Placeholder Image

Subtitles section Play video

  • A hundred trillion years from now, the last of a great civilisation hides in the darkness.

  • Throughout their glory days, their engineers worked entire star systems.

  • They dismantled planets and asteroids to construct an immense interstellar empire.

  • But now, in the twilight of their time, all of this is long gone.

  • All around them, the universe is dying as the last of the stars are going out.

  • Over countless millennia, the sky has continued to fade into an eternal night.

  • The aging universe gripped by desolation and decay,

  • And so, in the darkness, they wait for the end.

  • Long before they had realized it was coming

  • They knew that the universe was on a path of inevitable decline.

  • Methodically they hunted for a final place to wait out eternity.

  • And embarked on their last great feat of engineering.

  • Around a lost and lonely black hole, they built a new home. With demolished worlds as raw material, they

  • constructed a shell to completely enclose the darkness.

  • And within this thin shell, barely withstanding the gravitational grip of their savior,

  • They eked out their meagre lives.

  • The dwindling light of dying stars rained down upon their final home, Whilst the swirling black hole was harvested

  • to power their existence. But more than that, the black hole at their

  • heart gave them greatest gift of all, For the black hole gave them time.

  • No one remembered the name of the great scientist who had discovered the nature of time.

  • But the astro-engineers knew that time was not the same across the cosmos.

  • And here, within the immense gravity of the black hole, time trickled more slowly.

  • Whilst many years passed outside, mere moments flashed by within the immense sphere.

  • And so the last of the civilisation watched the future play out in front of them.

  • But they knew that they had only delayed, not averted, their ultimate demise.

  • And the darkness would inevitably envelop them forever and ever.

  • Of course, this story is little more than speculation.

  • But it is built on a scientific idea that changed our universe.

  • It’s been more than a century since Einstein’s relativity shook up our understanding of time

  • and space. But how does it really work? And what does

  • it actually mean? Both time and space seem so commonplace, so

  • obvious, so everyday. But beneath their ubiquity they hide a multitude

  • of unanswered questions - questions to which Einstein's theories only begin to answer.

  • What is space made of?

  • Does time exist?

  • And will hunting for their ultimate nature lead to sudden clarity, or will space and

  • time just become more elusive?

  • Einstein offered them lunch, and they accepted.

  • So he moved a whole bunch of papers from the table, opened four cans of beans with a can opener,

  • heated them, stuck a spoon in each and that was our lunch."

  • Albert Einstein was a busy man, and often missed lunch.

  • And that was back in 1915 - in the century since our lives have only become more chaotic.

  • And that is why a meal kit service like HelloFresh is so great.

  • Hellofresh delivers fresh, high quality produce straight from the farm to your door,

  • with more than 55 weekly meal options.

  • Great for everyone - especially if you want to get or stay fit and healthy. I am a big fan of fitness and eating the right

  • food - but in honesty sometimes there just aren't enough hours in the day and a microwaveable

  • meal seems like the only option. Hellofresh has saved me from this tasteless horror.

  • The kits are fool proof, genuinely really hard to get wrong, and that is coming from

  • an absolute cooking disaster. And last but definitely not least, a recent

  • survey has found their meals have been found up to 72% cheaper than dining out or grocery

  • shopping. Go to HELLOFRESH.COM and use

  • code HISTORY16 for up to 16 FREE MEALS and 3 surprise gifts. 16 free meals!

  • This is a great company, and a smart way to eat healthily - and the cherry on top is that

  • they are also carbon neutral. A big thanks to HelloFresh for supporting

  • educational content on YouTube.

  • As the lonely world lingered on,

  • Its beating heart warped the very fabric of the universe around it.

  • The civilisation had done everything they could to keep going, to put off the inevitable.

  • But try as they might, they could only bend reality. They could not break it.

  • "Behind it all is surely an idea so simple, so beautiful, that when we grasp it - in a

  • decade, a century, or a millennium - we will all say to each other, how could it have been

  • otherwise? How could we have been so stupid?"

  • What is space?

  • The question seems almost meaningless. As children we learn to describe our surroundings

  • as up-down, left-right, back-and-front. We call it three dimensional and are free

  • to explore each dimension. But just what is it, this universal platform

  • on which we play out our lives? It is a question that occupied the minds of

  • the earliest philosophers. In the fourth century BC, Plato declared that

  • space was theThe Nurse of Becoming”, a medium in which everything existed, but

  • with no qualities of its own - and his student Aristotle agreed that an empty void was impossible.

  • But it would be more than two thousand years before our concept of space was born.

  • By the coming of the seventeenth century, modern science was crystallizing.

  • The processes of the universe were being codified into physical laws.

  • And the understanding of these physical laws was evolving from myths and stories, to the

  • language of mathematics. Of course, Isaac Newton was at the forefront

  • of this revolution. But before he enters our stage, we must first

  • start with a boat. In 1632, Galileo published his seminal work

  • Dialogue Concerning the Two Chief World Systems”.

  • He was in his mid 60s by this point, and had already had multiple run-ins with the Roman

  • Inquisition for his assertions that the earth rotated around the sun.

  • So he had decided to skirt controversy, and spend the intervening years quietly cementing

  • his myriad ideas on space and the cosmos into a book.

  • And at one point within this book, he muses on a boat.

