Relation of time and speed of light

[ajb]

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?

Then you have to ask if we know 'why' steel is so hard... at some level it 'just is'. That is not to say that we cannot have some understanding of metalic structures, solid mechanics, solid state phsyics and so on. These give us an understanding of 'how' steel is hard, but 'why' is more of a philosophical question.

 

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.

In the context of the opening question, can there really be an answer to 'why' space-time comes with a Lorentzian signature metric? Maybe we could derive such notions from some other theory, but then we have to ask why that theory?

 

In short 'why' physical models work at all is a deep, but philosophical question.

Edited May 20, 2016 by ajb

[Strange]

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

 

 

That doesn't make much sense. Just making stuff up that has no basis in science doesn't show that things can move faster than light.

[Thorham]

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

 

It's not wrong, it's unknown, because:

 

1. We don't know all of reality, which means there may be places where the laws of physics are different.

2. We don't know if there are underlying mechanics that cause this maximum speed.

 

None of this is very useful right now, of course, but that's besides the point.

 

Then you have to ask if we know 'why' steel is so hard...

 

It's because the solid steel's atoms aren't moved out of the way by the finger, and they push back at the finger (more or less). Steel isn't hard, and it isn't solid. It's because of interactions of forces.

 

at some level it 'just is'.

 

At some level everything just is. Pretty useless, that. Why can a computer add 1 and 1? Because it just can. Right.

 

'why' is more of a philosophical question.

 

It only becomes a philisophical question when you get to the point when there are apparently no more underlying mechanics. Until then, why is a perfectly valid question.

 

In short 'why' physical models work at all is a deep, but philosophical question.

 

It's not deep at all. It's very simple. If the universe works in a logical manner, then you can describe it with any Turing complete language.

Edited May 20, 2016 by Thorham

[Strange]

 

It's not wrong, it's unknown, because:

 

1. We don't know all of reality, which means there may be places where the laws of physics are different.

2. We don't know if there are underlying mechanics that cause this maximum speed.

 

As always I assume that, this being a science forum, all statements are accompanied by "according to our best theories" and "consistent with the current evidence" and "as far as we know" etc.

 

Saying "oh we might learn something new in future" is slightly silly and spectacularly unhelpful.

 

Yes, one day we might find that black holes are full of chocolate or Pluto is inhabited by My Little Ponies or that to go faster than light you just need to say "Einstein" three times backwards.

 

But this is a SCIENCE forum. Where we discuss SCIENCE.

[Thorham]

Yes, one day we might find that black holes are full of chocolate or Pluto is inhabited by My Little Ponies or that to go faster than light you just need to say "Einstein" three times backwards.

 

And everyone knows that these things are completely absurd. Underlying mechanics and different physics in other places are of course valid hypotheses, especially when current theories are incomplete.

 

The big bang theory fails at a certain point, and quantum physics can't be merged with relativity. So apparently there's more to it then we know now. It's actually a certainty that there's more to it.

 

But this is a SCIENCE forum. Where we discuss SCIENCE.

Indeed, and science never got anywhere by clinging to broken theories.

[Strange]

And everyone knows that these things are completely absurd.

 

Which is something a lot of anti-science types like you say about much modern science.

 

 

Indeed, and science never got anywhere by clinging to broken theories.

 

And it never got anywhere with baseless speculation, either.

Edited May 20, 2016 by Strange

[Thorham]

Which is something a lot of anti-science types like you say about much modern science.

 

I'm NOT an anti-science type. I know science works, because I use some of the things it has produced on a dayly basis. Things which would be utterly impossible without modern science. Anti-science, how absurd

 

And it never got anywhere with baseless speculation, either.

I'm not speculating, all I said is that something is unknown because of certain reasons. As for baseless, if current theories are incomplete and break at some point, then there must be more, right? Guess what real physicists have been working on for decades now.

