speed of light?

[Stan the Bat]

Regarding space and time as the same thing .

If all space exists at the same time, does then all time already exist, therefore all things have already been predetermined.

[67Dino]

Stan the Bat said:

Regarding space and time as the same thing .

If all space exists at the same time, does then all time already exist, therefore all things have already been predetermined.

Smart question. That’s one view, and is a theory known as “the block universe”, which was Einstein’s perspective.

However, as well as the big issue this raises about free will, having everything predetermined (also known as “eternalism”) doesn’t sit well with the probabilistic nature of quantum mechanics. So there are also competing theories, the simplest of which is perhaps the “growing block universe” where as time passes the universe of spacetime grows.

Personally, I find the concept of time the most fascinating and slippery of all ideas in Physics. By which I mean, I haven’t a clue really.

[Fusion777]

Stan the Bat said:

Regarding space and time as the same thing .

If all space exists at the same time, does then all time already exist, therefore all things have already been predetermined.

Laplace wondered a similar thing, and came up with the idea of a "demon" that could predict the whole future if all information about the current state of the universe could be gathered. Of course, theories coming later such as Quantum Mechanics showed that knowing all this information would be impossible, so accurate predictions can never be made.

[Stan the Bat]

Quantum mechanics is what governs small dimensions ( so I understand).

But relativity governs large things ( I think)

So is spacetime large or small ?

[Derek Smith]

The universe after the Big Bang expanded at a rate faster than the speed of light. As with all theories it will be wrong I suppose, but let's run with it.

The 'explanation' given to me was that space was expanding and taking that into consideration, light did not exceed its own limitation. OK, I'll accept that without being able to understand it, but it is, to my view, a way around the limitation. It's a bit like ants; if there's one, there'll be lots of others. The only question is where.

[Dr Jekyll]

Stan the Bat said:

Quantum mechanics is what governs small dimensions ( so I understand).

But relativity governs large things ( I think)

So is spacetime large or small ?

Relativity governs fast things, which incidentally tend to be small.

[Fusion777]

Stan the Bat said:

Quantum mechanics is what governs small dimensions ( so I understand).

But relativity governs large things ( I think)

So is spacetime large or small ?

Quantum effects tend to be most pronounced on a very small scale, yes.

Depends which theory of relativity you're talking about. Special relativity technically affects all speeds and sizes of items, though special relativistic effects tend to be more pronounced when approaching the speed of light.

You're probably thinking more of general relativity, which describes spacetime, and tends to be over a larger scale.

A holy grail of physics is having a theory that can describe quantum mechanics and general relativity. That's where things like string theory and quantum loop gravity come in.

[annodomini2]

Stan the Bat said:

Quantum mechanics is what governs small dimensions ( so I understand).

But relativity governs large things ( I think)

So is spacetime large or small ?

QM is a better model for the very small.

GR is a better model for everything above the very small.

This is obviously based on interpretation of observations at the current time.

There are many hypothetical and theoretical competitors, but nothing has managed to de-throne them yet.

[skeeterm5]

67Dino said:

Personally, I find the concept of time the most fascinating and slippery of all ideas in Physics. By which I mean, I haven’t a clue really.

I agree with you on that point, the more you think about it the more complicated it seems to be and the more the explanations seems to have to become more complex to explain things.

It seems to me that we may be missing something really fundamental that would help explain and simplify the whole, maybe that is the grand unified theory or something similar.

[67Dino]

skeeterm5 said:

67Dino said:

Personally, I find the concept of time the most fascinating and slippery of all ideas in Physics. By which I mean, I haven’t a clue really.

I agree with you on that point, the more you think about it the more complicated it seems to be and the more the explanations seems to have to become more complex to explain things.

It seems to me that we may be missing something really fundamental that would help explain and simplify the whole, maybe that is the grand unified theory or something similar.

We certainly are missing something... Whatever it is, I’m pretty convinced time travel is possible. Seems to me it’s the only logical answer to the Fermi Paradox (ie where is everyone else?), namely that there are others in this Universe, they have just gone to live in a different time and tidied up behind them.

[Stan the Bat]

67Dino said:

skeeterm5 said:

67Dino said:

Personally, I find the concept of time the most fascinating and slippery of all ideas in Physics. By which I mean, I haven’t a clue really.

I agree with you on that point, the more you think about it the more complicated it seems to be and the more the explanations seems to have to become more complex to explain things.

It seems to me that we may be missing something really fundamental that would help explain and simplify the whole, maybe that is the grand unified theory or something similar.

