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Stephen Hawking's lecture "The Origin of the Universe" at the Hebrew University of Jerusalem, December 14, 2006

A special project of the knowledge site. The translation of the lecture as written by Hawking himself and delivered in English by the Hebrew University. Translation: Avi Blizovsky

Prof. Stephen Hawking in his lecture at the Hebrew University, December 14, 2006. Photo: Sasson Thirim for the Hebrew University Spokesperson's Office
Prof. Stephen Hawking in his lecture at the Hebrew University, December 14, 2006. Photo: Sasson Thirim for the Hebrew University Spokesperson's Office
According to the myths of the Bushongo people in Central Africa, in the beginning there was only darkness, water, and the great god Bumba. One day Bumba decided, while suffering from stomach pains, to vomit the sun out of him. The sun dried up some of the water and exposed the land. Still under enormous stomach pains, Bomba threw up the moon, the stars and several animals - the lion, the crocodile, the turtle and finally, the man.

This creation myth, like other creation myths, tries to answer the questions we all ask. "Why are we here? Where did we come from? The answer usually received was that humans are relatively recent creatures, because even in ancient times it was clear that the human race was constantly improving knowledge and technology, so it is clear that it has not been here for long. Or else it would have been even more developed. For example, according to Bishop Asher, the book of Genesis placed creation at nine o'clock in the morning on October 27, 2004 BC. On the other hand, the physical environment such as mountains and rivers changed very little during a person's lifetime. Therefore they were considered part of the permanent background, and either they existed forever as an empty landscape, or they were created at the same time that humans were created.

Not everyone, however, was happy with the idea that the universe had a beginning. For example, Aristotle, the most famous Greek philosopher, believed that the universe had existed forever. An eternal factor is more perfect than a created factor. He offered an explanation for the changes and developments we observe - according to him, floods or other natural disasters have brought civilization back to the starting point from time to time. The motivation for belief in the eternal universe was the desire to avoid using heavenly involvement to create the universe and set it in motion. On the contrary, those who believed that the universe had a beginning, used such creation as proof of the existence of God as the first cause or prime mover of the universe.

If someone believed that the universe had a beginning the obvious question was: what happened before the beginning. What did God do before he created the world? Has he prepared hell for people who ask these questions? The question of whether the universe had a beginning or not caused great concern to the German philosopher Immanuel Kant. He felt there were problems with either option.

If the universe had a beginning why did it have to wait an infinite amount of time before it was created? He called it a thesis. On the other hand, if the universe existed forever, why did it take so long to reach its current state? He called it an anti-thesis. Both the thesis and the anti-thesis depend on Kant's assessment, like everyone else's, that time is eternal, that is, it flowed from the infinite past to the infinite future, regardless of the existence of an existing or non-existing universe in the background.

This is still the image that runs through the minds of many scientists to this day. However, in 1915, Einstein presented the theory of general relativity. In this theory, space and time are no longer absolute, and do not constitute a fixed background for events. Instead, they are dynamic growths, shaped by the matter and energy in the universe. They were defined exclusively within the universe, so there is no meaning to talk about the time before the beginning of the universe. It's like asking if there is a point further south than the south pole of the earth. The time just wasn't set.

If the universe has not changed over time, as was commonly thought before the XNUMXs, there is no reason why time cannot be arbitrarily defined even far back. Everything that is called the beginning of the universe, will be an artificial factor in the sense that history can be extended back to earlier times. Therefore, it is possible that the universe was created last year, but with all the memories and physical evidence it would appear to be much older. This raises deep philosophical questions about the meaning of existence. I will address this by adopting what is known as the positive approach. According to this approach, we interpret our sensory input in terms of a model of the world we construct. It is impossible to ask whether this model represents reality, but only if it works. A model is a good model, first of all, if it interprets a wide range of observations in terms of a simple and elegant model, and in addition, if the model allows absolute predictions that can be tested, and possibly tried to be disproved, through observations.

