Bob Moler's Ephemeris Blog

Ephemeris for Friday, February 22nd.  The sun will rise at 7:31.  It’ll be up for 10 hours and 49 minutes, setting at 6:21.   The moon, 3 days before full, will set at 5:55 tomorrow morning.

Yesterday I talked about the invariability of the speed of light in a vacuum.  This would seem to put interstellar travel on the list of things that can’t be done.  Apparently General Relativity has ways of getting around.  I’ll leave that to smarter people to explain.  But one cool thing about the speed of light is that it allows us to see into the distant past.  The farther the object is away the farther back in time we can see it.  With the Hubble Space Telescope in its Deep Field images of galaxies can see back to within perhaps a billion years of the Big Bang, at least for a few galaxies.  The James Webb space telescope to be launched later this decade will explore, among other things more deeply into this unknown time to see how these galaxies formed.

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

Ephemeris for Thursday, February 21st.  The sun will rise at 7:32.  It’ll be up for 10 hours and 46 minutes, setting at 6:19.   The moon, half way from first quarter to full, will set at 5:21 tomorrow morning.

The speed of light at 186,000 miles a second or 300,000 kilometers a second.  It is the ultimate speed limit in the universe.  nothing with mass can match is speed.  But particles without mass, like photons, travel at that speed in a vacuum naturally.  That speed of light in a vacuum was a constant was postulated by Albert Einstein and was the central part of his Special Theory of Relativity published in 1905.  In physics the lower case letter c represents the speed of light in a vacuum.  And its figures in Einsteins most famous equation, which actually wasn’t part of special relativity: e=mc².  The equation that changed the world for good or ill.  Science itself is nether good nor bad.  It’s how that knowledge is applied.

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