Infinite time. Image: Darren Tunnicliff/Flickr
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Is there such thing as the beginning and end of time?

In homage to the 60th anniversary of the world’s first atomic clock, it's time to ask what time actually is and whether it even exists.

Every year, we travel through time.

In autumn, we travel forward in time by one hour, and in the spring, we travel back in time by one hour. Every four years we gain 24 hours in February, and every three or so years an extra second is added to a minute.

Time appears, and then – *poof* – disappears again. But, wait a minute (whatever a minute is). Time cannot spring in and out of existence, can it? Time loans the universe a second, an hour, or possibly a day until the deadline whereby the universe must pay time back, right? But where has time been all this time?

Time is hard to define. We measure time in years (the time it takes Earth to orbit the Sun), days (one rotation of the Earth) and lunar months (the time it takes the moon to wax and wane). Time – hours, minutes, seconds, milliseconds, nanoseconds  are all manmade constructs. We made them up.

And time is a concept that doesn’t necessarily apply to the universe.

Time has always been inextricably linked with the Sun. The ancient Egyptians and Babylonians used sundials that roughly divided daylight into 12 equal segments. 60-minute hours and 60-second minutes are the product of the ancient Mesopotamian sexigesimal (base 60) numbering system. The French attempted to use the decimal system (base 10 rather than 12) for time-keeping, but that never caught on. The Greeks improved the sundial by marking gradations on sundials to indicate the divisions of time during the day.

And then the Scientific Revolution (1550-1700) came along. According to Vincenzo Viviani, Galileo's first biographer, 20-year-old Galileo got bored during prayers at the Cathedral of Pisa in 1583. As he daydreamed, something caught his eye: a swinging altar lamp. Curiosity got the better of him and he swung the lamp to find out how long it took to swing back and forth. He used his pulse to time large and small swings.

Galileo discovered something remarkable that nobody else had: the period of each swing was exactly the same. Then, the pendulum clock was born – the most accurate way of timekeeping at the time. After that, other clocks had developed such as the H4 (1759), an accurate chronometer for the determination of longitude, and the Swiss (1944). It was only a matter of time until wristwatches became a fashion statement; everyone had to tell the time. 

In 1928, all other clocks were rendered redundant as a new clock was in town, one with no moving parts: the quartz crystal clock. Then, in 1955 physicists Louis Essen and Jack Parry developed, at the National Physical Laboratory, a clock unlike any other: Caesium I, the world first atomic clock. The atomic clock, now on display in the Science Museum, outperformed existing pendulum and quartz clocks. The clock kept time by counting the vibration of caesium atoms, it was so accurate that it would only gain or lose one second every 300 years.

And like that, time changed. No longer was a second defined as 1/86,400th (24 hours x 60 minutes x 60 seconds) of a day. In 1967, the 13th General Conference of Weights and Measured defined a second as, "9,192,631,770 periods of radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom".

The official atomic second is slightly shorter than Coordinated Universal Time (UTC). So every three years, a “leap second” is normally added to the year to make up the difference (before the first leap second was added in 1972, UTC was 10 seconds behind atomic time).

Since then, scientists have honed in on the model with incredible precision. The latest modification to the strontium lattice atomic clock is accurate to one second in some 15 billion years – that’s a bit longer than our universe has existed.

Now that the history lesson is over, what is time? To understand time you will have to do one little thing: give up all your intuitions about how time works. 

If you flick through a book, you’ll notice that the book doesn’t have infinite pages. It has a beginning, middle and end. Humans possess a thing called a narrative bias; we make sense of the world around us through stories.

All stories have a beginning, middle and end. To process the overwhelming information around us, our brain compresses information in narratively, dropping facts that don’t fit the story. We are the protagonist of our narratives, of course; complex characters with fears, hopes and mild insanities.

Everything beyond our skin is a prop, a two-dimensional character made to fit snugly into our story (“that hipster-looking dude in Pret with a MacBook”, “that phone-obsessed girl on the Tube”, “that saint who helped me carry my shopping bags”, etc.)   

This isn’t something you do on purpose; narratives are so important to your survival that it’s the very last thing you give up before you’re just a sack of skin. Without a narrative you wouldn’t have a conscious and without a conscious, there would be nothing but white noise ringing in your ears.

