it come from? ...
1
vote
1answer
79 views

What effects would a finding of Gravitational Repulsion Between Matter and Anti-Matter in the ALPHA Experiment have on Mainstream Theory? [closed]

The actual nature of the gravitational force between matter and anti-matter (attractive or repulsive) remains unsettled: See Are there experiments taking place right now that might show evidence for ...
16
votes
1answer
972 views

Does all hydrogen originate from the Big Bang?

I was wondering, if every single hydrogen in the universe originate from the time about ~3 min after the Big Bang. I know there are nuclear fusion processes going on in stars like the pp-chain ...
5
votes
6answers
1k views

What came first, the Universe or the Physical laws that govern the Universe? [closed]

This sounds like the Egg and the Hen question but I am curious about this. If universe came first and created physical laws for itself, then what created the law or the principle as a consequence of ...
0
votes
0answers
39 views

Could the Big Bang be the result of a decrease in entropy?

In my freshman engineering physics class I learned that a decrease in entropy, though hypothetically possible, is less statistically likely than either any or almost any other possible single ...
3
votes
2answers
160 views

Is entropy absolute (as in absolute temperature)?

Following this question on the Entropy at the Big Bang where I asked: Since Entropy always increases (in general); its expected that the entropy at the beginning of the universe should be the ...
0
votes
0answers
57 views

What started the Big Bang? [duplicate]

Is the Big Bang started everything, including time, what EVENT could ever occur outside time unless all events are non-temporal prior to and during the big bang?
4
votes
0answers
58 views

What would we observe as background on the sky if the big bang had never occurred?

The data we've received so far from satellites such as WMAP paints a near uniform distribution in intensity of the background radiation that we take as evidence that our universe had an origin, and ...
3
votes
1answer
91 views

Hawking in A Brief History of Time: No beginning or end of the Universe

I am reading Stephen Hawking's book - A Brief History of Time. I haven't studied cosmology and the related sciences. Nevertheless, I am interested to know few things regarding the extract taken from ...
1
vote
1answer
60 views

What was outside the singularity during the Big Bang? [closed]

What was outside the proposed singularity during big bang?What was the size of singularity?
0
votes
0answers
14 views

How is the Lyman alpha forest and Gunn-Peterson trough evidence for Reionization? [duplicate]

I'm trying to understand how the Lyman alpha forest and Gunn-Peterson trough are evidence for Reionization. From what I've read, the Lyman alpha forest tells us how much neutral hydrogen is in the ...
2
votes
3answers
100 views

How big bang could produce later collisions

The Milky Way and the Andromeda galaxies are supposed to "collide" in 4 billion years (collide in the sense of overlapping space, but nothing is really supposed to contact anything else). Assuming: ...
0
votes
1answer
26 views

Is there any possible evidence that can give us insight into what happened exactly at the Big Bang/why it happened?

It's mostly well accepted today that the Big Bang was the reason for today's universe, mostly due to the expansion, the cosmic microwave background etc. and mathematically the FLRW metric supports it. ...
19
votes
5answers
5k views

Does red shift evidence necessarily imply that the universe started from a singularity?

We are taught that the universe began as a singularity - an infinitely small and infinitely dense point. At the beginning of time there was a 'Big Bang' or, more accurately, 'Inflation'. The main ...
0
votes
0answers
25 views

Does the Big bang imply Absolute time

According to the current understanding the Big bang created space, so it has happened everywhere: dating events 'after the bing bang' would be an absolute time scale. More specifically, wherever you ...
0
votes
0answers
18 views

What was the value of the Hubble parameter at the Big Bang nucelosynthesis?

If we assume the middle of the BBN, ~300 seconds, I tried to calulate this using H(t)=1/2 t^-1 for a radiation dominated universe, which gives the value 5*10^16 km/s/Mpc. This value seems ridiculously ...
5
votes
1answer
83 views

Why quantum fluctuation existed before big bang?

I read somewhere that quantum fluctuation can give rise to a big bang and thus the creation of a universe which we know today, where do these quantum fluctuations come from if space is only created ...
0
votes
1answer
34 views

Is it possible for the universe to be already developed when the dark energy appeared and expansion started?

The main piece of evidence that supports Big Bang Theory is basically evidence that the expansion of the universe started long time ago (not necessarily from the begining of the universe). Is it ...
1
vote
3answers
67 views

Why didn't helium continue to generate after a few minutes post-Big Bang?

Helium stopped generating after a few minutes after the Big Bang, but what made it impossible for its generation to continue?
1
vote
1answer
56 views

How do we know that supermassive black holes formed in the early universe?

