# Time dilation (and length contraction).Watch

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#1
I'm seriously confused in regards to inertial reference frames, what exactly a stationary object relative to the frame of reference of 'insert object here' and whether to use t or t0 (proper time). I keep mixing up when to use proper time or just time.

If anyone can help, that'd be appreciated.
0
2 years ago
#2
A reference frame is viewing an object from another objects point of view. Imagine 2 boys (Boy A and Boy B) playing catch on a train that's travelling 40ms-1 moving left to right. Boy A throws the ball from left to right in the direction of travel to the train. So the ball is thrown at 3ms-1 in the same direction the train is moving. The boys observe the ball to be travelling at 3ms-1. This is the boys frame of reference, it's what they observe from their point of view. But their brother (Boy C) who is standing outside on the ground can see them through a long window on the train. Boy C will see the train moving at 40ms^-1 and the ball moving at 43ms^-1. So this is the frame of reference from Boy C. Since C was stationary outside the train he adds up the velocities of the train and the ball so that's why he observes the ball to be moving at 43ms^-1.......does that help?

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1
2 years ago
#3
In Einsteins theory of special relativity the speed of light is ALWAYS constant. Remember that rule. If an object is moving very fast such as 90% speed of light, it will cover a larger amount of distance in a shorter time scale. So we know the formula Speed =Distance /Time. If the distance covered in increased then the time must increase to keep the speed of light constant. If the time taken to cover that distance is longer then that means that time has slowed down. If that's confusing then watch some YouTube animations of it, that helped me

Lorentz contraction uses the same rule that lights speed is constant. Sometimes making time longer doesn't always keep the speed of light constant. So sometheing else happens where the width of the object decreases when moving at very high speeds like 90% the speed of light. We call this contraction of the object "Lorentz contraction"...... I don't know the exact physics to how am object decreases in width but apparently it does. Did that help?

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#4
(Original post by Jas1947)
In Einsteins theory of special relativity the speed of light is ALWAYS constant. Remember that rule. If an object is moving very fast such as 90% speed of light, it will cover a larger amount of distance in a shorter time scale. So we know the formula Speed =Distance /Time. If the distance covered in increased then the time must increase to keep the speed of light constant. If the time taken to cover that distance is longer then that means that time has slowed down. If that's confusing then watch some YouTube animations of it, that helped me

Lorentz contraction uses the same rule that lights speed is constant. Sometimes making time longer doesn't always keep the speed of light constant. So sometheing else happens where the width of the object decreases when moving at very high speeds like 90% the speed of light. We call this contraction of the object "Lorentz contraction"...... I don't know the exact physics to how am object decreases in width but apparently it does. Did that help?

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Thank you so much.
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