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Questions tagged [big-bang]

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.

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

This inflation is described by the Friedmann equations, a special case of the Raychaudhuri equation.

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Did the Big Bang happen at a point?

TV documentaries invariably show the Big Bang as an exploding ball of fire expanding outwards. Did the Big Bang really explode outwards from a point like this? If not, what did happen?
John Rennie
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Why are some people are claiming that the Big Bang never happened?

A news story is going viral on social media networks claiming that two physicists have found a way to eliminate the Big Bang singularity, or in layman's terms (as claimed by many sensationalist news articles): The Big Bang never happened at all. The…
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Why is there a scarcity of lithium?

One of the major impediments to the widespread adoption of electric cars is a shortage of lithium for the batteries. I read an article a while back that says that there is simply not enough lithium available on the entire planet to make enough…
Mason Wheeler
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Why didn't the Big Bang create heavy elements?

In the case of a supernova explosion it is possible to create heavy elements through fusion. Supernovae have a tremendous amount of energy in a very small volume but not as much energy per volume as there was in our early universe. So, what is the…
Alex
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What does one second after big bang mean?

Consider the following statement: Hadron Epoch, from $10^{-6}$ seconds to $1$ second: The temperature of the universe cools to about a trillion degrees, cool enough to allow quarks to combine to form hadrons (like protons and neutrons). What…
Yashas
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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 the universe was the size of the Solar System,…
cziko
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Does the universe have a center?

If the big bang was the birth of everything, and the big bang was an event in the sense that it had a location and a time (time 0), wouldn't that mean that our universe has a center? Where was the big bang? What is there now? Are we moving away from…
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How could quantum effects occur in the early universe without an observer?

In inflationary cosmology, primordial quantum fluctuations in the process of inflation are considered responsible for the asymmetry and lumpiness of the universe that was shaped. However, according to the Copenhagen interpretation, any random…
Alex L
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Is the Big Bang defined as before or after Inflation?

Is the Big Bang defined as before or after Inflation? Seems like a simple enough question to answer right? And if just yesterday I were to encounter this, I'd have given a definite answer. But I've been doing some reading while writing up my thesis…
Jim
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How can it be that the beginning universe had a high temperature and a low entropy at the same time?

The Big Bang theory assumes that our universe started from a very/infinitely dense and extremely/infinitely hot state. But on the other side, it is often claimed that our universe must have been started in a state with very low or even zero entropy.…
asmaier
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Is space really expanding?

In a book called "Einstein, Relativity and Absolute Simultaneity" there was this sentence by Smith: There is no observational evidence for a space expansion hypothesis. What is observed are superclusters of clusters of galaxies receding from each…
user311398
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Why was the universe in an 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 so far I understand most of general ideas he has…
Kristof Claes
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The age of the universe

Many times I have read statements like, "the age of the universe is 14 billion years" . For example this wikipedia page Big Bang. Now, my question is, which observers' are these time intervals? According to whom 14 billion years?
Yossarian
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Why haven't we seen the big bang?

The Andromeda galaxy is 2,538,000 light years away, so if we view Andromeda from a telescope, we see Andromeda how it was 2,538,000 years ago. Now the diameter of the visible universe is 92 billion light years so if we say that we are at the center…
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If the universe is expanding, what is it expanding into?

If the universe is expanding, what is it expanding into? When the big bang happened where did it occur? When the big bang happened how did it occur? Where did the energy come from? Energy can not be created or destroyed does that mean, energy has…
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