Relation of time and speed of light

[Raider5678]

Hello again.

 

I have a question about why time slows down the faster your going, and why time will not let you go faster then light. Now my reason for this question is that Steven Hawkings says that if your on a vehicle, that's moving near the speed of light, and someone on board were to run towards the direction the vehicle is traveling, time will slow down EVEN more so that they aren't moving faster then light. My question is WHY does time slow down? I understand that speed is how far you travel in a period of time, so time slowing down prevents you from going faster then light. I also understand the reason you can't get something to go faster then light, is that since nothing GOES faster then light, then nothing can push you faster then light. You can't even get to the speed of light because force is mass times acceleration (why isn't it speed?). That means if your moving closer to the speed of light it won't be pushing you as hard as it as in the beggining, making your acceleration slower and slower until it will amount to nothingband you aren't getting any closer to the speed of light. So that's what I understand, but why would time slow down the faster you go, and why doesn't the universe want you going faster then light?

[Delta1212]

That's just how the math works out/what we observe. I'm not sure we have a deeper answer for why the universe works the way that it does.

[pzkpfw]

... Steven Hawkings says ...

* Stephen Hawking

 

https://en.wikipedia.org/wiki/Stephen_Hawking

 

 

... because force is mass times acceleration (why isn't it speed?). ...

Put simply, things that are moving want to keep moving the way they are. It takes force to change their movement, speed them up, slow them down, change their direction - that's all acceleration.

 

... So that's what I understand, but why would time slow down the faster you go, and why doesn't the universe want you going faster then light?

The guts of it is that time just isn't the fixed thing we think it is. It was figured out before Einstein (see Maxwell) that what's actually "fixed" is the speed of light. What Einstein did was think that through.

 

Say your favourite pitcher or bowler can chuck a ball at 100 km/h. If they are standing still and chuck the ball at you, it hits at 100 km/h and hurts. What if they were standing on the back of a ute (small truck) doing 100 km/h towards you - if he or she threw the ball at you, it'd hit at 200 km/h, right? Turns out that's "wrong". Wrong in the sense that it's close-enough for day to day use, but actually not quite right. (It'd be 199.99999 km/h (I didn't calculate the exact number of nines)).

 

Because ... it's the speed of light that's fixed. Say that pitcher/bowler is shining a light at you. That light hits you at c, the speed of light. (Actually, c is the speed in a vacuum, so maybe you're wearing a space suit ...). What if they were on a spaceship coming towards you at 1,000 km/h and shine that light at you? That light would still be hitting you at c, not c + 1,000 km/h. Same if they were "standing still" and you were zooming towards them at 1,000 km/h.

 

How can light always be going at c regardless of the speed of the sender or receiver? It turns out that time and distance are the squishy things in the universe, because the speed of light is fixed.

 

See:

 

https://en.wikipedia.org/wiki/Velocity-addition_formula (Note that at "low" speeds, the effects is negligible).

 

https://en.wikipedia.org/wiki/Time_dilation (Note that we all think our time goes at 1 second per second, but other people not at a stand-still with us, will think we're slow, and we'll think they're slow).

 

https://en.wikipedia.org/wiki/Speed_of_light

Edited May 15, 2016 by pzkpfw

[ajb]

I have a question about why time slows down the faster your going, and why time will not let you go faster then light.

'Why' is not really the right question. The best we can say is that this is written into the Universe and that is that.

 

The closest to 'why' has to be the mathematics of our physical models. Basically, we can model the change in measurements of duration using special relativity, which gives us the mathematical framework, and that special relativity has been shown to agree with nature very well via experiments/observations.

[geordief]

Does th

 

'Why' is not really the right question. The best we can say is that this is written into the Universe and that is that.

The closest to 'why' has to be the mathematics of our physical models. Basically, we can model the change in measurements of duration using special relativity, which gives us the mathematical framework, and that special relativity has been shown to agree with nature very well via experiments/observations.

Is it helpful /correct to regard light as the speed of causality(or information) across a vacuum .?

[ajb]

Is it helpful /correct to regard light as the speed of causality(or information) across a vacuum .?

Sort of... information cannot be transmitted by any means faster than the speed of light. For instance, using quantum entangelment does not allow faster than light communication. In this sense, the speed of light defines causality.

[geordief]

Sort of... information cannot be transmitted by any means faster than the speed of light. For instance, using quantum entangelment does not allow faster than light communication. In this sense, the speed of light defines causality.

So is it possible to define the situation as the speed of light (and everything we know of) as being limited by the speed of causality or information (are they synonymous terms) rather than the other way round?

[ajb]

So is it possible to define the situation as the speed of light (and everything we know of) as being limited by the speed of causality or information (are they synonymous terms) rather than the other way round?

The 'speed of causality' sounds a strange way of putting it.

 

If we look at special relativity in particular (though the situation is similar in general) the causal structure of space-time is given in terms of 'light cones' and indeed the speed c is the maximium speed limit. (The maximum relative velocity any inertial observer can measure). I like to think of c as a universal constant that is written into the universe, it is a conversion factor allowing us to mix space and time. This constant c also describes the causal structure and it 'just happens' to be the speed of light in vacuum.

[geordief]

Well tachyons are not theoretically impossible ,I believe.