In the terms of the positivist approach, two models of the universe can be compared, one according to which the universe was created last year, and one according to which the universe has existed for a longer period of time. The model according to which the universe has existed for more than a year can explain the existence of identical twins, which had a prime factor over a year ago. On the other hand, the model according to which the universe was created last year, cannot explain such events. So the first model is better. It is possible to ask if the universe existed a year ago, or if it only seemed so. According to the positivist approach the two possibilities are the same.

In an unchanging universe, there would be no natural starting point. The situation changed radically, when Edwin Hubble began making observations with the XNUMX-inch telescope on Mount Wilson in the XNUMXs. Hubble discovered that the stars are not uniformly distributed in space, but cluster together in collections called galaxies.

By measuring the light from the galaxies, Hubble could determine their speeds. He expected that many galaxies would move towards us, and about the same number would move away from us. This is expected if the universe does not change over time. However, to his surprise, Hubble found that almost all galaxies are moving away from us. Moreover, the farther galaxies are from us, the faster they are receding. The universe was not stable over time, as everyone thought before. He is spreading. The distance between distant galaxies is increasing with time.

The expansion of the universe was one of the most important intellectual discoveries of the 20th century, or of any century. It changed the debate on whether the universe had a beginning. If the galaxies are moving away now, they must have been closer in the past. If their speed was constant, they should have all been at one point, 15 billion years ago. Was this the beginning of the universe?

Many scientists were still not satisfied with the fact that the universe had a beginning because all the laws of physics seemed to collapse. There will be those who will involve an outside agency, conveniently called God, to determine how the universe began. Therefore they tried to develop theories according to which the universe is expanding in the present, but it had no beginning. One of these theories was the steady state theory, proposed by Bondi, Gould and Hoyle in 1948. According to the steady state theory when galaxies are moving apart, the idea is that new galaxies will form from the material that was supposed to form in a continuous pattern throughout space. The universe has existed forever and should look the same every time we observe it. The latter feature was considered good learning from the positivist perspective, whereby it provided a prediction that could be tested through observations. The Cambridge Radio Astronomy Group, headed by Martin Ryle, conducted a survey of the weak radio sources in the early XNUMXs. These sources are more or less uniformly distributed across the sky, indicating that these sources are outside our galaxy. The further away the source, the weaker it will be on average.

The source state theory predicted the shape of the graph of the number of sources as a function of their strength. However, the observations showed that there are many more weak sources than the theory predicted, and this indicated that the density of the sources was higher in the past. This was contrary to the basic hypothesis of the steady state theory, according to which everything was fixed in time. For this and other reasons, the steady state theory was abandoned.

Another attempt to prevent the existence of a beginning to the universe was in the proposal according to which the universe once had a stage of contraction, but due to the rotation movements and due to local irregularities, not all the material fell to the same point. Instead, different pieces of matter missed each other, and the universe began to expand again, with its density remaining finite. Two Russians, Lifshitz and Khaltnikov, actually succeeded in proving that a general contraction without exact symmetry will always lead to a jump, while the density will remain finite. This result was very convincing according to the materialist dialectic of Marxism-Leninism, because it made it possible to avoid commenting on the questions about the creation of the universe. Thus it became a kind of belief for the Soviet scientists.

A selection of the slides presented by Hawking in his lecture. Photographs: Tal Inbar and Avi Blizovsky, The Knowledge Site
A selection of the slides presented by Hawking in his lecture. Photographs: Tal Inbar and Avi Blizovsky, The Knowledge Site
When Lipshitz and Khlatnikov published their claims, I was a 21-year-old young research student looking for something to supplement my PhD thesis. I didn't believe in their so-called proof, and I sat down with Roger Penrose to develop the mathematical techniques needed to investigate the issue. We have shown that the universe cannot jump. If Einstein's theory of general relativity is correct, there will be a singular point, a point where the density is infinite and where space-time is curved, where time had a beginning.

Observational evidence that proved the idea that the universe had a compressed beginning appeared in October 1965, a few months after my first singular result, with the discovery of the weak cosmic microwave background radiation that prevails throughout space. These microwaves are the same as those in the microwave oven, but they are much weaker. They would only manage to heat your pizza to a temperature of minus 271.3 degrees Celsius, not enough to defrost the pizza, let alone bake it. We can actually observe these microwaves ourselves. Move your TV to an empty channel. What percentage of the snow dots on the screen were created by the microwave background radiation. The only logical interpretation of the background radiation is that it is the radiation left over from the initial hot period when the universe was in a compressed state. As the universe expanded, the radiation cooled until it became the faint remnant we observe today.

