How Fast is Fast?
Back in the mid-nineties, when we first moved to Montana, the state had no posted speed limit on the Interstate highways. Seriously. The law stated you could drive what was “safe and prudent”. I remember taking my car up to about 97 miles per hour once on a long, straight stretch of road when no one else was around.
I’ve never been much of a daredevil.
What got me thinking about this was Curiosity’s recent landing on Mars. The craft that carried the one-ton rover to the Red Planet left Earth on November 26, 2011. That’s over eight months ago!
At 97 miles per hour, I felt like I was flying. I suppose the car vibrating so much I thought it might shake apart had something to do with my exhilaration. Yet, it’s hard for me to imagine being a professional race car driver, who regularly go twice that fast!
Commercial airliners generally travel around 400 miles per hour. A non-stop flight from Los Angeles to New York City takes about five and a half hours. The same trip took three days, or more, in the time of the Transcontinental Railroad over a hundred years ago. And folks at the time thought that was incredibly fast!
The speed of sound through air is a little less than twice that of the average airliner. While this is very fast, we still understand that sound is not instantaneous. This fact is most evident during a thunderstorm. We see a stroke of lightning, but the sound from that blast of energy doesn’t reach our ears until a few seconds later, depending on how far away the flash occurred. Most of us played the counting game when we were little to see if a storm was moving closer, or farther away, by counting those seconds between flash and rumble.
Our technology is such now that we have vehicles that can travel even faster than sound. Fighter planes and some other aircraft can exceed the sound barrier several times over. The now-decommisioned space shuttles
orbited the Earth at a speed of around 17,500 miles per hour. That means they could make a trip entirely around the Earth in less than an hour and a half. That’s fast! But, once we leave our cozy home, the distances, and speeds necessary to traverse them, become mind boggling.
The Apollo missions that traveled to the moon took close to three days to get there, even moving at an average speed of 2,000 miles per hour. The moon is about 240,000 miles from Earth. In contrast, Mars was approximately 127 million miles from Earth at the time Curiosity launched. The craft was traveling about 13,000 miles per hour when it entered the Martian atmosphere.
Think about that. Moving at that speed, you could make that cross country flight from LA to New York in less than fifteen minutes. Flight time to Mars? Over eight months.
Here’s one more tidbit to ponder. Most of us know and understand that even light, which seems instantaneous to us, travels at a certain speed: approximately 186,000 miles per hour. When the NASA scientists send instructions, moving at lightspeed, to Curiosity, it takes almost fourteen minutes to reach the rover from mission control here on Earth.
Next time, we’ll talk about the cosmic speed limit and if there’s any chance nature might actually have a “safe and prudent” policy like Montana used to, or if we’re stuck with the hard and fast limit of light. Right now, tell me what’s the fastest you’ve ever traveled! How did it feel? Are you a speed demon? Leave your answers in the comments!