Questions About Time and Space

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

This is the question which Einstein posed in his famous paper "On the General Theory of Relativity." He picked up his pen in 1916 and wrote: "I believe that if we understand the universe at a lower level than we understand it now, we shall soon be able to obtain a better understanding of it." A year later, he brought out his second little paper, "On the General Theory of Relativity," which was accepted for publication in the journal Monthly Review.

Einstein's thesis was that the universe was expanding (and so was time) at a rate of roughly one-quarter of a second per day. But his proof was not complete; his theory had to be modified to account for the fact that the universe was expanding at a rate of one-half of a second per day. The observation of an accelerating clock in the early 1920s confirmed Einstein's idea of the universe being expanding at a rate of one-sixth of a second per day.

The universe had a period of one-sixth of a second per day. And this was not the only rate of expansion.

The full picture of the universe was beginning to emerge. The time-dilation effect was becoming clearer; the speed of light was becoming clearer. What was the origin of this period of one-sixth of a second per day? It was an expanding universe.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The Spinoza of Scientific Knowledge

The Spinoza of Scientific Knowledge (1892) is perhaps the most famous example of the philosophy of science. It attracted attention in the late nineteenth century as a response to the work of Jacques Derrida, who had written an influential book, God and the Science of Nature. Derrida began by examining the arguments of the scientists. He found the evidence to be heavily inadequate. He also found it surprising that it seemed to be accepted unquestioningly by the public, that it was heard by many philosophers, and that its authors were treated as distinguished scientists.

This led him to conclude that science was nothing but the exercise of ordinary judgment, and that it is unimportant whether we are right or wrong. Which brought him to his own conclusion: "In the end, whether we are right or wrong, we are all the same. No matter which way we turn, we all fall down."

The Spinoza of Science is a classic on the philosophy of science, and there is no doubt that its authors were philosophers of science, or at least scientists. But they had to have been philosophers of science in order to be able to give us the idea of science as it is, which is not simply the pursuit of the theories and the theories are the application of the theories.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer is no. Time doesn't stop. Time doesn't move. It's the universe that does the moving.

Circular Space and Circular Time

One way to think about the idea of time as a circle is to imagine that we've got two planes of space in front of us. The first is circular, and it's curved in a spiral pattern.

The second plane is spherical, and it's curved in a straight line.

The first plane is called the circle. It's also called the plane of space.

So, when we look at the universe from one plane, it looks like a super-curved circle.

Well, that's because it is.

But when we look at it from the other plane, we're looking at a super-flat circle.

That's because it's, by definition, curved.

But when we look at the universe from the other plane, it looks like a straight line.

Well, that's because it is.

In fact, when we look at the universe from the two most distant planes, we're looking at a straight line.

What is the circle? It's a straight line.

What is the smooth plane? It's a straight line.

What is the spiral plane? It's curved in a curved plane.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

Or is it possible that the universe is expanding without accelerating, like a giant detonator, but yet accelerating at a constant rate?

The darker picture of the universe is that it is not expanding, but contracting.

(Some people say that the contraction is not a contraction at all, but an expansion, which is just as well, for as we've seen, everything is expanding in the universe. This is true of the light, the heat, the matter, and the electromagnetic energy.)

The contraction of the universe is possible because the universe expands in a way that is compatible with a principle of relativity. Einstein's theory explains the fine structure of the universe, the way that its structure is shaped by the interaction of everyday gravitational forces. The equation that determines the mass of the universe, defined by the force of gravity, is equal to the ratio of the total mass of the universe to the total mass of all the objects in the universe.

If we were to assume that the universe is like an iceberg, and that the only problem with it is that there is a lot of ice in it, we could say that it is shrinking because, as I have said, we are observed only with the aid of other instruments. But what if we were to assume that the universe is like a lake, and that the only problem is that there is a lot of water in it? Would the river run dry? Would the iceberg melt?

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture? Could we have a theory of time that would explain all the apparent endless loops of space and time?

In fact, the problem of time emerged only after the twentieth century. The dominant theories of physics at the time were the Newtonian and General Relativity. Newton's laws of motion were based on the laws of Newton's first law. These laws could be just as well applied to the universe, but in the process, Newton gave us the theory of space-time.

