“What is the time now? If no one asks about it, so I know it; if I want to explain it but someone on his question, so I don’t know.” This quote from the philosopher Augustine describes our relationship so well like no other. We all feel, how time crawls time to go, time flies. We know, intuitively, that every Moment of the future flows into the past, and short of our perception is captured: This is the present. But as soon as we try to grasp these perceived truths in words, contradictions. “I know that there would be no past time if nothing were to pass, no future, if nothing would be there. How are those two times, the past and the future, but since the past and the future is not yet?”, complains of Augustine. The time can turn a tidy of the Cerebral convolutions.

Since ancient times, philosophers and scientists argue the time. It has a beginning? Why is passing you? Does it even exist?

In physics, the hunt for the essence of time leads directly to the milestones in our understanding of the world. The Mechanics, the thermodynamics, the theory of relativity and quantum physics each provide pieces of the puzzle. In the process, deprive you of the time of all the properties that shape the way we feel for you. What remains is a confusing, alien construct. In his book “The order of time,” writes the physicist Carlo Rovelli: “to examine The time in such a way, as you hold a snowflake in the hands: The longer we look at it, the more it melts, until it is finally entirely disappeared.”

“The time is everywhere, but we understand you are nowhere”, says Renato Renner, Professor of Theoretical physics at the ETH Zurich. He is one of many researchers who devote themselves to this puzzle. Who solves it, will reveal a new, more complete view of reality. We were going to have to take the time ever really tells you the way to the future of physics: that long-awaited theory that describes the whole universe.

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What are the physics know about the time? To find out, is worth a trip in the history of science. It leads us to four theories that have revolutionized our understanding of the world step by step. On 5. July 1687, the British scientist, sir Isaac Newton, one of the most important works in the history of natural science: the “Philosophiae Naturalis Principia Mathematica” published. In it, he formulated a theory of gravity and the mathematical laws for the motion of bodies. However, Newton did even more: In the flick of the wrist, he rose time and space to the big stage of world events. “Absolute, true and mathematical time flows in itself and by their nature are uniform, without relationship to external objects,” he wrote. In the Hidden roll, therefore, inexorably to a cosmic clock of the whole of the world, and all things a precise duration and sequence presented.

This understanding of time appears to us to be immediately obvious. But Newton’s equations also something very Amazing to say about the nature of time. Because of his Mechanics does not distinguish between the past and the future. Would someone press a cosmic rewind button – Newton’s laws of motion would remain valid.

This sounds strange, but it is to illustrate. You think of the earth revolving around the sun. Two principles of classical Mechanics to determine the travel of planets. On the one hand, it urges the inertia to the straight and narrow path into space to fly. On the other hand, the force of gravity is pulling you (especially) in the direction of the sun. These conflicting forces the earth on its orbit. Suppose we could reverse the passage of time: What would change in your Orbit? The answer: not in the Slightest. All of the laws that determine their trajectory, applied in the same way as before. The earth would only change their direction of flight.

1850: The flowing time

For a celestial body through space grid, the direction of the time so no role. For a ball rolling over a pool table, she does that very well. Planetary, and ball follow both the laws of Mechanics. However, during the celestial body attracts over thousands of years, unperturbed in his tracks, the billiard ball after a few moments of momentum:. Would reverse the flow of time, would put the retired ball as if by magic in motion and getting faster. Any viewer would be clear that something is wrong here.

The crucial difference is the friction power. If the billiard ball rolls across the green felt and through a sea of air particles is of the essence is converted to kinetic energy by the friction in unrelenting heat and is lost.

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Here is a law of nature at work in this article are of particular importance: the Second law of thermodynamics. He says that certain processes without external influence, run in one direction only, never in the other. Friction slows down the billiard balls. Heat flows from the Hot to the Cold. Falling cups shatter, but they never spontaneously. The Second law of thermodynamics, for the first time in 1850, formulated by the German physicist Rudolf Clausius, is the only principle of classical physics that time is not reversible. Soon the idea came up, therefore, he could refer to the origin of the time arrow.

let’s take a closer look at the operations of the Second main clause describes. They have one thing in Common: the entropy increases. This of Clausius imagined size is colloquially referred to as a measure of disorder. The Second law States: In the past, things were more orderly. In the future, you will be disordered.

we Look at the entropy of a example: Pour milk in a Cup of coffee, hovering briefly as a bright cloud in the brown broth. The ingredients of milk and coffee are neatly separated. At this time, the entropy is low. However, the procedure does not last long: The molecules wriggle back and forth, collide and mix rapidly. Soon, the milk is distributed in the coffee. The entropy has increased. A victory of the probability is: There are only a few Possiblethe molecules of milk and coffee dates to be arranged, so that they are separated. However, there are many ways to arrange them so that we see a uniformly light-brown liquid.

entropy increases not only in the mess of milk coffee. It also rises in the shambles of a broken Cup. It rises in a friction warmed-up billiard ball, in which the molecules move more. Even more: it increases in the whole universe. In the world of entropy, there is no going Back. We can reduce the clutter in a place to take you elsewhere all the more stronger. A freezer, in the ordered form ice Crystals, generates more heat (and thus entropy), as it deprives the water.