Could they have existed from the very beginning? Could they be leftover fragments of the cosmic egg?
1
vote
1answer
43 views

What happens if an object stops orbiting the sun? [closed]

What would happen if an object (like a space ship) was to stop its orbit around the sun. would time slow down with that object (the same way time sped up for the characters in that great film ...
1
vote
0answers
36 views

Where is lithium in universe? [duplicate]

In the theory of big-bang elements were formed in a particular order. Firstly hydrogen and in last iron formed. But at third no. Lithium was formed which should be present in enormous amount in ...
3
votes
2answers
135 views

Does the second law of thermodynamics imply a spacetime beginning of the universe?

Recently I have been studying thermodynamics and I noticed a article by a religious person which says that the second law of thermodynamics proves that the universe had a beginning. A spacetime one. ...
1
vote
1answer
87 views

Why did the big bang happen when it did?

Was there time before the big bang? I assume there wasn't, so is it even logical to ask if there was anything before the big bang? If there was time before the beginning of the universe, what happened ...
0
votes
3answers
158 views

Infinite Universe and Big Bang

A common view now in the physics community is that the Universe is infinite in extent (which makes Hubble sphere an infinitely small part of the Universe). On the other hand, there is the Big Bang ...
0
votes
0answers
18 views

What other particles don't participate in BBN?

This is a follow up to an earlier question. Of the responses I got back, the general sense is that Dark Matter (DM) is a "thermal relic" from an earlier epoch of the universe when temperatures were ...
0
votes
2answers
377 views

Big Bang…or…Everywhere Stretch?

Recently I watched a minute-physics video that suggested that a better name for the beginning of time would be "Everywhere stretch" because there wasn't a space-time singularity that formed where the ...
0
votes
1answer
35 views

Why do “Quantum Fluctuations” need Inflation to grow into cosmic scales?

This is a follow up to How do quantum fluctuations lead to overdense regions in the CMB? (which still hasn't been answered). The general logic of Inflation (if anything about the theory can be ...
0
votes
0answers
39 views

Is a terminal gravitational center to the universe possible?

The current consensus is that there is no evidence of, or no way to tell whether or not there is a center to the universe. Considering our observable universe is only a small portion of what we know ...
0
votes
1answer
97 views

Is the Universe infinite or it's just expanding to infinity?

According to the WMAP data in the past years we can say that our universe is considered flat or at least nearly flat and we also know that flat universe is allowed to be both infinite or finite in ...
1
vote
0answers
32 views

The steady state theory, can it now be falsified on particle physics grounds, in addition to CMB data?

The steady state theory is no longer taken seriously by most physicists and the Big Bang theory is supported by an enormous amount of evidence, especially the CMB data. But from a quick scan through ...
3
votes
3answers
340 views

Is there an exact formal definition of the Universe?

I've read several articles about Observable universe, Universe and Hubble volume, including Wikipedia articles and other references. After this I wondered: Is there a formal, rigorous definition in ...
0
votes
1answer
58 views

Do sound waves travel before Big Bang?

So I was reading a Scientific American article about how the universe is spreading apart and how it is getting faster. But in the article there was something that baffled be and it was this "Sound ...
8
votes
2answers
306 views

Is it possible to look into the beginning of the Universe?

If we currently can look into some of the furthest stars, actually seeing the past Isn't it conceivable that given enough distance we should be able to see Parts of the Big Bang? If the Universe is ...
0
votes
2answers
2k views

Atoms pop out of nothing/vacuum/pre-big-bang?

I saw a great documentary last night about 'nothing'. It's about vacuums, and how if you have a total vacuum atoms will pop out of nowhere! Pretty crazy stuff. Atoms literally coming out of ...
0
votes
3answers
67 views

Why is the universe not uniform?

From my understanding, the Big Bang theory says the universe expanded from a state of infinite density and pressure. I feel that if this is true, this should lead to a universe where matter is ...
1
vote
0answers
32 views

Did the early universe violate the 2nd law of thermodynamics? [duplicate]

If the universe started out isotropic and homogenous and of all fundamental particles then how could there now be any concentration of energy anywhere? If you say that nothing is really homogenous ...
-3
votes
1answer
60 views

It's a Hypothesis about the Beginning of the universe [closed]

Let's take a piece of paper and plot a couple of dots in it. If we shrink the paper infinitely, at some point it would reach a state of infinite density, that is; a Singularity. But even at that ...
5
votes
6answers
538 views

Is it possible that galaxies' redshift is caused by something else than the expansion of space?

I was thinking that maybe photons loss energy naturally when they travel great distances. Or maybe the mass of all matter is increasing over time and therefore photons emitted in the past are ...