<p>The correct version of your first sentence would be something like:</p>

<blockquote>
  <p>Given our knowledge and the standard cosmological model, we estimate that the age of the universe is about 13.7 billion years old.</p>
</blockquote>

<p>Every work quotes slightly different values for the age, depending on methods, observations used, assumptions, etc. As example, the <a href="http://arxiv.org/pdf/1303.5076v1.pdf">first results</a> from the <a href="http://www.rssd.esa.int/index.php?project=planck">satellite Planck</a> report an age of 13.813, with an uncertainty of 58 million years (0.5%, to my knowledge one of the best).</p>

<p>So, first question is answered.</p>

<blockquote>
  <p>What methods did we use to discover this?</p>
</blockquote>

<p>About 100 years ago a number of people realized that our Galaxy is not the only one in the Universe and that the <strong>all</strong><sup>1</sup> other galaxies are receding from us with a speed increasing with distance (credit for this work is generally given to <a href="http://en.wikipedia.org/wiki/Edwin_Hubble">Edwin Hubble</a> for his Redshift-Distance relation for galaxies formulated in 1929). This together with the theoretical results from general relativity, brought scientists to believe that our Universe is expanding. Which means that in the universe's past it was smaller, much smaller than it is now <sup>2</sup>. </p>

<p>The age of the Universe depends on the rate of expansion at each time. To have this, you must estimate the mean composition of the universe (in various components like radiation, matter, dark energy, and curvature) and the present day expansion rate (also known as the <a href="https://www.cfa.harvard.edu/~dfabricant/huchra/hubble/">Hubble Constant</a>). Once you have this, it's <em>easy</em><sup>3</sup> to compute the age of the Universe.</p>

<p><strong>footnotes</strong></p>

<ol>
<li>except the ones in the local group that are gravitationally bound to us</li>
<li>side note: the cosmic microwave background (a radiation emitted about 13 and a half billions of years ago) provided in the 1964 a striking confirmation that the universe once was indeed much hotter and smaller</li>
<li>knowing what an integral is and with some basic of programming shouldn't be to difficult to solve equation 1 <a href="http://www.astro.umd.edu/~miller/teaching/astr422/lecture14.pdf">here</a></li>
</ol>

CC BY-SA 3.0
2013-10-17T12:41:07.743Z
2013-10-18T01:49:41.240Z
2013-10-18T01:49:41.240Z
Francesco Montesano
<p>We know that the universe is approximately 13.7 billion years old. What methods did we use to discover this? How sure are we about its accuracy?</p>

CC BY-SA 4.0
2018-07-31T06:51:12.813Z
The age of this universe is about 13.7 billions years old.  There are of course many theories and models that suggest multiple or an infinite number of universes https://en.wikipedia.org/wiki/Multiverse
IlludiumPu36
<early-universe>
Age of the universe
Rich
# Age of the universe

(Asked by: username_0 on 2013-10-17)

We know that the universe is approximately 13.7 billion years old. What methods did we use to discover this? How sure are we about its accuracy?

**Tags:** early-universe
> **Comments:**
> **username_1**: The age of this universe is about 13.7 billions years old.  There are of course many theories and models that suggest multiple or an infinite number of universes https://en.wikipedia.org/wiki/Multiverse  

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## 1 answers

### Answer by username_2 on 2013-10-17. Score: 15 | Accepted answer

The correct version of your first sentence would be something like:

> Given our knowledge and the standard cosmological model, we estimate that the age of the universe is about 13.7 billion years old.

Every work quotes slightly different values for the age, depending on methods, observations used, assumptions, etc. As example, the [first results](http://arxiv.org/pdf/1303.5076v1.pdf) from the [satellite Planck](http://www.rssd.esa.int/index.php?project=planck) report an age of 13.813, with an uncertainty of 58 million years (0.5%, to my knowledge one of the best).

So, first question is answered.

> What methods did we use to discover this?

About 100 years ago a number of people realized that our Galaxy is not the only one in the Universe and that the **all**1 other galaxies are receding from us with a speed increasing with distance (credit for this work is generally given to [Edwin Hubble](http://en.wikipedia.org/wiki/Edwin_Hubble) for his Redshift-Distance relation for galaxies formulated in 1929). This together with the theoretical results from general relativity, brought scientists to believe that our Universe is expanding. Which means that in the universe's past it was smaller, much smaller than it is now 2.

The age of the Universe depends on the rate of expansion at each time. To have this, you must estimate the mean composition of the universe (in various components like radiation, matter, dark energy, and curvature) and the present day expansion rate (also known as the [Hubble Constant](https://www.cfa.harvard.edu/~dfabricant/huchra/hubble/)). Once you have this, it's *easy*3 to compute the age of the Universe.

**footnotes**

1. except the ones in the local group that are gravitationally bound to us
2. side note: the cosmic microwave background (a radiation emitted about 13 and a half billions of years ago) provided in the 1964 a striking confirmation that the universe once was indeed much hotter and smaller
3. knowing what an integral is and with some basic of programming shouldn't be to difficult to solve equation 1 [here](http://www.astro.umd.edu/~miller/teaching/astr422/lecture14.pdf)


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