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The cold end of the universe

If the expansion of the universe is accelerating, then the end of the universe will become more and more sparse until it ends in cold death. Dr. Avishi Gal-Yam from the Weizmann Institute of Science tells about the exciting discovery of the 2011 Nobel laureates in physics

Milestones in the expansion of the universe. From Wikipedia
Milestones in the expansion of the universe. From Wikipedia

Since the dawn of history, humans looking at the sparkling night sky have wondered about the universe - its size, our position within it, and what the future holds for us. For hundreds and thousands of years, these issues occupied clergymen, writers, poets and artists, along with the first scientists and astronomers - in Babylon, Greece, Egypt, the cultures of the Far East - almost every human civilization has its own tradition regarding the heavenly bodies and their relationship to us, humans.

However, only in the last few hundred years, following the pioneering work of thinkers, inventors and astronomers such as Copernicus, Kepler, Galileo and Newton, the science of astronomy began to take its place among the natural sciences as a branch of quantitative and mathematical research of the universe. Einstein's theory of general relativity made it possible for the first time to try and quantitatively investigate the universe as a whole and to think about fundamental questions such as whether the universe is fixed and eternal or whether it evolves and changes, and what the future holds for us.

The world is getting farther and farther away

In the first part of the twentieth century, the science of cosmology (the study of the universe) took a giant step forward thanks to the famous American astronomer Edwin Hubble. Hubble discovered that the universe is full of galaxies (groups of billions of stars) whose shape is similar to that of the Milky Way galaxy in which we live.

Hubble was able to measure the distance to different galaxies and distinguish between nearby and distant galaxies. But his most surprising discovery was based on measuring the speed of movement of different galaxies. It turned out that the galaxies tend to move away from us and that the speed of moving away increases the greater the distance of the galaxy - nearby galaxies move away from us slowly, and distant galaxies move away from us at great speed.

The discovery, which was nicknamed "Hubble's law", was revolutionary because it implied that the universe is not fixed and eternal but changes and evolves - the fact that the galaxies are moving away from each other indicates that the universe as a whole is expanding.

This expansion can be visualized if we think of the universe as the surface of a balloon on which stars are drawn. When we inflate the balloon it expands and the distances between the stars (all of them) are increasing. If there were ants standing on each star and looking at each other, then from the point of view of each of the ants, all the other ants would move away and walk away. Moreover, the distance speed of distant ants was greater than the speed of distance of nearby ants.

Since Hubble's discovery (who died before winning the Nobel Prize, for which he was nominated), scientists have focused for decades on the study of the expansion of the universe. The main question was whether the speed of expansion is constant, or whether the expansion of the universe is slowing down.

The reason for assuming that the expansion of the universe will slow down over time is due to the influence of gravity. Between every two particles in the universe there is a force of gravity that causes them to be attracted to each other. Between very heavy bodies (such as galaxies) there is a strong gravitational force (although its strength decreases the greater the distance between the bodies).

Since all the galaxies in the universe attract each other, even if they are now moving away from each other, the effect of gravity will slow down the speed of their expansion and perhaps even lead, in the course of time, to the reversal of the expansion and lead to contraction (that is, that in the future all the galaxies in the universe will move towards each other).

If we return to our example of ants, we will imagine that each ant is standing on a small magnetic star, and also that the balloon on which they were standing exploded and threw the ants on their magnetic stars in all directions. Since the magnets attract each other, even if the ants are now moving away from each other, the attraction between them will reduce the speed of spread over time, and perhaps, if the magnets are strong enough, will eventually cause all the ants to re-converge at the same point.

The big contraction?
And back to our universe: measuring the speed of expansion and determining the rate of deceleration is of great importance - if we can prove that the rate of expansion of the universe is slowing down, it is possible that in the future the expansion will stop completely and all the galaxies will converge back to the same point. The universe, which began, so it is assumed, with a big bang that spread the matter in all directions, may end with a renewed contraction. This issue was the motivation for the research for which Perlmutter, Schmidt and Ries won the Nobel Prize in Physics this year.

