If the speed of light were infinite....

[Ouroboros]

Just something I read in an old New Scientist article 4 March 2017...

".... if the speed of light were infinite, massless particles and the information they carry would move from A to B instantaneously, cause would sit on top of effect and everything would happen at once". 

OK I get  that. Then it says ...

"The universe would have no history and no future, and time as we understand it would disappear." 

Why? 

 

 

[Paul67]

Ill, take a stab, say we now see a galaxy 10,000 light years away, so we see what was happening 10,000 years ago. If it was infinitely fast we couldnt see the past, only the now. However when we approach the current speed of light there are all sorts of distortions, you would see stuff happening almost like before it happened, I think

I think you might have answered it yourself in your opening sentence.

[Peter Drew]

And the 4th of March 2017 would never have happened.   

[andrew s]

1 hour ago, Ouroboros said:

Just something I read in an old New Scientist article 4 March 2017...

".... if the speed of light were infinite, massless particles and the information they carry would move from A to B instantaneously, cause would sit on top of effect and everything would happen at once". 

OK I get  that. Then it says ...

"The universe would have no history and no future, and time as we understand it would disappear." 

Why? 

 

 

I am not sure either statement is true. Newton managed a coherent model of the Universe he new with the assumption that the speed of light is infinite.

Regards Andrew 

[SilverAstro]

1 hour ago, Ouroboros said:

".... if the speed of light were infinite, massless particles and the information they carry would move from A to B instantaneously

Why? 

I cant do the  "why?", and science isnt too good at that either it is more about "how?" , but it is interesting that the question is relative ! oh ho !!

As far as the photon is concerned ( well, I know it doesnt concern itself really, but indulge me ) it does get from A to B instantly, time does not 'pass' for the photon. Nor for any other particle of invariant mass = 0 (what used to be called "rest mass"). The photon is the only one of im=0 (that we know of so far) that travels from anywhere to anywhere else, the gluon is always bound or confined in other particles, and the graviton has not yet been found, only postulated.

I think !

 

 

[SilverAstro]

15 minutes ago, andrew s said:

I am not sure either statement is true. Newton managed a coherent model of the Universe he new with the assumption that the speed of light is infinite.

I am not sure that is true either !   It hinges on the words "he knew" ie. wot he knew.  He new, (or maybe I should say there is a suggestion or interpretation that he may have ?)  that there was something wrong with the orbit of Mercury in his model but he chose not to make a big deal about it and no one else cottoned on for quite some time.

[saac]

I think I'm with Andrew on this one.  In our everyday interaction the speed of light to all practical extent could be considered infinite. When I look at my wrist watch the light illuminating it travels the short distance to my eye instantly (as far as I am concerned), increasing its speed would make no discernible difference to my understanding of the image of the watch face it conveys. Ok our view of extremely distant (earliest) objects in the universe would be different, but that is it, they would just be different. More than happy to be wrong, now, later or before I posted this  

 

Jim 

 

[andrew s]

21 minutes ago, SilverAstro said:

I am not sure that is true either !   It hinges on the words "he knew" ie. wot he knew.  He new, (or maybe I should say there is a suggestion or interpretation that he may have ?)  that there was something wrong with the orbit of Mercury in his model but he chose not to make a big deal about it and no one else cottoned on for quite some time.

Then take "he knew" out and I still stand bybthe statement I made. The error in the orbit of Mercury is not due to the assumption on the speed of light. What he did not know led to the Special Theory of Relativity and Quantum Mechanics. 

Regards Andrew 

[SilverAstro]

1 minute ago, andrew s said:

orbit of Mercury is not due to the assumption on the speed of light.

I know ! (this is the prob with texts!) I was addressing, worrying about, exploring your " Newton managed a coherent model", I dont think he would have considered it coherent if it is true that he knew about the Mercury problem and kept quiet, but SR answers it, coherently so far.

No worries, not a biggie, just interesting thoughts around another "what if" question.

 

[andrew s]

1 hour ago, Paul67 said:

Ill, take a stab, say we now see a galaxy 10,000 light years away, so we see what was happening 10,000 years ago. If it was infinitely fast we couldnt see the past, only the now. However when we approach the current speed of light there are all sorts of distortions, you would see stuff happening almost like before it happened, I think

I think you might have answered it yourself in your opening sentence.

No you would see things exactly as they happened and this is to all intents and purposes (except astronomy) is what we experience in every day life.

Nothing dissapears all seems perfectly normal.

Regards Andrew 

[SilverAstro]

But Newton was constructing a theory of gravity as well, not a theory on the speed of light, he assumed instant propagation of gravity (but didnt rely on it ) but now   we   I have bifuricated ! so I will let @Ouroboros get back to his topic

[Paul67]

19 minutes ago, andrew s said:

No you would see things exactly as they happened and this is to all intents and purposes (except astronomy) is what we experience in every day life.

Nothing dissapears all seems perfectly normal.

Regards Andrew 

That does make sense, think I was confusing travelling at light speed with seeing and still mish-mashed the two up.

[SilverAstro]

3 hours ago, Ouroboros said:

".... if the speed of light were infinite,

"The universe would have no history and no future, and time as we understand it would disappear." 

Why? 

Maybe I will have a go at the "Why?" after all     :-

If the speed of light were infinite then the relativistic mass of each and every photon would be infinite, requiring more energy for each than there is in the universe, which is absurd,  so such a universe could not have existed = no history, if it did not exist it could not have had a future, and we would not be here to understand any of it ! QED ?

