<p><strong>Models are uncertain</strong></p>

<p>I'm guessing that you are referring to age estimates of very old stars. The age of a star can be determined from certain observables, among one is its absolute luminosity, which in turn requires a precise measurement of its distance. Even today, the uncertainties involved yield estimates with mean values longer than the age of the Universe, which of course is impossible. For instance, the age of the star <a href="https://en.wikipedia.org/wiki/HD_140283" rel="noreferrer">HD 140283</a> was found as late as in 2013 to be $14.46\pm0.8$ billion years (Gyr). This is not really in conflict with the estimated age of the Universe, <a href="https://en.wikipedia.org/?title=Age_of_the_universe" rel="noreferrer">$13.798\pm0.037$ Gyr</a>; all this tells us is that our methods are still not perfect, but that HD 140283 was formed shortly after the Big Bang.</p>

<p><strong>Time dilation is small</strong></p>

<p>General relativity predicts that time evolves more slowly in a graviational field. This is with respect to an observer outside the gravitational field, and since there is no external observer wrt. the Universe, the global time of the Universe can be said to be the "right" time. You're right that in principle the total mass of the Universe makes time run slower than in a hypothetical, empty universe, but almost anywhere in the Universe, the gravitational field is way too weak to cause any noticeable dilation. Close to massive objects, time <em>does</em> run slow. On the surface of a star, the <a href="https://en.wikipedia.org/wiki/Gravitational_time_dilation" rel="noreferrer">time dilation factor</a> is roughly $(1 - GM/rc^2)^{-1/2} = 1.000002$. Inside the star, the factor is even closer to unity, because only the mass between the center and you contributes, so the farther you dive into the star (kids, don't try this at home), the <em>less</em> the time dilation. Only if you compress the star, so as to squezze it into a neutron star of a black hole, will you get a larger time dilation. For instance, at the "surface" of a black hole, time stops (but again, only wrt. an external observer; for the person at the surface, time evolves as expected)</p>

CC BY-SA 3.0
2015-06-22T20:20:42.607Z
thanks.  This makes sense.  So if I get your gist correctly, one would have to be outside the universe to notice the time dilation of it.  See...I knew there was a small piece I was missing in my logic.
BillDOe
CC BY-SA 3.0
2015-06-22T21:16:15.003Z
Well, yes, except there is no "outside the Universe". The Universe is everything.
pela
CC BY-SA 3.0
2015-06-22T21:29:14.703Z
re: "outside the Universe"  I didn't mention that because it seemed sorta obvious.
BillDOe
CC BY-SA 3.0
2015-06-23T08:34:32.753Z
Okay, sorry, I see :)
pela
CC BY-SA 3.0
2015-06-22T06:55:17.087Z
2015-06-22T06:55:17.087Z
pela
<p>A couple of decades ago I read an article (could have been either Astronomy, Space, or Science News) that suggested the contents of the universe may be older than the universe itself.  Of course, that result was so preposterous that it was summarily dismissed.  However, when I read that article, I thought it made sense.  Surely the universe is much more massive than its contents, so as General Relatively predicts, should experience time more slowly.  This conclusion seemed so obvious that a) a bunch of other folks much brighter than I would have thought of it, and b) therefore my conclusion is completely erroneous.  So my question is: why wouldn't the mass of the universe cause it to experience time at a rate slower than its contents as GR predicts?  (There are a couple of questions on SE that are similar, but I do not believe this is a duplicate.)</p>

CC BY-SA 3.0
2016-12-20T04:28:36.270Z
If things at high velocities experience time more slowly, then presumably the oldest thing is whatever stayed static in the middle of the universe.

(Sorry for my over-simplification. I am not familiar with mass causing time dilation, only speed.)
joeytwiddle
<universe><time-dilation>
Age of the universe vs. its contents
BillDOe
# Age of the universe vs. its contents

(Asked by: username_0 on 2015-06-20)

A couple of decades ago I read an article (could have been either Astronomy, Space, or Science News) that suggested the contents of the universe may be older than the universe itself. Of course, that result was so preposterous that it was summarily dismissed. However, when I read that article, I thought it made sense. Surely the universe is much more massive than its contents, so as General Relatively predicts, should experience time more slowly. This conclusion seemed so obvious that a) a bunch of other folks much brighter than I would have thought of it, and b) therefore my conclusion is completely erroneous. So my question is: why wouldn't the mass of the universe cause it to experience time at a rate slower than its contents as GR predicts? (There are a couple of questions on SE that are similar, but I do not believe this is a duplicate.)

**Tags:** universe, time-dilation
> **Comments:**
> **username_1**: If things at high velocities experience time more slowly, then presumably the oldest thing is whatever stayed static in the middle of the universe.  (Sorry for my over-simplification. I am not familiar with mass causing time dilation, only speed.)  

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## 1 answers

### Answer by username_2 on 2015-06-22. Score: 6 | Accepted answer

**Models are uncertain**

I'm guessing that you are referring to age estimates of very old stars. The age of a star can be determined from certain observables, among one is its absolute luminosity, which in turn requires a precise measurement of its distance. Even today, the uncertainties involved yield estimates with mean values longer than the age of the Universe, which of course is impossible. For instance, the age of the star [HD 140283](https://en.wikipedia.org/wiki/HD_140283) was found as late as in 2013 to be $14.46\pm0.8$ billion years (Gyr). This is not really in conflict with the estimated age of the Universe, [$13.798\pm0.037$ Gyr](https://en.wikipedia.org/?title=Age_of_the_universe); all this tells us is that our methods are still not perfect, but that HD 140283 was formed shortly after the Big Bang.

**Time dilation is small**

General relativity predicts that time evolves more slowly in a graviational field. This is with respect to an observer outside the gravitational field, and since there is no external observer wrt. the Universe, the global time of the Universe can be said to be the "right" time. You're right that in principle the total mass of the Universe makes time run slower than in a hypothetical, empty universe, but almost anywhere in the Universe, the gravitational field is way too weak to cause any noticeable dilation. Close to massive objects, time *does* run slow. On the surface of a star, the [time dilation factor](https://en.wikipedia.org/wiki/Gravitational_time_dilation) is roughly $(1 - GM/rc^2)^{-1/2} = 1.000002$. Inside the star, the factor is even closer to unity, because only the mass between the center and you contributes, so the farther you dive into the star (kids, don't try this at home), the *less* the time dilation. Only if you compress the star, so as to squezze it into a neutron star of a black hole, will you get a larger time dilation. For instance, at the "surface" of a black hole, time stops (but again, only wrt. an external observer; for the person at the surface, time evolves as expected)

> **Comments:**
> **username_0**: thanks.  This makes sense.  So if I get your gist correctly, one would have to be outside the universe to notice the time dilation of it.  See...I knew there was a small piece I was missing in my logic.  
> **username_2**: Well, yes, except there is no "outside the Universe". The Universe is everything.  
> **username_0**: re: "outside the Universe"  I didn't mention that because it seemed sorta obvious.  
> **username_2**: Okay, sorry, I see :)  

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