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.

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?

Author and nuclear physicist Professor Jim Al-Khalili looks at what led to the discovery that everything is made of atoms. The programme looks at how the discovery affected the scientific world including the atomic energy theories of Albert Einstein and Werner Heisenberg and quantum mechanics

Of all the objects in the cosmos, planets, stars, galaxies, none are as strange, mysterious, or powerful as black holes. Black holes are the most mind-blowing things in the universe. They can swallow a star completely intact. Black holes have these powerful jets that just spew matter out.
First discovered on paper, on the back of an envelope, some squiggles of the pen. The bizarre solution to a seemingly unsolvable equation, a mathematical enigma. Einstein himself could not accept black holes as real. People didn't even believe for many years that they existed. Nature doesn't work that way. Yet slowly, as scientists investigate black holes by observing the effect they have on their surroundings, evidence begins to mount.

We move around in space, but we are stuck in a prison of time moving ever forwards. Einstein said, 'The distinction between past, present and future is only a stubbornly persistent illusion.' Is our experience of the ticking clock merely a trick of the mind? Could science ever make the clock move backwards? Experiments in quantum physics are showing that the future influences the present: what happens later limits the choices we think we have now. The laws of physics say visiting or talking to ourselves in the past is possible – but changing history once we get there is not.

Today, we know black holes exist, and now scientists are trying to confirm that other holes lurk in hyperspace. Our infinite cosmos could contain a variety of "holes" such as black, white, "mini" and wormholes. White holes are the reverse of black holes; instead of matter being sucked into it, matter is ejected out. Wormholes are gateways in the fabric of space and time. They are included in Einstein's field equations as possibilities for their existence. Neither white holes nor wormholes have ever been found. Learn about new discoveries including, colliding binary black holes, intermediate black holes and manufacturing mini black holes.