Supermassive Black Holes

Horizon

30th November 2000 1 hour Season 37 Episode 17

In June 2000, astronomers made an extraordinary discovery. One that promises to solve one of the biggest problems in cosmology - how and why galaxies are created. Incredibly, the answer involves the most weird, destructive and terrifying objects in the Universe - supermassive black holes. Scientists are beginning to believe that these forces of pure destruction actually help trigger the birth of galaxies and therefore are at the heart of the creation of stars, planets and all life. Supermassive black holes are so extraordinary that until recently, many people doubted that they existed at all. The idea of giant black holes the size of the Solar System seemed more like science fiction that reality - such monsters would be so powerful that they could destroy the very fabric of the Universe. But in the last five years a series of discoveries has changed our understanding of supermassive black holes and galaxies forever. Using the powerful Hubble Space Telescope, scientists have been scanning nearby galaxies, searching for these giant black holes. It's a difficult job - by their very nature black holes swallow light - so can never be seen. So what scientists have been looking for is the effect of their massive gravity, hurling stars around them at immense speed. What they've found is more extraordinary than anyone could ever have imagined; not just evidence that these vast destructive monsters exist… but so far they're in every single galaxy toward which they have turned their telescopes. These giant agents of destruction appear to be common throughout the Universe. Scientists now think supermassive black holes are a fundamental part of what a galaxy actually is. Lurking at the heart of every single galaxy is a giant black hole of apocalyptic proportions - and that includes our own galaxy, the Milky Way. Astronomer Andrea Ghez has been studying the heart of the Milky Way for the last five years. What she's discovered is irrefutable evidence for a giant black hole, 3 billion times the size of our own sun. A black hole that could destroy the entire Solar System. And as Horizon was filming in July 2000, Ghez got some terrifying images - of the giant monster sucking up gas and stars at the galaxy heart. So what is this giant monster doing at the heart of our galaxy? What effect will this giant black hole 25,000 light years away have on us and the rest of the galaxy around it? These are questions that have been puzzling astronomers for the last few years - and in June, two separate groups of scientists found evidence that points to a startling answer. Rather than being destructive parasites, it seems that supermassive black holes may be essential in the very creation of the galaxies they live in. Exactly how our galaxy was created has mystified astronomers and physicists for years. Although there have been many theories, there's little evidence to explain how the gas in the early Universe condensed to form the galaxy we see today. Now scientists realise they've been missing a vital ingredient - a supermassive black hole. The immense gravity of a giant black hole might trigger the gas to collapse in the first place. By churning up the gas around it, a giant black hole would trigger the birth of stars, planets and life itself. Despite being the most destructive thing in the Universe, scientists now think our supermassive black hole could be crucial in creating the galaxy as we know it. The supermassive black hole in our own galaxy may be the reason we exist, but recent work suggests it may also be our end. At present Earth is so far away from the black hole that it can't affect us, but physicist John Dubinski thinks all that could change. In January 2000 he graphically simulated the final fate of our galaxy. In 3 billion years we will collide with the next door galaxy, Andromeda. The resulting apocalypse will force the Earth and our Solar System out of orbit. Dubinski has calculated a worrying 50:50 chance that we'll be sent hurtling in towards the black hole at the centre of this maelstrom. This would be fatal for the Earth.

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Season 37 · Episode 18

The Boy who was Turned into a Girl

In 1965 in the Canadian town of Winnipeg, Janet Reimer gave birth to twin boys - Bruce and Brian. Six months later a bungled circumcision left Bruce without a penis. Based on a radical new theory of gender development the decision was taken to raise Bruce as a girl. In 1967 Bruce became Brenda and for the next three decades this case would be at the heart of one of the most controversial theories in the history of science. The man behind this work was world-renowned psychologist Dr John Money. In the 1950s Dr Money developed a theory that revolutionised our understanding of gender. Money believed that what he called our 'gender identity' - what makes us think, feel and behave as boys or girls - is not fully formed by the time of birth. While we may have some innate sense of being a boy or a girl, for up to two years after birth, our brains are, in effect, malleable and we can be taught to grow up as either a boy or girl by how we are raised - by the toys we are given, the guidance we receive from adults and the clothes we are given to wear. This became known as the 'theory of gender neutrality'. Dr Money had reached this conclusion by working with a rare group of individuals born with ambiguous genitals - people known as intersexuals or hermaphrodites. Dr Money studied groups of intersex children, and concluded that these children could be brought up as either boys or girls regardless of their genetic or physical sex. The legacy of Dr Money's work was a revolution in the treatment of 'intersex'. From the 1950s to the present day many intersex children born with a tiny penis are reassigned as female even if they are actually genetically male. But not everyone agreed with Dr Money's theories. Since the 1950s a small group of scientists including Dr Milton Diamond have questioned John Money's work. Diamond believed that our sex is already defined in our brains before we are born. He was convinced that the power of our genes and hormones was so strong that no amount of nurturing could override them. But John Money's theory had already become firmly accepted around the world and the most dramatic confirmation of the theory came from one particular case - the case of Bruce Reimer. Bruce was a normal boy, not an intersex child, and yet the decision was made to turn this boy who had lost his penis, into a girl. Under the guidance of Dr Money and his team at Johns Hopkins University this baby boy was surgically changed into a girl. After surgeons at Hopkins had castrated baby Bruce, he became baby Brenda. The family were instructed how to bring up Brenda as a normal little girl. According to Dr Money's theory she would grow up believing herself to be female and would go on to live a normal happy life as a woman. It seemed the ultimate test that nurture could override nature. Thirty years after Bruce became Brenda, the impact of this extraordinary story continues. After almost 14 years living as a female, Brenda Reimer reverted to her true biological sex - the case of the boy who was turned into a girl had failed. Brenda took the name David and for the last twenty years he has lived anonymously in his hometown of Winnipeg. For almost all this time no one knew the outcome of John Money's celebrated case. But now that David has gone public, the case is being widely discussed once again and its impact on John Money's theory of gender development and the treatment of intersex children is being hotly debated.

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