Vacuum = Medium? (1 Viewer)

[eX-Bhai]

Is a vacuum classified as a medium?.. cauz im like totally lost about this Aether stuff.. if it isnt a medium, then it all makes sense..

 

[PLooB]

Aether was just a theory, which was later disproved.

I'm quite sure a vacuum is NOT classified as a medium, because transverse waves don't need a medium to propagate and transverse waves can travel through it while logitudinal waves (eg. sound) can not.

 

[COCO_moiselle]

no, a vacuum is definitely not a medium

- 19th century physicists concluded that light was a wave (from experiments such as Thomas Young's double slit experiment, Maxwell's mathematical equations & Helmholtz & Hertz's detection of these waves)

- since they thought that light was a wave, it must need a medium (as does sound, water & earthquake waves)

- noone could find such a medium, so they hypothesized the existence of aether as the mediujm for light & other EM waves

of course now, we know that light and EM waves do not need a medium to propagate and can travel in a vacuum. Therefore aether is not needed and therefore does not exist (occam's razor)

 

[eX-Bhai]

yea i kinda know that.. but when isaac newton stated that space was a vacuum since u couldnt hear any sounds from the sun.. why was it believed that light could not travel through a vacuum?... isnt that how the aether theory started.. they thought there must of been some sort of medium allowing for light waves to travel to earth?

 

[lollee]

That is exactley how the aether theory started the physicists of the day couldnt accept that light could travel without a medium so they theorised that there must be this medium called the aether. The Michelson -Morley experiment was designed to measure the Earths movement through this aether but the null result later lead to Einsteins conclusion that there was no aether

 

[Raginsheep]

Aether was just a theory, which was later disproved.

I'm quite sure a vacuum is NOT classified as a medium, because transverse waves don't need a medium to propagate and transverse waves can travel through it while logitudinal waves (eg. sound) can not.

The aether was never disproved. All the MM experiment did was show that the aether (if it existed) had no bearing on light. Later on, Einstien stated that the existence of aether was inconsequential when discussing light.

As for the original question, just say that light requires no medium for propogation and you'll be fine.

 

[Riviet]

Vacuum =/= Medium lol

 

[Wackedupwacko]

but because nobody wanted to play with aether anymore and einstein came up with relativity (somebody discover time travel and shoot him... it kills the brains studying it) the aether model is basically dead now... i doubt many physicists still believe there is one...

 

[eX-Bhai]

so a vacuum is not classified as a medium? but my physics teacher said it was.. so im kinda confused >_>

 

[Wackedupwacko]

most definately vacuum is NOT a medium....

 

[eX-Bhai]

oh ok.. thanks for all your help.. much appreciated

 

[airie]

The aether was never disproved. All the MM experiment did was show that the aether (if it existed) had no bearing on light. Later on, Einstien stated that the existence of aether was inconsequential when discussing light.

As for the original question, just say that light requires no medium for propogation and you'll be fine.

i thought that aether was this special frame of reference? and that einstein...sort of...CHOSE to believe that aether doesn't exist, cos otherwise it would mean that maxwell's proposal that all EM waves travel at the same speed was wrong? hmm can't remember now. eep. i'll check later and come back to this

 

[Wackedupwacko]

nah aether is a 19th c conception (i think its 19th... mayb from 18th dunno...) that there must be a medium for which EM waves (light to them cuz they havent discovered the other EM waves) could travel. its based around the theory that light is similar to sound (as waves) they refract, travel fast, etc... so they came up with the aether as a medium for it... which in trying to prove that it exists Michaelson and Morley basically proved they dun exist... then came einstein and he just totally ignored aether and said light is constant... and thus we sit here learning relativity

 

[Xayma]

nah aether is a 19th c conception (i think its 19th... mayb from 18th dunno...) that there must be a medium for which EM waves (light to them cuz they havent discovered the other EM waves) could travel. its based around the theory that light is similar to sound (as waves) they refract, travel fast, etc... so they came up with the aether as a medium for it... which in trying to prove that it exists Michaelson and Morley basically proved they dun exist... then came einstein and he just totally ignored aether and said light is constant... and thus we sit here learning relativity

Michelson and Morely didn't prove it didn't exist. They had a null result. No support for the aether but that didn't mean it doesn't exist.

 

[Riviet]

Xayma is correct.

I remember reading in the jacaranda physics textbook about M&M getting "null results" and couldn't disprove anything yet.

 

[airie]

just checked - and apparently maxwell calculated the speed of light (and EM waves), and some physicists at the time thought that this speed would only apply to light in a special frame of reference/inertial system, because of the thinking of classical physics where the addition/subtraction laws apply eg. speed of two trains passing each other etc. experiments carried out however proved otherwise, which meant that either maxwell's calculations of the light speed are invalid (since there was no difference between speed of light travelling parallel to the ground or perpendicular to it and thus did not satisfy the rules of classical physics), or that this special frame of reference - aether - does not exist. einstein chose to believe in the latter, since he figured that if the laws associated with the forces applied in all inertial systems, why not EM laws and other laws in physics? so he proposed these two postulates in his theory of special relativity: that all physical laws apply to all inertial systems without differences, and that the speed of light in vacuum is the same in all inertial systems. hmm. this textbook i check upon actually said that einstein believed that aether does not exist. surely that would be true? seems plausible to me thogh

 

[Riviet]

The only thing that is always constant is the speed of light.

 

[airie]

that's why it's a definition, not a measurement - the length of a metre is defined using the speed of light

 

[angmor]

c = constant. only space and time are relative therefore there is no no need for the aether

 

[Riviet]

My physics teacher argued that a vacuum could be considered as a medium because i medium does not necessarily mean that an energy source must "depend" on it to be transmitted, it can just be described as "light travelling through space, the medium". But that's just his point of view.