Physicist Jim Al-Khalili routinely deals with the strangest subject in all of science - quantum physics, the astonishing and perplexing theory of sub-atomic particles. But now he's turning his attention to the world of nature. Can quantum mechanics explain the greatest mysteries in biology?
Horizon looks at dark energy - the mysterious force that is unexpectedly causing the universe's expansion to speed up. The effects of dark energy were discovered in 1998 but physicists still don't know what it is. Worse, its very existence calls into question Albert Einstein's general theory of relativity - the cornerstone of modern physics. The hunt for the identity of dark energy is on. Experiments on earth and in space generate data that might provide a clue, but there are also hopes that another Einstein might emerge - someone who can write a new theory explaining the mystery of the dark energy.
Hannah starts her journey by asking whether everything could be bigger, finding out what life would be like on a bigger planet. As the Earth grows to outlandish proportions, gravity is the biggest challenge, and lying down becomes the new standing up. Flying in a Typhoon fighter jet with RAF flight lieutenant Mark Long, the programme discovers how higher G-force affects the human body, and how people could adapt to a high G-force world. But by the time Earth gets to the size of Jupiter, it's all over, as the moon would impact the planet and end life as we know it. Next, Hannah tries to make living things bigger. The programme examines the gigantopithecus, the biggest ape to ever exist, creates a dog the size of a dinosaur and meets Sultan Kosen, the world's tallest man. Humans are then super-sized with the help of Professor Dean Falk to see what a human body would look like if we were 15m tall. The sun gets expanded, and Professor Volker Bromm looks back in time to find the largest stars that ever existed, before the sun explodes in perhaps the biggest explosion since the big bang.
Time. We waste it, save it, kill it, make it. The world runs on it. Yet ask physicists what time actually is, and the answer might shock you: They have no idea. Even more surprising, the deep sense we have of time passing from present to past may be nothing more than an illusion. How can our understanding of something so familiar be so wrong?
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.
Scientists genuinely don't know what most of our universe is made of. The atoms we're made from only make up four per cent. The rest is dark matter and dark energy (for 'dark', read 'don't know'). The Large Hadron Collider at CERN has been upgraded. When it's switched on in March 2015, its collisions will have twice the energy they did before. The hope is that scientists will discover the identity of dark matter in the debris. The stakes are high - because if dark matter fails to show itself, it might mean that physics itself needs a rethink.