<p>I found an article by Wendy L. Freedman <a href="https://ned.ipac.caltech.edu/level5/Freedman2/Freed1.html" rel="nofollow noreferrer">Determination of cosmological parameters</a> which contained the following graphics</p>
<p><a href="https://i.sstatic.net/BhoOm.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/BhoOm.png" alt="Density over time" /></a></p>
<p>The corresponding references should be listed in the <a href="https://ned.ipac.caltech.edu/level5/Freedman2/Freed_references.html" rel="nofollow noreferrer">references of that paper</a></p>
<h3>References</h3>
<ul>
<li>The online article is also published as Invited Review given at the Nobel Symposium, <strong>Particle Physics and the Universe</strong>, Haga Slott, Sweden, August, 1998. Published in Physica Scripta, Vol. T85, 37-46, 2000.</li>
<li><a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/denpar.html" rel="nofollow noreferrer">http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/denpar.html</a> offers a value of 1.02 +/- 0.02 and dates back to the 2000s</li>
</ul>

CC BY-SA 4.0
2021-01-27T21:07:50.683Z
I need help understanding the first reference. I'm interested in $\Omega$, but this reference is only about estimates of $\Omega_m$, which is just one component of $\Omega$. Were the other components assumed to be 0 or near-0 at the time? And if so, did they really think that the universe is strongly hyperbolic? Or did they realize that they were missing something? (The other reference was very useful, thanks!)
Casper
CC BY-SA 4.0
2021-01-27T21:14:20.063Z
@Casper Maybe you want to ask a follow-up question? This aside: Have you seen https://ned.ipac.caltech.edu/level5/Freedman2/Freed7.html and what it says about an [Einstein-de Sitter universe](https://en.wikipedia.org/wiki/Einstein%E2%80%93de_Sitter_universe)? The latter Wikipedia link also makes some historical remarks, e.g. https://archive.org/details/cosmologycontrov00helg
B--rian
CC BY-SA 4.0
2021-01-26T13:27:55.110Z
2021-01-26T13:27:55.110Z
B--rian
<p>From the reference in <a href="https://physics.stackexchange.com/q/590317/">this answer</a> I learned that our current estimate for the density parameter (i.e., the density of the universe divided by the critical density, which determines the shape of the universe) is 0.9993 +/- 0.0019. But I’m also interested in the history: how our estimates of this parameter have changed since the first attempts at measuring it were made.</p>
<p>I have tried to find this information myself, and once again I have failed. Can anyone please help me?</p>
<p>I don’t need a complete year-by-year account – a few historical highlights will do. (But I do need sources.)</p>
<p>I have also asked this question on Physics StackExchange, but there have been no responses. I suppose this is a better forum to ask.</p>

<cosmology><history><density><resource-request>
Historical estimates of the density parameter
Casper
# Historical estimates of the density parameter

(Asked by: username_0 on 2021-01-23)

From the reference in [this answer](https://physics.stackexchange.com/q/590317/) I learned that our current estimate for the density parameter (i.e., the density of the universe divided by the critical density, which determines the shape of the universe) is 0.9993 +/- 0.0019. But I’m also interested in the history: how our estimates of this parameter have changed since the first attempts at measuring it were made.

I have tried to find this information myself, and once again I have failed. Can anyone please help me?

I don’t need a complete year-by-year account – a few historical highlights will do. (But I do need sources.)

I have also asked this question on Physics StackExchange, but there have been no responses. I suppose this is a better forum to ask.

**Tags:** cosmology, history, density, resource-request


---

## 1 answers

### Answer by username_1 on 2021-01-26. Score: 1 | Accepted answer

I found an article by Wendy L. Freedman [Determination of cosmological parameters](https://ned.ipac.caltech.edu/level5/Freedman2/Freed1.html) which contained the following graphics

[![Density over time](https://i.sstatic.net/BhoOm.png)](https://i.sstatic.net/BhoOm.png)

The corresponding references should be listed in the [references of that paper](https://ned.ipac.caltech.edu/level5/Freedman2/Freed_references.html)

### References

* The online article is also published as Invited Review given at the Nobel Symposium, **Particle Physics and the Universe**, Haga Slott, Sweden, August, 1998. Published in Physica Scripta, Vol. T85, 37-46, 2000.
* <http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/denpar.html> offers a value of 1.02 +/- 0.02 and dates back to the 2000s

> **Comments:**
> **username_0**: I need help understanding the first reference. I'm interested in $\Omega$, but this reference is only about estimates of $\Omega_m$, which is just one component of $\Omega$. Were the other components assumed to be 0 or near-0 at the time? And if so, did they really think that the universe is strongly hyperbolic? Or did they realize that they were missing something? (The other reference was very useful, thanks!)  
> **username_1**: @username_0 Maybe you want to ask a follow-up question? This aside: Have you seen https://ned.ipac.caltech.edu/level5/Freedman2/Freed7.html and what it says about an [Einstein-de Sitter universe](https://en.wikipedia.org/wiki/Einstein%E2%80%93de_Sitter_universe)? The latter Wikipedia link also makes some historical remarks, e.g. https://archive.org/details/cosmologycontrov00helg  

---

