# History question on aether

## Main Question or Discussion Point

I'm working problems on vibrations in crystal lattice for solid state, and a thought occurred to me. Early 20th century and late 19th century scientists supposed an aether for light to pass through. It seemed reasonable at the time - waves travel in a media.

However, EM waves are transverse. How did they (or did they?) account for the fact that there were no longitudinal light waves?

Another take on the question is this: what material allows transverse but not longitudinal waves? Am I missing something simple?

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ZapperZ
Staff Emeritus
I'm working problems on vibrations in crystal lattice for solid state, and a thought occurred to me. Early 20th century and late 19th century scientists supposed an aether for light to pass through. It seemed reasonable at the time - waves travel in a media.

However, EM waves are transverse. How did they (or did they?) account for the fact that there were no longitudinal light waves?
Hum... I'm not sure why they would need to account for light being only a transverse wave. After all, back then, sound waves was only longitudinal. So if something can be only longitudinal, why can't light be only transverse?

Another take on the question is this: what material allows transverse but not longitudinal waves? Am I missing something simple?
I can't come up with something off the top of my head. Maybe someone else has an obvious example.

Zz.

I can't come up with something off the top of my head. Maybe someone else has an obvious example.
Waves on the surface of a liquid, perhaps? But that's not exactly "in a media" the way the OP wants.

ZapperZ
Staff Emeritus
Waves on the surface of a liquid, perhaps? But that's not exactly "in a media" the way the OP wants.
I guess if you consider different types of waves propagating in (or using) the same medium, that would certain qualify. I don't know of any in which the same type of waves in the same medium have both transverse and longitudinal.

This is not a medium, but phonons have both "optical" and "acoustic" modes/branches.

Zz.

There is no known material that can support transverse displacement oscillations. But a lattice that has an O(3) member at each node can support tranverse 'spin' waves.

jtbell
Mentor
After all, back then, sound waves was only longitudinal.
Can't sound waves in a solid medium be either transverse or longitudinal? Seismic waves, which are sort of like sound, can be either transverse or longitudinal (S and P waves). I don't know when that was discovered, though.

Yes, I could be wrong.

"A new sample holder for excitation of transverse sound waves" Applied Physics A (2002)

A simple non-resonant sample holder with inclined electrodes is described by means of which transverse sound waves in the GHz range are easily generated by an evaporated piezoelectric layer. Because of its small size it is especially well suited for cryostat applications.
I'm not sure if the 'transverse' above just refers to the sample orientation. GHz sound ?

[Edit-------------------------------------------------------------------]
From here

http://www.seismo.unr.edu/ftp/pub/louie/class/100/seismic-waves.html

I learn that P-waves are compression waves like sound, but S-waves are shear waves, like a carpet being shaken. So not sound.

Modern aether theorists admit that it has to be unphysical to carry the two transverse components, and also have non-local causality.

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If the ether (space) is in tension, it can support transverse waves - just as does a stretched string. Robertson and others have explained cosmological red shift as a stretching of space ..There was an interesting theory by MacCullagh (1839) that treated particles as dislocations (voids in the continuum) which gave a decent account of light propagation

Thanks for your replies! They've given me a direction for more research in the topic.