 

If they did exist our "universe" would be a subset of a wider universe whose laws we would be subject to but which might not affect us so that we would notice.

 

They way you have described the situation would indeed apply** to this subset of this possible universe (which is only a theoretical possibility I agree and also possibly wrong)

 

**I cannot personally say one way or the other on account of my lack of study but I have no reason to doubt you.

 

 

By the way do you not like the phrase "speed of causality" as expressing the fastest possible speed that things can theoretically affect one another? Could it be formalized?

[ajb]

Well tachyons are not theoretically impossible ,I believe.

We know that (standard) tachyons are unstable and will decay quickly to non-tacyonic particles. So we don't really expect them to be realised in nature.

 

 

 

By the way do you not like the phrase "speed of causality" as expressing the fastest possible speed that things can theoretically affect one another? Could it be formalized?

The speed of causality sounds like causality is changing at some rate. That is why I do not like the phrase.

[geordief]

We know that (standard) tachyons are unstable and will decay quickly to non-tacyonic particles. So we don't really expect them to be realised in nature.

 

 

 

 

The speed of causality sounds like causality is changing at some rate. That is why I do not like the phrase.

Sorry ,no that is not what I meant by it. The agency responsible for things affecting one another would be fixed but the outcome would be variable as it would depend on distance as one example.

 

Hope I am not waffling too much but I have this idea that there could be a "fastest possible" way that things could interact or impact on each other.

 

With the universe as we know it this seems to be be closely related to light or em radiation.

 

Could this relationship (if I have correctly -or even closely -identified it) be not set in stone?

[ajb]

Sorry ,no that is not what I meant by it.

Exactly, so I think it is not the best term to use.

 

 

....idea that there could be a "fastest possible" way that things could interact or impact on each other.

So by an interaction one means 'exchange properties'. For example, two particles via virtual particles exchange energy and momentum. These intreaction are subject to causality.

 

 

With the universe as we know it this seems to be be closely related to light or em radiation.

Indeed, because light rays are deeply tied to the notion of causality.

[geordief]

 

 

 

Indeed, because light rays are deeply tied to the notion of causality.

That is very interesting . Perhaps I have taken in enough for now

[Raider5678]

Ok. Wow. So say 2 rays of light were to pass each other in the vaccum of space. From the point of view of one ray of light, the other is going a little less then c, or is it going half the speed of c? C = speed of light in vaccum.

[ajb]

Ok. Wow. So say 2 rays of light were to pass each other in the vaccum of space. From the point of view of one ray of light, the other is going a little less then c, or is it going half the speed of c? C = speed of light in vaccum.

The 'point of view' of a light ray is not what we usually mean when we talk about observations in special relativity. In particular, there is no inertial frame of reference for which a photon can be considered to be at rest. The 'point of view of a photon/light ray' is not a good notion in special relativity. A photon is not an inertial observer and so one has to take care with the concepts in inertial frames and translating them to other more general frames..

Edited May 15, 2016 by ajb

[Prophet12A]

Raider,

 

Perhaps its an error to believe nothing can travel faster than the 'speed of light in a vacuum'.

[Strange]

Raider,

 

Perhaps its an error to believe nothing can travel faster than the 'speed of light in a vacuum'.

 

 

Do you have any reason for suggesting that?

[Raider5678]

Raider,

 

Perhaps its an error to believe nothing can travel faster than the 'speed of light in a vacuum'.

 

Hmmm, I thought about this. In a technical sense things CAN travel faster then light! Surprise! Time slows down though, so nothing can. The faster you get time always slows down enough so you aren't going faster then light.

[swansont]

Raider,

 

Perhaps its an error to believe nothing can travel faster than the 'speed of light in a vacuum'.

 

 

Perhaps it is. But the evidence we have and the wildly successful model it confirms say that it's not.

[Strange]

In a technical sense things CAN travel faster then light!

 

 

Which technical sense is that?

[swansont]

In a technical sense things CAN travel faster then light!

 

 

But these are acausal and/or carry no information

[Thorham]

'Why' is not really the right question. The best we can say is that this is written into the Universe and that is that.

 

That's a little simple, isn't it? 'Why' questions are fine. Why can't I push my finger through solid steel? Shouldn't be to hard to answer, right?

 

A better way of saying this is that you just don't know. There's always the possibility of underlying mechanics that cause these phenomena. Us not knowing doesn't mean 'why' questions aren't right.

[Raider5678]

Which technical sense is that?

In the sense that you would be going faster then light if it weren't for time slowing down stopping you from going faster. I fear I have gotten into a DEEP political debate, so I won't be able to explain it into too much detail.

[Strange]

In the sense that you would be going faster then light if it weren't for time slowing down stopping you from going faster. I fear I have gotten into a DEEP political debate, so I won't be able to explain it into too much detail.

 

 

I don't see it as political, just wrong. There is NO sense in which you would be going faster than light.

[Raider5678]

I don't see it as political, just wrong. There is NO sense in which you would be going faster than light.

This isn't the political debate..... That's another topic...

Either way let's imagine time didn't slow down the faster you got. Light moves at 300S. You're in a ship and your traveling 400S somehow. Now you factor in time, and your both moving at the same speed.

S = 1,000,000 meters p/s

Edited May 19, 2016 by Raider5678