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.

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Hydrogen in a glass of water

One of the great Sagan quotes is that we are made of star stuff - meaning the atoms in our bodies were formed from stellar nucleosynthesis. However, what about the hydrogen in a glass of water? Would ...
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183 views

Is the universe bounded?

As I understand it nobody can pinpoint an objective "center" of the universe nor "where" the Big Bang happened. It seems the observable universe is limited by our event horizon at some 14 billion ...
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Age of the universe and the singularity at the Big Bang

Using the standard model of cosmology we calculate the Hubble time to obtain an estimate of the age of the universe. This model assumes a beginning of time in the past. But that point is a true ...
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My question is about big bang theory [closed]

Oh srry my english is weak i am only 11 years old but i love physics my question was accourding to maxwell and enistien nothing can go faster than light and if we give an object enough energy to move ...
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109 views

How can we say time began at big bang?

I have seen many times scientists refer to time when Big Bang took place and space and time born out of singularity. 'Beginning of Time' is a very misleading statement,because process of beginning ...
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22 views

Rate of expansion of universe during big bang [duplicate]

We say big bang was the explosion not in the space but of the space itself that took place in a fraction of seconds. Speaking practically, we say the universe has no edge and is infinite. If the ...
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Is it possible that dark-matter is composed of a large number of neutrinos from the big bang? [duplicate]

They seem to have all the properties of dark-matter (massive, with no electromagnetic interaction). Could it be that many of the neutrinos produced since the big bang have formed massive neutrino ...
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Is it possible that there are still gravitational waves of the big bang?

We already discovered the cosmic background radiation what are the 'leftovers' of electromagnetic radiation of the big bang. Probably gravitational waves of the big bang (if they exists) would be to ...
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Can space expand with unlimited speed?

According to this article on the European Space Agency web site just after the Big Bang and before inflation the currently observable universe was the size of a coin. One millionth of a second later ...
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Gravitational wave of Big bang? [duplicate]

Questions about the g-wave caused by the big bang: 1)was there a g-wave produced? 2) when will it reach us? 3) will it be too weak for us to detect(atleast now?)?
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44 views

Did the strong force trigger inflation?

I understand there can only be speculative theories regarding this epoch, but it would be great to know if this theory has some level of acceptance in the physics community. If the strong force is ...
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66 views

Is there a truly stationary frame of reference? (part deux) [duplicate]

I wonder if the belief that there is no truly stationary frame of reference is really true. Here's my thinking, please poke holes in it and/or mock me :) As we understand it, before the big bang the ...
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36 views

How is the potential infinitude of the universe compatible with the Big Bang?

I know no physics, but I read that while the observable universe is finite, for all physicists know the universe is infinite. How is this compatible with the Big Bang hypothesis? Does it mean that it'...
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323 views

Is there a “CGBR”?

The recent discovery by the LIGO made me wonder about this. We know that there exists a CMBR, Cosmic Microwave Background Radiation, a blanket of electromagnetic energy covering the universe, made by ...
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20 views

Light from the big bang [duplicate]

Considering that the Big Bang all started from a single point in space time, and the light emitted from it has been spreading outwards in all directions ever since, how do we, from earth, see the ...
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41 views

Precise definition of “Observable Universe” and its alternatives

The Observable Universe is generally said to contain all space that could "in principle" have had a causal impact on Earth, but the exact limits of the "in principle" causal interaction go unspecified....
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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 ...
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104 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 ...
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147 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 ...
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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 ...
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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 ...
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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 ...
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558 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 ...
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92 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 ...
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63 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? ...
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100 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 ...
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999 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 ...
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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 ...
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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 ...
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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 ...
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105 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 ...
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124 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?
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15 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 ...
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3answers
109 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: ...
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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. ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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?
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50 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 ...
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37 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 ...
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2answers
253 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. ...
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116 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 ...
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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 ...
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2answers
506 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 ...
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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 ...