If you’re confronted with the thought that the beginning and the end don’t exist – they’re just a manmade invention used to perceive the space around us – your brain will fall into a state of disarray (cognitive dissonance). The cure is to either accept the new belief and ignore/disregard the old belief, or vice versa.

So it's high time you threw your thoughts on time out of the window.

Time is inextricably related to space, so to understand time you must understand spacetime. Why? Because the speed of light in a vacuum is independent of the motions of all observers (particles count as observers). This is Albert Einstein’s theory of special relativity (presented in 1905).

To understand special relativity you must first familiarise yourself with the speed equation: speed (s) = distance (d)/time (t). 

The speed of light is the same for all observers, and this is known as “c” for constant (as in c in E=mc2, where is E is energy and M is the mass of an object). So the speed of light for any observer is constant regardless of the speed the observer is going. For the speed of light to remain constant, something in the speed equation has to give way, that something is time. It turns out time slows down when you travel faster and faster, nearing the speed of light. What could be 10 minutes for the object could be 20 minutes for the observer. So what’s the future for the fast-moving object could be the past for the slow-moving observer, and vice versa. 

This relativistic effect is called time dilation. So the faster an object travels, the slower the time passes. That’s why moving clocks are slower than stationary ones. For example, observer A is on a slow-moving train called "train A". She measures time using her wristwatch. Observer B, passing train A at high speed, has the exact copy of A’s wristwatch. Yet, from the point of view of A, B’s wristwatch runs more slowly than her own. And this is why Einstein said “time is an illusion”.

In addition, fast-moving objects cover a greater distance during a fixed time interval than slower-moving objects. So back to the speed equation: 

Special relativity also applies to the concept of simultaneity. If observer A judges two events to be simultaneous, observer B, moving relative to A, might not agree. Discrepancies in the order of events can occur as a result of the invariance of the speed of light. This YouTube video explains this concept visually. 

According to Merrian-Webster’s definition, spacetime is “a system of one temporal and three spatial coordinates by which any physical object or event can be located”. So if spacetime isn’t constant, then what is? The spacetime interval.  The spacetime interval is the spacetime difference between two separate events. The equation:

(Spacetime interval)2 = (the distance between two events)2 – (speed of light)2  x (the time between two events)2

Since the equation involves subtraction, the spacetime interval can be positive, negative or zero. When the spacetime interval is positive, two events are said to be seperated by "space-like interval". In a space-like interval, nothing can get from one event to another, and there are always observers who disagree about which of the two events happened first. In a YouTube video, physicist Professor Brian Cox of Manchester University gives an example: "The Sun is eight light-minutes away  it takes light eight minutes to get from the Sun to the Earth. If the Sun exploded now, it will take me eight minutes to notice. So let's say the Sun explodes, and from my point of view, four minutes elapsed. I still don't know it's exploded, so there's nothing the Sun can do to cause something to happen on the Earth  it's completely disconnected from it for eight minutes".

In a space-like interval, the order of events can be swapped. Person X moving at near-light speeds past the Solar System could see person Y talking about the Sun exploding eight minutes after the Sun has exploded, and person Z could see person Y talking the Sun exploding eight minutes before the Sun has exploded. 

When the spacetime interval is negative or zero, two events are said to be separated by "time-like interval" and "light-like interval", respectively. In both cases, signals or things can get from one event to the other, and everyone agrees on its sequence. In a YouTube video, Professor Cox gives an example: "If I throw a ball at you and I knock you off the wall. The ball caused you to fall off the wall. There's no way in Einstein's theory that could cause you to swap the order of events around. . . you couldn't fall off the wall and then I throw the ball". 

So although we can't agree about past, present, future, time or distance, we all agree about causality. This might seem weird because we think time is responsible for causality, but it's actually the other way around. Agreeing about temporal anything is because of causality. You could say causality is the only thing that’s "real". So what does causality have to do with spacetime? Everything.

Shortly after Einstein's theory of relativity was proposed, Hermann Minkowski, Einstein’s former mathematics professor, noticed the spacetime interval resembled a weird version of a “distance” formula called the “non-Euclidean geometry”. So he proposed something pretty epic: maybe reality   the universe we're living in   isn’t a 3D space that evolves in time, maybe it’s a 4D “non-Euclidean” space that’s just there. Ie, what if spacetime has just always existed? No evolution. No time. Just there.

