Looking back in time

[worthj1970]

Would it be theoretically possible to look far enough into space (and time) and see an early version of our own galaxy?

 

[nacnud]

No.<br /><br />Athough looking far way you could find a galaxy in a state eqivalent to a younger milky way.

 

[jcdenton]

You're thinking about a universe with boundaries, where light is eventually bounced back at us. That's not the way it is. The furthest we've ever looked in to the universe was light coming from 13 billion years ago as seen in this picture.<br /> <div class="Discussion_UserSignature"> </div>

 

[jcdenton]

Yup.<br /> <div class="Discussion_UserSignature"> </div>

 

[nacnud]

IIRC the observable universe is much smaller than the actuate universe because of the expansion of the universe exceeds that of light after a certain distance.<br /><br />For example consider two galaxies a long way apart, the universe is expanding and the distance between the two galaxies is increasing. If the expansion is enough a beam of light from one galaxy will never reach the other because the space between the two galaxies is increasing faster than the light beam can cross it.<br /><br />I think the latest measurements give the diameter of the universe as ~156 billion light years while the observable universe is about ~26 billon light years across (I've no idea how this is measured).<br /><br />I think that this shows that space is not curved back on itself at less than these distances so looking into space to view your current position in the past is not possible in the universe as it stands today. <br /><br />The exception would be if you could find a suitably dense object that bent light around and back on itself. <br />

 

[siarad]

You mean as <br /> Later results tend to be against it

 

[lewcos]

I think that there is no way to look back beyond a certain point.<br /><br />If the universe started at one point in space, then the light from the early galaxies is long "past" us. This is because light travels faster than our expansion so we could never look back to the early stages.<br /><br />If, as some here have suggested, the universe did not start at any one single point, then looking at far distances may mean that we are looking at older galaxies or younger or the same, since they may have formed at the same time as us but just in a different place.<br /><br />So I believe that it's simply impossible to know what you are looking at, even when looking far away.

 

[worthj1970]

I guess that's what I was thinking. The thought occurred to me after reading something on how black holes can warp light. Along a similar line I was curious how we know the universe is expanding and not rotating since rotation seems to be common in the universe, at least that which I can see (moons around planets, planets around suns, suns around the core of a galaxy).

 

[earth_bound_misfit]

Damn good point, but alas we need the experts on these forums to take a stab at that. <div class="Discussion_UserSignature"> <p> </p><p> </p><p>----------------------------------------------------------------- </p><p>Wanna see this site looking like the old SDC uplink?</p><p>Go here to see how: <strong>SDC Eye saver </strong>  </p> </div>

 

[nacnud]

It would show up in the cosmic microwave background radiation though wouldn't it, but it doesn't.

 

[dark_energy]

Ok, so galaxies we see far away are as they were x billion years ago, does that mean, that if we look far back enough, that we can see...nothing? Or that we can see the creation of the big bang? I'm confused. Can some of the galaxies we see billions of lights away be our own galaxy billions of years ago? :S <div class="Discussion_UserSignature"> </div>

 

[adzel_3000]

<br /><br />I think it might be best to understand your definition of “see.” <br /><br />A microwave image of the entire sky was created with the COsmic Background Explorer (COBE) satellite. The COBE microwave explorer was able to “see” in microwave radiation and using this observatory scientists were able to see the relic radiation that was created by the Big Bang. The map it created shows temperature and density variation in the early universe. The spots are the oldest most distance structures known. These temperature variations appear only a million years after the Big Bang which occurred roughly 15 billion years ago. Stars, galaxies and clusters condensed out of these early variations.<br /><br />Other experiments have backed up this data, including mapping done by MAXIMA and BOOMERANG. What these maps show is an era in the history of the Universe that is approximately a few hundred thousand to roughly one million years after the Big Bang occurred. The Wilkinson Microwave Anisotropy Probe (WMAP) has improved on the COBE data. Indeed, the WMAP provided the first detailed, all-sky picture of the early universe. The WMAP revealed ancient temperature and therefore density fluctuations that correspond to the matter globs that eventually became stars and galaxies. <br /><br />The James Webb Space telescope will be able to “see” in infrared to a time less than half a billion years after the Big Bang. This is around the time that the density fluctuations seen by WMAP and COBE are condensing into early stars and protogalaxies. This will be an exciting mission and will be launched in the 2012 time period. This is why JWST has been dubbed “the first light machine.”<br /><br />You can’t see yourself if you look back in time with a telescope. This is because you and the telescope and the galaxy that contains you is your effective point of reference. The galaxy is like a floating island, adrift in time and space. You are traveling with it on its journey.<br /><br />--A3K<br /><br />

 

[alokmohan]

Such a good reply and correct also.

 

[newtonian]

adzel_3000 - Excellent post.<br /><br />Thank you.<br /><br />In harmony with your post, but with a little added detail and documentation:<br /><br />Yes, the early universe was dark, we could never see it as no photons escaped. However, we can see back to the moment of creation by the observed cosmic symphony of our universe that would also be a different kind of seeing.<br /><br />Scientific American recently had two articles on this cosmic symphony in which the authors noted that the sound waves that originated structure in our universe have awesome harmonious overtones, similar to a beautiful Strativarius violin.<br /><br />Here is an excerpt documenting some of the details, from:<br /><br />SCIENTIFIC AMERICAN FEBRUARY 2004<br />THE COSMIC SYMPHONY<br />By Wayne Hu and Martin White<br /><br />page 46:<br /><br />Sounding Out Origins<br /><br />WHEN DISTANCES in the universe grew to one thousandth of their current size - about 380,000 years after the big bang - the temperature of the gas decreased enough for the protons to capture the electrons and become atoms. This transition, called re-combination, changed the situation dramatically. The photons were no longer scattered by collisions with charged particles, so for the first time they traveled largely unimpeded through space. Photons released from hotter, denser areas were more energetic than photons emitted from rarefied regions, so the pattern of hot and cold spots induced by the sound waves was frozen into the CMB. At the same time, matter was freed of the radiation pressure that had resisted the contraction of dense clumps. Under the attractive influence of gravity, the denser areas coalesced into stars and galaxies. In fact, the one-in-100,000 variations observed in the CMB are of exactly the right amplitude to form the large-scale structures we see today [see "Reading the Blueprints of Creation," by Michael A. Strauss, on page 54].<br /><br />Yet what was the prime mover, the source of the initial disturbances that triggered

 

[alokmohan]

So thrilling we may watch big bang.Kudos to inflation theory.