# The aether

1. Feb 23, 2005

### jenst

I've never understood how the aether was dispensed with. It is said that Maxwell's equations don't require it. If that is the case, then where do the x, y and z axes come from if not from an aether.

2. Feb 23, 2005

### Andrew Mason

You may be confusing 'inertial reference frame' with the aether. A mass that is not subject to a net force (ie is moving at uniform velocity) defines an inertial reference frame - all points in the universe at all times can be expressed as coordinates in that reference frame and the laws of physics as measured in that frame will be the same as that measured in any other inertial reference frame. The aether was thought to define a particular inertial reference frame, based on the theory that the aether acted as the 'medium' for light. Its non-existence does not imply anything about other inertial reference frames.

AM

3. Feb 28, 2005

### reasonmclucus

The idea of an aether was dropped in part because of false assumptions in the Michelson-Morley experiment. Michelson theorized the idea of an "aether wind" that would affect the speed of light. Light going against the wind would travel at a different speed than light traveling with the wind. He cited the example of two people swimming in water.

The problem with the analogy is that a person swimming in water is not even the same as a wave moving through water. Moveover, water waves, unlike light waves don't all travel at the same speed. The wave produced by dropping a pebble in a pond travels at a much slower speed than a wave produced by a tsunami.

4. Mar 3, 2005

### evthis

space without ether is unthinkable

in Ether and the Theory of Relativity, Albert Einstein eventualy writes:"According to the general theory of relativity, space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense."

5. Mar 3, 2005

### Staff: Mentor

There are several threads with this quote explained: it is the accepted view of the physics community that Einstein's aether is not the lumiferous aether of the 19th century. It doesn't have several features that were key elements of the lumiferous aether. Namely, there is no physical medium (ie air for sound waves) and there is no motion through it.

6. Mar 3, 2005

### evthis

Einstein stated that there must be an aether for the propogation of light....why would he say this if light didn't need a physical medium for which to travel through?

7. Mar 3, 2005

### Staff: Mentor

Because he was defining a new aether. Essentially, he was saying, there is still 'something' there, it just isn't what we used to think it was.

8. Mar 3, 2005

### evthis

So what properties does this new aether require for it to be able to propogate light?

9. Mar 6, 2005

### reasonmclucus

An aether composed of photons, possibly in a zero energy state, would allow waves to propagate through it in much the same way waves propagate through water or air. Some event would create an energy pulse that would transmit energy from photons to adjacent photons much like water waves transmit energy pulses from water molecules to adjacent water molecules.

In a wave the energy moves from source of the energy to the receiver of the energy rather than having the elements of the medium move from point to point.

A photon aether could also allow photons to move from point to point in the same way that water molecules, or drops, move from point to point.