How is the universe like a board game?
This isn't a riddle or a joke,
it's an analogy proposed by the physicist Richard Feynman,
who compared scientific investigation
to watching the gods play some complex game like chess.
In both cases, when we first start watching,
we have no idea what's going on.
But gradually we learn to recognise the board, the pieces,
how they interact, and start deducing the rules,
that is, the workings of the universe.
But sooner or later,
something's going to catch us off guard.
For example, in chess, a pawn can only move
one square at a time.
But if it reaches the far side of the board,
it gains the powers of a queen
and starts zooming around all over the place.
We have no way of predicting this until we see it,
but when we do, we're forced to re-examine
all the rules we thought we'd learned.
And sometimes this is exactly what happens in science.
Take the work of Vera Rubin.
Born in Philadelphia in 1928,
as a child, Vera loved stargazing,
which in due course led her into astronomy.
Unfortunately, this field turned out to be
a lot less than welcoming,
which caused problems throughout her career;
observatories that banned women
from using their telescopes;
colleagues who tried to take credit for her work;
scientific societies that literally
wouldn't allow women through the front door.
Nevertheless, she persisted,
gaining a PhD and a professorship
and turning her attention
to the movements of galaxies.
At the time,
not much was known about how galaxies rotate,
but the general assumption
was that they would follow the same laws
Isaac Newton formulated in the 17th century.
Gravity draws objects with mass together,
and the closer they get, the faster they move.
We see this at work in our solar system,
where Mercury orbits the Sun
at about ten times the speed of Pluto,
and it seemed reasonable for Rubin to expect
she would find the same thing happening in our galaxy:
The Milky Way.
But she didn't.
Instead, she found something that made no sense.
Objects at the edges of the galaxy
were moving at the same speed as others nearer its centre,
much faster than most astronomers would have expected,
like a pawn on a chessboard
that's unexpectedly started whizzing about.
This challenged much of what astronomers believed,
and implied that something fundamental
about their understanding of the universe was wrong.
This isn't something anybody likes to hear,
and Rubin's observations were not warmly received.
She knew that for them to be taken seriously,
she'd need a lot more data.
So over the next decade and a half,
she authored and co-authored papers detailing
observations of nearly a hundred galaxies,
all of which showed the same thing:
velocities that defied our understanding
of how galaxies should rotate.
By 1980, the sheer volume of this data,
including that from other astronomers,
had become too great to ignore,
forcing the astronomical community
to ask the all-important question:
What could explain these speed-limit-smashing rotations?
One idea that had been around since the 1930s,
but hadn't gained much support
was that there's more to space than meets the eye,
that there's some incredibly heavy,
yet completely invisible "stuff"
holding everything together:
what physicists and astronomers called "dark matter."
What Rubin had discovered
was the first convincing evidence
for this powerful, yet puzzling, substance.
Most scientists now believe that dark matter makes up
a quarter of the universe's mass.
Pretty amazing,
given we still have basically no idea what it is.
There are several theories that it's made up of neutrinos;
elementary particles that don't interact with light;
or tiny subatomic black holes,
each with the mass of a mountain;
or some other kind of particle,
unknown to modern physics.
Some believe it doesn't exist at all,
and we just need to tweak Newton's laws a bit.
That theory has its difficulties,
and many have dismissed it.
But interestingly, not Vera Rubin herself,
who always believed in keeping an open mind.
For now, this remains one of science's greatest mysteries.
But with a new generation of instruments
and experiments taking shape,
the hunt for answers is only just beginning.
What is certain
is that in the cosmic chess game of the universe,
dark matter represents a whole new dimension of play.
That's no small thing.
Getting people to truly reconsider
what they're convinced they know
takes a huge amount of evidence
and decades spent studying things
many see as a waste of time.
The fact that these weren't the only struggles Rubin faced
makes her achievements all the more remarkable.
Since her death in 2016,
her work has been honoured in numerous ways,
but many argue that the recognition
she received in life fell short of what she was due,
in particular being consistently overlooked
for a Nobel Prize.
Nonetheless, the thriving research field
surrounding dark matter today
is testament to Rubin's work, that of her colleagues,
and the idea that in science, with enough data,
there's no rule that can't be rewritten.