Okay, I know several people who have been waiting for me to get off my duff and talk about the speed of light.  This is Frank’s post, since he solved the riddle first Saturday.

To just blurt it out, the-speed-of-light-is-exactly-299,792,458-meters-per-second-in-a-vacuum.  That means that light will travel 299 million, 792 thousand, 458 meters in a second.  That’s about 300,000 kilometers per second, and about 186,000 miles per second.  The speed of light has been fixed with the increased accuracy of the definition and measurement of the meter.  The meter is defined as the distance light will travel in a vacuum in 1/299,792,458ths of a second.

Doesn’t that just give you goose bumps?  Take a look at this:

This is to scale. As you watch it, about 1.25 sec will pass as the little beam of light goes from the Earth to the Moon. That's how long it really takes.

To understand the speed of light, it might help to understand what exactly light is.  And what it is not.  I’m not going into the history of light, because I think everybody deserves to sit in college philosophy classes and suffer (I had to).  You go read Aristotle, I’ll read Einstein.  Believe it or not, there have been theories on the subject of light since the 6th century BCE.  As early as this the ancient Hindus were kicking around atomic theory.  By the 5th century BCE the Greeks were jumping in with some pretty interesting theories.  By 55 BCE, Lucretius (a Roman) wrote:

“The light & heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove.” – On the nature of the Universe

Remember, this was 55 BCE.  There wasn’t anything even close to a telescope hanging around at the time.  This is also an interesting attempt to nail the concept of light down to the physical world, and get it out of the realm of religion.  Unfortunately, 55 BCE is believed to have been the year of Lucretius’s death (at the age of 43), so perhaps it didn’t work out so well for him.

Light exists as a wave-particle duality.  This isn’t really that special, because all matter is believed to exist in the same state of duality.  This whole concept is the foundation of quantum mechanics, and you’re just going to have to trust me here.  Just imagine a tiny little packet called a photon traveling through space as a wave, and you’re there.  That’s light.  What you “see” is only how your brain interprets the nerve impulses which have been fired by the photons.  You know that light exists much wider, deeper, and larger than we can see without some seriously expensive equipment.  Here is what you don’t see:

Light spectrum by Philip Ronan, all rights reserved.

There have been several good attempts to measure the speed of light through history.  In 1676 Danish Physicist Ole Romer used a telescope to watch the motions of Jupiter and Io, and calculated that it took 22 minutes for light to traverse the diameter of the orbit of the Earth.  Of course, nobody knew the size of the diameter of the orbit of the Earth.  If they had, Ole’s calculations would have set the speed of light at 227,000,000 m/s.  I have to say, that’s a pretty decent working hypothesis.

Several things are believed to be apart from the speed of light “speed limit”; most interestingly tachyons and quantum entanglements.  In the case of quantum entanglements, since you can’t pin down the exact position of a subatomic particle at any given moment, no information or mass is actually transmitted, therefore it doesn’t violate the speed limit (gotcha!).  Tachyons are tiny little critters, hypothetical really, that are limited to the space portion of the energy-momentum graph.  They can’t go slower than too fast, in other words.  They lose energy and cease to exist.

What you do see, by Ibrahim Lujaz, all rights reserved.

I’m sure as our knowledge of the universe around us increases, we’ll get a better understanding of light, it’s speed limit, and what is or is not bound to it.  I’ve been told that for every “law”, there is something which exists outside of it.  Thanks, Frank.