After the first appearance of relativity, scientists realized that the universe had different properties depending on the position of the observer. If we observe the universe at a fixed point in space, such as the Earth, then our observations are quite limited. We can't look at the universe from any point in space. When we look from any point in space, we cannot look back. We can only look down into space. We can only look up into space.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

In any case, the answer is a resounding yes. The universe is expanding, and that's why we can now see light of infinite wavelengths through it. The universe grows in all directions, but the curve of space-time is always curved, and this is the reason there are stars and galaxies. It is this curvature which allows us to see the universe as it is. Quantum Mechanics, one of the most important developments of the 20th century, tells us that this curvature is absolutely constant. It is not a feature. That is why quantum mechanics is so important.

But what about the constant curvature of space-time?

No problem. Quantum mechanics tells us that the universe is finite, that it is infinite in dimensions, and that it also extends infinitely in dimensions. All of this falls into the box of the universe, and the universe is exactly the same size as the box. But what about the laws of quantum mechanics which describe all this?

Quantum mechanics gives us the laws of quantum gravity, a category of physical laws which explains how the universe's energy is conserved. The laws of quantum physics tell us that if the universe were to end in a singularity, it would destroy all of its components.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

After the success of the theory of relativity, Einstein had a brilliant idea. He proposed that there was no "space-time continuum," the idea that space and time are independent. Instead, time and space are interdependent. Time in Einstein's conception is a continuous stream of events, each event going on in its own place within the space-time continuum.

This idea of continuity was the basis of quantum mechanics, the basis for the theory of relativity. But it was also the basis of the theory of relativity itself. Einstein thought that the universe was expanding, but he thought that it was also shrinking. He thought that the universe was expanding, but he thought that it was shrinking. He thought that the universe was expanding, but he thought that it was shrinking. He thought that the universe was expanding, but he thought that it was shrinking. He thought that the universe was expanding, but he thought that it was shrinking. And finally, as he approached the end of his life, he wrote a classic study in which he proposed that it was all really the same!

But Einstein's theories are not standards. They are not theories in the sense that the standard hypothesis of physics was in the nineteenth century. They are not theories of cause and effect, or even general relativity. Instead, Einstein's theories are theories of space-time, of time as a continuum of events, and of the infinite nature of time.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer is a resounding "yes", and the idea is a subject of frequent discussion in particle physics. But where exactly does time go?

The answer lies in the universe's geometry.

One of the easiest ways to see how the universe works is by looking at the shape of the universe. It looks a bit like a spiral, in which the black hole at the centre is so massive that it consumes the light from the light source at the end, producing a black hole.

That's a pretty neat way to think about the universe, but it doesn't tell us much about what it is.

There is another way to see the universe: by considering how it stretches out.

There is, of course, a black hole at the centre of your universe, but in every other universe, the black hole is "sliced out", as Einstein said, by the light from the source at the end of the universe. In the case of our universe, the universe has shrunk down to a single point, so that it may be said to stretch out.

But wait, there's more!

One of the most famous ideas in particle physics is that the universe expands outward at an ever-increasing rate. That means that it is expanding at enormous speeds as it moves along the path of the expansion of space. On the surface, this seems obvious, but in fact it is not so.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture? The answer is yes—and it's not the whole picture.

Think of the universe as a computer. Each computer on the machine runs its own program, but the program runs on the same computer's processor. The processor may be the same as that which runs the machine, but what is the operating system? What are its permissions? What is its configuration? What are its files? What are its memory cards? What are its operating systems? What are its window managers? What are its audio and video drivers? What are its printers? What are its scanners? What are its media players? How many copies of its operating system is it running? What is its multimedia player? How many copies of its media player is it running? What is its network connection? What is its radio receiver? What is its video camera? What is its video recorder? What is its tape recorder? What is its tape player? What is its LED camera? What is its lights? What is its microphone? Any of these devices can be programmed to record, play, and record again.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

All that is known about the universe is that it is expanding. But the universe was expanding as well. The universe was like the sun, expanding and cooling, in a perpetual and rapid cycle. It was an object in space, but it was also a fluid in space. (That also sounds like a universe in which time and space are equal, but that is not quite so.)

The sun itself, of course, is a moving object in space. It moves on its axis, as long as it takes to reach the red spot of the sun. But it also rotates in its orbit. If the sun were a red-spot, it would have a rotation rate of about one revolution a second. But if it were a yellow-spot, then it would have a rotation rate of about three revolutions a second! The sun is a moving object in space because it has a swimming motion, and it is a moving object in time because it has an oscillating motion.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

From the first post, I've assumed that Einstein's theory of relativity requires a circular universe, but I'm glad to see that the Universe Research Institute has turned up the heat and done some rigorous calculations. The result is a circular universe in which the speed of light is constant. It's a very novel result, and it's pretty well confirmed by the work Einstein did in the 1930s. It is, however, not certain that it is correct, because Einstein's theory of relativity is threatened by the fact that the speed of light is always in a constant state.

