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- So our laws of physics can explain the 5% of stuff
that we know of,
but to explain the missing 95%,
we need something that goes beyond what we know already,
beyond our current laws of physics.
I'm Jo Dunkley and I'm a cosmologist.
Cosmology is the study of the universe as a whole thing.
It means trying to understand how it began,
what it's made of, how it's got to be where it is today,
and what's gonna happen to it in the future.
So when we look into space,
there's no reason why the things that we see
should be all that's out there.
You see the bright lights of the stars,
but there may be something more.
One of the reasons that we've come to know
that there must be something out there
is that actually we can weigh the whole universe,
we can actually weigh on average the whole of space.
As cosmologists we've actually done that
and then you can go and look and see
what you can see with your telescopes.
And you can match those up
and you find there's a piece missing.
What we can see, matter that we know of,
that we are made of, particles that we know of,
is only 5% of the total stuff that's out there.
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So we give this 95% of stuff two names.
There's a part called dark matter
and there's a part called dark energy.
The dark matter seems to be an invisible particle
that feels gravity but doesn't emit any light
and just, you know, could just pass straight
through our body without noticing it.
Dark energy on the other hand,
which is actually makes up about 70% of that total
is really mysterious.
It's stuff that seems to be making space
grow faster and faster.
It might just be the energy of empty space itself,
but we're really not sure if that's what it is
and we don't really have any kind of understanding
of why it should be there.
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So one of the ways to try and see invisible things
is to look at distant light
and see how that light is affected
by the invisible contents.
So what I do is measure light that has that set off
14 billion years ago
and is traveling to me now
and reaching me now.
But on its path,
it's encountered all this invisible dark matter on its way.
And the more that there is,
the more of it actually bends that lights path
in the gravity of this invisible matter itself.
And so we can look at these incredibly distant
rays of light,
either coming actually from distant galaxies
or from the very beginning of the universe.
And we can see how much it gets bent by gravity
and then can infer where
and how much of this stuff there is.
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As an example, if we had no dark energy,
things would tend to collapse in space.
More often you would get big cosmic structures of galaxies
and clusters of galaxies grouping together
and growing bigger and bigger.
So one of our goals
is to look over this billion-year history.
How these giant cosmic structures
of clusters of galaxies,
how they have grown and whether
and how this dark energy seems to be spreading them apart.
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We don't know how big a deal this is.
Dark matter could just be a new particle
that could then fit in as a fairly minimal extension
of the standard model of physics.
In solving dark matter and dark energy,
it might be something bigger,
it might be something that would lead
to an entire paradigm shift in our understanding of physics.
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So we're looking forward to many new telescopes
in the 2020s
that will look for this invisible stuff in different ways.
So our main goal is to see how light
from distant objects
gets bent by the gravity of all this invisible stuff,
to try and work out what it is.
And so big new telescopes coming in the 2020s
are going to measure billions of galaxies
and we'll look how the light from them
is subtly distorted by this invisible stuff.
And we're actually going to measure light
even from before there were galaxies,
from the beginning of the universe,
the most distant light of all
and see how that's been bent by all this invisible stuff.
I'm Jo Dunkley and I'm a forward thinker.
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