Hi, I wanted to know if there is a flaw in an analogy from the book "elegant universe" by Brian Greene. When he explains relativity, he uses a carnival ride where you spin in a cylinder as an example to explain how space warps. He says that while the ride is spinning, if one person were to measure the circumference of the ride with a ruler, and compare it with the radius of the ride (measured while the ride is spinning), you would get a result different from the 2 pi r rule. He says that the ratio between the circumference and the radius will be greater than 2 pi r.
This is because the ruler contracts when you are measuring the circumference, while as you measure the radius it does not.
The problem is, wouldn't the ride itself contract as well to the same degree as the ruler contracts? So when you measure the circumference of the ride, the outside should measure to be the same whether you are moving or not, since any contraction of the ruler should also apply to the ride itself. And when you measure the radius, you would not feel any contraction, and you would get the same result moving or standing anyway.
What is wrong?
This is because the ruler contracts when you are measuring the circumference, while as you measure the radius it does not.
The problem is, wouldn't the ride itself contract as well to the same degree as the ruler contracts? So when you measure the circumference of the ride, the outside should measure to be the same whether you are moving or not, since any contraction of the ruler should also apply to the ride itself. And when you measure the radius, you would not feel any contraction, and you would get the same result moving or standing anyway.
What is wrong?