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Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: petelamana on 20/02/2018 13:44:14

Title: Why must c be an absolute "speed limit"?
Post by: petelamana on 20/02/2018 13:44:14
I have a simple, and yet nagging question...

Why must the speed of light, c, be an absolute "speed limit"?

Why can't something, anything exceed 299,792,458 m/s?  Why can something go 299,792,459 m/s?
Title: Re: Why must c be an absolute "speed limit"?
Post by: Kryptid on 20/02/2018 14:17:01
Strictly-speaking, it is possible in theory for an entity to move faster than light. Such things are called "tachyons". However, they have the opposite problem that normal matter does: they cannot slow down to below the speed of light. So far, no tachyons have been definitively detected.

Normal matter cannot reach or exceed the speed of light due to energy requirements. The closer an object with mass gets to the speed of light, the more its mass increases and the more energy it requires to move faster. At low, everyday speeds, it isn't noticeable. Very close to the speed of light, the energy requirements explode exponentially. Both mass and kinetic energy approach infinity as you zero in on light-speed. Since there is no method of giving infinite energy to matter, all matter is stuck below the light-speed limit.
Title: Re: Why must c be an absolute "speed limit"?
Post by: wolfekeeper on 20/02/2018 15:42:17
Objects are held together by electrostatic forces, which are mediated by photons that travel at the speed of light. That means if you wobble an electron it takes a tiny moment for the forces on the proton to respond; and also when an object moves the electric field is no longer spherically symmetric, it becomes ellipsoid.

It takes an infinite amount of energy to make an object go faster than light, but if somehow an object found itself going faster than light, the electric fields wouldn't keep up with the electrons and protons, so they would no longer be bound together as atoms and molecules and the object would fall to pieces.
Title: Re: Why must c be an absolute "speed limit"?
Post by: geordief on 20/02/2018 16:53:08
Can the question also be asked "Why is there any maximum speed limit?"

As far as I  have understood , there must be a maximum speed limit and  it looks like c is it since it lies at the heart of all processes that have been observed .

It is the fastest that any object has been observed to go  and since there must be a maximum speed  of some kind the c is the obvious candidate.

I have also understood that c is a function of both the permittivity and the permeability of a vacuum.

So if these observed values were different ,c would also have a different value.

But there would still be a maximum speed limit.
Title: Re: Why must c be an absolute "speed limit"?
Post by: jeffreyH on 20/02/2018 17:19:08
Objects are held together by electrostatic forces, which are mediated by photons that travel at the speed of light. That means if you wobble an electron it takes a tiny moment for the forces on the proton to respond; and also when an object moves the electric field is no longer spherically symmetric, it becomes ellipsoid.

It takes an infinite amount of energy to make an object go faster than light, but if somehow an object found itself going faster than light, the electric fields wouldn't keep up with the electrons and protons, so they would no longer be bound together as atoms and molecules and the object would fall to pieces.

Now that is a very interesting post.
Title: Re: Why must c be an absolute "speed limit"?
Post by: Janus on 20/02/2018 17:43:13
I have a simple, and yet nagging question...

Why must the speed of light, c, be an absolute "speed limit"?

Why can't something, anything exceed 299,792,458 m/s?  Why can something go 299,792,459 m/s?
It boils down to the nature of time and space and their interrelationship to each other.   The speed of c plays an important part of that relationship.      It is the invariant speed for the Universe (the speed everyone measures as having the same value with respect to themselves) Newtonian physics also can be said to have an invariant speed, but it is infinite in value.   c is finite.
Once you have a finite invariant speed, it automatically falls out that it becomes the universal speed limit. 

If you are asking why the universe has an finite invariant speed, then the best I can say is that you should be glad that it does.  Many of the fundamental interactions that allow complex structures, from subatomic particles on up, to even exist rely on Relativity and the fact that this finite invariant speed exists.    In other words, it might not even be possible for a universe without it to have the type of complexity needed for beings capable of asking the question to form in the first place.
Title: Re: Why must c be an absolute "speed limit"?
Post by: chiralSPO on 20/02/2018 18:36:15
I have heard the fact that there is a "speed limit" invoked as evidence supporting the Simulated Universe theory (the idea that are universe is actually a complex simulation--I am not a big fan of this idea, because I am not sure if it is falsifiable, but at any rate, I don't think we have any evidence either way, so I am willing to entertain the notion periodically...)

If I were the Programmer, I would probably have (or need) a maximum speed at which simulated information could move about. That the universe appears to expanding at superluminal speeds at the edges of our observable universe could also be a nice trick invoked to prevent the Processor from needing to crunch infinitely many operations per unit time (of course, once we start thinking about the universe in which our universe exists, who knows if "time" is meaningful.)

