# Do you know why I pulled you over?

Probably for speeding.. I mean, you going 80 in a 50 zone is ridiculously fast right? No. Not even close. In fact, it’s probably one of the slowest things on this planet in respect to physics. Of course a snail crawling across the sidewalk is slower than your Civic racing down the highway, but I’m not an Malacologist, I’m a physicist.

So, just what is speed? Defining speed is simple – it’s the time it takes for an object to move between two or more set points. Assuming that the object has constant acceleration, the speed will increase exponentially. Wait, what? Yes, if an object with mass is accelerating in a vacuum with a force that is increasing indefinitely, then it will continue accelerating until an opposing force acts upon it. Newtons first law! We all know that the previous statement is technically invalid, since an object with mass can not exceed c, aka. the speed of light in a vacuum. Oh wait, you don’t know the speed of light? You should have it memorized if you’re reading this blog; I totally didn’t just Google the result for myself because I totally remembered that off the top of my head. It’s 299,792,458 meters per second.

But wait, there’s more, call now and get more numbers, because we all know that space isn’t a perfect vacuum. There is some pressure, but it’s not exactly 0. The speed of light that we’re seeing in our eyes right now, is not light traveling at c, it’s traveling below c. That’s right, I said it – Earth is slowing the speed of light. Well, not Earth exactly, the air on Earth is slowing it down, a substantial amount too; roughly 90km/s slower. The speed of light traveling through glass is about 200,000km/s. Lot’s of numbers being thrown around there, but good information to know. What about other things in the universe?

Felix Baumgartner recently broke the fastest free fall record of a human outside of a vehicle, traveling at a top speed of 1 342km per hour. He broke the speed of sound (1 236km/h at sea level). There’s that thing again, “at sea level”, a factor that is required in my field. Remember, above we stated that light is slower at sea level than it is in a perfect vacuum, so yes, the speed of sound at sea level is a bit slower than way up in the Stratosphere. The speed that Felix broke was a bit lower than the speed on land, but not by much. The speed of sound in the Stratosphere is about 1083km/h. Regardless of the difference, he still broke the records, so there’s no doubting that.

Michael over at VSauce recently had one of my to-date favorite videos, the weight of a shadow (opposing, the weight of light). He explains that the force in which light, a photon, collides with an object of mass, does move it slightly – how much is almost immeasurable. One of my favorite things he calculated was that the weight of the city of Chicago, increases by 350lbs on a sunny day. Enough talk, video time!

Jeff Wilton

Jeff is the founder and owner of Everyday Science Stuff. ESS is a one man operation, with the core belief that all education should be served without crippling debt tuition, without revenue generating ads and without any restrictions of any kind such as paywalls, forced login and account creations, geographical restrictions, and so on.