This 4D space would be spacetime, where its points correspond to all events, ever:

Image: YouTube screengrab

To support Minkowski's proposal, a 2014 paper published in journal Physics Letters B, says the universe had no beginning and will have no end (a "block universe"), according to a new model that applies quantum correction terms to complement Einstein’s theory general relativity. The model also helps solve the problem of dark matter and dark energy.

What some cosmologists now believe is that rather than matter collapsing, causing a “Big Bang”, the matter bounced (“the Big Bounce”). Ie, they believe the universe has energy levels and goes through a cycle of collapses and bounces.

“[The Big Bounce] is actually in doubt because we now know that our universe is not going to re-collapse. It is actually going to expand forever because of dark energy. 70 per cent of our universe is made of an unknown type of force or energy that we call “dark energy”, whose main impact on the universe is to make the expansion of the universe accelerate with time – so not only is the universe growing with time, it’s growing at an ever accelerating speed,” says astrophysicist Roberto Trotta of Imperial College London to the science radio talk show The Naked Scientists, based at the University of Cambridge.

“The Big Crunch will end the universe and the end will be a state of darkness where all the matter will have been sucked into black holes . . . but it’s about 200bn years in the future so we’ve got nothing to worry about,” he adds. 

Our perception of time and space is arbitrary and inherently meaningless. It’s like the xy-grid we used in school. It’s useful for talking about the information dotted on it, but on its own is meaningless – it's just there. The information dotted on the grid would always be, regardless of the xy-grid.  

Are you real? Sort of. If you are the sequence of events at which you were present then you are a non-Euclidian geometric object in 4D space. Ie, you are your own spacetime interval – you are a line segment that joins the events from your birth to your death. Do you move around that line segment? No. You are it. There is no motion in spacetime – it’s tenseless. The manmade concept of past/future/present tense is ultimately meaningless (remember the xy-grid analogy). So your future isn’t predetermined, it already exists.

An analogy to understand spacetime: imagine we're all reading The Lord of the Rings. We agree on the events of the story, but we don’t agree on where they happened on the page, how many pages there are between events, and the order of some of those events, and yet, we’re all reading the same book. But only there are no pages...no numbers...and there is no book. All of it is a figment of our imagination in order to perceive whatever it is.

The illusion of space and time is explained visually in a YouTube video by research scientist Gabriel Perez-Giz of New York University.

If we throw Einstein’s theory of general relativity (published in 1915) into the mix, the idea of space and time becomes even more complex. There could be multiple spacetimes (universes called "multiverse") with different dimensions, making it hard to ascertain which one this – the one we’re living in – is.

“[Some researchers] postulate the existence of parallel universes, so our universe is made of [a 4D universe], but what if there were additional dimensions – that we cannot actually penetrate ourselves,” Trotta says on The Naked Scientists radio show.

To conclude, why do we perceive spacetime as, well, space and time? No one knows. Not yet, at least. 

Tosin Thompson writes about science and was the New Statesman's 2015 Wellcome Trust Scholar. 

Photo: Getty
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The moonwalkers: what it's like to belong to the world's most exclusive club

"The blue and the white and the brown just hung in the blackness of space."

It’s been almost 50 years since man first walked on the moon – and there were only a grand total of six missions.

From 1969 until 1972, as humanity reached out into space, these men – and they were all men – were at the forefront of scientific research and discovery.

But in 2017, the six survivors – now with a combined age of 505 – are the rare members of an exclusive club. The other six moonwalkers have already passed away.

Astronaut Buzz Aldrin was on Apollo 11, Charlie Duke was on Apollo 16 and Harrison "Jack" Schmitt was an Apollo 17 moonwalker. For the first time, at the Starmus festival in Trondheim, Norway, the three have come together to discuss their experience.

The three share “a special relationship, no question about it”, according to Duke. He tells me: “Our experiences are different but they’re the same in so many respects.”

