# dating the universe **URL:** \ **Category:** Factual Questions\ **Created:** [May 12, 2001, 10:09pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256 "2001-05-12T22:09:30Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [May 12, 2001, 10:09pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256/1 "2001-05-12T22:09:30Z")
no, this is not a megalomaniacal sex fantasy. when looking at receding pulsars etc, how can we tell the difference between the expansion of space and the movement of a star through space? Seems as if the latter would introduce some significant relativistic effects, thereby fucking our equations. later, jb ---
**Author:** ![MrDeath](https://avatars.discourse-cdn.com/v4/letter/m/22d042/32.png) [@MrDeath](https://boards.straightdope.com/u/MrDeath)\ **Post date:** [May 12, 2001, 10:24pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256/2 "2001-05-12T22:24:28Z")
> [@](#): > > \*Originally posted by jb\_farley \* > \*\*no, this is not a megalomaniacal sex fantasy. > \*\* Aren’t you a little young to be going out with the universe? I mean it’s what, a billion times your age? When it was your age, it was still opaque! > [@](#): > > \*\* > when looking at receding pulsars etc, how can we tell the difference between the expansion of space and the movement of a star through space? Seems as if the latter would introduce some significant relativistic effects, thereby fucking our equations. > \*\* First off, the astronomers and physicists are smart - they already take into account the relativistic effects. One of which is red shift, the thing that tells us how fast things are receding from us. And that’s all we know. The farther out things are (using our various yardsticks), the faster they’re receding. The most appealing explanation anyone’s come up with so far is various flavours of the Big Bang. But there _are_ competing theories. A new steady-state theory has emerged that its proponents claim fits the observations better than the Big Bang theories. This theory says, okay, maybe the universe _has_ been around forever, and is infinite in size, and things are moving away from one another while new matter is being spontaneously created, everywhere in space, at a really slow rate, but enough to fill in the gaps. ---
**Author:** ![Doubleclick](https://avatars.discourse-cdn.com/v4/letter/d/b2d939/32.png) [@Doubleclick](https://boards.straightdope.com/u/Doubleclick)\ **Post date:** [May 12, 2001, 10:25pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256/3 "2001-05-12T22:25:11Z")
> [@](#): > > \*Originally posted by jb\_farley \* > \*\*no, this is not a megalomaniacal sex fantasy. > when looking at receding pulsars etc, how can we tell the difference between the expansion of space and the movement of a star through space? Seems as if the latter would introduce some significant relativistic effects, thereby fucking our equations. > > later, > > jb > > \*\* I’m going for broke here…but would it not have somthing to do with the measurment of the red shift? (I comparison to the red shift measuments of other stars.) ---
**Author:** ![jb\_farley](https://avatars.discourse-cdn.com/v4/letter/j/9d8465/32.png) [@jb\_farley](https://boards.straightdope.com/u/jb_farley)\ **Post date:** [May 12, 2001, 10:32pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256/4 "2001-05-12T22:32:58Z")
**Doubleclick** - but I can’t see how we can determine if red shifting is caused by movement of space (carrying the pulsar etc away from us), or the movement of the object away from us. I I understard that we have cosmic yard-sticks, but I wonder how we have buttressed them, at least in regards to the abovementioned doppler shit. I’m sure physicists have done so; I simply have no idea where to look. **MrDeath** , I love you. [Nobody else](http://boards.straightdope.com/sdmb/showthread.php?threadid=37468) had ever heard of that steady-state theory. Any more details? thanks, jb ---
**Author:** ![Doubleclick](https://avatars.discourse-cdn.com/v4/letter/d/b2d939/32.png) [@Doubleclick](https://boards.straightdope.com/u/Doubleclick)\ **Post date:** [May 12, 2001, 10:46pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256/5 "2001-05-12T22:46:31Z")
> [@](#): > > \*Originally posted by jb\_farley \* > \*\ ***Doubleclick** - but I can’t see how we can determine if red shifting is caused by movement of space (carrying the pulsar etc away from us), or the movement of the object away from us. > > I I understard that we have cosmic yard-sticks, but I wonder how we have buttressed them, at least in regards to the abovementioned doppler shit. I’m sure physicists have done so; I simply have no idea where to look. > > \ > > thanks, > > jb \*\* Hey, like I said, I was going for broke with taht answer with the hops that some one coulw expand on it. I tried. 🙂 ---
