## The speed of light

How does science work? And what's all this about quantum mechanics?

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gaffo
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Joined: Mon Nov 27, 2017 3:15 am

### Re: The speed of light

Cerveny wrote:
Fri Feb 22, 2019 7:44 pm
The speed of light is probably somewhat related to the speed of Universe
FYI physicists assume light and matter behave the same way "at the edge of the universe" as here.

so the same speed of light, chemistry of the elements "out and over there" as here at home.

Scott Mayers
Posts: 1646
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### Re: The speed of light

bahman wrote:
Thu Jan 31, 2019 10:05 pm
The speed of light is a speed at which all events are observed simultaneously. I am wondering why this speed is finite.
If you were moving AT the speed of light AND if this speed were the maximum speed of anything, you technically would not be able to 'observe' anything because your constitution (the matter you are made up of) would also have every point in it translating in one direction, lacking the capacity to BE anything with dimensional functions. That is, you couldn't even have an atom existing at that speed because no electron, for instance, could translate sideways against that path around the nucleus without contradicting it to be at its maximum speed at all points.

As to why there is assumed any finite speed limit at all, ask yourself what might occur IF there were no speed limit to anything?

Certainly if no limits exist as some 'law', we should expect anything regardless of size to have infinite variations in speed. For instance, we should see some identically Sun-sized objects moving at different speeds. If distributed upon all the sky, we should see a variation of close or near stars moving at different speeds in all directions. Because such speeds would also not limit the speed of light, such a single star say moving perpendicular to us should appear as a permanent streak or line through the heavens, some would be so quick as to not appear at all, or some would be at least wondering more plentifully than the planets ("Planets" is a word meaning 'wondering through the 'plane' of view of our sky).

What, you should also ask, is the likelihood of us not being hit by things of all different speeds of any size in any period long enough to survive to see anything at all?

Another point was made by a guy named Obler: he asked why do we not see the sky filled with light everywhere on the assumption of light itself having no speed limit? [This also assumes an infinite size of the universe as well. But if it were finite, we'd still require asking why the size of such a universe is finite and would require a limit in time AND space. This would still mean that given that finite space per finite time, would suggest a fixed maximum speed:

Fixed maximum of SPACE = SPEED LIMIT of the UNIVERSE
Fixed maximum of TIME

So this would at least still beg a finite speed existing somewhere.

So a fixed limited speed has to be inferred unless we and our total observable universe are some unusually and statistically rare place indeed. I'll leave you with this to speculate on. But there are many other thought experiments one can think of similarly that can show we require something fixed about speed of anything at least matter-like or energy-like.

socrat44
Posts: 58
Joined: Tue Jan 15, 2019 4:20 pm

### Re: The speed of light

@Scott Mayers
one thought experiments :
you are swimming in a smock ocean and no
''matter-like or energy-like'' around you:
do you really swimming or it is only your dream ?
can you swim independently ?
P.S.
Light can ''swim'' independently.
Second Postulate of Special Relativity
The speed of light c is a constant,
and independent of the relative motion of the source.
========

Cerveny
Posts: 586
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Location: Czech Republic
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### Re: The speed of light

gaffo wrote:
Sat Feb 23, 2019 4:36 am
Cerveny wrote:
Fri Feb 22, 2019 7:44 pm
The speed of light is probably somewhat related to the speed of Universe (History) growth,
no, no relation, the "speed" of the universe is due to the expansion of space, 97 precent of the universe is "Speeding" out faster than light.
Cerveny wrote:
Fri Feb 22, 2019 7:44 pm
with the speed of time. mc^2 thus can be considered analogous to the universal kinetic energy of mass m.
light is without mass, only mass provides kinetic energy.
Does expand “empty” space, is it diluting? The logic says not - empty space is growing, crystalizing. In case of dilutation all cosmology (constants) lost fixed base, it must be downgraded at the phenemenology, in fact... Another question: Does expand Einstein’s future (cone) too? Is not it already unlimited? Forget “expansion”, it is all such silly:(

As for kinetic energy of photon, see photoelectric effect or Crookes mill...
Last edited by Cerveny on Wed Feb 27, 2019 10:44 am, edited 1 time in total.