Aldrin – unable to appear in person due to doctor’s orders – quips on camera from his home in Florida that President Dwight Eisenhower was advised that they should send a philosopher or maybe a poet up. His response, possibly apocryphal, came: “No, no - I want success."

As a result, it is up to these scientists to find the words to describe the off-Earth adventure which is the defining event of a moonwalker's life. 

A poetic description comes from Texan resident Duke. First and foremost a test pilot, his interest in space was piqued by the launch of Sputnik, the first artificial satellite, in 1957. He joined Nasa in 1966.

Now 81, Duke served as mission control support throughout many Apollo missions, most notably as the voice of Capsule Communicator when Neil Armstrong and Aldrin landed on the Moon in 1969.

He tells me: “Once we left Earth’s orbit, we turned our spaceship around and there was the whole Earth 40,000km away.

“The blue and the white and the brown just hung in the blackness of space. That contrast between the vivid blackness and the bright Earth – this jewel of Earth I like to call it - was right there.”

Aldrin started his career as a mechanical engineer, before joining up as a jet fighter in the US Air Force during the Korean War.

His gung-ho spirit and enthusiasm for space have not deserted him even at the age of 87 – he appears onscreen at the festival wearing a "Get your ass to Mars" T-shirt.

The most memorable experience for him came when he congratulated Neil Armstrong, the first of the team to walk on the moon (he died in 2012). But in the lunarscape, memories get confused – the men remember the moment differently.

“After the landing, I looked over at Neil, and we smiled. I remember patting him on the back and he remembers shaking hands. So here were two first-hand witnesses and we couldn’t agree on what actually happened when we got there.”

For Aldrin, the significance of the moonwalk was looking at the moon’s surface from close-up – the lunar soil, or regolith – and what happened when an astronaut's boot stepped onto it. 

“It was so remarkable, the way that it retained its exact form,” he marvels, 48 years on.

Aldrin's fascination with the moon's surface was shared by Schmitt, the 12th, and so far, last, man to walk on the Moon. A trained geologist, he was also the first scientist to do so.

In Schmitt's case, the rocky surface of the moon was enough to draw him into lunar research, which he still conducts at the age of 81.

“The commander told me as soon as I got out I had to look up and see the Earth," he recalls. "I said ‘Well, chief, you’ve seen one Earth, you’ve seen them all’."

In truth, having spent three days looking at the Earth from his craft, Schmitt’s priority was in looking down at the new surface under his feet.

After landing in a valley deeper than the Grand Canyon, his chief concern was just getting to work collecting samples in a lifesize laboratory.

While the moment on the moon may be the initiation into an elevated celebrity, it is followed quite literally a fall back to earth. 

In his post-Moon life, Duke found God.

“A lot of us have a letdown [afterwards]," he admits. Duke was 36 when he landed on the moon in April 1972. By December, the Apollo programme was over. "In January ’73, the thought occurred to me, ‘what am I going to do now?’"

Achieving his life's ambition before hitting middle age turned out not to be as satisfying as he expected. "Because you’d climbed the top, you got to the ultimate high when you were still a young man - and the drive that took you to the ultimate high was still there," he says. "That was a struggle."

In the years since, Duke has looked at his experience as a religious one. Yet he insists God wasn’t present for him when he touched down on the lunar body.

“The Moon flight was not a spiritual experience," he says. "I didn’t understand the wonder of God’s universe. I was enjoying the beauty and the excitement of this mission.”

The three men agree that Mars is the next step for the future of humanity, but there are safety and speed concerns.

“There is potential important work to be done in better physiological understanding of human exposure to long duration space flight which is going to happen whenever we go to Mars,” says Schmitt.

“Anything we do as human beings that’s productive and worthwhile carries risk, either physical of psychological. Radiation, physiological exposure to weightlessness for long durations, and the danger of landing on a distant planet where the atmosphere is not going to be much help - but you do accept the risk that it might end up as a one-way trip.”

But after all of that - the life, the death, the heartache - Duke says he would go back up there if he could.

“At my age now I wouldn’t volunteer to go to Mars - but I would volunteer for a round-trip to the Moon again.”

Starmus Festival runs in Trondheim until Friday June 23. For more information, visit Starmus.

Kirstie McCrum is a freelance journalist. Follow her @kirstiemccrum.

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