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Explaining the sped of light

T

T.G.G. Moogly

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The speed of light is constant. Doesn't matter the position or speed of the observer. This we know.

So is this because the speed of light is really just the speed of the expanding space?
 
To answer your question, NO.

How do you conclude that the expansion of the universe has anything to do with the speed of light between the Sun and Earth or the speed of light in your living room?

We can explain that the speed of light is a constant but the answer to the question of why can only be, "because that is the way it is", the same as why the mass of a neutron is what is and the charge of electron is what it is. Could they be different? We don't know but we have never seen them to be different.
 
Good video, but I wonder about an example of a very old object that is seen by us now. Say it is a galaxy that is 13 billion years old. IIRC, it will be about 31 billion light years away. I forget the terminology for distance, is it comoving distance?

So, does that mean that in the 13 billion year since the object was at that location there was (18 billion years*c) distance of space created between us? Actually, it was probably more than that.
 
Gila Guerilla said:
joedad said:
The speed of light is constant. Doesn't matter the position or speed of the observer. This we know.

So is this because the speed of light is really just the speed of the expanding space?
Click to expand...

But the speed of light is not constant, it varies depending on what medium it is passing through.
Click to expand...
Photons can only move at c. When light propagates through a medium it is being absorbed and re-emitted numerous times. The frequency at which that occurs depends on the frequency of the light. That absorption and re-emission slows down the propagation of light through a medium. The speed of the photons, and thus the speed of light itself, is always constant.
 
joedad said:
The speed of light is constant. Doesn't matter the position or speed of the observer. This we know.

So is this because the speed of light is really just the speed of the expanding space?
Click to expand...

If the Lorenz transformations truly are what is happening, then time stops for a photon as it travels through the universe. The universe also becomes infinitely flat for that photon perpendicular to the direction it travels. So this means that it has always existed from one side of the universe to the other side. It is our observation of it that gives us the illusion that it is moving. It's like finding a perfectly one dimensional string, and when it expands into a two dimensional object, there is something stretching with it.

So, I think you are kind of right, except that instead of light travelling through the universe, it grows with it from one end of the universe to the other.
 
joedad said:
The speed of light is constant. Doesn't matter the position or speed of the observer. This we know.

So is this because the speed of light is really just the speed of the expanding space?
Click to expand...
I have two separate notions of an expanding universe, and I'm not sure which one is accurate.

One notion is where the objects in the universe are simply (simply) moving further apart (perhaps due to gravitational forces). Imagine dumping some trash on the ground. The objects in the yard will simply (simply) move further apart (perhaps due to occasional wind gusts). Every hour, we could take distance measurements and calculate average speed.

The second notion also has the effect of objects moving further apart but because of a stretching of space itself. If an earthquake creates an occasional opening gap, the trash will have a greater distance and therefore a greater average speed.

In the first instance, the actual distance measurement and average speed is merely a function of simple things like wind whereas the second notion, the added distance measurement and added average speed is a function of more complex things like actual space expansion.

The thing is, what do we really mean by expanding space? Is it figurative and thus like the first notion, or is it literal and thus like the second notion?
 
Particles without rest-mass (such as photons) do not experience time, and so speed is a meaningless concept for such objects. (As is sped :p )

From the reference frame of any entity with rest-mass, such particles always appear to propagate at c.

This is unrelated to any expansion of space.
 
bilby said:
Particles without rest-mass (such as photons) do not experience time, and so speed is a meaningless concept for such objects. (As is sped :p )

From the reference frame of any entity with rest-mass, such particles always appear to propagate at c.

This is unrelated to any expansion of space.
Click to expand...
My understanding of the red shift of distant objects is that space is expanding. The reason more distant objects are more red-shifted is because the intervening space is expanding, and the more intervening space there is the more expansion, and hence the greater red shift.

Further I understand that because of this there is a cosmic event horizon beyond which we cannot see because it is essentially the same as the event horizon at a black hole.

So if a photon is everywhere all the time then it must be expanding, must be part of spacetime. Right?
 
ryan said:
bilby said:
Particles without rest-mass (such as photons) do not experience time, ...
Click to expand...

