# Can we really know the age of something?

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#### lewcos

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If there was a big bang, I would assume that all the material was exploded in all directions. If there is a point in space that represents the actual bang, then anything on the far side of that point would be traveling in the opposite direction as we are on earth. If we view those objects and try to date them using the redshift, wouldn’t we be seeing them as older than they really are based on the fact that they are further away?<br /><br /> <br /><br />To try to illustrate this, assume there were two people standing back to back with a light post inbetween them. They begin walking in opposite directions. If they stop at the same time and turn around and look towards the light post, both will have traveled the about the same distance and thus be about the same light years away from the light post. However, if one person views the other person, they will seem twice as far away and thus twice as old. How do scientists know what they are looking at in the sky is not that same effect?<br /><br />

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#### lewcos

##### Guest
Is my question not clear or is it just too obscure of a question?

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#### nacnud

##### Guest
The big bang doesn't have a centre as such. All space is expanding which is different to matter expanding as from an explosion. In one sense there is no centre, in another every point is the centre. Its not an easy concept to understand. At the moment we see all the galaxies travelling away from us but this is because space between us and them is expanding not because we are at the centre of the expansion. <br /><br />The measure of red shift is really a measure of how much space has expanded between us and them.<br />

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#### lewcos

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"In a one sense there is no centre, in another every point is the centre. "<br /><br />Umm - no disrespect at all but that sounds like a wishy washy explanation to me. <br /><br />My understanding of the "big bang" is that it originated from a highly concentrated point in "space"- I understand it is a theory but if that theory is to be accepted for arguments sake, doesn't my problem still have to be accounted for when they measure how old things are?

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#### mkofron

##### Guest
<blockquote><font class="small">In reply to:</font><hr /><p>Umm - no disrespect at all but that sounds like a wishy washy explanation to me. <br /><br />My understanding of the "big bang" is that it originated from a highly concentrated point in "space"- I understand it is a theory but if that theory is to be accepted for arguments sake, doesn't my problem still have to be accounted for when they measure how old things are?<p><hr /></p></p></blockquote><br /><br />It's not wishy washy at all. There is no center of the universe. <br /><br />Here is a primer on the Big Bang which includes a section of how age is determined.<br /><br />http://www.umich.edu/~gs265/bigbang.htm

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#### alokmohan

##### Guest
Space is like a ballon,all points are centre.

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#### lewcos

##### Guest
If all points are center, how can anything be moving away from anything else?

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#### dan9678

##### Guest
Lewcos,<br /><br />The observation that all points in our universe are move away from each other is by far the most important ever made by an Astronomer (Hubble). It is not wishy washy and all I will say here is it is that this observation is well worth exploring.<br /> <br />You're not in Kansas anymore!

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#### lewcos

##### Guest
Dan,<br /><br />I did not say that the observation that all points are moving away from each other was wishy washy - maybe you should read a little more closely before posting. I agree with that observation. I just didn't understand how the big bang could have happened from "everywhere" at the same time - that is what I called wishy washy. <br /><br />BTW - mkofron - thanks for that article it is interesting - still reading it.

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#### dan9678

##### Guest
I understood you just fine. You said nacnud's explanation seemed wishy washy and it is not. <br /><br />Sorry if my reply was confusing. <br />

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