Although Penrose's and Shelley's singularity theories predicted that the universe had a beginning, they did not explain how it was created. The equations of general relativity are supposed to collapse at a singular point. Thus Einstein's theory cannot predict how the universe began, but only how it will develop after it began. There are two approaches that can be taken for reasons of things we do not understand. One of them is the point of view of Pope John Paul II at a conference dealing with cosmology held in the Vatican, the Pope said that there is no obstacle to exploring the universe after it was created. However, it is not possible to investigate the starting point itself because this is the moment of God's creation and work. I was happy that he didn't pay attention to the research I presented at the conference, and I offered the explanation for the beginning of the universe. I'm glad they didn't hand me over to the Inquisition, like Galileo.

The other explanation for our results, which was accepted by most scientists, is that this point in the beginning of the universe indicates that Einstein's theory of general relativity collapses in the strong gravitational fields that prevailed in the early universe. It should be replaced by a more complete theory. This could be expected in any case, because general relativity does not take into account the small scale of the structure of matter, which is controlled by quantum theory. This does not normally matter because the scale of the universe is enormous, but when the universe was Planck size, a billionth trillionth of a trillionth of a centimeter, these two scales come together, and quantum theory must also be taken into account.

To understand the origin of the universe, we are required to combine general relativity with quantum theory. The best way to do this is by using Feynman's idea about the sum of histories. Richard Feynman was a colorful guy, who played bongo drums in a strip club in Pasadena, and was one of the talented physicists at the California Institute of Technology. He proposed that the system moves from state A to state B through every possible course of history.

Each of the history tracks has some amplitudes or intensities, and that the chance of the system getting from point A to point B is given by adding the intensities to each of the tracks. There may even be a story that the moon is made of blue cheese, but the power is so low, it's bad news for mice.

The chance of reaching the current state of the universe is given by adding all the strengths to all the histories that end in the current state. But how did these histories begin? This is the origin question in a different way. Does it take a creator to issue a decree to start the universe? Or the initial state of the universe is also determined by the laws of science.

In fact, these questions will arise even if these histories are drawn backwards into the infinite past. However, they become more immediate if the universe was indeed created 15 billion years ago. The question of what happened at the beginning of time is similar to the question of what happens at the end of the world, when humans thought the world was flat. Is the world a flat plate, with a great sea stretching beyond the edge? I conducted an experiment to test this. I circled the world and didn't fall.

As we all know, the idea of ​​what happened at the end of the world was solved when humans realized that the world is not flat, but has a curved surface. Time, however, seems different. It appears to be separate from space, and that it operates in the structure of a railroad. It had a beginning, and there is someone who set the trains in motion.

Einstein's theory of general relativity united time and space into space-time, but time was still different from space, and served more as a corridor, whether it had a beginning and an end or whether it lasted forever. However, when combining relativity with quantum theory, Jim Hartle and I realized that time can behave just like another direction in space under extreme conditions. This means that we can get rid of the statement that time had a beginning in the same way that we got rid of the end of the world. It is possible that the beginning of the universe is like the South Pole on Earth, with latitudes playing the role of time. The universe began as a point at the south pole, and as we move north, the latitudes representing the size of the universe, will expand. The question of what happened before the beginning of the universe will become a meaningless question because there is nothing south of the South Pole.

Time, as measured in latitudes, began at the South Pole, but the South Pole is a point like any other, or so I was told. I've been to the Antarctic, but not the South Pole. The same laws of nature exist at the South Pole, as elsewhere. This would eliminate the old objection that the universe had a beginning, and that the starting point is one where the ordinary laws of nature collapse. The beginning of the universe will be governed by the laws of science.

