| MadSci Network: Astronomy |
Dear Stewart, Whenever we look deep into the Universe, we are looking into the past. So even if you could see “around” the Universe, you’d be looking so far into the past that there would be really nothing to look at. The oldest objects we can see with the Hubble telescope are close to 13 billion years old. We can look back even farther by observing the cosmic microwave background, which dates back to about 300,000 years after the Big Bang, or about 13.7 billion years ago. Before that, the Universe was opaque. In any case, light will not go “around” the Universe at all unless the Universe is closed. “Closed” means that the overall geometry of the Universe is that of a sphere, and that the Universe’s expansion will gradually halt and reverse, resulting in a “Big Crunch”. This is almost certainly not the case; there is nowhere near enough visible matter and energy for the Universe even to be flat, although cosmologists now strongly believe that there is enough dark matter and energy around to make it so. There is some work now being done to see if the cosmic microwave background shows signs that we are seeing the same region when we look in opposite directions. If so, this would mean we’d be seeing halfway around the Universe in either direction. Not quite the same as seeing the back of your head, but remarkable nonetheless. The EPR paradox has to do with quantum mechanics and measurements done on correlated particles a great distance apart. What we find, consistently, is that there is NO superluminal communication from one to the other; the postulates of quantum mechanics must simply be accepted. Here are some links you may find useful: The Cosmic Microwave Background Radiation http://map.gsfc.nasa.gov/m_uni/uni_101Flucts.html Hubble Views Edge of Universe? http://quest.arc.nasa.gov/hst/QA/Hubble_Views/Edge_of_Universe.1 The EPR Paradox and Bell's Inequality Principle http://math.ucr.edu/home/baez/physics/Quantum/bells_inequality.html Hubble Space Telescope Project http://hubble.nasa.gov/
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