 

And then there's the following problem: What if physicists come up with a great theory of everything we know? What then? Is that the end, because there's no reason to look for more?

 

Basically what you're saying is that types like me are anti-science because we assume there's more out there to be discovered then we know now (something that has been shown time and time again in the past), and that's obviously ridiculous.

Edited May 20, 2016 by Thorham

[Strange]

Basically what you're saying is that types like me are anti-science because we assume there's more out there to be discovered then we know now (something that has been shown time and time again in the past), and that's obviously ridiculous.

 

Not at all. Everyone knows there is more to be discovered. That is what makes science so exciting.

 

It is the attitude that because we don't know everything, then everything we know must be wrong. Which is just silly.

[Thorham]

It is the attitude that because we don't know everything, then everything we know must be wrong. Which is just silly.

Of course it is, and I don't think that.

[Raider5678]

Thorham, why are you downvoting everyone of stranges comments? Downvoting them doesn't make them any less true, just saying.

 

Strange, anyway, yeah, nothing can move faster than light, and I won't try to explain my "philosophical" technical point lol. I wasn't saying something could move faster than light btw, so don't mistake that as me trying to argue with modern science, because I wasn't trying to.

[Thorham]

Thorham, why are you downvoting everyone of stranges comments? Downvoting them doesn't make them any less true, just saying.

 

The first post I down voted was a bad counter to what I said, namely that something is unknown for some specific reasons, while ignoring the rest of my post entirely. The second post I down voted made both an assumption that's not true, and an accusation that's not true.

 

I said that it's unknown that the speed of light is the maximum speed. Nothing wrong with that statement, and it's not speculation. I'm also NOT anti-science.

Edited May 20, 2016 by Thorham

[swansont]

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

 

 

 

IOW, if things were different, they'd be different.

 

Trivially true, and of no actual useful content.

 

It's not wrong, it's unknown, because:

 

1. We don't know all of reality, which means there may be places where the laws of physics are different.

2. We don't know if there are underlying mechanics that cause this maximum speed.

 

None of this is very useful right now, of course, but that's besides the point.

 

It's more to the point than you're allowing. Science always has to be interpreted in terms of the best theories and data we have. And that says that the laws of physics are the same everywhere. Calling it unknown is a cop-out. We do know that massive bodies can't travel faster than c, according to our best understanding of physics. That last bit is usually omitted from discussion, because it gets tedious tacking on the same disclaimer, "according to our best understanding of physics," all the time.

[Thorham]

Science always has to be interpreted in terms of the best theories and data we have. And that says that the laws of physics are the same everywhere. Calling it unknown is a cop-out.

 

It's not a cop-out, because we can't test that. It might not even be testable in principle. Claims like that shouldn't be part of any theories.

Edited May 20, 2016 by Thorham

[Delta1212]

 

It's not a cop-out, because we can't test that. It might not even be testable in principle. Claims like that shouldn't be part of any theories.

It's indirectly testable. You can create models that simulate how things should behave according to the physical laws as we understand them here, and then see whether what we see elsewhere in the universe matches with that.

 

And by and large it does.

 

The one area we really can't test is whatever lies beyond the observable universe, but there is every reason to believe that we will never be able to interact with anything beyond that, so if the laws change somewhere out past our little bubble of observable universe, it's unlikely that we will ever know about it or that it will ever affect us in any way.

[Strange]

 

It's not a cop-out, because we can't test that. It might not even be testable in principle. Claims like that shouldn't be part of any theories.

 

 

It is not a claim, it is a rational default position. With no evidence that the laws of physics are different elsewhere, why would you claim they are? (That was the point of the "chocolate" comment earlier. You can't just make up stuff like "the laws of physics are different over there".)

 

Of course, everyone concedes that they could be different. And experiments have been done to test it. So far there is no evidence against the default position. That is how science works.

[Thorham]

It's indirectly testable. You can create models that simulate how things should behave according to the physical laws as we understand them here, and then see whether what we see elsewhere in the universe matches with that.

