Tyson begins the episode by explaining the nature of the speed of light and how much of what is seen of the observable universe is from light emanated from billions of years in the past. Tyson further explains how modern astronomy has used such analyzes via deep time to identify the Big Bang event and the age of the universe. Tyson proceeds to describe how the work of Isaac Newton, William Herschel, and James Clerk Maxwell contributed to understanding the nature of electromagnetic waves and gravitational force, and how this work led towards Albert Einstein's Theory of Relativity, that the speed of light is a fundamental constant of the universe and gravity can be seen as distortion of the fabric of space-time. Tyson describes the concept of dark stars as postulated by John Michell which are not visible but detectable by tracking other stars trapped within their gravity wells, an idea Herschel used to discover binary stars. Tyson then describes the nature of black holes, their enormous gravitational forces that can even capture light, and their discovery via X-ray sources such as Cygnus X-1. Tyson uses the Ship of Imagination to provide a postulate of the warping of spacetime and time dilation as one enters the event horizon of the black hole, and the possibility that these may lead to other points within our universe or others, or even time travel. Tyson ends on noting that Herschel's son, John would be inspired by his father to continue to document the known stars as well as contributions towards photography that play on the same nature of deep time used by astronomers.

Professor Jim Al-Khalili investigates the most accurate and yet perplexing scientific theory ever - quantum physics. At the beginning of the 20th century scientists were led into the hidden workings of matter, into the sub-atomic building blocks of the world around us. They discovered phenomena unlike any encountered before - a realm where things can be in many places at once, where chance and probability call the shots and where reality appears to only truly exist when we observe it. Albert Einstein hated the idea that nature, at its most fundamental level, is governed by chance. Jim reveals how, in the 1930s, Einstein thought he'd found a fatal flaw in quantum physics because it implies that sub-atomic particles can communicate faster than light in defiance of the theory of relativity. In the 1960s the scientist John Bell showed there was a way to test if Einstein was right and quantum mechanics was actually mistaken. Jim repeats this critical experiment - with shocking results.

Dr Hannah Fry explores a paradox at the heart of modern maths, discovered by Bertrand Russell, which undermines the very foundations of logic that all of maths is built on. These flaws suggest that maths isn't a true part of the universe but might just be a human language - fallible and imprecise. However, Hannah argues that Einstein's theoretical equations, such as E=mc2 and his theory of general relativity, are so good at predicting the universe that they must be reflecting some basic structure in it. This idea is supported by Kurt Godel, who proved that there are parts of maths that we have to take on faith.

Hannah then explores what maths can reveal about the fundamental building blocks of the universe - the subatomic, quantum world. The maths tells us that particles can exist in two states at once, and yet quantum physics is at the core of photosynthesis and therefore fundamental to most of life on earth - more evidence of discovering mathematical rules in nature. But if we accept that maths is part of the structure of the universe, there are two main problems: firstly, the two main theories that predict and describe the universe - quantum physics and general relativity - are actually incompatible; and secondly, most of the maths behind them suggests the likelihood of something even stranger - multiple universes.

We may just have to accept that the world really is weirder than we thought, and Hannah concludes that while we have invented the language of maths, the structure behind it all is something we discover. And beyond that, it is the debate about the origins of maths that has had the most profound consequences: it has truly transformed the human experience, giving us powerful new number systems and an understanding that now underpins the modern world.

Hannah then explores what maths can reveal about the fundamental building blocks of the universe - the subatomic, quantum world. The maths tells us that particles can exist in two states at once, and yet quantum physics is at the core of photosynthesis and therefore fundamental to most of life on earth - more evidence of discovering mathematical rules in nature. But if we accept that maths is part of the structure of the universe, there are two main problems: firstly, the two main theories that predict and describe the universe - quantum physics and general relativity - are actually incompatible; and secondly, most of the maths behind them suggests the likelihood of something even stranger - multiple universes.

We may just have to accept that the world really is weirder than we thought, and Hannah concludes that while we have invented the language of maths, the structure behind it all is something we discover. And beyond that, it is the debate about the origins of maths that has had the most profound consequences: it has truly transformed the human experience, giving us powerful new number systems and an understanding that now underpins the modern world.

On November 25th, 1915, Einstein published his greatest work: General Relativity. The theory transformed our understanding of nature’s laws and the entire history of the cosmos, reaching back to the origin of time itself. Now, in celebration of the 100th anniversary of Einstein’s achievement, discover the inside story of Einstein’s masterpiece". The story begins with the intuitive thought experiments that set Einstein off on his quest and traces the revolution in cosmology that is still playing out in today’s labs and observatories. Discover the simple but powerful ideas at the heart of relativity, illuminating the theory—and Einstein’s brilliance—as never before. From the first spark of an idea to the discovery of the expanding universe, the Big Bang, black holes, and dark energy, NOVA uncovers the inspired insights and brilliant breakthroughs of “the perfect theory.”

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.