The standard answer to "does ether still exist?" is a confident no. But this confidence rests on a conflation: the word "ether" is taken to mean the rigid, mechanical medium of the 1800s, and since that was abandoned, the question is considered closed.
Let us ask a different question: does space have physical properties?
If the answer is yes — and every experiment says it is — then the only remaining issue is what we call it.
Experiment 1: The Casimir Effect
In 1948, Hendrik Casimir predicted that two uncharged, parallel conducting plates placed close together in a vacuum would experience an attractive force. The force arises because the vacuum between the plates supports fewer electromagnetic modes than the vacuum outside, creating a pressure imbalance.
Steve Lamoreaux confirmed this experimentally in 1997, measuring the force to within 5% of the theoretical prediction. The force is real, measurable, and arises from the properties of "empty" space.
A void with no physical properties does not exert forces. The vacuum does.
Experiment 2: The Lamb Shift
In 1947, Willis Lamb and Robert Retherford measured a tiny splitting in the hydrogen spectrum that could not be explained by the Dirac equation alone. The and levels, predicted to be degenerate, are separated by approximately 1,058 MHz.
The explanation: the electron interacts with vacuum fluctuations — the zero-point field of quantum electrodynamics. These fluctuations cause the electron's position to jitter, smearing out the Coulomb potential and slightly shifting the energy levels.
Lamb received the Nobel Prize in 1955. The vacuum fluctuations responsible for the shift are properties of space itself.
Experiment 3: Spontaneous Emission
An atom in an excited state will emit a photon and decay to its ground state, even in a perfect vacuum with no external radiation present. Why?
In QED, the answer is that the atom couples to the vacuum electromagnetic field. The vacuum is not empty — it is a sea of zero-point fluctuations at every frequency. These fluctuations stimulate the transition.
Without a physical vacuum field, there is no mechanism for spontaneous emission. Every LED, every laser, every star that shines does so because space has electromagnetic properties.
Experiment 4: Analog Hawking Radiation
In 2016, Jeff Steinhauer at the Technion created an acoustic black hole in a Bose-Einstein condensate and observed spontaneous phonon emission at the sonic horizon — the analog of Hawking radiation. The result was published in Nature Physics.
This works because a flowing fluid medium produces an effective spacetime geometry identical to the Schwarzschild solution. The horizon (where flow speed equals sound speed) splits vacuum fluctuations, producing thermal radiation.
This is not a metaphor. The mathematics is identical. And it demonstrates that a physical medium — a superfluid — naturally generates the gravitational phenomena we observe.
Experiment 5: Vacuum Permittivity and Permeability
The speed of light in vacuum is:
This is not a postulate. It is derived from two measured properties of space: its electric permittivity ( F/m) and its magnetic permeability ( H/m).
These constants describe the electromagnetic response of the vacuum. They determine how electric and magnetic fields propagate, how fast they travel, and how they interact with charges. They are, in every functional sense, the material properties of a medium.
The impedance of free space, , is a measurable quantity with the units of resistance. Empty space has impedance. This is not the behaviour of nothing.
The Higgs Field: The Modern Ether
The Higgs field has a nonzero vacuum expectation value of 246 GeV pervading all of space. Particles acquire mass by interacting with this field. It functions as a superconducting condensate that breaks electroweak symmetry.
This is a field that fills all space, has a definite energy density, and determines the properties of matter. If this is not an ether, the word has no meaning.
The Ether Physics Programme
The monograph at etherphysics.org identifies the ether with a superfluid Bose-Einstein condensate — a specific physical system whose collective excitations reproduce the phenomena of gravity, quantum mechanics, and electromagnetism.
The acoustic metric of this superfluid is the Painleve-Gullstrand metric (Section 3). Its field equation is the Einstein equation (Section 3). Its zero-point fluctuations produce the correct dark energy density (Section 4). And its phase transition from superfluid to normal explains why MOND works in galaxies but fails in clusters (Section 4).
Does ether still exist? The vacuum has permittivity, permeability, impedance, zero-point energy, and a Higgs condensate. It exerts forces, shifts atomic levels, and radiates at horizons. It determines the speed of light and the mass of every particle.
The only question is whether we are willing to say so.