In the early XNUMXs, Saul Perlmutter from the Lawrence Berkeley Research Laboratories in California, along with Brian Schmidt and Adam Reese who were at Harvard at the time, began planning a measurement of the expansion rate of the universe using a new method based on observations of exploding stars called type Ia supernovae.

The idea behind the method was this: in 1993, the American astronomer Mark Phillips showed that explosions of this type are "standard candles", that is, the intensity of radiation emitted from them at the source can be calibrated.

If we know the radiation intensity of a distant source and how much radiation we have measured here, on Earth, we can deduce from this the distance of the light source (just as when we see the headlights of a car at night, we can soon estimate its distance since the intensity of the headlights of cars is known to us).

That is, if we can measure the luminosity of distant supernovae, we can know the distance to these galaxies. At the same time, it is possible to measure the distance speed of the galaxies in which the supernovas exploded using the Doppler effect (as Hubble did a long time before) and determine whether the relationship between the distance and the speed of expansion is constant, or whether it is different for very distant galaxies.

Since the light from distant galaxies was emitted a long time ago, the measurement makes it possible to measure whether the speed of expansion now is different from what it was in the past. Both groups planned to measure in this way the expected slowdown due to the force of gravity (that is, they expected to find that the speed of expansion today is smaller than it was in the distant past).

A battle of minds
Both groups made the measurements at about the same time and were in fierce scientific competition. Towards the end of 1998, both groups accumulated a lot of data: Perlmutter had measurements of a greater number of supernovae (42, to be exact), while Schmidt and Ries had fewer measurements, but with a higher level of accuracy.

The data analysis was conducted simultaneously by Perlmutter and his team at Lawrence Berkeley Labs and by Adam Rees who moved to the University of California, Berkeley, less than a mile apart.

The two groups aspired to be the first to announce the result of the measurement and at the end of 1998 two articles were submitted for publication (Perlmutter's article was published in January 1999, a few weeks after Rees and Schmidt's article).

The results shocked the astronomical community. The two groups independently measured the change in the expansion rate of the universe and discovered that the universe is not slowing down, but that the expansion is accelerating. Some invisible force overcame gravity and caused the galaxies to move away from each other at an increasing rate.

The scientific breakthrough was due to the fact that physicists did not know then (and still today) about any force that could cause a phenomenon like the one measured. The explanation for the phenomenon is called "dark energy" which is assumed to exist in the universe and causes the accelerated expansion, but the nature of this energy is still largely unknown.

Two reasons made the generally skeptical physics community accept the new result relatively quickly. One is that two competing groups arrived at the same results independently (that is, using observations of different supernovae and analyzing the data with different methods).

The second reason was that it was clear, especially to Perlmutter, that the experiment was designed to measure the expected deceleration of the universe rather than the detected deceleration. When scientists discover a result opposite to what they expected, their colleagues tend to be less concerned that the scientists influenced the results (even subconsciously) to their liking.

Since the initial discovery in 1998, the results have been repeatedly confirmed by additional and much larger samples of type Ia supernovae, as well as by analysis of other measurements (such as the cosmic background radiation) that confirmed the results of Perlmutter, Schmidt and Riess.

Is the future of the universe in danger?

Perhaps the most dramatic of the implications of the laureates' research is the implications for the future of the universe. If the expansion of the universe is accelerating then the galaxies will move away from each other forever. The universe that started with a big bang will not come back together ("the big squeeze") but will become thinner and colder and colder, less and less new stars will be formed in it and end up dying a "cold death".

A speculative possibility that has been raised even assumes that the speed of expansion will continue and increase even more, until the accelerated expansion tears the galaxies apart, followed by the solar systems, the stars, the planets and even the atoms themselves - this horrifying hypothesis regarding the future of the universe is known as "the big rip" ). In any case, the discovery of the three prize winners is critical to understanding the evolution of the universe and its future.

