In this episode, Helen seeks out the colours that turned planet Earth multicoloured. To investigate the essence of sunlight Helen travels to California to visit the largest solar telescope in the world. She discovers how the most vivid blue is formed from sulfur atoms deep within the Earth's crust and why the presence of red ochre is a key sign of life. In gold, she discovers why this most precious of metals shouldn't even exist on the surface of the planet and in white, Helen travels to one of the hottest places on Earth to explore the role salt and water played in shaping planet Earth.

In the dark depths of the oceans, nearly 90% of all species light up the darkness from within. These creatures flash, sparkle, shimmer, or simply glow. Whether it’s to scare off predators, fish for prey, or lure a mate, the language of light is everywhere in the ocean depths, and scientists are finally starting to decode it. Discover surprising ways to harness nature’s light—from tracking cancer cells to detecting pollution, lighting up cities, and even illuminating the inner workings of our brains.

In this episode, Michael demonstrates how our society is built on our search to find the answer to what makes up everything in the material world. This is a story that moves from the secret labs of the alchemists and their search for gold by the stone of the philosophers to the creation of the world's first synthetic dye - Purple - and onto the invention of the transistor. This quest may seem abstract and highly theoretical. Yet it has delivered the greatest impact on humanity. By trying to answer this question, scientists have created theories from elements to atoms, and the strange concepts of quantum physics that underpin our modern, technological world.

Al-Khalili travels to northern Syria to discover how, a thousand years ago, the great astronomer and mathematician Al-Biruni estimated the size of the earth to within a few hundred miles of the correct figure. He discovers how medieval Islamic scholars helped turn the magical and occult practice of alchemy into modern chemistry. In Cairo, he tells the story of the extraordinary physicist Ibn al-Haytham, who helped establish the modern science of optics and proved one of the most fundamental principles in physics - that light travels in straight lines. Prof Al-Khalili argues that these scholars are among the first people to insist that all scientific theories are backed up by careful experimental observation, bringing a rigour to science that didn't really exist before.

Without the chemistry of photosynthesis, ozone, and a molecule called Rubisco, none of us would be here. So how did we get so lucky? To find out, host David Pogue investigates the surprising molecules that allowed life on Earth to begin, and ultimately thrive. Along the way, he finds out what we’re all made of—literally.

Just about every solid, liquid, or gas in the world as we know it begins with reactions between individual atoms and molecules. Host David Pogue dives into the transformative world of chemical reactions, from the complex formula that produces cement to the single reaction that’s allowed farmers to feed a global population by the billions.