32 | New Scientist | 2 November 2019
The return of the
aether
A shadowy substance killed by Einstein may be
making a comeback, finds Brendan Foster
A
S FAR as dead ideas go, the
luminiferous aether is among the
deadest. Over a century ago, it picked
a fight with Einstein’s theory of relativity
and lost. Few victories in modern physics
have been so total. Today, relativity offers
us our best picture of the large-scale structure
of the universe. It is a byword for human
achievement and scientific progress.
The aether, if it gets mentioned at all, is an
embarrassing footnote in its rise to glory.
But relativity has run into difficulties of its
own. Its failure to explain the behaviour of the
universe at the smallest scales suggests that
some more fundamental theory is waiting to
take its place. Einstein’s universe is also plagued
by dark forces that his theory cannot cast out.
In an astonishing twist of fate, the key to
relativity’s salvation could lie in the aether.
Since the early 2000s, a small group of
researchers have claimed that this invisible,
space-filling substance could have the
power to unify physics. Then, in late 2018,
two independent groups suggested that
the similarity between the aether and the
shadowy powers that populate our cosmos
may not be mere coincidence. For one team,
the aether is a dead ringer for dark matter.
For another, it could explain away dark energy.
For others still, it might even be both.
The hunt is now on to see if it really is out
there. The biggest laughing stock in physics
may yet have the last laugh.
The best way to conceive of the aether
(or ether, as it is now more usually called)
is as a sort of faint, universe-spanning jelly,
through which all the stars, planets and
galaxies slowly wade. This is not what makes
it absurd. After all, vast invisible entities are
widespread in contemporary physics – from
the Higgs field that endows some fundamental
particles with mass, to the mysterious pull
of dark matter and dark energy that make up
95 per cent of the known universe. LOGAN ZILLMERFeatures