Problems with this theory include, "well this doesn't answer anything, it just puts the 'real' universe beyond our observation," and "wouldn't a Simulator need some sort of universal frame of reference?"

(these are the sorts of ridiculous answers that can come up when "why" questions are posed)
Title: Re: Why must c be an absolute "speed limit"?
Post by: petelamana on 20/02/2018 18:46:38
(these are the sorts of ridiculous answers that can come up when "why" questions are posed)

My apologies.  I will endeavor to phrase my post questions more succinctly.
Title: Re: Why must c be an absolute "speed limit"?
Post by: chiralSPO on 21/02/2018 02:47:38
(these are the sorts of ridiculous answers that can come up when "why" questions are posed)

My apologies.  I will endeavor to phrase my post questions more succinctly.

I'm mostly ribbing :) But if you haven't come across it yet, this is worth a watch:

Title: Re: Why must c be an absolute "speed limit"?
Post by: evan_au on 21/02/2018 08:39:42
Quote from: petelamana
Why must the speed of light, c, be an absolute "speed limit"?
c isn't an absolute speed limit, absolutely everywhere, absolutely all the time.

If you are in a gravitational well*, your time is slowed compared to points outside this gravitational well.
- It is possible to see things happening outside this gravitational well that are happening slightly faster than the speed of light.
- So the speed of light is an absolute limit here, but it's not necessarily an absolute limit there.
- If you then travel over there (so "there" is now here), you would find that things here are not now exceeding the speed of light.

This is why some aspects of relativity are expressed as being measured in a "small" room - because if you measure on larger scales, the results can be different.

*we are in the Earth's gravitational well, which is in the Sun's gravitational well, which is in the galaxy's gravitational well...
Title: Re: Why must c be an absolute "speed limit"?
Post by: opportunity on 21/02/2018 09:42:58
Well, let's say "infinite speed" is a no go, because according to the "big bang" theory light travelling at infinite speed would be technically unregistrable and completely futile to the idea of an "expanding" universe.

So, let's talk about "variable speed".

"Variable speed" suggests many other factors we well know in physics must also be variable, which gives a "Gooey" understanding of reality for our reference as humans.....like silly-putty.

A constant speed for light can't be as simple as relying on an "expanding" universe, or even our own relativite rigidity as conscious beings.

If I could suggest "space" has a tolerance for light, like it acts as a "wall", seeming to give light "mass" qualities perhaps, like light is stuck in it somehow at a certain rate of progression. Of course we've heard of the mythical "ether", yet, the question remains, why is light stuck at "c".

If we form our theories on the universe using "c".....i just casn't help thinking a steady state universe is what this is...... did light expand at a constant rate from the big bang? Why? It's like the cops already set the speed limit.....how?



Title: Re: Why must c be an absolute "speed limit"?
Post by: geordief on 21/02/2018 10:36:34
Quote from: petelamana
Why must the speed of light, c, be an absolute "speed limit"?
c isn't an absolute speed limit, absolutely everywhere, absolutely all the time.

If you are in a gravitational well*, your time is slowed compared to points outside this gravitational well.
- It is possible to see things happening outside this gravitational well that are happening slightly faster than the speed of light.

References? I find that hard to believe but ,as they say argument from incredulity is no argument.

(I am aware of  expansion ongoing at superluminary speeds but that is unconnected. Also entanglement does not allow for information transfer at  superluminary speeds either....

Also aware that time passes everywhere at 1 sec per second. What is your scenario exactly in this case? )
Title: Re: Why must c be an absolute "speed limit"?
Post by: Colin2B on 21/02/2018 10:56:03

References? I find that hard to believe but ,as they say argument from incredulity is no argument.

Also aware that time passes everywhere at 1 sec per second. What is your scenario exactly in this case? )
The reference is GR.
Scenario as @evan_au says is "If you are in a gravitational well, your time is slowed compared to points outside this gravitational well."

PS it is also confirmed by experiment and by operation of GPS
Title: Re: Why must c be an absolute "speed limit"?
Post by: geordief on 21/02/2018 11:24:47

References? I find that hard to believe but ,as they say argument from incredulity is no argument.

Also aware that time passes everywhere at 1 sec per second. What is your scenario exactly in this case? )
The reference is GR.
Scenario as @evan_au says is "If you are in a gravitational well, your time is slowed compared to points outside this gravitational well."

PS it is also confirmed by experiment and by operation of GPS
Well how does that affect the measurement of c? How much faster than c  do or can  (information bearing ?)  processes seem to happen outside a gravitational well for an observer inside it?

