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Video transcript

you've probably heard that the top speed of some type of aircraft is Mach is Mach 2 or maybe watch some type of no science fiction movie or some type of fighter movie where they say we are going to travel at Mach at mach 1.8 and you had a sense because they're using it in the same context that you would use a speed that this is some type of speed that these numbers represent some type of speed and if you assume that you are right and the speeds they represent are actually a multiple or depending on how you want to view it multiple or fractions of the speed of sound in that medium so if you want if someone tells you that the Mach number is 2 what that tells you is that they are traveling they are traveling two times the speed speed of sound in that medium for those conditions and I make those last two I guess qualifiers on it because the speed of sound is not always the same it has a different speed depending on whether it's traveling in air or water or even depending on what makes up the air and even if it is only traveling in a certain type of air with a certain you know with a certain makeup of mix of gases it'll also change depending on the temperature so if you're if you're at if you're at sea level at roughly about 20 degrees Celsius the speed of sound is 300 so sea level do a different color maybe blue for sea level so if you're at sea level if you are at sea level the speed of sound is about 340 meters per second this is a 20 degrees Celsius sort of a nice comfortable temperature at at sea level which is roughly about 760 760 miles per hour now if the temperature were to drop so if temperature goes down if the temperature goes down so does the speed of sound Sound speed also goes down and likewise if the temperature goes up the speed of sound goes up so when someone tells you that something is traveling at Mach 2 they're saying it's traveling at two times the speed of sound for that medium usually they're talking about something traveling through air and for the speed of sound at the temperature that they're going through so if they're traveling you know if there's some super high altitude and normally to travel at these types of speeds you have to be at a fairly high altitude where the air is less dense you are also traveling in an environment where the temperature is significantly lower than six you know then twenty degrees Celsius so the speed of sound so you might say hey does that mean if someone's traveling at Mach two does that mean that they're definitely traveling at 680 meters per second or at 1520 miles per hour and of course whenever someone gives you an air speed it's relative to the air and the answer is no they're probably going to be traveling a little bit slower than that because at the altitude that they're traveling the speed of sound is slower now there are people you know there are ground speed records where they are traveling in kind of the Mach range where their velocities are high enough to stay it in terms of Mach and for those types of situations they are traveling at multiples of 760 miles per hour 340 meters per second now you're probably saying hey who is this this this person right here that that I've cut and pasted from Wikipedia this is Ernst Mach and this is what the Mach number this is who the Mach number is named after Ernst Ernst Mach and he was this Austrian physicist and philosopher he did a ton of research on shock waves and sound waves and whatnot so the Mach number is named after him