The picture that Jim Hartle and I have developed, of a spontaneous quantum creation of the universe, is somewhat similar to the formation of steam bubbles in boiling water. The idea is that most of the possible histories of the universe would be like the surface of these bubbles. Most of the small bubbles will pop and disappear immediately. This is analogous to mini-universes that may expand but may also collapse back in while still being microscopic in size. There are probably some alternate universes but they are not interesting because they do not survive long enough to develop galaxies and stars, let alone intelligent life. Some of these small bubbles, however, will grow to a size that prevents them from collapsing. They will continue to spread at an increasing rate, and will also create the bubbles we see. This is equivalent to universes that will begin to expand at an increasing rate. This phenomenon is called inflation, as prices rise from year to year.

The world inflation record was recorded in Germany after World War II. Prices have increased 10 million times in a period of 18 months. However, this does not compare to the inflationary swelling of the early universe. The universe expanded a million trillion trillion times in a tiny fraction of a second. Unlike price inflation, inflation in the early universe was a very good thing. She created a large uniform universe, as we see. However, it will not be completely uniform. In the sum of the histories, the histories that are somewhat irregular, will have as high a probability as a universe with a uniform and regular history. The theory therefore predicts that it is likely that the early universe was completely uneven. These small irregularities will create small differences in the density of the microwave background radiation from different directions. The cosmic microwave background radiation was observed by the MAP satellite, and was found to have the type of variability observed, so we know we are on the right track.

The irregularity in the early universe is significant because there are areas where the density is higher than in other areas. The gravitational attraction in which there is overdensity, will slow down the expansion of the universe in the region, and eventually they will cause the region to collapse and form galaxies and stars. This agrees well with our mapping of the microwave sky. This is essentially the parent template of the structure of the universe. We are a product of the quantum fluctuations in the very early universe. God really does play dice.

We have made great progress in the field of cosmology in the last hundred years. Einstein's theory of general relativity, and the discovery of the expansion of the universe, shattered the old picture of the steady state in which the universe had existed forever. Instead, general relativity predicts that the universe, and time itself, will begin with a big bang. She also predicts that the universe will end in a black hole. The discovery of the microwave background wave radiation, and observations of black holes support these conclusions. This changed the picture of our universe, and reality itself.

Although general relativity predicts that the universe must have emerged from a period of high curvature in the past, it does not predict how the universe emerged from the big bang. However, the theory of relativity by itself cannot answer the central question of cosmology, why the universe is the way it is. However, if general relativity is combined with quantum theory, it may be possible to predict how the universe was formed. It will spread forever at an ever-increasing rate. During the inflationary period the merger between the two theories predicts that these small fluctuations will develop and lead to the formation of galaxies, stars and all other structures in the universe.

At the end of his lecture, Hawking receives a gift from the university administration - a facsimile copy of Einstein's original paper in which he developed the formula for energy depending on mass and the square of the speed of light. Photography: Tal Inbar and Avi Blizovsky
At the end of his lecture, Hawking receives a gift from the university administration - a facsimile copy of Einstein's original paper in which he developed the formula for energy depending on mass and the square of the speed of light. Photography: Tal Inbar and Avi Blizovsky

This would confirm the observations of the inhomogeneities in the microwave radiation, which would have exactly the predicted properties. So it seems that we are on the right path to understanding the origin of the universe, although much more work is required. A new window on the early universe will open when we can discover gravitational waves by accurately measuring the distances between two spacecraft. Gravitational waves propagate freely to us from early times, without being disturbed by matter on the way. In contrast, light is often scattered by free electrons. The scattering continues until the electrons freeze, after 300 thousand years.

Despite the considerable successes, not all problems have been solved. We still do not have a good theoretical understanding of the observations showing that the expansion of the universe is accelerating again, after a long period of deceleration. Without such an understanding, we cannot be sure what the future of the universe is. Will it continue to spread forever, is inflation a law of nature? Or will the universe collapse back at some point? New observational results and theoretical developments are added all the time.

Cosmology is an active and exciting subject. We are getting closer to answering old questions - why are we here, where did we come from?

Thank you for listening to me.

15 תגובות

  1. What is the advantage of a man in all his labor that he toils under the sun.
    Under the sun there is no advantage, but the shadow from the sun has an advantage.

  2. "personal theory"

    You cannot "shrink" time. This sentence does not make sense.