Scott Mayers
Posts: 1646
Joined: Wed Jul 08, 2015 1:53 am

### Re: The speed of light

socrat44 wrote:
Sat Feb 23, 2019 8:59 am
@Scott Mayers
one thought experiments :
you are swimming in a smock ocean and no
''matter-like or energy-like'' around you:
do you really swimming or it is only your dream ?
can you swim independently ?
P.S.
Light can ''swim'' independently.
Second Postulate of Special Relativity
The speed of light c is a constant,
and independent of the relative motion of the source.
========
Your translated English is hard to follow. But it sounds like a type of thought experiment Einstein did imagine. If you pretend that you are the only thing in the Universe, you have nothing to compare any 'speed' to. One can extend this to having two people. Using two skaters, for instance, might question if they are spinning with respect to each other. Can you infer they are 'spinning' or not? One proposal is to say you can if they are fully extended away from each other similar to the effects of a centrifuge.

Replace the people with imaginary masses and some string connecting the two. If they do not come together as we expect is natural for masses with gravity to do, if the string remains taught with the masses not coming together, it might suggest spinning is occurring. ....But spinning relative to what, if not some background?

We cannot seem to answer this except to realize that for such to be realized true, an imaginary 'observer' is needed as a third independent thing/mass in this space. So, if 'space' is itself not something itself we can observe directly, then 'speed' is determined as referent changes with respect to other masses. A third mass is thus needed (as a relative 'observer') to notice the two other objects change with respect to each other. IF all mass is not created nor destroyed, AND this implied that all masses are on par with each other as equivalent references relative to one another, then the 'limit' of speed is only defined by the relative factors that make them move with respect to one another, not to some needed background.

For example, let us now imagine then that we are in an ideal spaceship in which we can use any atom's energy it contains in both traditional 'fuel' AND the very components of the ship to accelerate with respect to some original platform we take off from. An ideal third 'observer' is what acts to 'measure' the relative distance of change in space when the craft first leaves that platform. It doesn't matter how fast that frame of reference is with respect to anything else.

When we burn fuel, it basically requires losing mass to the spacecraft to accelerate. Since we imagine we can use all the atoms of the craft to be fuel, the more we accelerate, the more mass we require to lose in order to get faster. But since the space ship is 'finite', then we are limited to accelerate no faster than the fixed quantity of atoms of the craft. Thus, ....for any fixed mass, there is only a fixed maximum speed that anything can be accelerated to because it loses mass used as fuel until it has no mass at all.

This 'proves' in a thought experiment how and why a fixed speed is required about anything observable in space, which includes that which we use to interpret something sensed most remotely, such as light. Therefore, light, being the phenomena we perceive observations fastest with is also our means to map the fastest speed limit to.

socrat44
Posts: 58
Joined: Tue Jan 15, 2019 4:20 pm

### Re: The speed of light

Scott Mayers wrote:
Sun Feb 24, 2019 7:55 am
socrat44 wrote:
Sat Feb 23, 2019 8:59 am
@Scott Mayers
one thought experiments :
you are swimming in a smock ocean and no
''matter-like or energy-like'' around you:
do you really swimming or it is only your dream ?
can you swim independently ?
P.S.
Light can ''swim'' independently.
Second Postulate of Special Relativity
The speed of light c is a constant,
and independent of the relative motion of the source.
========
Your translated English is hard to follow.
. . .
If you pretend that you are the only thing in the Universe,
you have nothing to compare any 'speed' to.
One can extend this to having two people.
Using two skaters, . . .

. . . masses . . .

. . . . 'observer' is needed.
@Scott Mayers
Yeah, it seems i understand you:
without an observer or a fixed point
we don't know if there is a movement.
Thanks
Attachments
observer.jpg (8.59 KiB) Viewed 569 times

socrat44
Posts: 58
Joined: Tue Jan 15, 2019 4:20 pm

### Re: The speed of light

Second Postulate of Special Relativity
Does movement exist if neither observer nor fixed point around?