**Author:** ![Doubleclick](https://avatars.discourse-cdn.com/v4/letter/d/b2d939/32.png) [@Doubleclick](https://boards.straightdope.com/u/Doubleclick)\ **Post date:** [May 12, 2001, 10:48pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256/6 "2001-05-12T22:48:48Z")
> [@](#): > > \*Originally posted by Doubleclick \* > \*\* > Hey, like I said, I was going for broke with taht answer with the hops that some one coulw expand on it. > > I tried. 🙂 \*\* My god…ignore the spelling… ☹ ---
**Author:** ![MrDeath](https://avatars.discourse-cdn.com/v4/letter/m/22d042/32.png) [@MrDeath](https://boards.straightdope.com/u/MrDeath)\ **Post date:** [May 12, 2001, 10:59pm UTC](https://boards.straightdope.com/t/dating-the-universe/65256/7 "2001-05-12T22:59:26Z")
> [@](#): > > \*Originally posted by jb\_farley \* > \*\ ***MrDeath** , I love you. \*\* Sorry, I’m taken. You’ll have better luck with the universe. > [@](#): > > \*\*I understard that we have cosmic yard-sticks, but I wonder how we have buttressed them, at least in regards to the abovementioned doppler shit. I’m sure physicists have done so; I simply have no idea where to look. > > … > > Nobody else had ever heard of that steady-state theory. Any more details? > \*\* Please tell me you mean doppler _shift_! 🙂 A good discussion of how astronomers calibrate the cosmic yardsticks can be found [here.](http://www.worc.ac.uk/departs/envman/staff/rowland/ums/env/eis/StarGen/cosmyard.html) Basically, we can tell how far away certain stars are by ‘proper motion’, or how they ‘move’ in the sky as the Earth orbits the sun. Then we estimate how far away certain other stars are, that are too far away for us to make out their proper motion (it strikes me that if we orbited a telescope out to, say, Jupiter, we could get a much better picture of these distances!), and from this we can estimate how far away the nearer galaxies are, and from that we can estimate how far away more distant galaxies are, and so forth in a bootstrap of literally cosmic proportions. Some of it is guesswork, but the correlations are so good that even if we’re off by an order of magnitude as to _how fast_ things are moving away, there’s no doubt that they _are_ moving away. I read about the steady-state theory several years ago, and it was in one of Scientific American, Discover or Astronomy (those being the only three scientific magazines I have time to read - I’m really a math nerd). ---
**Author:** ![Philbuck](https://avatars.discourse-cdn.com/v4/letter/p/e9a140/32.png) [@Philbuck](https://boards.straightdope.com/u/Philbuck)\ **Post date:** [May 13, 2001, 12:40am UTC](https://boards.straightdope.com/t/dating-the-universe/65256/8 "2001-05-13T00:40:14Z")
> [@](#): > > \*Originally posted by jb\_farley \* > \*\*Doubleclick- but I can’t see how we can determine if red shifting is caused by movement of space (carrying the pulsar etc away from us), or the movement of the object away from us. \*\* I think that the main point is that on large scales, the redshift is dominated by the Hubble flow, i.e. the peculiar velocity of the galaxy is not a significant fraction of the recessional velocity. On shorter scales, one could examine the redshift of a galaxy relative to the others in its cluster. All galaxies in a small enough area should have approximately the same redshift; distortions from that should be explainable by examining the relative positions of the galaxies. Of course, as mentioned, distance measurements on these scales are far from an exact science, so figuring out who’s clustered with whom in what structure is indeed a nontrivial task. > [@](#): > > \*\ ***MrDeath** , I love you. [Nobody else](http://boards.straightdope.com/sdmb/showthread.php?threadid=37468) had ever heard of that steady-state theory. Any more details? > \*\* I don’t know of any particular great addition to the steady-state theory of late; mostly it’s just been modified slowly over the last 50 years (in fact, these days it’s referred to as the “quasi-steady state” theory). There were a pair of dueling articles in _Nature_ a few years ago that nicely summarized the respective arguments for Big Bang and steady state. I think I’ve hunted down the citation for one; it’s called “The Case for the Relativistic Hot Big Bang Cosmology”, by Jim Peebles et al., in _Nature_ **352** , p. 769, 1991. I can’t find the cite for the companion article, but I’m just about positive that this is the right issue. It may be too old for whatever recent developments you’ve heard about, but might be worth a look anyway.