The scientific revolution started by the three prize winners is today perhaps the biggest mystery in physics: what is dark energy and how difficult it is to explain it using the basic laws of physics.

Thousands of researchers around the world - experimentalists and theoreticians, astrophysicists, cosmologists, particle physicists and gravity theory researchers are working on formulating and examining explanations for the surprising measurements from 1998, so the awarding of the award is in my opinion highly deserved (even if, quite rarely, all its recipients are quite young and continue to be active and leading scientists in their field).

The three laureates have many connections with colleagues in Israel, including joint research with astrophysicists from various institutions in Israel. Prof. Adam Rees won the Sackler Prize on behalf of Tel Aviv University in 2004 and Prof. Brian Schmidt last visited the Weizmann Institute about three years ago.

One of the subjects that continues to occupy us is the attempt to understand the nature of the exploding stars that the award winners used so successfully, in order to assess how accurate such measurements can be reached.

Research in astrophysics and cosmology continues to develop rapidly, and there are certainly many more surprises ahead of us before we fully understand the universe and the laws of physics according to which it operates.

Dr. Avishi Gal-Yam is an astrophysicist from the Department of Particle Physics and Astrophysics at the Weizmann Institute of Science and an expert on supernovae.

33 תגובות

  1. The theoretical explanation I know is that the universe is bipolar - that the dark energy pushed the galaxies onto the fabric of space-time that expands up to the Maxwell point. This is the point that represents the polar force from which the universe began its existence.
    After the maximum point the universe will drain over billions of years onto a shrinking space-time fabric
    Up to the other pole of the universe - its end point. Food for thought.

  2. Our view of the universe stems from a fundamental error. We look at ourselves as if we are in the center of a ball that keeps on expanding in 4 dimensional space.
    In fact, we are outside the sphere in 5 dimensional space. (The fifth dimension is dark energy).
    This situation is difficult and even incomprehensible to us, because it is impossible to illustrate it physically. Basically because of this structure, a major collapse will occur, even though we are currently in accelerated expansion.
    My other, crazier assumption is that dark energy is not dark at all. The entire universe has more electrons than atoms. As we know, the electrons repel each other and this is the source of the accelerated repulsion. It can be proven that the effect of the electromagnetic field in space is stronger than the gravitational field. I am currently in the process of measuring the amount of electrons in the universe.
    Then I will calculate the effect of the interaction between the two fields, the gravitational field versus the electromagnetic field.
    So of course there will be no dark energy and no plaster.

  3. thanks Michael.

    As of now I am not convinced. I went and looked through his comments (not all of them. He writes a lot), and unfortunately (and maybe also unfortunately) I didn't find a solid skeleton in them.
    But what interests me, beyond the dry facts, is also the mindset that brings people to believe what they believe.
    I am also interested in myself. For example, why do I not believe in an intelligent creator while most of humanity does believe in him? Why does most of the world prefer the lie to the truth? I believe that beyond denouncing vanity beliefs, this puzzling human aspect must be examined and understood.

  4. jubilee:
    If you are convinced by Yehuda's words, I invite you to write to me and I will show you where you went wrong.

  5. To Yuval Chaikin
    Let it be clear that I was asked by the website not to repeat my unconventional ideas again and again, but only to respond to questions. I respect the wishes of the site.
    If you have a specific question I will be happy to answer
    If you want and for anyone who wants, my email
    Happy holiday
    Sabdarmish Yehuda

  6. withering!
    "Dark matter is so named because of its weak to zero interaction with electromagnetic radiation." Because of this, the phenomenon is only observed at distances of the order of billions of light years. And if the product of the density of the dark matter by the distance it extends is the same as the product of the density of the atmosphere by the distance it extends, then the phenomena are similar to the same extent.