There's already a problem with that: We can only use telescopes to examine the observable universe, so we can't observe everything that's going on out there, which means we can't even say for certain that the laws of physics are the same everywhere in the observable universe.

 

Of course it's not unlikely to be true, but it's still not known for sure.

 

And by and large it does.

 

I don't doubt it.

 

The one area we really can't test is whatever lies beyond the observable universe

 

Not yet, no.

 

there is every reason to believe that we will never be able to interact with anything beyond that

 

According to what we know now, which doesn't mean a whole lot. And yes, that's not very useful right now. I just don't like words like never and can't, see below.

 

so if the laws change somewhere out past our little bubble of observable universe, it's unlikely that we will ever know about it or that it will ever affect us in any way.

 

If we don't mess up, we're probably going to be here for an exceedingly long time. I'm not willing to say it's unlikely when there's potentially several hundreds of millions of years of development ahead of us.

With no evidence that the laws of physics are different elsewhere, why would you claim they are?

 

I didn't claim they are, I said they might be different.

[Raider5678]

IOW, if things were different, they'd be different.

 

Trivially true, and of no actual useful content.

Evil liar

Not really. That thought experiment was just something that had occured to me and I got the stupid idea of mentioning it. My bad.

[Strange]

There's already a problem with that: We can only use telescopes to examine the observable universe, so we can't observe everything that's going on out there, which means we can't even say for certain that the laws of physics are the same everywhere in the observable universe.

 

 

As, by definition, we are not causally connected to the non-observable universe it doesn't really matter. It can't make any difference.

 

 

 

I didn't claim they are, I said they might be different.

 

OK. How about this for a deal: whenever someone writes a statement about science, "X", you will interpret it to mean, "It appears to be that, according to our current best theories and consistent with observations (within certain error bounds) X may be the case."

 

And we can all assume you will respond with your deeply insightful and profoundly thought provoking, "ah, but it might not be" without you actually having to do it.

 

That way we will all save a lot of time.

 

Or you could just stop being contentious by repeatedly posting the trivially obvious.

[Thorham]

OK. How about this for a deal: whenever someone writes a statement about science, "X", you will interpret it to mean, "It appears to be that, according to our current best theories and consistent with observations (within certain error bounds) X may be the case."

 

It's not unreasonable to assume that people just write what they mean. You write impossible, it means impossible. I've seen this before. A universe from nothing, for example. Sounds like utter nonsense because you think of absolute nothingness, which is actually what it should mean. Isn't the case, nothing means something, and I find it ridiculous. Writing what you mean prevents this kind of confusion:

 

There is NO sense in which you would be going faster than light.

 

This reads as if it's utterly impossible. A simple 'Not possible under current theory.' sounds much less definitive, is not longer to write, and doesn't need interpretation. You'd think that in science people would use language in a more exact way.

 

That way we will all save a lot of time.

 

Or you could just stop being contentious by repeatedly posting the trivially obvious.

 

Look, you said:

 

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

 

To which I responded that it's unknown. If it's so trivially obvious, why argue against it?

[swansont]

There's already a problem with that: We can only use telescopes to examine the observable universe, so we can't observe everything that's going on out there, which means we can't even say for certain that the laws of physics are the same everywhere in the observable universe.

 

 

 

And yet using telescopes allow us to test the principle. Can we test everywhere? No, of course not. But we can interpolate and extrapolate. There are areas of the earth where nobody has tested to see if gravity is present, but given the tests we have and the theory behind it, it seems silly to suggest that we can't make claims about gravity being present everywhere on earth.

[Thorham]

And yet using telescopes allow us to test the principle. Can we test everywhere? No, of course not. But we can interpolate and extrapolate. There are areas of the earth where nobody has tested to see if gravity is present, but given the tests we have and the theory behind it, it seems silly to suggest that we can't make claims about gravity being present everywhere on earth.

