# Relativity: Explaining Length Contraction from γL to L

• Tonyt88
In summary, two balls are moving towards two people standing in the same line with a proper distance of L between them. However, due to length contraction, the distance between the balls appears to be γL to the people. This causes the balls to pass the people simultaneously, as measured by them. If the people catch the balls, the proper distance between the balls becomes L, which is shorter than the initial proper length of γL. This can be explained by considering the frame in which the balls are initially at rest, where spatially separated events that are simultaneous in one reference frame may not be simultaneous in a reference frame in motion relative to the first frame.

#### Tonyt88

Relativity

Two balls move with speed v along a line toward two people standing along the same line. The proper distance b/w the people is L, and the proper distance b/w the ball is γL [Note: γ is gamma]. Due to length contraction, the people measure the distance b/w the ball to be L, so the balls pass the people simultaneously (as measured by the people). Assume tha the people's watches both read T at this time. If the people catch the balls, then the resulting proper distance b/w the balls becomes L, which is shorter than the inital proper length of γL [Note: γ is gamma].

By working in the frame in which the balls are initially at rest, explain how the distance b/w the balls decreases from γL to L.

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Hint: Spatially separated events that are simultaneous in one reference frame may not be simultatneous in a reference frame in motion relative to the first frame.

## 1. What is relativity?

Relativity is a theory developed by Albert Einstein that explains how time and space are relative to an observer's perspective. It states that the laws of physics are the same for all observers, regardless of their relative motion.

## 2. What is length contraction?

Length contraction is a phenomenon in which the length of an object appears shorter when it is moving at high speeds relative to an observer. This is due to the effects of relativity on space and time.

## 3. How does length contraction work?

Length contraction is based on the Lorentz transformation, which is a mathematical formula that relates the measurements of space and time between two frames of reference. It shows that as an object's velocity increases, its length in the direction of motion decreases.

## 4. What is γL in the explanation of length contraction?

γL, also known as the Lorentz factor, is a mathematical term used to calculate the amount of length contraction that occurs at a certain velocity. It is equal to 1 divided by the square root of 1 minus the square of the object's velocity divided by the speed of light squared.

## 5. Can length contraction be observed in everyday life?

Yes, length contraction can be observed in everyday life, but only at extremely high speeds close to the speed of light. This is why we do not notice it in our daily experiences. However, it is a crucial concept in understanding the effects of relativity in the universe.