Title: Re: Why must c be an absolute "speed limit"?
Post by: opportunity on 21/02/2018 12:01:29
I thought the gravitational well is currently held by the Planck scale? Shouldn't light consider a blockade anything lower than that? Apparently there's a lot of energy per cubic metre below that which light clearly bounces off, doesn't get into, right?
Title: Re: Why must c be an absolute "speed limit"?
Post by: opportunity on 21/02/2018 12:11:19
I thought the gravitational well is currently held by the Planck scale? Shouldn't light consider a blockade anything lower than that? Apparently there's a lot of energy per cubic metre below that which light clearly bounces off, doesn't get into, right?

When I talk about light considering a blockade there, I'm  giving light some type of "wow, I'm at the Plank scale, and according to humans I can't go deeper" thing.

That's a wall, right? Why is the speed of light consequential of the Planck scale?

If I was light, I'd be happy with electron shells.

We can theorise things to connect dots, but we can't, shouldn't screw around badly, not too much, with how nature shows itself to us. Maybe? What if we're wrong about the sub-elemetary particle realm, you know, "not quite right yet". Can we have that discussion?

It's underatandble. On the small scale there's is a volcano of energy available on the Planck scale, and on the large scale we can't work out where all the forces comply? That's so stupid, apologies for saying that. Doesn't the large scale imply the small scale and vice-versa?
Title: Re: Why must c be an absolute "speed limit"?
Post by: geordief on 21/02/2018 12:33:23
I thought the gravitational well is currently held by the Planck scale? Shouldn't light consider a blockade anything lower than that? Apparently there's a lot of energy per cubic metre below that which light clearly bounces off, doesn't get into, right?

When I talk about light considering a blockade there, I'm  giving light some type of "wow, I'm at the Plank scale, and according to humans I can't go deeper" thing.

That's a wall, right? Why is the speed of light consequential of the Planck scale?

If I was light, I'd be happy with electron shells.

We can theorise things to connect dots, but we can't, shouldn't screw around badly, not too much, with how nature shows itself to us. Maybe?

I don't understand your post (my level of understanding no doubt) but are we not really firstly considering the maximum speed of information?

Does Planck level have any bearing on that?

Do permittivity or permeability  have any role at those levels?
Title: Re: Why must c be an absolute "speed limit"?
Post by: opportunity on 21/02/2018 12:39:29
No, no effect, that's the idea of the Planck scale. It's like if you're light and you dive deep and hit a level, that's the Planck scale. No reflection though, apparently.....only the "bequeathment" of "mass" via equations.....and yet the energy according to equations there is immense. I thought if light could disobey it could do anything?

I'm sorry if that's not making sense. If it's not, just ignore this.

I question the idea of the Planck scale also, and how light and mass has an actual speed of light bearing there.....like it's a "limit".......we talk about limtis.....here's a limit.

I'm hopeless. The subelementary particle realm to the Planck scale is more immense than us to the Kuiper belt, maybe even to Alpha Centauri and beyond, and it seems a question of introversion, looking within...beyond the idea of a fundamental particle? Drink that idea in. Apparently there's no inner universes there either.

As a scale, it's the most vast "nothing", and then we hit the Planck scale. That's an impressive equation to consider, even for light.

Why can't we ask if the Planck scale limits light? Is the Planck scale something of convenience in bridging an absolute abyss itself of mathematical uncertainty, or really something that limits light through such scales with nothing else from the atom to itself to account for?
Title: Re: Why must c be an absolute "speed limit"?
Post by: jeffreyH on 21/02/2018 14:02:06
Just to be absolutely, unequivocally clear. There is a mass/energy equivalence and not a matter/energy equivalence. Puppypower is posting nonsense.
Title: Re: Why must c be an absolute "speed limit"?
Post by: Colin2B on 21/02/2018 14:31:32
Just to be absolutely, unequivocally clear. There is a mass/energy equivalence and not a matter/energy equivalence. Puppypower is posting nonsense.
Iíve removed the offending post to new theories
Title: Re: Why must c be an absolute "speed limit"?
Post by: opportunity on 21/02/2018 14:37:43
Newton offered formulas for gravity.

Einstein offered relativity for "objects" and time.

Dirac offered what is very little understood, the increase of energy with bodies moving closer together in a field influence.

Many then sought particle and anti-particle obliteration to accommodate for Dirac's ideas regarding energy.

The search is then, as that unfolded, "energy equivelenace" which pre-supooses it seems an equation to balance everything?

