Discovery changes everything we thought we knew about speed of light

Contributed by
Mar 28, 2013, 5:53 PM EDT

The speed of light is always the same, right? Well ...

Take a look at your old physics textbooks for a moment and you'll probably read that the speed of light is a constant. It's 186,000 miles per second, 299,792,458 meters per second, and this is non-negotiable. That's just how fast light movies, and there's no changing it. As it turns out, that doesn't seem to be entirely true.

According to a new study by Marcel Urban from the University of Paris-Sud, the speed of light in a vacuum can actually vary by 50 quintillionths of a second. Yeah, that's a very, very, very small change in something so fast, but what's more interesting is why this seems to happen.

See, we tend to think of a vacuum as a place of nothingness, but that's not actually true. Tiny particles can flash in and out of even the most perfect vacuum, and based on how many there are at any given moment, and how energetic they are, the speed of light increases and decreases.

That's intriguing enough, but it's not the end. These findings, along with findings by physicists Gerd Leuchs and Luis L. Sánchez-Soto, from the Max Planck Institute for the Physics of Light in Erlangen, Germany, seem to indicate where the speed of light actually comes from. See, the presence of these particles not only affects the speed of light. They also affect what can get in and out of a vacuum. Taking all this into account, it seems that the speed of light actually comes from charged particles in the universe. How many there are affects how fast light moves. All this might not mean much now, especially when you're thinking about how small those speed fluctuations are, but as physicists work to test these findings, we could find out even more fascinating things.

(Christian Science Monitor via PopSci)