Black Holes

Transcript

Black holes are among the most fascinating objects in our universe, and also the most mysterious. A black hole is a region in space where the force of gravity is so strong, not even light, the fastest known entity in our universe, can escape. The boundary of a black hole is called the event horizon, a point of no return, beyond which we truly cannot see.

When something crosses the event horizon, it collapses into the black hole’s singularity, an infinitely small, infinitely dense point where space, time, and the laws of physics no longer apply.

Scientists have theorized several different types of black holes, with stellar and supermassive black holes being the most common. Stellar black holes form when massive stars die and collapse. They’re roughly 10 to 20 times the mass of our sun and scattered throughout the universe.

There could be millions of these stellar black holes in the Milky Way alone. Supermassive black holes are giants by comparison, measuring millions, even billions of times, more massive than our sun.

Scientists can only guess how they form, but we do know they exist at the centre of just about every large galaxy, including our own. Sagittarius A, the supermassive black hole at the centre of the Milky Way, has a mass of roughly four million suns and has a diameter about the distance between the earth and our sun.

Because black holes are invisible, the only way for scientists to detect and study them is to observe their effect on nearby matter. This includes accretion disks, a disk of particles that form when gases and dust fall toward a black hole, and quasars, jets of particles that blast out of supermassive black holes.

Black holes remained largely unknown until the 20th century. In 1916, using Einstein’s general theory of relativity, a German physicist named Karl Schwartzschild calculated that any mass can become a black hole if it were compressed tightly enough.

But it wasn’t until 1971 when theory became reality. Astronomers studying the constellation Cygnus discovered the first black hole. An untold number of black holes are scattered throughout the universe, constantly warping space and time, altering entire galaxies, and endlessly inspiring both scientists and our collective imagination.

A: Stephen Hawking was very special in more ways than one so for this week’s podcasts we’re looking at an extraordinary life.
B: Yes, Hawking was the world’s best known scientist but he was also the world’s best known sufferer of motor neurone disease.
A: He was born in Oxford in 1942 and he won a scholarship to study physics at University College Oxford he obtained a first-class degree in 1962 and went on to Cambridge University to do a postgraduate course in physics and cosmology.
B: And it was while it Cambridge that he was diagnosed with a form of motor neuron disease (ALS) and this was a 1963 shortly after his 21st birthday.
A: Doctors expected him to live for only two more years but both he and his girlfriend Jane refused to be daunted by the fact that Stephen had just been diagnosed with a terminal disease. They married two years later and had three children.
B: In fact as we all know Hawking went on to live for another 55 years and died at the age of 76.
A: He once said although there was a cloud hanging over my future I found to my surprise that I was enjoying life in the present more than before I began to make progress with my research.
B: He also declared my goal is simple it is a complete understanding of the universe why it is as it is and why it exists at all.
A: So, obviously an extremely intelligent and determined man but why did he become so famous?
B: Well firstly, it was because of his research on black holes the Big Bang and how the universe began.
A: But Richard that was all in the academic world while he was doing his research.
B: Yes, he actually shot to stardom as far as the public were concerned with the publication of his book a brief history of time from the Big Bang to black holes.
A: Yes, Hawking decides in 1982 to write a popular book about the universe that would be accessible to the general public instead of publishing with an academic press he signed a contract with a mass-market publisher.
B: It was published for the first time in 1988 and it rose quickly to the top of the bestseller lists both in the US and the UK and it remained there for months.
A: It sold 10 million copies and was translated into 40 different languages.
B: He even appeared on the front cover of Newsweek.
A: No doubt though it was also his appearance that kept him in the public eye the fact that he had these amazing ideas but could neither walk nor talk.
B: Yes, he’d been using a wheelchair since the late 60s and had already lost the use of his voice he used a computer program to speak for him although for some reason he was given an American accent.
A: Towards the end of his life with mobility increasingly reduced more sophisticated technology was used to translate his brain patterns or facial expressions into words.
B: But perhaps along with the image of Hawking lop-sided in his chair there is the one of him floating.
A: Yeah in 2006 Hawking revealed in a BBC interview that one of his greatest unfulfilled desires was to travel to space.
B: On hearing this Richard Branson offered a free flight into space with Virgin Galactic which of course Hawking immediately accepted.
A: Now Stephen Hawking is among the things that he loved.
B: The most the stars.

British icons: Stephen Hawking