It sure beats watching Ch4 news

 

[SilverAstro]

19 hours ago, andrew s said:

I am not sure either statement is true. Newton managed a coherent model of the Universe he new with the assumption that the speed of light is infinite.

Oh, its all gone quiet ! So returning to Newton :

He managed a (reasonably) coherent model of the Universe on the assumption of infinite speed of propagation of gravity.  - de-bifuricate ing

He knew that the speed of light was finite, he knew of Romers determination of it

"In his 1704 book Opticks, Isaac Newton reported Rømer's calculations of  *" from https://en.wikipedia.org/wiki/Speed_of_light "

and he knew that in vacuum there was no difference in the speed of the different colours of light since the astronomers reported no variation in the apparent colour of Io.

*[it in 1676 ]

[andrew s]

2 hours ago, SilverAstro said:

Maybe I will have a go at the "Why?" after all     :-

If the speed of light were infinite then the relativistic mass of each and every photon would be infinite, requiring more energy for each than there is in the universe, which is absurd,  so such a universe could not have existed = no history, if it did not exist it could not have had a future, and we would not be here to understand any of it ! QED ?

It sure beats watching Ch4 news

 

If you use SR to determine the relativistic mass ( energy momentum 4 vector) you can't have an infinite speed of light. For as c goes to infinity SR goes to Newtonian!

Regards Andrew 

[SilverAstro]

9 minutes ago, andrew s said:

energy momentum 4 vector

Yes   but if I had said that I would have lost half  ( or maybe more ! ) of my audience

whereas we all know, in the vernacular, that it is plain silly to talk of accelerating photons to infinite speed, cos we all know that it cant happen, B.Cox and Einstein frequently say it cant But that doesnt seem to stop people wistfully imagining the impossible.

 

[andrew s]

22 minutes ago, SilverAstro said:

Yes   but if I had said that I would have lost half  ( or maybe more ! ) of my audience

 

The SGL audience are like gulons and confined to the forum.

Regards Andrew 

[SilverAstro]

mea culpa

[cloudsweeper]

OK, I'll risk it.  We are moving through spacetime  at the speed of light.  When at rest, we move through just time at c; when travelling at c, there is no sense of space/distance (as when riding a photon you get from Andromeda to Earth instantly).  So - if c were infinite, there would not be any time - or it would all be happening at once.  Or something.

Wasn't AE a genius?

Doug.

[Ouroboros]

44 minutes ago, cloudsweeper said:

OK, I'll risk it.  We are moving through spacetime  at the speed of light.  When at rest, we move through just time at c; when travelling at c, there is no sense of space/distance (as when riding a photon you get from Andromeda to Earth instantly).  So - if c were infinite, there would not be any time - or it would all be happening at once.  Or something.

Wasn't AE a genius?

Doug.

Yes, I think it must be something like that. I have the impression the article was considering what would happen to time in relativistic physics if the speed of light were infinite. 

[andrew s]

3 hours ago, cloudsweeper said:

 When at rest, we move through just time at c

This seems to be a complete contradiction.

3 hours ago, cloudsweeper said:

Wasn't AE a genius?

Yes

3 hours ago, cloudsweeper said:

  We are moving through spacetime  at the speed of light. 

No we are not. We move through time at one second per second and most of the time remain in the same place in space. None of this depends on the speed of light.

4 hours ago, cloudsweeper said:

 when travelling at c, there is no sense of space/distance (as when riding a photon you get from Andromeda to Earth instantly).  

They are perfectly well defined for particles with zero rest mass. Objects with finite rest mass can't travel at c whatever it's value.

Regards Andrew 

[cloudsweeper]

Well I did say I was taking a risk! 

From Professor Brian Greene's The Fabric of the Cosmos, page 49:

Special Relativity declares that the combined speed of any object's motion through space and its motion through time = c.  The idea that nothing can travel at c refers solely to motion through space.  But we are talking about an object's combined motion through space and time.  When a parked car moves away, some of its light-speed motion is diverted from motion through time into motion through space, keeping their (the motions) combined total unchanged.  Maximum speed through space is reached when all light-speed motion through time is fully diverted into light-speed motion through space.  Light is a special case in that it achieves such total diversion....moving at light-speed through space leaves no motion for travelling through time.  Time stops when travelling at c through space.  A watch worn by a particle of light would not tick at all.

Back to me:

Not easy concepts.  Part of the problem with comprehension is I believe that we intuitively separate space and time (as in the Newtonian model), whilst Einstein blew that separation away.  Professor Greene's explanation sheds light on this issue.

Doug.

 

[andrew s]

Doug can you give the formula from the book that justifies the first statement in your quote as I don't have the book. I have not come across such a formulation before.

 

The standard formulation relates the proper distance between events on a world line. 

Regards Andrew 

[cloudsweeper]

9 minutes ago, andrew s said:

Doug can you give the formula from the book that justifies the first statement in your quote as I don't have the book. I have not come across such a formulation before.

 

The standard formulation relates the proper distance between events on a world line. 

Regards Andrew 

Andrew - Greene doesn't back this up with maths unfortunately.  I studied QM at uni, but sadly not Relativity, so I found Greene's book one of the most enlightening sources for the subject.  You can pick up a copy on Amazon for not very much:

https://www.amazon.co.uk/s/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords=fabric+of+the+cosmos

Regards,

Doug.

[andrew s]

Thanks Doug, I will probably down load it to read while baby sitting my granddaughter next week. In the evening while she is asleep!

In the end I note that as c goes to infinity the equations of SR go to Newton's and

 c is finite and so how the Universe would be if it were infinite is mute.

Regards Andrew