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Physics/Regarding light years



How do the scientists say a particular star/galaxy is far away from earth as more than 1 billion light years away and so-on. If a particular star/galaxy is that far, its light wouldn't have reached us or if it reached us, how do the scientists know about its distance.


They have something called a "standard candle" that they use.  The current standard is a supernova.  The universe is about 14 billion years old, so of course it can reach us.  The supernovae have a standardized brightness because they happen (according to the best theory we have now) at a certain size of star via a certain mechanism.  Therefore we can tell how far away the galaxies that the supernovae are in, by their peak brightness.  It's actually not that hard, now that we know what to do.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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