 I was watching YouTube and I came across some people who say that passenger jet airplanes are not really traveling as fast as we're told. And I wondered, is there a way to look at the video evidence and find out? Oh, and what does this have to do with the shape of the Earth? Guess what? There are people who really do think that the Earth is literally flat, as in not the shape of a globe, but flat. And they think that the government is lying to us about all these things. Now, this is a whole rabbit hole if you start looking into this with a whole bunch of weird related ideas. Earth is a level, motionless plane. If anyone was to Google world time zones to the sun, moon, and stars revolving over and around us. They would find only flat maps just as you experience every day. The debate is over. Just like a rainbow. It looks like it's curving when it's actually not. The Earth is flat. The sun does not rise and set. You can't show me the curve. If I have a question, why do people think the Earth is flat? I have a surprising answer, and that's because it is flat-ish. It's pretty much flat everywhere you look. The horizon is flat. You can't see a curve. So I suppose at first glance it seems flat. But how would you know if it's actually flat everywhere, or if it's just a slight curve on a really big globe? That brings up the philosophical idea of epistemology. One day I might make a whole video about conspiracy theories, evidence, truth, rationality, belief. But for now, I'll leave that all aside and take a look at a small, related question. How fast do passenger jets fly? So it turns out that sizes and speeds are all sort of related to the shape of the Earth and flight paths and distances between cities. So how fast do jets fly? Well the standard answer is more than 500 miles per hour at cruise altitude and about 150 miles per hour when taking off and landing. But there are some people who think that this is all a big lie and that planes don't really fly that fast. Now I'll back it up, just got to see this. It's ground speed. Ground speed can't be more than 50, 60 miles an hour. Look at that. Really slow, guys. That plane is going really slow. To my eyes. Guys, I swear that looks 60, 70 miles an hour. Okay, so who's right? I'm going to show you how to use a little bit of simple math to find out. First of all, here's a quick description of how to measure speed. Speed is just a ratio, a fraction, distance divided by time. So if a train goes 50 miles in one hour, we say it's going 50 miles per hour. That's the same speed as going 50 miles per 60 minutes or going 5 miles in 6 minutes. These are all just different fractions with the same value. As another example, if a car goes 500 feet in 2 seconds, that's 250 feet per second. Or you can convert that to miles and hours to get 170 miles per hour. So that's all you need. Distance divided by time and that gives you speed. Let's take a look at some examples with jets. There are two basic techniques. First, let's take a look at some videos taken from inside the plane where the camera is moving against the background and we're calculating the speed of the camera. In this video from a plane landing in San Diego, we can see that it's near the intersection of 46th Street and C Street. Later, it's at Pacific Highway, right next to the runway. That's a distance of 4.6 miles. Next, we need time. The plane crosses the first location at 8.32 in the video and the second location at 10.12 in the video, which is 100 seconds later. Speed is distance divided by time, so it's gone 4.6 miles in 100 seconds and that turns out to be an average speed of 165 miles per hour. Here's a second video from the same airport where the speed is about 144 miles per hour using the same kind of math. Next, here's a video from LAX, my home airport. At 453 in the video, the plane goes by a parking lot and one minute later, it goes by the in and out near the end of the runway. That's a distance of 2.7 miles in one minute, which averages to more than 160 miles per hour. P.S., if you've never been to in and out, you should try it sometime. It's really good and it's right near LAX if you're ever flying through there. Here's one last example using that same technique. Here's a flight in the 747 at cruise altitude and speed going across Lake Tahoe, flying straight and level. The point under that eye in the logo crosses 11.3 miles across the whole lake in just 70 seconds and that works out to be 580 miles per hour. Next, I'm going to show you a second technique with a stationary camera. You'll need to have access to video editing software where you can add a timecode so you can measure individual frames of a video. Then you can calculate the speed of a plane from just a second or two of footage, though it's a bit harder. Here's a Boeing 777 landing in Turkey. Now it might look like it's going the same speed as that bus, but that's just because it's farther away. You can get the speed by watching how long it takes for the entire plane to cross a particular point. So remember, speed is distance divided by time, so the distance in this case is the entire length of the plane and the time is 29 frames. So it took 29 frames for that plane to cross that distance. So then you just do distance divided by time and that turns out to be 170 miles per hour. Here's another example of the Airbus A380, the largest passenger plane in the world. It passes a particular point in 32 frames, which is 1.067 seconds, for a speed of at least 150 miles per hour. Later on in the same video, there's an A380 flying at cruise altitude and that one is going much faster, taking only 9 frames or 0.3 seconds to travel its whole length, which is a speed of 540 miles per hour. Now this technique is not super precise because we're dealing with such short time scales, but I think that we're within 10% of the right answer. Finally, one last example. Here's another A380 flying at about 440 miles per hour because it takes 11 frames to travel its own length. Okay, so there you have eight different videos from six different people using two different mathematical techniques to show that planes really do fly pretty fast. And I'm using just some basic math with some basic measurements, the length of planes and Google Maps. Oh, wait a minute. The government is lying to us about the size of planes and Google Maps is lying to us too. Well, if you believe that those are lies also, then I don't know if there's much I can say, but yeah, I don't know what to say to that. If you have any questions or comments, please leave them below. If you have any suggestions about how to improve the accuracy of any of these calculations, I'd like to hear from you. And please be sure and like this video and subscribe if you want to see some more stuff. Alright, have a good day. Talk to you later.