Home > Concepts, Ephemeris Program > 03/23/2015 – Ephemeris – Olbers’ Paradox or why it’s dark at night

03/23/2015 – Ephemeris – Olbers’ Paradox or why it’s dark at night

March 23, 2015

Ephemeris for Monday, March 23rd.  The Sun will rise at 7:40.  It’ll be up for 12 hours and 17 minutes, setting at 7:58.   The Moon, 3 days past new, will set at 12:12 tomorrow morning.

Why is it dark at night?  It seems like a dumb question but it isn’t, or wasn’t when the question was first asked by Henrich Wilhelm Olbers who lived from 1768 to 1840.  The dark sky problem is called Olbers’ Paradox.  If the universe was uniformly filled with stars and infinite in size all the stars would overlap giving a bright sky, day or night.  The fact that it doesn’t tells us something about the universe.  Stars are not uniformly scattered throughout the universe, they are bound up into galaxies, also the more distant stars in their galaxies are red shifted, losing energy.   Also if the universe is really infinite, parts of it are receding faster than the speed of light, so we can’t see them.   Receding faster than light, how can that be?  Though matter cannot move faster than light, space can expand faster than light.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.


Olbers' Paradox

“Olbers’ Paradox – All Points.” Credit: Kmarinas86, Licensed under CC BY-SA 3.0 via Wikimedia Commons


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