Time Dilation: Exploring the Phenomenon of Speed and Time

[Mayankv1994]

Would I be correct to say that time would not dilate at all if I were to be sedentary throughout my life? & is it also correct to say that even for us individuals time dilates relative to each other? For example, we all move around, do things & time passes by, but though the difference may be minute, doesn't time dilate at different rates for all of us considering how some of us tend to walk/run/travel more than others in our lives?

Secondly, what is the reasoning behind time being 'slowed down' when we travel at speeds close to the speed of light when we have not yet crossed the speed of light boundary?

Cheers
Mayank

 

[ghwellsjr]

Would I be correct to say that time would not dilate at all if I were to be sedentary throughout my life? & is it also correct to say that even for us individuals time dilates relative to each other? For example, we all move around, do things & time passes by, but though the difference may be minute, doesn't time dilate at different rates for all of us considering how some of us tend to walk/run/travel more than others in our lives?

Secondly, what is the reasoning behind time being 'slowed down' when we travel at speeds close to the speed of light when we have not yet crossed the speed of light boundary?

Cheers
Mayank

It's really hard to tell, based on your questions in your first paragraph, whether you have a good understanding of Special Relativity, but your second paragraph suggests that maybe you don't, so let me ask you some questions.

In your first paragraph, you talked about how time dilates and in your second paragraph you asked about "time being 'slowed down'". Do you see these two as the same thing or something different? And secondly, why are you concerned that "we have not yet crossed the speed of light boundary"?

 

[Mayankv1994]

I don't, actually I don't even take physics in school, I just got done with my GCE O Levels & in my free time found this branch of physics to be interesting so I just started reading up.

Well I'd think they're the same thing since when time is dilated it ticks slower relative to a clock held by an individual who's not moving. Time being slowed down would also therefore mean the same thing then in my opinion (however distorted it is).

I realize now that my last question was pretty badly phrased, so I meant to ask, why when we're not moving faster than the speed of light, is time slowed down/dilated? Isn't time dilation intended to prevent us from going any faster than the speed of light? I didn't mean to make the last phrase the focus of the question, my bad!

 

[JesseM]

Well I'd think they're the same thing since when time is dilated it ticks slower relative to a clock held by an individual who's not moving. Time being slowed down would also therefore mean the same thing then in my opinion (however distorted it is).

One thing to understand is that in relativity, speed is relative--there's no objective sense in which we can say one object is "moving" while the other is "not moving". Acceleration is non-relative though (someone who accelerates will feel G-forces), so if you have one person moving at constant velocity while another departs from them, later accelerates to turn around, and returns, then the one who accelerated between meetings will have aged less than the one who didn't (see the twin paradox).

I realize now that my last question was pretty badly phrased, so I meant to ask, why when we're not moving faster than the speed of light, is time slowed down/dilated? Isn't time dilation intended to prevent us from going any faster than the speed of light? I didn't mean to make the last phrase the focus of the question, my bad!

One way to derive the conclusion of time dilation is to think of the light clock--you can make a clock by having light bounce up and down between two mirrors, but in a frame where the mirrors are moving the light will have a longer path to travel between them since it has to travel horizontally as well as vertically, so if it still travels at the same speed of c in this frame, it must take longer to bounce between mirrors in the frame where the light clock is moving. And the laws of physics must work the same way in every frame, so if a non-light clock keeps pace with a light clock when they are at rest relative to you, the clocks must still keep pace with one another when moving relative to you, so if the light clock slows down in your frame then any other type of clock must do so too. Brian Greene has a good discussion of the light clock on pages 37-41 of his book The Elegant Universe (if you read this section on google books you may want to start on page 28 where he first outlines the basic principles of relativity).

 

[birulami]

...you can make a clock by having light bounce up and down between two mirrors, but in a frame where the mirrors are moving the light will have a longer path to travel between them since it has to travel horizontally as well as vertically, so if it still travels at the same speed of c in this frame, it must take longer to bounce between mirrors in the frame where the light clock is moving. ...

At this point it helps me usually to remember that light is an electromagnetic wave. Further, all chemical reactions pretty much depend on electromagnetic interactions. Like the light travels a longer path, so do the interactions that drive chemical reactions. Consequently they are now slower. The same holds likely even for other forces than the electromagnetic. As a result my metabolism as well as all the things around me "tick slower" in every regard we can use to define "ticking". This, of course, from the perspective of an outside observer with respect to whom I am moving.

 

[Mayankv1994]

Thanks guys