Thank you for downloading this episode of In Our Time for more details about In Our Time

and for our terms of use please go to bbc.co.uk slash radio 4.

I hope you enjoy the program.

Hello, something in our universe is missing or rather almost everything, most of the matter

in existence.

Scientists first noticed this in the 1930s observing that galaxies were moving much faster than

expected and at such speed should have dispersed or evaporated.

They theorized that there must be something as yet unknown keeping the galaxies in place.

The Swiss astronomer Fritz Zwicky called in the 1930s called this missing matter.

At first and later as we know it now, dark matter.

At least one of our guests today claims that once we do know what dark matter is we will

have solved one of the greatest mysteries and signs linking the big bang with the creation

of galaxies, planets, earth and everything on it including us.

The immediate discussed dark matter are Carlin Crawford, Public Astronomer, the Institute

of Astronomy, University of Cambridge and Gresham Professor of Astronomy and Green Reader

in Physics at the University of Nottingham and Carlos Frank, Ogden Professor of Fundamental

Physics and Director of the Institute for Computational Cosmology at the University of

Durham.

Carlin Crawford, what's the start of the story of the discovery of dark matter?

The primary evidence for dark matter is astronomical observations.

As you said in your introduction, the story starts back in the 1930s with the astronomer

Fritz Zwicky who was identifying, classifying, studying clusters of galaxies.

...