What makes this even more remarkable is that when I last wrote about Einstein's theory of relativity, I had little idea of how it was going to turn out. But now, thanks to a new conference in Zurich, I know what it is: Einstein's theory of relativity is the same as Newton's law of gravitation.

The new theory of relativity is based on a strange theorem called the "brute force" – a concept that has never before been used to describe such a peculiar phenomenon. If you can think of a force that is strong enough to overcome gravity, you can derive the force required to effect the bending of light, which is why light is always in motion. That is why it is so much easier to shift an object in a circle around a central point than it is to rise up out of a zigzag into the centre of a circle.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer is yes, and it is quite simple. The universe is a giant black hole. The hole is being pulled outward, contracting, expanding, and contracting again and again. The thing is, it is impossible to see with the naked eye. It is undulating, like a snake in the grass, and, unlike a snake, it does not spin around.

The black hole is like a giant ball of frothy black matter in a gas-filled universe. It is extremely dense, sleeping at the center, surrounded by a vast expanse of hot gas and dust.

When the black hole is observed, the temperature of the gas fires up. The black hole spins rapidly, shooting out a magnetic field and spewing out a stream of hot plasma. The black hole is like a giant laser gun firing away from a weapon in a gunfight.

The black hole is a giant black hole in a world as hot as the sun. The sun is one of the largest objects in the universe, and the object that is most likely to have formed it is the one that is now in orbit around the black hole.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

It turns out that we are not alone in trying to answer these questions. In the fall of 2009, the physicist Richard Feynman, who inspired the movie "2001," published a paper in the Journal of the Royal Society hinting at a version of the universe which is expanding but is also shrinking. It is based on his work on the theory of quantum gravity.

In the basic view, the universe has two dimensions: space and time. At the boundary between the two, the universe curves around a central point, called the singularity, and we see nothing but the curved line that leads to the singularity.

In Feynman's view, this line is not a line of sight but a line of pressure, and its edge is flat.

In his model, if you were to stick a razor blade through the edge of the universe, you would reach the singularity. But now, the razor would be curved, and you would have to slice through the edge of the universe to reach the singularity.

In the end, the universe is expanding, but it is shrinking in some other way.

This view was based on a remarkable observation by the late physicist Stephen Hawking in 1963.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

It's easy to see that the answer to this question is not obvious. If time is circular, what, exactly, can we say about it?

What about the question of space and time?

'Age' is quite a nice word. It gives us the idea of a person's life. The term is modern, but it was coined by a Roman philosopher, Quintilian, who lived in the first century B.C. The idea was that life is only a series of periods of increasing and decreasing duration.

It seems to me that this is an old idea. At the beginning of the last century, we saw that life was a relatively short period of time. We saw that the process of death was relatively simple. But then, slowly, the course of our life passed away. Years passed by, and then, over all, we saw that it took some time to die – and that death still seemed to follow us.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

One of the most famous proofs of the Big Bang is that the universe has not a finite size. But if we were to fit an infinite space in front of an infinite time, we would need to find a time machine. These machines might be located at the edge of the universe, maybe even beyond it. They are all but impossible to construct. The fact that they are impossible makes them seem like mere pieces of work. But they prove that the universe is not finite.

In all this, the problem of time is not so much the problem of the universe as of the universe itself.

The view that the universe is expanding is correct, but it is equally true that the universe is shrinking. It may be that the universe is expanding faster than it is shrinking. It may also be that the universe is shrinking faster than it is expanding. But, in any event, the beginning of this expansion is still close to us. It's only a question of how far we will come.

The universe is expanding at three times the rate that it is shrinking. It is an expanding universe, and it will continue to expand until the universe is as large as our own universe.

The universe is expanding at six times the rate that it is shrinking. It is an expanding universe, and it will continue to expand until the universe is as large as our own universe.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer is no. "The universe is elastic," Einstein said. "It is not bounded, but it is not flat."

The universe is like a wheel, spinning endlessly. But, Einstein said, "it is turned round and round." Thus it is possible for it to move in a straight line, and for it to turn in an arc. "The braille wheel" is a result of the infinite possibilities of the universe.

