Size of the Universe?

[itsawonder]

Was watching "Naked Science" program about how the universe was formed etc. Chart was shown that stated that the universe was 13-15 billion years old amd that the DIAMETER of the universe was "SIXTY TRILLION" light years across.<br /><br />My question is if the universe is 13-15 billion years old how could the diameter be 60 trillion light years across, and how could this possibly be measured?<br /><br />Thanks in advance for clearing this up for me.

 

[weeman]

The expansion of the Universe is traveling either close to the speed of light, at the speed of light, or faster than the speed of light. Due to the red shifts of distant galaxies, it indicates to astronomers that the galaxies are moving away from us. Since we see the red shift from galaxies in ever direction in the sky, we come to the theory that the entire universe is expanding. With very distant galaxies (12-13 billion lightyears away), their redshifts almost appear as if the galaxies are expanding away from us at or faster than the speed of light. Of course the galaxies themselves can't travel faster than light, but the very dimensions of space are most likely not bound by any speed limit.<br /><br />So, when light left an object say, 10 billion lightyears away, its light had to travel against the expansion of the universe to reach us. If light leaves point A, and travels to point B, it will take longer to reach point B if it is in an expanding space. If the oldest light we can see is on the order of 13-15 billion years old, then the universe might be far, far larger than that if it took longer than 13-15 billion years to reach us.<br /><br />A------------------------ />B<br /> 14bly<br /><br />The above diagram is how far apart B is from A when A's light left it. However, since A and B are expanding apart, this is their distance when A's light finally reaches B (below diagram).<br /><br />A----------------------------------------------------------------- />B<br /> 60bly<br /><br />I hope that helps clear things up. Although I have never heard the estimate of 60 trillion lightyears. Are you sure it wasn't 60 billion? That seems much more plausible <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[weeman]

To enlighten on my post a little bit, if you are not familiar with the red shifts, it is a process also know as the doppler shift. It works in the same ways with both light and sound. When an object is moving towards us, its light will be slightly more shifted to the blue end of the spectrum. When it is moving away, its light will be slightly shifted to the red end of the spectrum.<br /><br />This works the same with sound as well. If a car is coming towards you, its sound will have a higher frequency than when it is moving away from you. When it is coming towards you, the waves are getting sort of scrunched, giving it a higher frequency sound. So, when the car moves away from you, the waves are being stretched, giving it the deeper, lower frequency sound. <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[ianke]

You might check a wikipedia article 'observable universe" . It gives a pretty good size explaination, and sights other places to look for more details.<img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>