    Thanks. I will look for the opportunity

  7. I have written to Yuval Chaikin about this many times and I don't feel like repeating it again. Try to write in Google - Sabdarmish Yehuda Gravity. Or even Sabdarmish Yehuda - the scientist and I am sure you will find an explanation for my ideas. If you have trouble, then I will look for links on the subject.
    Good Day
    Sabdarmish Yehuda

  8. to camila
    I'm sorry, but I tried to understand how the granny wheels correspond to the ether or the dark mass, but my reading comprehension could not get to the bottom of your example. But I must state that I do not want the grandmother to go to a dark hospital lacking energy and life
    Lots of health
    Sabdarmish Yehuda

  9. Yehuda,
    If Grandma had wheels, she would probably fall right away, break her pelvis and be rushed to a hospital until she returned her soul to the Creator, and hence we wouldn't see Grandma sitting in the park knitting a sweater. Do you understand from this sentence that I think grandma rides on wheels? (I'm sorry for the spichiometric wording, but it's really about understanding what is called at a basic level).

    You wrote: "It is not impossible that the redshift is caused by the dark matter in a manner similar (and perhaps identical) to the redshift of sunlight as it passes through the atmosphere."
    Don't you know that the reason dark matter is called that is because of its weak to zero interaction with electromagnetic radiation? Therefore it is clear that it is not possible that the red shift is caused by it in a similar way (and certainly not the same) as the phenomenon of the red sun at sunset (which is primarily optical)?

    What is the point of your musings and your "theories" if you often show ignorance of the facts and non-rational thinking. I understand if a person is trying to learn and understand something about a field in which he is not well versed, I can even understand a person who has a certain idea and he presents it to professionals in this field (or as close to it as possible). (After all, I also presented here in the past my nonsensical thoughts on the subject of the expansion of the universe and the meaning of space and I asked for an opinion from those who clearly understand more than me in this area). What is beyond my understanding is why people insist on rejecting ideas that are full of failures at the most basic levels, whether in understanding things or in knowing the known facts, and still believe that there is a good chance that their ideas are superior to thousands and thousands of other minds who surely know the material better, and all this without being able to bring Something real to back up their arguments (like Danny Shechtman brought for example when the scientists were wrong in evaluating his findings). Sometimes it seems to some of the commenters here as if any opinion that differs from the scientific consensus has a tremendous chance of being correct because here, the fact is, the scientists did an unforgivable injustice to Shechtman, and not only to Shechtman, but to scientific truth itself! Come on, don't you have the slightest sense of discomfort that you are trying to juggle large thought structures that rely on a lot of facts, observations and experiments, most of which you obviously don't know, and those that you do know, I doubt if you fully understand them? Why is it not enough to ask the opinion of the professionals in the field (I am not one of them, certainly not in the field of physics) and try to deal seriously with what they answer?

  10. Yuval Chaikin
    So as I understood, you claim in advance that there is no acceleration in the expansion and therefore there is no need for dark energy, but, you do accept the existence of the dark mass.
    I claim that there is an acceleration in the expansion of the universe but I do not accept the dark mass and energy as an explanation and explain it in my own way. without them. I think the particles moving in the vastness of the universe which we both agree is not empty, can do the job:- dusting, galaxy movement and accelerated expansion.
    Happy holiday
    Sabdarmish Yehuda

  11. Thanks Yehuda. Now everything is clear.

    Faith is a concept that I associate with religion. I try not to define my attitude to matters of science in terms of belief or disbelief.
    For a long time I believe that the space of the universe is not an empty space but is full of matter involved in both gravitation processes and optical phenomena. In recent years, evidence of the existence of such a substance has been found, which strengthens my opinion.
    On the other hand, I believe that a simpler explanation can be found for the phenomenon whose discovery led to the assumption of the existence of dark energy, one based on dark matter. This explanation makes unnecessary the acceleration of the expansion of the universe and with it the dark energy.
    As mentioned, I do not believe or do not believe but only make assumptions. Simple explanations, even those that contradict my assumptions, are usually welcomed.

