# When time slows down for us on Earth, are we traveling closer to the speed of light

## Main Question or Discussion Point

When I started playing football as a wide receiver I remember several times when the ball was passed to me that time seemed to slow way down and it took forever for the football to get to me.

We know that time slows down as we get closer to the speed of light, but obviously I'm not traveling at any greater speed. So what is causing time to slow down? I've also heard of this time slow down happening when people have a car accident.

Maybe this is more of a psychology question than a physics question, but I'm just wondering if there is a physics explaination for this phenomenon.

Thanks

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Yeah that seems like it's more your mind's interpretation of time, no human can travel anywhere near fast enough to notice time dilation.

ZapperZ
Staff Emeritus

When I started playing football as a wide receiver I remember several times when the ball was passed to me that time seemed to slow way down and it took forever for the football to get to me.

We know that time slows down as we get closer to the speed of light, but obviously I'm not traveling at any greater speed. So what is causing time to slow down? I've also heard of this time slow down happening when people have a car accident.

Maybe this is more of a psychology question than a physics question, but I'm just wondering if there is a physics explaination for this phenomenon.

Thanks
There isn't. It isn't even related to relativity, since the proper time doesn't change at any speed.

Zz.

If you were to experience actual time dilation you wouldn't even be able to sense it, because the firing of neurons in your brain would also slow down, and your whole sense of time would be proportional.

You only notice time dilation in other reference frames, so no, this wouldn't be the appropriate explanation. To notice time dilation, you would have to somehow be in a different reference frame than the rest of the world, which of course is not the case.

There is a relation.

In relativity the functions of your body speed up or slow down depending on your relative velocity. This is because the speed of forces (the electric force specifically) in your cells is invariant. A lorentz transformation shows that the path is longer between reference frames.

In a high adrenaline situation the functions in your body also speed up, though it is due to a chemical reaction.

ZapperZ
Staff Emeritus

There is a relation.

In relativity the functions of your body speed up or slow down depending on your relative velocity. This is because the speed of forces (the electric force specifically) in your cells is invariant. A lorentz transformation shows that the path is longer between reference frames.
Er.. come again? In this paragraph, you contradict yourself.

If the "speed of forces" is invariant, then it doesn't matter what frames you are in. Yet, you then show that a lorentz transformation shows something different in each reference frame, which means that whatever it is in NOT invariant.

The functions in your body does NOT slow down or speed up, because presumably you are not having an out-of-body experience and you stay in the same reference frame as your body. So your proper time does not change.

Zz.

Er.. come again? In this paragraph, you contradict yourself.

If the "speed of forces" is invariant, then it doesn't matter what frames you are in. Yet, you then show that a lorentz transformation shows something different in each reference frame, which means that whatever it is in NOT invariant.

The functions in your body does NOT slow down or speed up, because presumably you are not having an out-of-body experience and you stay in the same reference frame as your body. So your proper time does not change.

Zz.
The speed of the electromagnetic force that ultimately determines the chemical reactions in your body is invariant. So to someone in a relative reference frame the distance this force must travel is longer, the speed at which these chemical reactions happens is slower or faster relative to them.

Correct, you do not experience any difference within your reference frame, you think at the rate you think. So if you slow down your chemical reactions enough to live longer, you do not experience a longer life, you just live longer relative to someone in another frame.

The speed of the electromagnetic force that ultimately determines the chemical reactions in your body is invariant. So to someone in a relative reference frame the distance this force must travel is longer, the speed at which these chemical reactions happens is slower or faster relative to them.

Correct, you do not experience any difference within your reference frame, you think at the rate you think. So if you slow down your chemical reactions enough to live longer, you do not experience a longer life, you just live longer relative to someone in another frame.
I'm not sure what you're trying to say here. The speed of the electromagnetic force (i.e. the speed of light) is always the same in every reference frame. What slows down in an accelerated reference frame is time. And in order for this effect to be noticable when catching a football, the football would have to be thrown in a highly accelerated reference frame, in which case you'd be unable to catch it for reasons unrelated to relativistic effects.

Perhaps you could clarify what you mean.

I'm not sure what you're trying to say here. The speed of the electromagnetic force (i.e. the speed of light) is always the same in every reference frame. What slows down in an accelerated reference frame is time. And in order for this effect to be noticable when catching a football, the football would have to be thrown in a highly accelerated reference frame, in which case you'd be unable to catch it for reasons unrelated to relativistic effects.

Perhaps you could clarify what you mean.
Time is just a measurement. You can't say time slows down without a physical explanation.

To simplify things instead of using a human body lets use a light clock. A light clock being two mirrors parallel to each other with light bouncing back and forth between the mirrors, counting one unit of time each time it makes a full cycle.

Now the speed of light is constant in all reference frames. So if you accelerate (in a perpendicular direction to the motion of the light) this clock to a relative reference frame and observe the path of the light ray from your rest reference frame you will see that the length the light travels is longer before it hits each mirror. So the clock relatively slows down. It is precisely because the speed of light is a constant that this is possible. This is why clocks measure "time" as slowing down.

The human body is just a complex light clock.