Episode 21: Broadcasts from the cosmos..


Research on radar during the Second World War led to the discovery of radio broadcasts from the cosmos. First of all, radio waves from violent solar storms were noticed and soon after that a cacophony of signals from the stars. A new science was born and radio astronomers started to build giant dishes to listen in to the cosmos, including the great 250 foot diameter radio telescope at Jodrell Bank, the brainchild of Bernard Lovell.

In 1967, a field near Cambridge saw a very strange new sort of telescope consisting of a thousand wooden posts and 120 miles of wire. It was with this that Jocelyn Bell discovered a regular cosmic heartbeat repeating every 1.337 seconds. At first the researchers wondered if it might be a signal from an alien civilisation but then theorists proposed just such a radio signal coming from an ultra dense spinning neutron star, the collapsed core of an exploded star or supernova. Soon dozens of these pulsars were known, taking physics to a new level.

Episode 22: Squashed stars and black holes.

As long ago as 1783 the rector of a small Yorkshire church suggested that the gravity of a very massive star might be strong enough to pull its light back and prevent it from shining. It was not until the 1930s that Subramanyan Chandrasekhar suggested a mechanism through which such a star might form, but even then he was ridiculed by his peers. But slowly, the concept of a black hole gained ground and in the late 1960s, the first x-ray telescope in space pinpointed the first black hole to be discovered in orbit around a normal star, and x-ray source known as Cygnus X-1.

A black hole seems to defy notions of common sense and even of normal physics. Light, information and hapless travellers would have no escape from its gravity. At its heart, matter and even space and time would be squashed out of existence. Yet there is a small theoretical chance that someone entering a spinning black hole might survive to emerge in another universe.

Episode 23:Violent Universe..

Only in the last half-century or so have there been telescopes powerful enough to study distant galaxies beyond our Milky Way in much detail. Cygnus A came to astronomers attention first as a radio source -- the second strongest in the sky. Then optical astronomers realised that it was a pair of galaxies colliding with one another. And it is a colossal 700 million light years away making its radio output a million times more powerful than that of our Milky Way. There was something very energetic going on in its core, shooting out great jets of high energy particles emitting radio waves.

The next breakthrough came from an object that is even more distance --2.5 billion light years. At its heart was something 40 times more luminous than a normal galaxy yet no bigger than the solar system. These mysterious powerhouses were named quasi-stellar radio sources and got abbreviated to quasars. The consensus now is that they are super massive black holes millions or even billions of times the mass of our Sun, gobbling stars and gas in the centres of galaxies.

Episode 24: The dark side of the cosmos.

You might think that trillions of stars in billions of galaxies would be enough to keep any astronomer happy, but no. In 1933 Fritz Zwicky realised that a huge cluster of galaxies is being held together by something more powerful than the gravitational pull of the visible matter. He was ignored. In the 1960s, Vera Rubin was coming to the same conclusion from studying the rotation of stars within individual galaxies. The conclusion was inescapable: all the visible stars and gas adds up to just a fraction of the total matter in the universe. There is dark matter out there and nobody knew what it was.

Nobody knows to this day, though now there are many theories and a new generation of elaborate experiments in particle accelerators and, shielded from radiation, deep underground to try to detect elusive dark matter particles.

Episode 25: Design or accident: Why me?

Given all that we now know about the formation of stars and planets and the evolution of life on Earth it might seem as if the mystery is being taken out of the universe. Far from it. There is a deeper mystery. It turns out that there are no fundamental reasons that we know of in the laws of physics why various constants of nature should have the values that they do. But if they didn't have those values, stars would not form or shine for long, they wouldn't create the elements essential for building planets and life nor be able to sustain them for long. The universe would be still-born.

Of course, we can only observe a universe that is just right for life. This is known as the anthropic principle and has far-reaching consequences. Some argue that it makes the universe very special, as if we were meant to be. Others suggest that we inhabit one of the few bio friendly corners in an almost infinite multiverse of possibilities.

Friday 25 June 9.00pm - Omnibus edition

Astronomer and writer Heather Couper presents an omnibus edition of the latest episodes in her narrative history of astronomy and our place in the cosmos. This week: chance and purpose in a violent universe.