First Postulate of Special Relativity
Does movement exist if neither observer nor fixed point around?
======

Scott Mayers
Posts: 1646
Joined: Wed Jul 08, 2015 1:53 am

### Re: The speed of light

socrat44 wrote:
Mon Feb 25, 2019 10:42 pm
Second Postulate of Special Relativity
Does movement exist if neither observer nor fixed point around?

First Postulate of Special Relativity
Does movement exist if neither observer nor fixed point around?
======
No, the postulates are:
1. First postulate (principle of relativity)

The laws of physics are the same in all inertial frames of reference.

2. Second postulate (invariance of c)

As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body. Or: the speed of light in free space has the same value c in all inertial frames of reference.

"Postulates of Special Relativity" from Wikipedia entry of this title
The first one is saying that for any subjective place of consistent observation one can be in, the physical laws appear to be equal to any other experience if one were in a different one. This is Galilean Relativity where Galileo recognized (or thought-experimented about) that if you are on a moving platform, like a train, when you toss a ball directly up in the air, to you it will fall down in the same apparent line you tossed it up in, regardless of your faster speed relative to the ground. This means you can predict that if the person on the ground were to toss the ball up in the air, he too would see the same phenomena relative to him. And this holds for a train that might be on some track of the roof the train moving. To those in such an imaginary train, those who repeated this experiment for themselves, would have the same relative result.

The second postulate is an extension of the first more specifically about the phenomena of the measurable speed of light IN that frame. [not what it might appear as looking to someone else's different frame of constant change]. So if you had some apparatus set up in the particular train you are in, for instance, that measures the speed of light, light would appear as equal to the same measure.

This second postulate to me is superfluous except to an underlying expectation that light is also the fastest rate measurable in any frame. The example about tossing the ball is sufficient and needs only the first postulate but the second one was likely to imply that there IS a maximum measurable limit to speeds, which we accept light is its representative maximum.

The extended thought experiments regarding whether movement in space with or without other observers around to determine anything is a philosophical thought experiment that motivates the internal thinking that helped him to derive his hypotheses only. These are not essential to the actual theory beyond a means to how the theory's postulates may have been thought about and to how the interpretation of the final conclusions make sense by those postulates being interpreted in that fashion.

Scott Mayers
Posts: 1646
Joined: Wed Jul 08, 2015 1:53 am

### Re: The speed of light

Note, by the way, when the thought experiments about moving platforms or trains are discussed, it is also assumed that these frames are 'closed' or, not open to the outside in a way that effects what you observe. For instance, if you were on a train car that was an open flatbed, the faster you go the stronger the wind FROM the outside frames have upon your observation. This includes what anyone would literally 'see' through any windows, something that a lot of books written by even apparently authoritative scientists incorrectly use to explain the theory.

gaffo
Posts: 3239
Joined: Mon Nov 27, 2017 3:15 am

### Re: The speed of light

Cerveny wrote:
Sat Feb 23, 2019 5:57 pm
gaffo wrote:
Sat Feb 23, 2019 4:36 am
Cerveny wrote:
Fri Feb 22, 2019 7:44 pm
The speed of light is probably somewhat related to the speed of Universe (History) growth,
no, no relation, the "speed" of the universe is due to the expansion of space, 97 precent of the universe is "Speeding" out faster than light.
Cerveny wrote:
Fri Feb 22, 2019 7:44 pm
with the speed of time. mc^2 thus can be considered analogous to the universal kinetic energy of mass m.
light is without mass, only mass provides kinetic energy.
Does expand “empty” space, is it diluting? The logic says not - empty space is growing, crystalizing. In case of dilutation all cosmology (constants) lost fixed base, it must be downgraded at the phenemenology, in fact... Another question: Does expand Einstein’s future (cone) too? Is not it already unlimited? Forget “expansion”, it is all such silly:(

the univese - space/time/ect is a expanding into.................."something" we know nothing about. with space.time.etc. maybe/probably.

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