<p>In and of itself, no the expansion of the universe is not proof of the big bang. Other theories could be constructed that would also be explained by the expansion. For example Fred Hoyle and others proposed the <a href="https://en.wikipedia.org/wiki/Steady_State_theory" rel="nofollow">Steady State Theory</a> which proposed that new matter was constantly being created thus causing the expansion. A the time there was no other evidence for either theory so either could have been true.</p>

<p>However, when you couple the expansion with other evidence such as the <a href="https://en.wikipedia.org/wiki/Cosmic_microwave_background" rel="nofollow">cosmic microwave background radiation</a> discovered in 1964 then it does strengthen the case for the big bang being the cause.</p>

CC BY-SA 3.0
2016-10-28T18:01:03.667Z
This is just wrong. The Steady State Theory proposed by Hoyle does indeed predict the random creation of matter out of nothing, but **not** as a means of explaining the expansion. The reason this was put in the theory was to allow for the universe to remain "steady" (e.g., constant density, etc.) throughout it's infinite existence. Obviously if its expanding, it should get less dense meaning it isn't static and Hoyle disliked that so he proposed that matter is constantly created to make it static. He had no explanation for what caused the expansion.
zephyr
CC BY-SA 3.0
2014-05-23T01:25:39.317Z
The ratio of hydrogen to helium in the universe is easy to measure, and is exactly what is predicted by the Big Bang theory.
Marc
CC BY-SA 3.0
2014-05-17T10:40:25.930Z
2014-05-17T16:22:36.823Z
2014-05-17T16:22:36.823Z
ChrisF
<p>Whether the big bang <a href="https://astronomy.stackexchange.com/questions/53684/is-big-bang-a-theory-or-a-model?noredirect=1&amp;lq=1">is a theory or a model</a>, it cannot be &quot;proved&quot;. Scientific models and theories can only be <em>falsified</em>.</p>
<p>I think what you mean is - <em>are there other pieces of evidence that are used to support the big bang model?</em> Or possibly <em>are there other pieces of evidence that support the idea that the universe was once very small and very hot?</em></p>
<p>The answer is yes. Probably the two most important pieces of evidence are found in the cosmic microwave background and the primordial abundances of deuterium and helium.</p>
<p>Both of these are direct and inevitable consequences of having initial conditions of a very hot (<span class="math-container">$&gt;10^{10}$</span> K) and dense universe about 13.8 billion years ago that expanded adiabatically. In particular they both feature evidence that can bee seen in the universe today (the temperature of the CMB and primordial abundances measured from pristine materials or very old stars) that depend on a single free parameter - the photon to baryon ratio. To me, the fact that these very dissimilar phenomena, that are produced when the universe was about <span class="math-container">$10^{10}$</span> K and <span class="math-container">$3000$</span> K respectively and at densities differing by many orders of magnitude can be simultaneously reproduced is perhaps the biggest success of the model.</p>

CC BY-SA 4.0
2023-05-14T17:47:16.567Z
2023-05-14T17:47:16.567Z
ProfRob
<p>Gravity holding our universe together if you look at the universe from outside of the universe you will see avery things all the galaxy avery things in our universe holds together and avery things are moving because of matmtics of universe.</p>

CC BY-SA 4.0
2023-05-14T10:42:11.933Z
As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Community
CC BY-SA 4.0
2023-05-14T10:42:47.397Z
This does not provide an answer to the question. Once you have sufficient [reputation](https://astronomy.stackexchange.com/help/whats-reputation) you will be able to [comment on any post](https://astronomy.stackexchange.com/help/privileges/comment); instead, [provide answers that don't require clarification from the asker](https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead). - [From Review](/review/late-answers/32367)
GrapefruitIsAwesome
CC BY-SA 4.0
2023-05-14T08:11:41.533Z
2023-05-14T08:11:41.533Z
Seyed Mohammad Mahini
<p>Is the expansion of the universe proof of the Big Bang theory?</p>

<p>Or are there other proofs?</p>

CC BY-SA 3.0
2014-05-16T20:33:09.233Z
http://en.wikipedia.org/wiki/Big_Bang#Observational_evidence
Florin Andrei
<big-bang-theory><expansion>
Is the expansion of the universe proof of the big bang?
Kilise
# Is the expansion of the universe proof of the big bang?

(Asked by: username_0 on 2014-05-16)

Is the expansion of the universe proof of the Big Bang theory?

Or are there other proofs?

**Tags:** big-bang-theory, expansion

> **Comments:**
> **username_1**: http://en.wikipedia.org/wiki/Big_Bang#Observational_evidence  

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## 3 answers

### Answer by username_2 on 2014-05-17. Score: 4 | Accepted answer

In and of itself, no the expansion of the universe is not proof of the big bang. Other theories could be constructed that would also be explained by the expansion. For example Fred Hoyle and others proposed the [Steady State Theory](https://en.wikipedia.org/wiki/Steady_State_theory) which proposed that new matter was constantly being created thus causing the expansion. A the time there was no other evidence for either theory so either could have been true.

However, when you couple the expansion with other evidence such as the [cosmic microwave background radiation](https://en.wikipedia.org/wiki/Cosmic_microwave_background) discovered in 1964 then it does strengthen the case for the big bang being the cause.

> **Comments:**
> **username_4**: The ratio of hydrogen to helium in the universe is easy to measure, and is exactly what is predicted by the Big Bang theory.  
> **username_3**: This is just wrong. The Steady State Theory proposed by Hoyle does indeed predict the random creation of matter out of nothing, but **not** as a means of explaining the expansion. The reason this was put in the theory was to allow for the universe to remain "steady" (e.g., constant density, etc.) throughout it's infinite existence. Obviously if its expanding, it should get less dense meaning it isn't static and Hoyle disliked that so he proposed that matter is constantly created to make it static. He had no explanation for what caused the expansion.  

---

### Answer by username_5 on 2023-05-14. Score: 6

Whether the big bang [is a theory or a model](https://astronomy.stackexchange.com/questions/53684/is-big-bang-a-theory-or-a-model?noredirect=1&lq=1), it cannot be "proved". Scientific models and theories can only be *falsified*.

I think what you mean is - *are there other pieces of evidence that are used to support the big bang model?* Or possibly *are there other pieces of evidence that support the idea that the universe was once very small and very hot?*

The answer is yes. Probably the two most important pieces of evidence are found in the cosmic microwave background and the primordial abundances of deuterium and helium.

Both of these are direct and inevitable consequences of having initial conditions of a very hot ($>10^{10}$ K) and dense universe about 13.8 billion years ago that expanded adiabatically. In particular they both feature evidence that can bee seen in the universe today (the temperature of the CMB and primordial abundances measured from pristine materials or very old stars) that depend on a single free parameter - the photon to baryon ratio. To me, the fact that these very dissimilar phenomena, that are produced when the universe was about $10^{10}$ K and $3000$ K respectively and at densities differing by many orders of magnitude can be simultaneously reproduced is perhaps the biggest success of the model.


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### Answer by username_6 on 2023-05-14. Score: -5

Gravity holding our universe together if you look at the universe from outside of the universe you will see avery things all the galaxy avery things in our universe holds together and avery things are moving because of matmtics of universe.

> **Comments:**
> **username_7**: As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).  
> **username_8**: This does not provide an answer to the question. Once you have sufficient [reputation](https://astronomy.stackexchange.com/help/whats-reputation) you will be able to [comment on any post](https://astronomy.stackexchange.com/help/privileges/comment); instead, [provide answers that don't require clarification from the asker](https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead). - [From Review](/review/late-answers/32367)  

---