So the increase in entropy is responsible for the fact that time flows in one direction only? Some physicists are of this opinion. However, the theory has two major weaknesses. First, it is not before an important criterion of Quality to say about the behavior of the time, you can experimentally check – in physics.

Secondly, the entropy increases, not always and everywhere at a constant speed. There are numerous situations in which it decreases fixed. When the earth cools at night, decreases the entropy of the surface; instead, the entfleuch increase heat radiation out clutter in All. On the speed of the clocks has no influence. “Locally, entropy can decrease without the time running backwards,” says Renner.

1905: The relative time

Perhaps local conditions are not able to change the course of time? You could believe, if not a physicist named Albert Einstein between 1905 and 1915, had shown the opposite. His thought experiments led him to the realization that the time of the site can take place very different quickly. Newton had made a mistake: time is not absolute, it is relative. But it is not the entropy, which influences your speed. It are difficult to force and motion.

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makes The theory of relativity makes any notion to destroy the us to make intuitively from the nature of time. We have to give up the Belief that for all of us exists a uniform time. The opposite is the case: Each point in space has its own time. Even for your head, time passes differently than it is for your feet. There is no “Ur-period”, we are the things can measure. If a clock goes fast or slow, can only say, if we compare it with another clock. In the world of relativity, we always need to have a reference system.

Einstein’s first brilliant insight was that moving clocks go slower than stationary clocks. Is illustrated in the famous twin paradox: a twin on earth (the reference system), while the other is into space travel. Because the spacecraft from earth’s perspective moves very quickly, and stretches for the space travelers of the time. He realizes it is From his point of view, the clock is ticking on the space ship with the same speed. But when he returns after many years to the earth, he is amazed that his twin is more aged than he is. For the home there is more time remaining for the farewell passed for the traveler.

How strong this effect is depends on the speed. The physicist Richard Muller provides in his book “Now”, the following calculation example: The clock of a GPS satellite, the grid with 14 000 km/h around the earth, at the end of the day compared to earth clocks of 7.2 micro-seconds. Sounds like a smidge. But the navigation system did not take into account this from Einstein’s formulas resulting delay, in addition, would the calculated GPS Position after 24 hours, 2.2 kilometers.

The extreme case of time dilation experience light particles. With about 300 000 kilometers per second, you can reach the maximum speed in the universe. A particle of light, a clock in your Luggage, would you would in our view be still. It would be possible, and of the laws of nature allowed it to move with superluminal speed, you could even travel back in time.

But that’s not enough of the oddities. Einstein’s second great insight was that large masses of slow down time – and the more, the stronger its gravity is. On the mountain, further away from the center of the earth, time passes faster than in the valley. At head height it goes faster than at the height of the feet. On earth passes faster than on the mass of the sun richer.

Why influenced the force of gravity the speed of clocks? This effect stems from the fact that space and time exist independently of each other. They are a four-dimensional space-time, an elastic Structure, the elastic surface of a balloon. Large masses of dents cause skin in this cosmic rubber. You stretch, literally, the time.

In Einstein’s General theory of relativity, space and time are two sides of the same coin. They are described mathematically as a Whole. The formulas provide both the right not to March in the direction of. This raises the question: Why do you behave so obviously different? “That time is not flowing, the room is very mysterious,” says Dieter Lüst, Director at the Max-Planck-Institute for physics in Munich. Einstein himself moved elegantly out of the affair in which he explained the difference to the illusion. “For us faithful physicists, the separation between past, present, and future has only the significance of a stubborn Illusion,” he wrote in a condolence letter to the sister of a deceased friend.

The theory of relativity not only throws our image of an evenly flowing, for all applicable time on the bunch. It robs us of the idea that there is a General presence. We remember the two twins: One in space, one on earth. How can the Offspring know what makes his brother in the space ship “now”? We have already noted that the time flies for both of different. Information such as “five years after departure” for the brothers, so different meanings.

And if one of the other radios, to ask what he’s doing now? Also this does not work: communication can only go at the speed of light. If the area the driver is in the neighboring galaxy on the go, you need the Signal years, to run to him and back again. Just like the word “here”, “now” from a certain distance, no sense. “Our presence does not extend to the entire universe,” writes Carlo Rovelli. “It is like a bubble that surrounds us relatively closely.”