What are we looking for exactly? A correct and useful way to more efficenitly use travel through space?
Title: Re: Why must c be an absolute "speed limit"?
Post by: Colin2B on 21/02/2018 14:42:44
I thought the gravitational well is currently held by the Planck scale?
I donít understand your comment, or your 3 subsequent posts below.
Nothing in the planck constant or length implies a speed limit, that comes from Maxwellís equations not Planck.
Title: Re: Why must c be an absolute "speed limit"?
Post by: opportunity on 21/02/2018 14:46:15
I thought the gravitational well is currently held by the Planck scale?
I donít understand your comment, or your 3 subsequent posts below.
Nothing in the planck constant or length implies a speed limit, that comes from Maxwellís equations not Planck.

You'll have to help me here. Quanta is an atomic phenomena. I'm like you, "how does that work on the Planck scale"?
Title: Re: Why must c be an absolute "speed limit"?
Post by: Colin2B on 21/02/2018 17:45:29
"how does that work on the Planck scale"?
Nothing on the Planck length or constant implies a speed limit. Need to look elsewhere eg Maxwell
Title: Re: Why must c be an absolute "speed limit"?
Post by: evan_au on 21/02/2018 21:06:09
Quote from: geordief
How much faster than c  do or can  (information bearing ?)  processes seem to happen outside a gravitational well for an observer inside it?
It depends on your frame of reference.

If you manage to position yourself close to the event horizon of a supermassive black hole (without getting scattered into an accretion disk), time is slowed dramatically, and events outside the galaxy could appear to be happening much faster than the speed of light. It just depends on how close you can get to the event horizon.

And that's ok, because in General Relativity, everything is Relative to your frame of reference (including your local speed of light in a vacuum, which is always c).

Quote from: opportunity
On the small scale there's is a volcano of energy available on the Planck scale, and on the large scale we can't work out where all the forces comply?
A development quite independent of the Plank scale is String Theory.

In this hypothesis, the universe consists of more dimensions than our familiar 4 dimensional spacetime - as many as 10 dimensions, in some versions.

The reason we don't see these extra dimensions is because they are "rolled up" really small. So you really can't travel very far along these dimensions before you end up where you started.

If correct, these rolled up dimensions would have a major impact on the world around us - if we imagine subatomic particles as waves, only waves that have an integer number of wavelengths along these dimensions could be stable; all others would interfere with themselves and collapse. This would affect fundamental aspects of our universe, including the speed of light.

But for now, string theory is just a hypothesis - it has managed to reproduce Einstein's General Relativity (apparently including the fact that gravitational disturbances travel at the speed of light), but has not yet reproduced Maxwell's equations of electromagnetism, or the Standard Model of subatomic particles.

See: https://en.wikipedia.org/wiki/Superstring_theory#Extra_dimensions
Title: Re: Why must c be an absolute "speed limit"?
Post by: jeffreyH on 21/02/2018 22:15:53
String theory isn't simple enough to be correct. Quantum mechanics is simple and self contained. As is special relativity. Once you start having to expand the complexity to try to make sense of a theory then you are obviously on the wrong course. The blindingly obvious is being missed somewhere.
Title: Re: Why must c be an absolute "speed limit"?
Post by: opportunity on 22/02/2018 00:09:24
String theory isn't simple enough to be correct. Quantum mechanics is simple and self contained. As is special relativity. Once you start having to expand the complexity to try to make sense of a theory then you are obviously on the wrong course. The blindingly obvious is being missed somewhere.

Completely agree.

If there is an elegant solution available, it more than likely will make quantum mechanics and relativity crystal clear. Considering how to avoid string theory also means re-addressing the same questions that lead to string theory yet with different answers.
Title: Re: Why must c be an absolute "speed limit"?
Post by: jeffreyH on 22/02/2018 12:12:12
It is always worth revisiting the history of science. Reading the biographies of the science pioneers can give a better insight into the development of ideas and theories. It will never be easy to overturn a mainstream theory without a well grounded understanding of the background of its development. Also an understanding of the mathematics is a necessity.
Title: Re: Why must c be an absolute "speed limit"?
Post by: phyti on 22/02/2018 17:05:31
No one mentioned the fact that energy is transferred at c, therefore the faster an object moves, the more time required to accelerate the object. Time dilation prevents an object from reaching c.
It is the same reason for the (obsolete) increase in relativistic mass.
Title: Re: Why must c be an absolute "speed limit"?
Post by: Colin2B on 22/02/2018 18:23:38
Maybe I need show how it is broken, but I run the risk of  censor due to misunderstanding.
No problem, show us in New Theories