Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Harri on 20/01/2017 08:30:47
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The earth is rotating I assume in one particular direction around an axis at just over 1000 mph. Hopefully correct so far? A car traveling on the earths surface at 100 mph is viewed by an observer in space to be traveling at just over 1100 mph. If it travels in the direction of the earths rotation. What if the car is traveling in the opposite direction of the earths rotation? Is the answer obvious?
If a vehicle on or above the earth was traveling against earths rotation at just over 1000 mph would it be viewed to be stationary from space?
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Yes, that's correct.
Because you can never say who is moving or stationary you would need to choose an observation point such that the distance between it and the earth doesn't change.
Remember, you can also view the car as the fixed point and the distant observer as moving.
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would [the vehicle] be viewed to be stationary from space?
Bear in mind that you have just canceled the Earth's rotation of 1700 km/h (40,000km in 24 hours), or a bit lower if you don't live on the equator.
- But the Earth is orbiting the Sun at around 110,000 km/h (300M km x pi in 365 days).
- And the Sun is orbiting the galaxy (and taking Earth with it) at around 800,000 km/h (one orbit in about 250 million years).
- So a distant observer would not consider you to be stationary in space.
Also note that the car's wheels feel a force pushing up from the roadway (or a jet plane feels a force pushing up from the air).
From the viewpoint of General Relativity, this upward force is equivalent to a continuous acceleration of the vehicle. So an external observer sees the vehicle behaving differently than an object which is in free fall (not accelerating). This latter is called an inertial frame of reference.