What is time?

[guitarfrk451]

Basically, my meter is not the same is your meter if we are moving at different speeds (and subject to different velocities and potentials).

 

well..yes and no

[iNow]

well..yes and no

Care to elaborate? Yes and no, what?

[Baby Astronaut]

The coordinate system you use to measure length depends on speed. Space isn't Cartesian. Length isn't an absolute.

Can you explain this a bit more clear? The idea of relative space is totally foreign to me, never heard of it. Also, I'm not familiar with many physics terms.

 

I understand different speed frames measuring different time rates. Isn't there a simple equivalent for teaching relative space?

 

For example, I don't know what Cartesian means in that sense, nor what you mean by "Length isn't an absolute".

[swansont]

Can you explain this a bit more clear? The idea of relative space is totally foreign to me, never heard of it. Also, I'm not familiar with many physics terms.

 

I understand different speed frames measuring different time rates. Isn't there a simple equivalent for teaching relative space?

 

For example, I don't know what Cartesian means in that sense, nor what you mean by "Length isn't an absolute".

 

Length depends on the frame in which you measure, similar to time. Moving objects length-contract. You can't use a simple x-y-z coordinate system to measure things, and have that mean anything in another frame, because the transformation from one system to another isn't linear (Galilean).

[Mr Skeptic]

It's all a result of the constant speed of light. The laws of physics say that light moves at c, and also that you can't tell how fast you are moving if you are in a closed room. But suppose you have a clock that uses light and mirrors. When the light hits one side your clock goes "tick" and when it hits the other side, "tock". If you are moving relative to someone else in the direction the light is moving, and you each have clocks as described above, then you will both disagree as to how long it takes for the light to go from one end of the clock to the other, which means that your clocks are not synchronized. Also, if your clock is sideways, then the person who says you are moving will say your light is going diagonally, and therefore also traveling a longer distance and taking longer. But you will observe that the light clocks will both be synchronized, and also be synchronized with all your other clocks. But if you say that both your light clocks are synchronized, then the person who says you are moving will say that they must be different lengths to be synchronized. So he observes that his measure of length must be different from yours, since as far as you can see, both clocks are just as long.

 

You can think of it as the changes required to make it so that everyone measures light at the same speed regardless of how fast they are traveling, but also be unable to tell whether or how fast they are moving.

[Baby Astronaut]

 

Does your clock example work like shown in the image?

 

The light moving forward would make the "tick" sound, and the light moving away at their back would make the "tock" sound.

 

"A" is holding the clock sideways.

 

Is that what your example was meant to show? If so, it the relativity of space just seems like a way to ease a math problem, rather than actual differences as with time being relative.

 

I mean, when two people travel at far different speeds, they are really experiencing the difference, and not even perceiving it. Thus "relativity" with space doesn't seem to be the same concept as relativity of time. Because in your example, the people are aware of the differences, but those seem virtual, not real.

[Baby Astronaut]

The laws of physics say that light moves at c, and also that you can't tell how fast you are moving if you are in a closed room. But suppose you have a clock that uses light and mirrors....

Whoops, I thought you meant the light would hit the walls of a closed room (forward and rearward). Disregard my previous statements/questions.

 

I understand now. A stationary clock holder would perceive a difference in the clock of a moving clock holder.

 

But wouldn't the moving clock holder also perceive a difference, since in relativity the stationary clock would shrink?

[Mr Skeptic]

Nope! If the person moving with the clock could tell the difference, then he could tell how fast he were going. The person moving with the clock could just as easily say that it is the other person who has the funny clock. They can tell that they are moving relative to each other, but neither can say which of them is moving.

[Jacky.Wang]

Time,I think people usually use a kind of concept to calculate the physical or chemical process.Then time was found by people.But think that is time existed?No,I think he just a kind of concept,but not a object,such as distance.We always said 1m,2m,but you can not found that in fact you have found a object to describe the distance.Time is the same,time is just a concept,but not a object.So it is hard to describe what time is but you can found them here because you always can found a object to describe time.Such as mind in your brain,you can touch mind?