But the spiral wheel of the universe is not. Einstein never made such a claim. He had rather said that it was "like the sun on the earth," and, when he did so, he was not referring to the sun as it moves in the sky, but to its motion in space.

The sun is not stationary. The sun never lies in the sky. It has a radiant path on which it moves about once every two hours.

It is always moving in the direction of the earth, and in a larger circle than the sun itself.

We are often asked why we see the sun at certain times of the year. The answer is that the sun is a rotating mirror. But it is no mirror. It moves in constant motion and is always curved.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

One way to find out is to ask two questions. First, can we measure the expansion of the universe? That's the same question that forms the basis of modern cosmology. Einstein's theory of general relativity, which makes the universe look like a curved disk, considers what happens to the speed of light when it is slowed by the gravitational attraction between two objects.

In the second part of this three-part series, we will explore Einstein's theory of radiation, which might be more relevant to the question of time.

Fisher's circle

The universe is thought to contain a number of fundamental particles, which are now known to be particles of string theory. One of these particles, known as the "fisher's circle," is the smallest known particle of string theory.

In the first part of the series, we compared the speed of light with the speed of light in a mirror. In the second part, we will compare the speed of light with the speed of light in a telescope.

When the mirror is behind the telescope, the image of the distant universe looks like a black hole. But when the mirror is behind the telescope, the image of the distant universe looks like a black hole.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer to these questions lies in Einstein's theory of relativity, which is still the dominant theory of the discipline. In a nutshell, it is the theory that underlies the science of physical space and time.

Specifically, Einstein's relativity theory predicts that the universe is expanding. That means that it's changing direction every day, and the speed of light is accelerating. But, as Einstein told me, it's in the nature of things that accelerating things is what causes space and time to change. So when we measure the speed of light, we are measuring the speed of an invisible object moving at the speed of light.

I asked Einstein to explain what, exactly, is a "divergent universe." He was unafraid to tell me what he meant. "A divergent universe is a universe whose space and time are both finite," he explained. "We have two inner worlds, one which is flat and the other which is curved. The flat universe is the place where all of us live, and the curved universe is the place where we live. But it's a divergent universe. It has a curve on one side and a flat on the other."

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

In a paper published in the Journal of Theoretical Physics, David McMillan and colleagues find that the universe has no limit to the speed of light. While scientists have long been hunting for a way to measure the speed of light, there are extremely few ways to measure it.

To find out, McMillan and colleagues used a device that, like a classical pendulum, spins a spring to spin the pendulum in either direction. The spring is connected to a "dipole" with its two ends bent downwards. The dipole is connected to the supply of electricity from a nearby battery, and the tap is connected to a feed line. McMillan's electricity condenses into heat, which heats the tap, which heats the dipole, which heats the dipole. This continues until, at its last turn, the dipole is turned in the opposite direction, and the tap is turned on.

McMillan and colleagues measure the temperature of the tap as it is turned on by measuring the voltage across the circuit. They use this to measure the voltage applied to the dipole. Then they measure the amount of energy they get from the heating and cooling of the tap.

McMillan and colleagues find that the whole of the universe is expanding through time. In fact, the universe is expanding at the speed of light.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The result is that our universe is a snapshot, a record of a very interesting time in the history of the universe. It is an extraordinary record, with many of the features we observe today. For example, the universe is expanding, but it's also shrinking. And it's expanding, so it's losing gravity, but it's also expanding, so it's losing gravitational force.

It is a remarkable record, with many features that we never noticed before. For example, we know that our universe is expanding, but that it's also shrinking. In fact, it's expanding, and it's shrinking. That's one of our most startling observations, that the universe is expanding.

The other remarkable feature of the record is that it's expanding slowly. Consider that it is shrinking slowly. The universe is expanding faster than light. But it's shrinking, so it's losing gravity. It's shrinking, so it's losing gravitational force.

What is this shrinking? It's the result of a process called dark energy. Dark energy is the hidden energy behind the universe. It's like the wind. It is the invisible energy behind the universe that is slowly pulling the universe apart.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer to this question is an enormous one—there is no end to the universe. All that we know for sure about the nature of the universe is that it is finite. This is because, as we have seen, it is finite in scale. The universe is not finite in its capacity to go on forever. If it were, then there would be no time. But if it were infinite, and if it were moving on an infinite loop, then it would be finite in its capacity to do that.

So even if the universe is finite in its capacity to go on forever, it is still finite in its capacity to make changes. It is finite in its capacity to make one change, and so on.