    "Is there a reasonable situation that we only spent 6 days or so according to the count of the Jewish people???" – Are you seriously asking?

    In short, ask your God to give you some sense, because you seem to be afflicted with irrationality.

  3. It is always interesting to delve into the past and discover the source... and indeed according to my theory based on the thesis of a physical contraction of the universe... it is very possible that the time we live in is also shrinkable. A kind of time jump or alternatively. After all, time is a function that suits us humans... Imagine a parallel universe without times.. where the laws of physics are different, fire and water together in harmony. Imagine our world alive and existing without times. Ours, so to speak. It is written "A thousand years in your eyes today is yesterday" and the world was created in 7 days....If a thousand years for us humans is a day in the eyes of the Most High that works according to laws of probability and physics different from those known to us so far. ???And here I link the thesis of contraction and terms of my logic the same physical law that is responsible for the contraction of the universe can also act on the contraction of time..and more and more and it doesn't end, you only need a muse

  4. Hawking is a genius, but there is a limit to his understanding of the workings of the universe.

    Everyone who writes a comment here feels smart and draws conclusions based on that
    Opinions of simple scientists, a bunch of twittering parrots

  5. Tobacco, you are wrong. If the acceleration increases in direct proportion to the distance from us, it means that when they were closer, the acceleration was less, not greater. And that is why they continue to move away with acceleration and not at a loss.

  6. Tobacco, you are wrong. If the acceleration increases in direct proportion to the distance from us, it means that when they were closer, the acceleration was less, not greater. And that is why they continue to move away with acceleration and not at a loss.

  7. Something is not clear to me.

    Matter is made up of atoms and their parts (protons, neutrons and electrons) and sub-particles.
    No matter how big the space between the particles, i.e. the emptiness, even if we assume that the "internuclear space" is large
    At a trillion times the volume of the particles themselves, it's still hard to understand
    that the compression of the universe at the beginning of the bang was such that all the matter in the universe was concentrated in such a small point.

    Is there no limit to the degree of compression of the material?

    Can anyone explain?

  8. I actually understood, if something explodes for example, the material disperses uniformly or according to the explosion, here there is an additional factor waves or quantum fluctuations that intervened in the manner of dispersion.

    Very interesting, thanks!

  9. Correct me if I'm wrong.
    If distant galaxies accelerate faster and faster in direct proportion to the distance from us, that means that in the past the acceleration of the universe was greater, the conclusion from this is that we are at the end of the acceleration phase and before the deceleration phase, right?

    Tabak Aaron

  10. To Camille, sorry for the delay in replying. The explanation is quite simple. If the universe was perfectly smooth when it was still the size of the tiny fraction of a millimeter as Hawking presented, even when it swelled it would have remained uniform, and matter would have been scattered everywhere. Because of the quantum fluctuations that caused unevenness when the universe was tiny, clumps formed when the universe swelled (another word for inflation). Those clumps eventually became galaxies. If matter and energy were not concentrated in clumps, galaxies would not have been formed, stars would not have been formed, and of course no planets and humans either. This is what he meant when he said "we are a product of the quantum fluctuations in the very early universe". Hope I helped.

  11. Aaaah
    What happened here in the meantime?
    The acceleration in the expansion of the universe is due to the contraction of time. The entire universe is in a black hole of the Roy Kerr type, which converges to a point
    Singular. The existing universe is drawn to a point that does not exist in our time. Our choice is to move forward to the mirror universe that is ahead in time from us. Or converge to a singular point and start from the big bang. How do you do it? This is a question that even Einstein could not answer (and later Steven too). Hint In the mirror universe we will be looked at like monkeys in the zoo (Darwin agrees).
    Regards to Steven and tell him to think fast before the world ends.

  12. The article itself is understandable to the rabbi, i.e. the sequence of sentences, but the ideas are complicated and the lack of scientific education is the problem

    Sample sentence:
    We are a product of the quantum fluctuations in the very early universe

    A complicated sentence, I assume that anyone who has not fully understood the quantum theory, will not understand this sentence.


  13. Nice article and thanks for the translation.
    But it seems to me that I need to do homework to understand the scriptures.

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