141–150 of 191 posts
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So essentially the speed at which the plane's shadow on earth travels while projecting on level ground.
Mh no, the shadow's position depends not just on the planes movement, but also on earth's rotation and trajectory.
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Mh no, the shadow's position depends not just on the planes movement, but also on earth's rotation and trajectory.
Is that not also true of the plane's projection onto the Earth's surface?
Earlier quoted context omitted.
Mh no, the shadow's position depends not just on the planes movement, but also on earth's rotation and trajectory.
Is that not also true of the plane's projection onto the Earth's surface?
Earlier quoted context omitted.
Is that not also true of the plane's projection onto the Earth's surface?
I don't think so, since projection would be like taking the line between the center of the earth and the plane and finding where that intersects the surface of the earth. That doesn't depend on the trajectory of the earth through space.
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https://www.grc.nasa.gov/www/k-12/airplane/move.html ground speed is the speed of the plane, relative to an observer on the ground, air speed is how fast the people on the plane are going relative to themselves. Airspeed = Ground Speed - Wind Speed (wind blowing towards front of plan is positive, tailwind is negative)
> are going relative to themselves. You mean relative to the air outside the window. Relative your yourself you're always standing still.
I'll show myself out.
This is probably a stupid question, but how is "ground speed" measured? Is it how quickly the airplane moves past a fixed point at it's altitude, or along the earth's surface? I.e. the plane is effectively moving along the surface of a sphere, but if the plane is 30,000 ft up, then the radius of the plane's sphere is 30,000 ft greater than the radius of the "ground" so traveling at the same angular velocity will requ…
The radius of the earth + 30,000 ft is about 0.14% more than just the radius of the earth. Basically ignore it, unless you are programming guidance control systems.
"Assume the Earth is a perfect sphere, and its circumference is 25,000 miles. You have a 25,000 mile long rope looped all the way around the Equator, so it is tight against the surface. Now you want to raise the rope one foot in the air, all the way around. How much more rope do you need?"
I thought about this and said, "You need a lot more rope! I don't know how much, but it will be a lot. It has to reach all the way around the Earth, only higher!"
Of course the real answer is "You only need about three more feet. To be specific, you need another 3.14159... feet."
That's all you need to raise a rope a foot in the air, all the way around the Earth.
For those of you who find this interesting, there's a whole site dedicated to this: https://groundspeedrecords.com/ 801 MPH is not even close to the record, even for a 787.
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Wind is "named" after where it comes from. If you fly north, and the wind is a north wind, you fly slower. (This terminology is in line with what GP said.) Then, ground speed = air speed - wind speed. Thus, GP seems to have either the sign wrong, or ground and air speed mixed up (but not both :-)
> Wind is "named" after where it comes from. This is absolutely true, but has always infuriated me because it seems needlessly contrary as compared to the way we speak about anything else travelling in a direction as read from a compass. Does anybody know why it's the case?