  • More specifically - the life of a sailor locked below deck in a windowless cabin.

  • With plates and knives and a goldfish in a bowl on the table - a collection of birds,

  • flies, and butterflies. Just what does the sailor experience?

  • Tied up in port, the cabin is a picture of serenity, and all is calm as the goldfish

  • swims happily in its bowl. On the table, plates and cutlery remain in

  • their place, and the flying creatures happily flutter about.

  • But finding itself in rough seas, the cabin heaves and falls with the ship.

  • Plates and cutlery are wrenched off the table, water spills from the goldfish bowl.

  • On calm seas with wind-filled sails, the ship would speed up.

  • The sailor would feel this change, and see things sliding off the table.

  • But when the wind finally drops, the ship sails smoothly on the glassy sea.

  • Inside the cabin, all would be calm, serenity returning.

  • For the sailor, it would be as if the ship was still in port and was not moving at all.

  • A dropped plate would fall straight to the floor, and the sailor would sit comfortably

  • in their chair. And it was here Galileo realised something.

  • Without a window to reveal the truth, there are no experiments the sailor could do to

  • reveal whether the ship was moving or not. He concluded that there must be no absolute

  • concept of being at rest in space. Instead, everyone must experience any smooth,

  • uniform motion in the same way. All uniform motion must feel like simply being

  • still. Galileo declared, therefore, that any uniform

  • motion is simply relative to any other uniform motion.

  • And with this, the first theory of relativity had been born.

  • Galileo´s sailor floats gently on their sailboat, on seas near the earth's equator - rotating

  • at 1600 km an hour around the earth, which in turn orbits the sun at 67,000 km an hour,

  • which in turn orbits the milky way at 720,000 km an hour, which in turn is travelling towards

  • the Andromeda galaxy at 403,000 km an hour. And yet he feels nothing on his vast journey

  • millions of kilometres from his starting point. Unfortunately upon publishing the book, Galileo

  • once again fell foul of the Catholic Church - and was found guilty of heresy for his heliocentric

  • view of the cosmos. The work was banned, and would not be removed

  • from the church´s Index of Forbidden Books until 1835.

  • Within a few decades of Galileo´s downfall, two of Europe’s greatest minds were arguing

  • about the nature of space. One of them, Isaac Newton, was born in England

  • in 1642, within a year of Galileo’s death. He needs little introduction, and is known

  • now as one of the greatest thinkers of his age, perhaps one of the greatest of all time.

  • Whilst not forgotten, his opponent, Gottfried Leibniz, is somewhat less well known today.

  • Born in 1646 in what is present-day Germany, he was a leading thinker of his day, writing

  • on mathematics and philosophy. He pondered deep metaphysical questions, including one

  • that still haunts physicists and philosophers to this day - why there is something rather

  • than nothing. It was in the development of calculus that

  • the two men´s feud began. Whilst Leibniz published his work first, Newton

  • claimed that he had stolen his ideas. As president of the Royal Society at the time,

  • Newton set up a committee to investigate the dispute.

  • Unsurprisingly the committee found in favour of Newton.

  • And so this animosity carried over to their second disagreement.

  • A simple question: What happens to a spinning bucket of water?

  • Space, Newton declared, was a universal absolute, a rigid stage on which motion was played out.

  • And both would exist in a universe devoid of matter to experience any motion.

  • To argue his point, Newton asked us to think of a bucket of water.

  • If the bucket sits at rest, the surface of the water would be flat and level.

  • But if we spin the bucket, the water spins too and its surface becomes curved.

  • Newton askedJust what is the water spinning with respect to?”

  • Newton claimed that the acceleration of the spin was relative to an absolute space - something

  • separate to the object itself - spinning a bucket in an empty universe would also curve

  • the surface of the water. But to Leibniz, space in an empty universe,

  • devoid of any matter, simply made no sense. The properties of objects, Leibniz claimed,

  • are essential in defining their meaning. Space only has meaning, in the relative locations

  • of objects. And similarly, time only had meaning when

  • discussing the relative motions of objects. Without matter Leibniz said, space and time

  • simply have no role, and hence no existence. Sadly, Liebniz died in 1716, with the argument

  • still in full swing - but it was Newton's ideas that stuck.

  • Absolute space, in its own nature, without relation to anything external, remains always

  • similar and immovable, Absolute, true, and mathematical time, of itself, and from its

  • own nature, flows equally without relation to anything external."

  • This so-calledabsolute space and timewould be the accepted science for nearly two

  • centuries - but with the caveat of Galileo´s rejection of absolute rest. Absolute space

  • may have won the debate - but absolute rest, a fixed point - was still an impossibility.

  • Relativity was still part of the argument. But that only applied to space.

  • Time was a totally different matter. With its implicit direction, time appeared

  • totally distinct. For Newton and Galileo, everyone’s clock

  • across the universe ticked with absolute synchronicity. A universal beat that ran through every event

  • in the cosmos. A second on Earth the same as a second everywhere

  • else. But is this true?

  • Is time malleable or an unswerving metronome that drags the cosmos forward? Does it itself

  • have properties or is it defined only by the events that run in its current?

  • To answer these questions we must begin not with physicists wondering about clocks, rulers

  • and motion. But with heat.

  • In the distant future universe, around the aging black hole, our dying civilization sits