Various eminent scientists explain the current knowledge of Black Holes and try to answer the question, do they really exist? New discoveries are challenging everything we know about black holes -- astronomers are beginning to question if they even exist. The latest science tries to explain how they work & what they look like, despite the fact we've never actually seen one.
The two great theories of Einstein's General Relativity and Quantum Mechanics don't work together to explain Black Holes which is a big problem. Other theoretical constructs such as Gravastars and Planck stars have been postulated but proving their existence is just as difficult as that of Black Holes. So where next?

Time i s a concept which is so familiar, and yet recent discoveries have revealed it to be far stranger than we could have possibly imagined. In the final programme in the series, Brian explores the enigma of time - a phenomenon we take for granted but which is one of the biggest mysteries in the universe. He recalls highlights from his TV series that touch upon this conundrum.

One of the Universe's most enduring mysteries is Time Travel. In this episode, we explore the possibilities. Discover why Time Travel into the future is unavoidable in the Einsteinian world of Relativity. As for the past... the laws of physics do not tell us it's impossible, but the bizarre consequences of going into the past and altering the future make for mind-bending science. Finally, we go for the future by traveling to the nearest star, 4.3 light years away... in only 45 days. Our destination may be an Earth-like planet; a planet scientists are now hunting for, and may find in the next 3 to 4 years.

We feel it every moment of our lives but for physicists, gravity is the longest running unsolved mystery of the universe. Why do all objects that have mass pull on one another? Cutting-edge theories are proposing unexpected answers: Gravity could be another force in disguise, a thermodynamic mirage, or even, a shadow of a hidden holographic universe. If so, the force that holds us to the surface of the earth, and holds the earth in orbit around the sun, may be a trick of the mind. We feel it, but it may not be real. Is Gravity an Illusion?

Is Time Travel Possible? Stephen Hawking explores the world's favourite scientific 'what if?' He explores all the possibilities, warping the very fabric of time and space as he goes. From killing your grandfather to riding a black hole, we learn the pitfalls and the prospects for a technology that could quite literally, change everything.

Explore the myths, misconceptions, truths & amazing mysteries of our unique universe. Could life exist on Mars? Is time travel possible & does Einstein's theory of relativity support it?