<p>The main evidence of the Big Bang is the cosmic microwave background (CMB). You can find details here: <a href="https://en.wikipedia.org/wiki/Cosmic_microwave_background" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Cosmic_microwave_background</a>.</p>
<p>The CMB is the remnant of the Big Bang. The highly energetic radiation at that time is now stretched to form microwaves with the expansion of the universe and now can be detectable at each part of the universe. The uniformity, isotropy, redshift, and overall consistency of the CMB with the predictions of the Big Bang theory provide strong evidence that our universe began in a hot, dense state and has been expanding ever since.</p>
<p>Suggestion: Baryon Acoustic oscillators(BAO), cosmological redshift.</p>

CC BY-SA 4.0
2024-01-12T15:43:03.207Z
Extreme redshift of distant galaxies is also a strong point worth mentioning
4NT4R3S
CC BY-SA 4.0
2024-01-12T17:15:17.537Z
Cosmological redshift could be one point but it does not verify the big bang. It does hold true for other theories such as steady state.
Universe_explorer080
CC BY-SA 4.0
2024-01-12T17:16:47.640Z
It does not directly verify the big bang, but it does imply expansion, which is thought to be a result of the big bang.
4NT4R3S
CC BY-SA 4.0
2024-01-12T17:28:42.657Z
Yes. But the main point is it is true for other theories also. Baryon acoustic oscillators are more prominent proof of the Big Bang than cosmological redshift.  But yes It is worth mentioning that's why I have also suggested that at the end.
Universe_explorer080
CC BY-SA 4.0
2024-01-12T17:54:04.360Z
I agree about the other bits of evidence - BAO is pretty solid proof as well.
4NT4R3S
CC BY-SA 4.0
2024-01-12T13:47:56.097Z
2024-01-12T13:47:56.097Z
Universe_explorer080
<p>According to conventional Astrophysics:</p>
<p>The main evidence supporting the Big Bang theory comes from multiple observations and scientific principles:</p>
<p><strong>Cosmic Microwave Background (CMB)</strong>: The detection of the cosmic microwave background radiation provides strong evidence for the Big Bang. This faint radiation is essentially the afterglow of the initial hot and dense state of the universe, supporting the idea that the universe began as a hot, dense point and has been expanding ever since.</p>
<p><strong>Redshift of Galaxies</strong>: The observation that distant galaxies are moving away from us and that their light is shifted towards the red end of the spectrum (redshift - i.e. the <a href="https://en.wikipedia.org/wiki/Doppler_effect" rel="noreferrer">Doppler shift effect</a>) supports the concept of an expanding universe. The farther away a galaxy is, the greater its redshift, suggesting a common point of origin in the past.</p>
<p><strong>Abundance of Light Elements</strong>: The Big Bang theory successfully predicts the observed abundance of light elements in the universe, such as hydrogen and helium. The early conditions of the universe during the first few minutes of the Big Bang were conducive to the formation of these elements.</p>
<p><strong>Large-Scale Structure of the Universe</strong>: The distribution of galaxies and galaxy clusters in the universe, as observed through large-scale surveys, aligns with the predictions of a universe that originated from a hot and dense state and has been expanding over billions of years.</p>
<p>These pieces of evidence, combined with the mathematical framework of general relativity and the consistency of the Big Bang theory with various astronomical observations, collectively make a compelling case for the reality of the Big Bang.</p>

CC BY-SA 4.0
2024-01-12T17:06:09.287Z
We used to have an alternate theory, the steady state cosmology, which also demanded the Hubble redshift. It didn't match the other stuff, though.
John Doty
CC BY-SA 4.0
2024-01-12T16:54:21.890Z
2024-01-12T16:54:21.890Z
Brendan Darrer
<p>What is the main evidence that the <a href="https://en.wikipedia.org/wiki/Big_Bang" rel="nofollow noreferrer">Big Bang</a> is real. Why can we know that the big bang exists. In a short summary,
the evidence? In your owns words?</p>