Would you mind backing that claim up?
Click to expand...

Well, from a layman POV, I have read that neutrino oscillation is proof that neutrinos must have at least some mass or they would not experience time and change type.


Gluons are massless force carrying particles and also do not oscillate between types. Photons are not multi type.

Probably there is some info on this blog, which is probably the best for scientifically literate laymen:

https://profmattstrassler.com

It would probably be best to send most particle physics type questions to the search bar of that blog first.
 
ryan said:
bilby said:
Particles without rest-mass (such as photons) do not experience time, ...
Click to expand...

Would you mind backing that claim up?
Click to expand...

It's a consequence of simple arithmetic. As we know from the twin paradox, the moving observer experiences time passing more slowly than his stay at home twin. The faster his journey, the less time he experiences; For a journey that takes place entirely at c, the apparent time elapsed is equal to the time as measured by the stationary observer, multiplied by zero.
 
bilby said:
ryan said:
Would you mind backing that claim up?
Click to expand...

It's a consequence of simple arithmetic. As we know from the twin paradox, the moving observer experiences time passing more slowly than his stay at home twin. The faster his journey, the less time he experiences; For a journey that takes place entirely at c, the apparent time elapsed is equal to the time as measured by the stationary observer, multiplied by zero.
Click to expand...
They experience neither time nor space for all intents and purposes.
 
And this is where the road divides.
One path for those who think matter creates consciousness,
Another for those who think consciousness creates matter.

Either matter is sentient or it is not.
 
Space is expanding on the scale of distant galaxies and such. What that means is for any observer in this Universe, there is a distant point in any direction that is essentially beyond our ability to see because to do so means photons, to reach us would have to be travelling faster than speed of light. Apparently in a billion years we would no longer be able to see anything from the earliest days of the big bang because of this.

And that explains Olber's paradox.

In say about ten billion years, a future civilization would not be able to observe much of the early era of the Universe as we can today. We live in a cosmologist's Golden Age as far as observation goes. This all is a problem for Process theology, whose panentheistic God is claimed to be dependent on matter. Such a God would someday be master of a mainly empty heat dead Universe.

I have no idea what that would mean for planet Kolob.
 
migrant said:
And this is where the road divides.
One path for those who think matter creates consciousness,
Another for those who think consciousness creates matter.

Either matter is sentient or it is not.
Click to expand...

Matter is conscious, but only in certain very rare configurations. Such configurations might evolve in the right conditions, but those conditions are themselves fairly rare. It's needlessly confusing to say 'matter creates consciousness' IMO, and likely to mislead people into thinking you embrace pantheism.

Perhaps it's better to say 'consciousness requires matter' (which clearly rules out consciousness as the origin of matter). </2c>
 
I may be confirming your worst fears bilby, but I do regard matter as the product of consciousness.
Simply because it fits my overall view of the world, making sense with what I experience, yet being far too complex for comprehension on my level.
To clarify, or possibly cause further confusion, I agree with C S Lewis's words :-
"I do not have a soul, I am a soul. I have a body". For me, this says that my consciousness can exist without the body, but not vice versa.
I must emphasise that although my view differs from yours, I am not here to argue with your understanding of the world -- I think we just see different sides of the same coin. A coin which has as many sides as observers.

To scuttle back to the topic, there is no proof that I'm aware of that light travels at all.
But I do know the speed of dark.
 
migrant said:
I may be confirming your worst fears bilby, but I do regard matter as the product of consciousness.
Simply because it fits my overall view of the world, making sense with what I experience, yet being far too complex for comprehension on my level.
To clarify, or possibly cause further confusion, I agree with C S Lewis's words :-
"I do not have a soul, I am a soul. I have a body". For me, this says that my consciousness can exist without the body, but not vice versa.
I must emphasise that although my view differs from yours, I am not here to argue with your understanding of the world -- I think we just see different sides of the same coin. A coin which has as many sides as observers.

To scuttle back to the topic, there is no proof that I'm aware of that light travels at all.
But I do know the speed of dark.
Click to expand...

The existence of anaesthesia demolishes your hypothesis completely.

When your overall view of the world conflicts with clearly demonstrable facts, it's time to change your view.
 
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