    Happy Holidays to you too

  12. Yuval Chaikin, I will try to explain it again.
    I believe:-
    A. that the redshift is proof of the expansion of the universe
    B, I don't believe in dark mass and energy.

    But if in fact the dark mass and energy exist, then really, as you say, we need to check if they are not responsible for part of the visible red shift.
    I hope now I am understood
    Happy holiday
    Sabdarmish Yehuda

  13. Yehuda
    First, thanks for the support ♥
    Second, it's a little difficult for me to follow your logic ("It should be investigated if part of the redshift is not caused by the possibility of the existence or the existence of dark energy, which I also do not believe in"), but I hope that at the end of the day I will succeed 🙂
    Feasts for joy - holidays and times for joy, and you rejoiced in your feasts and were only happy

  14. To Yuval Chaikin
    First of all, contrary to your opinion, I think that the phenomenon of the redshift does show the expansion and even the acceleration of the universe. It just fits what I think about the universe. I don't think that dark matter exists, but it should be investigated if part of the red shift is not caused by the possibility of the existence or the existence of dark energy, which I also do not believe in.
    Let it be clear that I greatly appreciate your serious approach to not take things for granted and to doubt and not to stop investigating the doubts you have.
    Happy holiday
    Sabdarmish Yehuda

  15. The key word here is "if". The Nobel Prize, however prestigious it may be, is not a scientific seal of approval. It is still not completely clear that there is no other explanation for the redshift phenomenon.
    Today we know For sure About the existence of an entity that was named "dark matter". Dark matter fills the space of the universe and interferes with the processes of light passing through it. It is not impossible that the redshift is caused by the dark matter in a manner similar (and perhaps identical) to the redshift of sunlight in its passage through the atmosphere.

  16. Camilla and Yehuda.

    The expansion of the universe, as Camilla mentioned, is of the order of the intergalactic magnitude, meaning that the galaxies are moving away from each other but are not expanding themselves. The reason for this (as Camila pointed out) is that within the galaxies the gravitational energy is dominant in relation to the dark energy.
    By the way, the galaxies are getting bigger and bigger, this is because gravity is dominant even on the scale of the galaxy clusters and thus large galaxies swallow up small galaxies and create bigger and bigger galaxies.
    As for the moon moving away from the earth, this is unrelated and due to completely classical tidal forces,
    By the way, these forces may sometimes push a moon away and sometimes attract it (as in Phobos, the moon of Mars).

  17. I know that the big bang is not compared to an explosion but to a situation where space is constantly expanding.
    But can't it still be that we are still in the acceleration phase of the bang like flying fragments and accelerating at first from a stationary state to deceleration?
    Another theory is, could it be that we are witnessing evidence of the same inflationary swelling that is at the base of the Big Bang?

  18. Dear Carrie
    The universe has been expanding for billions of years without stopping and even cooling down
    We don't need a sweater and it shouldn't bother us because we have a warm sun that warms us happily and even makes sure we can undress without getting cold.
    And regarding the prophecies that the world will come to an end, well the dates they gave you are a bit wrong and it will happen more or less on 21.10 in the year 5,000,000,000 which is still a bit far. So, our warm sun will spread and swallow us with or without a sweater.
    So the moral is that you should be careful when someone or something undresses near you!
    Happy holiday Carrie
    And we will be happy to answer your other questions
    Sabdarmish Yehuda

  19. Hello everyone and happy holiday
    Regarding the expansion of the universe, these are things that will happen in the near future or it will take years because I simply did not understand the matter that much even though it is an interesting topic and if so then it means that it will also affect the earth

    I would appreciate the answers...

