From: Ray ®	09/11/2001 17:19:43
Subject: re: AVIATION FAQ	post id: 490480
Why doesn't the earths rotation effect flight times? From: Peter B ® the fact that the journey was quicker against the Earth's rotation has nothing to do with the Earth's rotation. What it relates to is the direction of prevailing winds. Let's go through the points. 1. The Earth is rotating. At the Equator the surface of the Earth moves at just over 1000km/h. 2. Everything on the surface of the Earth stays on the surface of the Earth. Therefore, everything on the surface of the Earth moves at the local speed of the surface of the Earth. For example, just over 1000km/h on the Equator. 3. The Earth's atmosphere also rotates with the Earth (give or take the effect of the Sun warming the air, causing winds). This is why we don't have winds of several hundred kilometres an hour, which is what would happen if the atmosphere didn't move with the Earth's surface. 4. If you were to take off and fly along the Equator against the rotation of the Earth, you have a speed relative to the surface of the Earth. You also have a "speed" relative to a non-rotating Earth (I use the term "speed" cos it isn't a real speed). Say your speed relative to the surface of the Earth was 1500km/h. But if you're flying against the rotation of the Earth, your "speed" relative to a non-rotating Earth would be just under 500km/h (remember points on the Equator move at just over 1000km/h). All this effectively means (in this case) is that you wouldn't experience sunrise and sunset like people on the surface of the Earth. Remember, when a plane takes off, it effectively already has the speed of the Earth's surface built into its "speed".