 

All of reality is a little bit larger than the earth

 

Assuming things to be true locally is very different from assuming them to be true everywhere.

Edited May 21, 2016 by Thorham

[Raider5678]

All of reality is a little bit larger than the earth

 

Assuming things to be true locally is very different from assuming them to be true everywhere.

Dude, none of your arguments are making sense. By hey, I want to play. I can't see you, so you don't exist. You know, its kind of hard living life by that logic huh?

[Thorham]

Dude, none of your arguments are making sense. By hey, I want to play. I can't see you, so you don't exist. You know, its kind of hard living life by that logic huh?

 

Eh, what you're saying is exactly what I was arguing against

 

I started out by saying that something is unknown, nothing more. I'm literally the last person who would claim that something doesn't exist just because I can't see it

[ajb]

It's because of interactions of forces.

Which we have to describe using models... but why are there interaction forces in the first place?

 

At some level everything just is. Pretty useless, that.

Indeed, so in physics we build models and mechanism to describe what we see. There is no meaningful answer to 'why' in physics. The closest we can get is a description of the mechanisms involved.

 

It only becomes a philisophical question when you get to the point when there are apparently no more underlying mechanics. Until then, why is a perfectly valid question.

But why do these mechanisms 'exist'?

 

 

 

 

It's not deep at all. It's very simple. If the universe works in a logical manner, then you can describe it with any Turing complete language.

First you have this 'if' as I highlight above. But then why should Universe be logical and be described by mathematics?

 

I can show you example of how parts of the Universe can be described using mathematics, but 'why' mathematics works people debate and it is a philosophical question.

 

 

Assuming things to be true locally is very different from assuming them to be true everywhere.

This is true, but we need to be careful by what you mean by 'local' and 'everywhere'.

 

 

Physics works here on Earth. Physics work in our Solar system. Using astronomy we can test if our local physics applies on a larger scale. So far there is no reason to think that the physics on Earth is different to the physics on say any exoplanet found so far. We have some gaps with dark matter and the motion of galaxies, but that does not suggest that the physics on Earth is different to that in the galaxies we have obsevered: dark matter contribution to physics in our Solar system are tiny.

 

We then look at cosmology and see if we have some understanding of our observable Universe. And again, it seem that we can take what we know about our local physics and apply it to the Unievrse. For instance, the laws of thermodynamics that were discovered in the labs of Victorians seems to apply to cosmology. So far, we have some gaps (dark matter, dark energy, large scale gravity etc.) but the basic physics seems to hold.

 

 

So we take it as a working assumption that we can take physics and apply it to any part of our observable Universe.

Of course this may not be the case and some observation could over throw this. Everyone accepts this, but right now there is no reason not to think that the laws of physics are universal.

 

Back to the opening post... we know that general relativity is a good model (or framework) to describe the gravitational physics of the Solar System. We also know that general relativity is good for other astrophsyical phenomena (i.e. gravitational waves), and we think that it is a good framework for cosmology.

 

General relativity and special relativity tell us that space-time comes in built with a 'causal structure'. Loosley, this tells us nothing can have a relativistic speed great that the speed of light. Why this is so? No idea... the best we can do is present the mathematics and show how that agrees with our observations.

Edited May 21, 2016 by ajb

[Strange]

To which I responded that it's unknown. If it's so trivially obvious, why argue against it?

 

 

Because this is a SCIENCE forum. If someone says that it is possible to travel faster than light, then I expect them to explain how that is possible within known SCIENCE.

 

I would be delighted to be proved wrong, but as far as I know it is impossible to travel faster than light in current known SCIENCE.

 

The fact that there is an annoying kind in the corner who keeps saying "but it might not be" with no rational basis, evidence or theory doesn't change that. It just gets tedious after a while. Please stop doing it.

 

Actually, on second thought, carry on. That is what the ignore function is for.