    P.S. I know it's not so related, there was a prophecy 5 months ago that the world would end on 21.5/21.10 and now the same one who prophesied it predicts that next Friday XNUMX/XNUMX will be Judgment Day

    Hope this is not true

    Shabbat Shalom and happy holiday

  20. Dear Camila
    I carefully read the comments I respond to.
    In your response you wrote:
    "If everything had spread proportionally, then the rulers would also have spread in the same ratio and we would not have been able to detect any changes." End quote.
    I understood it simply, if rulers also spread, then Camila's intention is that the distances between the molecules spread.
    If that was not your intention. I apologize.
    And by the way, I think that the distances between the stars of the galaxy are also expanding as a result of the expansion of the universe, and gravitation cannot change that. An example? The moon is pulled by the earth's gravity and also moves away from the earth.
    But let's not start a new conspiracy war
    Happy Holidays
    Sabdarmish Yehuda

  21. Yehuda,

    The expansion of the universe refers to the entire space, including that found between the stars in the galaxies, but as far as I know, this does not affect the size of the galaxies, just as an expanding puddle of water does not affect the size of a styrofoam ball floating on the puddle. The forces that hold together the styrofoam particles in the ball outweigh in this case the force exerted by the spreading liquid. Can Zvi, Ehud or someone else with a close enough background express an opinion or even a rough estimate of the expected impact?

    You attributed to me a claim that I did not claim, on the contrary, it is clear from my words that I do not believe that there is expansion in all things including "rulers" and I even gave an example of why this cannot be the case. Yehuda, please read the things a little more carefully...

  22. I personally wish for the Big Rip. That would be the most interesting end to the universe. Instead of a cold and boring death of an infinite, empty, cold and dark universe. Instead of a universe with one massive singularity (which will eventually decay too, if Hawking radiation similarly affects supersingularities). Instead, the universe itself will "explode" all at once. In my opinion this is the best definition of a big bang. Who knows, maybe the universe before ours ended its life in its own rupture.
    I invite all physicists to correct me or give their interpretation of the meaning of such a tear.

    P.S. While reading, the double meaning of the name (Rip=RIP) suddenly jumped out at me. And this is another reason why this is the best option for the future of the universe.

  23. A thought without a solution:
    If the center of mass of the universe 14 billion years ago was at one point and after the big bang
    The center of mass is shrinking and spreading everywhere, is it correct to say that its hold on the organs of the universe
    is getting weaker and therefore the speed of their distance is increasing (delayed the first push from the big bang)?

  24. to camila
    When talking about the expansion of the universe today, it is customary to point out that it is only about the spaces between the galaxies and not the galaxies themselves where the force of gravity dominates. That's why I stated that if the spaces between the stars within the galaxies also expand, then what we will get are larger galaxies in a larger universe and in fact without practical change, that is, if the volume of a galaxy was, for example, a billionth of the volume of the universe, then even after the expansion it will be a billionth of the volume of the universe.
    But Camila is even bolder, and claims that maybe the distances between the atoms will also increase and then the bar will increase in such a way that the whole universe will increase??
    What can I tell you Camila?, which is interesting food for thought!!
    Happy holiday and Happy Holidays!
    Sabdarmish Yehuda

  25. I have an interesting question.
    Does the expansion of the universe affect time?
    Does time slow down/speed up or stay the same as a result?

  26. Yehuda, you are obviously wrong. If everything were to spread relatively, then the bars would also spread in the same ratio and we would not be able to detect any changes, not even the cooling of the background radiation (which means a gradual transition to longer wavelengths). Therefore, it is a fact that not everything expands following the expansion of the universe. What holds the structure of the galaxies is mainly (if not only) the force of attraction between the masses that make up the galaxy. The galaxies are moving away from each other at an increasing speed, but they themselves do not change significantly due to the expansion of the universe. Right now it seems that the distant future is cold and dark (and some would say that the near future too...)

  27. Note that although everything will expand, but if the galaxies themselves also expand, what we will get will be a larger universe with larger galaxies so that the ratio will be preserved. Although it will be colder
    But maybe by then they might discover some cosmic greenhouse effect and a savior will come to the universe
    Happy Holidays
    Sabdarmish Yehuda

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