Archive
02/26/2013 – Ephemeris – Light: Is it particles or waves, or is it both?
Ephemeris for Tuesday, February 26th. The sun will rise at 7:24. It’ll be up for 11 hours and 2 minutes, setting at 6:26. The moon, 1 day past full, will rise at 7:47 this evening.
Yesterday I talked about light in terms of waves and wavelengths. Light has a dual identity because I also acts like particles. They’re called photons. The shorter the wavelength the more energy the photon has. Light’s wave property explains how light is bent when it passes through a lens, and why stars in telescopes have diffraction rings and spikes. However CCD cameras and other light detection devices work because light also is particles. Some are sensitive enough to count photons one at a time. What’s even crazier is that particles like electrons also behave like waves. This is quantum mechanics, the physics of the nano world. Astrophysicists, what professional astronomers really are, work with the micro and the macro universe.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The proof of the pudding, quantum pudding that is, is the famous double slit experiment. There’s a nice animated video on YouTube featuring “Dr. Quantum” to blow your mind about electrons acting like waves. Click here.
02/25/2013 – Ephemeris – Electromagnetic spectrum
Ephemeris for Monday, February 25th. The sun will rise at 7:26. It’ll be up for 10 hours and 58 minutes, setting at 6:25. The moon, at full today, will rise at 6:40 this evening.
With the moon so bright I’ve been talking about light our last couple of programs. When I talk about light I’m talking about electromagnetic radiation, its whole spectrum, not the single octave of frequencies that we perceive as visible light. On the long end is radio waves, like those you are hearing me now by, microwaves of radar and those microwave ovens. Then there’s infrared we sense as heat on our skin, and then visible light. Shorter wavelengths and higher frequencies we have ultraviolet, x-rays and finally gamma rays. The final three are harmful to us and our atmosphere generally protects us from it. Astronomers have learned to observe the universe in all those wavelengths. And found a universe that is quite amazing and dangerous.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Electromagnetic Spectrum. Credit: Inductiveload, NASA.
02/22/2013 – Ephemeris – Speed of light: hinderance and help
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.
02/21/2013 – Ephemeris – Speed of light
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.
Bob Moler's Ephemeris Blog 