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©Courtesy of NASA

so What did we learn? Time in nature is not, as it appears to us. It passes non-uniformly, but at different rates. It is with the space. It has no unified presence. These are the consequences of Einstein’s theories for the nature of time. You are strange, but physicists undisputed. This Unity is lost when we enter leave the vast Expanses of the cosmos and in the world of the microscopic.

1926: quantum time

The model of quantum mechanics describes the behavior of the smallest particles, such as atoms, electrons, or particles of light. Your equations were in the first half of the 20th century. Century developed, and are one of the best substantiated theories of physics. Countless experiments confirm your predictions. However, although the formulas appear to be correct, argue researchers since its written about how the nano world map, actually looks like.

quantum put all kinds of exotic properties. You can seemingly arise from nowhere and disappear without trace. You are in the same Moment at different locations. Take at the same time, the conflicting States. As soon as we perform a measurement, they seem to decide arbitrarily for a place or a state. What is happening in this Moment, is still the subject of heated debate.

The time is in this jumble at first glance unremarkable. In the original quantum mechanics equivalent to Newton’s ideas. As in the classical Mechanics of processes is not more and not less have a duration. “The laws of motion of the particles run in both directions,” says Dieter Lüst. There is no prescribed time arrow, and also not confusing, woven, rubber-like space-time. Instead, there is probably something even Weirder. What if the time is as crazy as the elementary particles themselves?

Many sizes in the realm of the very smallest are quantized – they are made up of small, indivisible units. Matter and radiation are composed of, for example, from elementary particles. Also the energy is quantized: particles you need to capture always in tiny packages, or give up. You behave as if you were climbing an invisible staircase. The energy is not enough to hop to the next higher level, they fall back to their previous levels.

Why should not also the time from the smallest units? Then you would not flow continuously, but a trickle, like the grains of an hourglass. It is established that there is a smallest time interval, beyond which the laws of physics apply. Its duration is calculated from the equations of quantum physics, and three constants of nature. This is the smallest time interval is 5,39116 •1044 seconds. This is about ten trillion trillion (1025) times shorter than what can be measure the most accurate atomic clocks.

The future of

With the grain of the time we leave the world of experimental evidence and enter the realm of speculation. There are different interpretations and further developments of quantum physics exist; they all describe the role of the time a little differently. For our history of of any importance: The time in quantum physics, other properties as in the theory of relativity. It is not intertwined with the space, but goes on regardless.

Thus, the time marked one of many contradictions between the two theories, our world, describing both excellent – the quantum physics in the Small, the theory of relativity in the Large. The unsolved mystery of the time researchers are painfully reminded that you have recorded with both theories, only two borders of the world tissue.

to a lot of But perhaps the time can just assign the path to a more comprehensive picture of the nature of a theory that the entire universe unit describes, from the smallest elementary particle to the largest Galaxy. “If we want to bring quantum physics and relativity together, we need a common understanding of the things of which you speak”, says Renato Renner. His research group at ETH Zurich tries to get with thought experiments, a concept of time that is the same in both worlds equally valid. To do this, you will be charged, for example, the behavior of the imaginary quantum watches. The physicists want to know: Go big watches other than small, because of the relativity theory to change from the territory of quantum mechanics in this?

There are already concrete approaches to unify quantum physics and relativity theory. One of them is the existence of space postulated time-atoms: tiny, indivisible building blocks of space and time. If such Structures exist, they behave the same way a physicist would expect from the smallest of particles. However, these particles do not exist in space or time: they only form in space and time. Unimaginable and yet, perhaps real. “Tiny quantum fluctuations of space-time could be for the structure formation in the early universe”, says Dieter Lüst.

Such thought experiments have the Power to bring to light hidden aspects of reality to light. What you have taught us over time, is still a piece of work. The overwhelming majority of the laws of nature are not part of distinguishes between past and future: a jigsaw Puzzle. There is no generally valid today: another piece of the Puzzle. The time part does not flow evenly, but from place to place at different rates: a third Puzzle. The time is, at least on the big stage, not regardless, but with the space interwoven with a fourth piece of the Puzzle. Maybe the time part, just like matter, is made up of tiny building blocks: a fifth Puzzle.

reset all the pieces together, you have to be willing to part with cherished Beliefs. “The concept of time is so fundamental that it is difficult to talk about it, without anticipating it,” says Renato Renner. Our language, our logic, our Intuition: they are all imbued with it. “The genius of the theory of relativity was to throw self-evident ideas. What we need now, is a still more radical step.”

Renner believes that the necessary paradigm shift in the science is already in progress. The time, he says, is ripe for a new understanding of time.