We certainly are missing something... Whatever it is, I’m pretty convinced time travel is possible. Seems to me it’s the only logical answer to the Fermi Paradox (ie where is everyone else?), namely that there are others in this Universe, they have just gone to live in a different time and tidied up behind them.

Nah.

[67Dino]

Stan the Bat said:

67Dino said:

skeeterm5 said:

67Dino said:

Personally, I find the concept of time the most fascinating and slippery of all ideas in Physics. By which I mean, I haven’t a clue really.

I agree with you on that point, the more you think about it the more complicated it seems to be and the more the explanations seems to have to become more complex to explain things.

It seems to me that we may be missing something really fundamental that would help explain and simplify the whole, maybe that is the grand unified theory or something similar.

We certainly are missing something... Whatever it is, I’m pretty convinced time travel is possible. Seems to me it’s the only logical answer to the Fermi Paradox (ie where is everyone else?), namely that there are others in this Universe, they have just gone to live in a different time and tidied up behind them.

Nah.

Excellent response. I wish all opinions on PH were as succinct.

[Stan the Bat]

I'm an expert doncha know.

[Dr Jekyll]

67Dino said:

We certainly are missing something... Whatever it is, I’m pretty convinced time travel is possible. Seems to me it’s the only logical answer to the Fermi Paradox (ie where is everyone else?), namely that there are others in this Universe, they have just gone to live in a different time and tidied up behind them.

But why haven't time travellers from other periods come here? You still have unbalanced net migration to explain.

[Krikkit]

skeeterm5 said:

67Dino said:

Personally, I find the concept of time the most fascinating and slippery of all ideas in Physics. By which I mean, I haven’t a clue really.

I agree with you on that point, the more you think about it the more complicated it seems to be and the more the explanations seems to have to become more complex to explain things.

There's nothing particularly "slippery" about time in this context, it's just that the translation into the real world from the maths that actually expresses it isn't up to the job.

[67Dino]

Krikkit said:

skeeterm5 said:

67Dino said:

Personally, I find the concept of time the most fascinating and slippery of all ideas in Physics. By which I mean, I haven’t a clue really.

I agree with you on that point, the more you think about it the more complicated it seems to be and the more the explanations seems to have to become more complex to explain things.

There's nothing particularly "slippery" about time in this context, it's just that the translation into the real world from the maths that actually expresses it isn't up to the job.

I’m not sure I agree. I’ve a degree in Physics and know that lots of concepts are hard to grasp due to the maths being different to the familiar world we inhabit. Time has this plus it is also still debated if it is even is a real thing at all. Quantum mechanics doesn’t even care which way it flows which raises some real questions at its existence. That seems pretty slippery to me…

[NMNeil]

One thing being overlooked is just how incredibly slow the speed of light actually is.
I'm open to correction but the closest solar system to ours is Alpha Centauri. If you could travel at 10 times the speed of light it will still take you about 3 months to get there even ignoring acceleration to that speed and deceleration at the end.
Grab a beer and a comfy chair to get a better idea.
https://www.youtube.com/watch?v=1AAU_btBN7s

[Dr Jekyll]

NMNeil said:

One thing being overlooked is just how incredibly slow the speed of light actually is.
I'm open to correction but the closest solar system to ours is Alpha Centauri. If you could travel at 10 times the speed of light it will still take you about 3 months to get there even ignoring acceleration to that speed and deceleration at the end.
Grab a beer and a comfy chair to get a better idea.
https://www.youtube.com/watch?v=1AAU_btBN7s

More a case of how ridiculously big the universe is but I take your point.

[robemcdonald]

What you really need is a piece of paper and a pencil.

[eharding]

Dr Jekyll said:

NMNeil said:

One thing being overlooked is just how incredibly slow the speed of light actually is.
I'm open to correction but the closest solar system to ours is Alpha Centauri. If you could travel at 10 times the speed of light it will still take you about 3 months to get there even ignoring acceleration to that speed and deceleration at the end.
Grab a beer and a comfy chair to get a better idea.
https://www.youtube.com/watch?v=1AAU_btBN7s

More a case of how ridiculously big the universe is but I take your point.

Both measures are simply a reflection of how vanishingly brief the human lifespan is in the scheme of things.

A species with an individual lifespan of tens or hundreds of millennia probably wouldn't be so grumpy and bent out of shape about how unfair the scale and fundamental speed limit of the universe are.

Edited by eharding on Sunday 24th July 23:47