The discussion revolves around the nature of the medium through which light propagates. Participants explore whether light requires a medium, what that medium could be, and the implications of various theories, including classical and quantum perspectives. The conversation touches on historical concepts like the aether and contemporary understandings of electromagnetic fields and space-time.
There is no consensus on whether light requires a medium, with multiple competing views presented. Some participants firmly believe light does not need a medium, while others explore the idea of electromagnetic fields and space-time as potential mediums.
Participants highlight the historical context of the aether theory and its implications for modern physics, noting that doubts about the necessity of a medium for light may challenge foundational concepts in physics.
Nope, doesn't need a medium or an astrologer:) Just a good storyteller like Einstein:)Doc Al said:Light does not require a medium.
Classically? The electro-magnetic field.aiop said:Waves on water require water to move, sound waves require a medium of the like. My question is what do light waves move in. Empty space contains not much more then low density hydrogen, what medium could light possibly be moving in.
aiop said:Empty space contains not much more then low density hydrogen, what medium could light possibly be moving in.
As have all subsequent experiments with ever greater precision and a multitude of techniques.pixel said:The famous Michelson-Morley experiment failed to find evidence of this.
It would seem to me that space time is this fundamental layer on which all the rest of the fields exist. While true that light does get affected by space-time, but so is everything else regardless if charged, neutral, magnetic or relativistic. Anything that has energy gets affected by space-time.BillTre said:Could one say the medium through which light moves is space-time?
Without space-time, there would be nothing for the light to do movement-wise.
Also a warped space-time affects the movement of the light.
No. Although it makes sense to speak of moving in space (the position changes with time), it is not at all clear what could be meant by moving in space-time - what's changing with respect to what?BillTre said:Could one say the medium through which light moves is space-time?
jtbell said:One could say that the electromagnetic field that permeates the universe is the "medium" for light.
BillTre said:Perhaps my understanding of medium is limited.
How is it defined?
davenn said:as a substance for the/allows the wave to propagate ( supports the wave propagation)
How? What are it's properties that are harnessed for propagation of light? For example, air has mass/density, pressure and elasticity (compressibility) that enables sound propagation.BillTre said:So why not space-time?
It allows light to propagate.
russ_watters said:How? What are it's properties that are harnessed for propagation of light? For example, air has mass/density, pressure and elasticity (compressibility) that enables sound propagation.
One of the key characteristics of a medium is that it has a rest frame. Spacetime does not. If you were to make such a statement then you could only do it by redefining the term "medium" to get rid of that key feature.BillTre said:Could one say the medium through which light moves is space-time?
There is NO medium necessary for light...what else is there to add?...how do you go from this point?BillTre said:Thanks @russ_watters and @lychette.
So, sounds like you guys are saying the defining property of a medium, in this sense, is that the medium is involved in the movement of a wave itself (a propagated displacement), such as water or air waves move through a medium of water or air because the water or air molecules are actually moving (up and down or back and forth) instead of just something it moves through.
In which case it seems to me that space-time would be the medium for gravity waves but not light waves, but no one has said that (at least in a way that I understand).
Seems to be required for propagation, affects the propagation of light (as ether was claimed to do).
You should never worry about causing upset here!BillTre said:My questions were directed at getting a better understanding of how the word medium was defined in this context.
In the process, I have been exploring other
It seems to me that the term medium has 2 characteristics relevant to the situation (based on responses):
1) basis of a propagated wave, such as air or water waves, little bits that move in response to their neighbors.
2) having a rest frame of reference (had not thought of that before)
This is getting at a definition, which is what my initial post was about.
Sorry to upset you.
lychette said:wasn't that called the aether 100 years ago?
lychette said:What is slightly worrying is that a fundamental basis of modern physics can be doubted (that there is a 'medium' necessary for the transmission of light) doubting this means that all the conclusions based on this premise are also doubted. Anyone with these doubts should look at the evidence in modern physics and re-asses their doubts.
You are moving from one point in time to another.Nugatory said:...it is not at all clear what could be meant by moving in space-time - what's changing with respect to what?
Or: "Your position in space time is a continuous, non-constant function of your experienced proper time", thus avoiding the term "move".David Lewis said:You are moving from one point in time to another.