This is not an easy question, but it is one that is not entirely hopeless. If we accept the theory of evolution, the universe is finite in its capacity to remain unchanged. Even in the case of the universe, however, it is finite in its capacity to continue to evolve. Hence, the universe is not finite in its capacity to remain unchanged, but it is not finite in its capacity to change.

The same concept holds good for the universe as a whole. It is finite in its capacity to change. If such is the case, then, if we were to suppose that the universe had a beginning and a future, there is no reason to suppose that it would be finite in its capacity to change.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

If you were to ask a man what is the most important and useful thing about our universe, you would probably say that it is the way we live. That is, we live in a world where there are laws governing all the things in it.

But these laws are not all that we observe. There are other laws that we observe, too.

In the first part of this book I refer to the laws of thermodynamics, in which a single atom is the most complicated thing that we observe. I show that when we examine the effects at work in the atoms of a single atom, we can find that we can observe thermodynamic effects in all the bodies of our universe.

The collapse of a star in our own solar system is an excellent illustration of this principle. In a star's formation, it has been taken as given that its atoms are made up of a single group of matter, the so-called central nucleus, which has a dense, compact structure. The nucleus is very thin and curved. It is therefore obvious that the distinctive characteristic of any star is that it is a dense cluster of hot, dense, heavy elements.

It is also obvious that it is a cluster of stars. The central star has a very small mass. The smaller stars are not very bright, but they are bright enough that they receive much larger amounts of light from the surrounding stars than from our own sun.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer is yes. It turns out that time is a vector space. A vector space is an infinite set of possible paths, of which we have just one.

We can think of a vector space as a collection of distinct paths. It is a collection of different points on a path, which have different properties apart from being identical. All paths converge to a single point on the path.

That is, the path is a vector.

One way of saying this is to say that a vector is a vector of points that satisfy the laws of motion of a vector.

Now, a vector has a unique identity function. If you want to make a vector of points point up, you need to find a point on the path that satisfies the identity function of that vector.

It will be convenient to say that a vector is a map, which means that a map is a collection of points.

Of course, a vector is a map if there were just one point on the path. There is also a map of the vector. So if there were just one point, there would be only one map. How could we find that point?

Well, we can define it as that point that we defined in the definition of the vector.

The only thing we need to do is to take the identity of the vector and the map together and come up with a map.

We will call that point.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture? There is no doubt that space is expanding, and with it the universe as a whole. Yet it's also shrinking. It's a tight squeeze, and our universe is in a perpetual state of expansion. We think of space as expanding, but it actually doesn't. The universe is expanding, but it's also shrinking.

The Universe is populated by intelligent life, and they are always changing. Their lives are influenced by their surroundings, and we only glimpse glimpses of them through our telescope. But although we see them through our telescopes, they are not really us. The sun is at the center of the universe, and our Earth is only a speck of light in the darkness, an infant moon that never sets.

Our view of the universe is always being expanded. But our view of the universe also grows larger. The universe can't be the same everywhere. Every space station has been constructed from the same materials. Every star has been fitted with a precise, reliable lens. Every star has been lit up and orbitated by the same light. Every astronomical instrument has been set up to measure the temperature of the stars. But what has been the temperature of the stars? How did they get there? How did they get so bright?

A series of observations has led to a very simple answer: the stars are getting dimmer.

The universe is expanding. But what if it's also shrinking in the same time? Can it be that it moves on an infinite loop, shrinking and expending endlessly? Does that mean that time is circular? Did Einstein get us only half of the picture?

The answer is no, according to Richard Feynman, a theoretical physicist at the California Institute of Technology. He argues that the universe is round because it is an expanding process.

"The universe is like a ball that continues to spin and expands," he says. "And the ball is round, because it is moving along with the universe. The universe is like the sun, which is moving along with the earth."

In Feynman's view, the universe is like any other body in the universe. It is a huge blob of gas and gas is expanding at an ever-increasing rate. But the universe doesn't seem to be shrinking, either.

"I would think that the universe is expanding at about the rate of about a thousand centimeters per second," says Feynman. "Maybe that's the rate at which it could expand without stopping. I would say that while it's expanding, it's still expanding at a rate that would give it a diameter of about a million kilometers."

This is a fascinating idea, but perhaps not a very modern one. In his book, Feynman writes that "the universe is finite, and it is expanding in a finite amount of time."

But if we believe Feynman, the universe is expanding at a rate of about a million kilometers per second. Then we can see that it is circular.