CC BY-SA 4.0
2024-01-12T09:36:58.827Z
Please read https://astronomy.stackexchange.com/help/how-to-ask on how to ask good questions. It includes presenting your own research / search results and explaining why or how the results you get are insufficient. It's often a good idea to put as much work into a question as you expect another person to put into an answer. (We can help you with your homework, but we are not your homework ghost writers)
planetmaker
<cosmology><big-bang-theory>
Big bang cosmology
Brendan Darrer
# Big bang cosmology

(Asked by: username_0 on 2024-01-12)

What is the main evidence that the [Big Bang](https://en.wikipedia.org/wiki/Big_Bang) is real. Why can we know that the big bang exists. In a short summary,
the evidence? In your owns words?

**Tags:** cosmology, big-bang-theory
> **Comments:**
> **username_1**: Please read https://astronomy.stackexchange.com/help/how-to-ask on how to ask good questions. It includes presenting your own research / search results and explaining why or how the results you get are insufficient. It's often a good idea to put as much work into a question as you expect another person to put into an answer. (We can help you with your homework, but we are not your homework ghost writers)  

---

## 2 answers

### Answer by username_2 on 2024-01-12. Score: 2 | Accepted answer

The main evidence of the Big Bang is the cosmic microwave background (CMB). You can find details here: <https://en.wikipedia.org/wiki/Cosmic_microwave_background>.

The CMB is the remnant of the Big Bang. The highly energetic radiation at that time is now stretched to form microwaves with the expansion of the universe and now can be detectable at each part of the universe. The uniformity, isotropy, redshift, and overall consistency of the CMB with the predictions of the Big Bang theory provide strong evidence that our universe began in a hot, dense state and has been expanding ever since.

Suggestion: Baryon Acoustic oscillators(BAO), cosmological redshift.

> **Comments:**
> **username_3**: Extreme redshift of distant galaxies is also a strong point worth mentioning  
> **username_2**: Cosmological redshift could be one point but it does not verify the big bang. It does hold true for other theories such as steady state.  
> **username_3**: It does not directly verify the big bang, but it does imply expansion, which is thought to be a result of the big bang.  
> **username_2**: Yes. But the main point is it is true for other theories also. Baryon acoustic oscillators are more prominent proof of the Big Bang than cosmological redshift.  But yes It is worth mentioning that's why I have also suggested that at the end.  
> **username_3**: I agree about the other bits of evidence - BAO is pretty solid proof as well.  

---

### Answer by username_0 on 2024-01-12. Score: 5

According to conventional Astrophysics:

The main evidence supporting the Big Bang theory comes from multiple observations and scientific principles:

**Cosmic Microwave Background (CMB)**: The detection of the cosmic microwave background radiation provides strong evidence for the Big Bang. This faint radiation is essentially the afterglow of the initial hot and dense state of the universe, supporting the idea that the universe began as a hot, dense point and has been expanding ever since.

**Redshift of Galaxies**: The observation that distant galaxies are moving away from us and that their light is shifted towards the red end of the spectrum (redshift - i.e. the [Doppler shift effect](https://en.wikipedia.org/wiki/Doppler_effect)) supports the concept of an expanding universe. The farther away a galaxy is, the greater its redshift, suggesting a common point of origin in the past.

**Abundance of Light Elements**: The Big Bang theory successfully predicts the observed abundance of light elements in the universe, such as hydrogen and helium. The early conditions of the universe during the first few minutes of the Big Bang were conducive to the formation of these elements.

**Large-Scale Structure of the Universe**: The distribution of galaxies and galaxy clusters in the universe, as observed through large-scale surveys, aligns with the predictions of a universe that originated from a hot and dense state and has been expanding over billions of years.

These pieces of evidence, combined with the mathematical framework of general relativity and the consistency of the Big Bang theory with various astronomical observations, collectively make a compelling case for the reality of the Big Bang.

> **Comments:**
> **username_4**: We used to have an alternate theory, the steady state cosmology, which also demanded the Hubble redshift. It didn't match the other stuff, though.  

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