Einstein's theory of general relativity was able to explain everything. Until the discoveries that shocked her: that the universe is not static but expanding; And there are countless other galaxies besides ours. So what is the missing element in the equation?
Article: Bat-Sheva and Gon-Galamidi, a young Galileo
Not so many years ago there lived a young boy with one big dream in his heart: to understand the mysteries of the universe. The boy studied and researched, pondered, imagined and asked questions. He didn't give up until he was the most famous scientist in the world: Albert Einstein. Even when he was already a famous scientist, his great dream remained: to describe everything in our universe - the billions of galaxies, stars and the forces acting between them, with the help of one beautiful and simple equation. And if Einstein wants, Einstein succeeds. Ummm… almost.
It's just geometry
Einstein came up with a great theory called "general relativity". General relativity is essentially an extension of Newton's theory of gravity, which describes the forces of attraction between objects with mass (matter). Newton's theory of gravitation explains how we are attracted to the Earth (and therefore have weight), how the Moon is attracted to the Earth (therefore orbits it) and how the Earth is attracted to the Sun (therefore orbits it). Only one big secret overshadowed Newton's theory: no one really understood the meaning of this mysterious force of gravity, which acts on all objects in the universe.
Then came Einstein, and with the help of his general theory of relativity he was able to explain the force of gravity - simply by the geometry of the universe: there is no mysterious force of gravity that tries to catch all the stars or galaxies, they simply change the structure (geometry) of space itself.
It goes like this: a star that is in space curves the space around it, and therefore everyone who falls into the area will follow the curvature and act as if they are drawn towards the center of the star. The idea is simple: try to take a heavy ball and place it on a mattress. The ball distorts the mattress and creates a hollow around it. Now try to place another heavy ball next to it. The second ball also creates a coil around it. And if the balls are close enough, they will "fall" into each other's bowl and get closer until they stick together! The heavier a ball we place, the bigger and deeper the bowl that will be formed around it. This is also the case in the world of gravity: massive stars curve the space around them more, and therefore their gravitational pull is stronger.
If general relativity is correct, Einstein thought to himself, then it predicts the existence of the most illusory star in the universe: a star so massive and dense that instead of bending the space around it, it literally "tears" it apart! Can you imagine what would happen if you put a small tennis ball weighing a hundred tons on the mattress? These small, dense stars simply create "holes" in space. When objects fall into these "holes", they no longer have a chance to get out. Even light, moving at a speed of 300 thousand kilometers per second, cannot escape from these "holes". And if there is no light coming from them, they will always be black, because they cannot be seen. This is why they were named "black holes".
There is nothing else
Following an observation made during a solar eclipse that coincided with the prediction of the theory of general relativity, on November 7, 1919, the "Times" newspaper from London reported: "A revolution in science, a new theory of the universe, Newton's ideas collapsed!" - And Einstein overnight became a kind of celebrity-scientist known all over the world. The world celebrated, but one difficult and stubborn question never stopped bothering the great scientist.
In those days, the telescopes were not so sophisticated, and astronomers could only see the stars that are in our galaxy - the Milky Way galaxy. Einstein had no way of knowing that besides the Milky Way there are billions of other galaxies. For him, the universe is our galaxy, and there is nothing but it. Although the stars in the galaxy move around its center, the general structure of the galaxy is preserved, and the star maps drawn by astronomers hundreds of years ago have not changed since then. So what's the wonder that Einstein insisted on believing that the entire universe is static?
A strange and mysterious power
Here's exactly the problem: if there are so many stars in the universe, then they have to get closer to each other because of gravity. What it means? that the universe cannot be static. According to the known laws of gravity, the stars will not stop until they fall and crash into each other and the entire universe collapses in on itself. So how is it possible that the universe is not in the process of collapsing after all?
Think about it this way: you see an object flying in the air and not falling, you will immediately conclude that there are two possibilities - someone threw it at a high speed up and at the moment it is still moving up following the throw; Or a small motor is attached to it, and it constantly exerts force on it and does not let it fall. These are also the two possibilities of our universe: it is now in the process of expansion and expansion due to a huge primordial force exerted on it; Or there is a mysterious driving force that works against gravity.
The first option is of course completely opposite to the idea of a static universe - it speaks of a universe that is in the process of expansion. The stubborn Einstein, who fully believed in a static universe, immediately chose the second option. He added to his equation, which describes the forces in the universe, a strange and mysterious force, and defined it as a "repulsive force" that opposes the force of gravity.
Do you think Einstein was happy with this addition? Not really. Scientists don't like "mysterious" powers that just pop up. But Einstein had no choice. This was the only way he could continue to believe that the universe was static and also that his theory of general relativity was correct.
expanding and spreading at a dizzying pace
As the years passed, telescopes became more and more sophisticated, and scientists could see further and more clearly. At the beginning of the twenties of the last century, countless other galaxies besides our Milky Way were discovered, and the exploration of the universe reached new heights.
Einstein closely followed all these interesting discoveries, but he certainly did not expect the sensational discovery of Astronom Vesto Sleeper - this discovery shook his whole world: Sleeper discovered that the galaxies in the universe are constantly moving away from each other!
Besides that, a few years later the famous astronomer Edwin Hubble discovered that the farther the galaxy is from us, the faster it moves away. This discovery left no room for doubt: our universe is not static at all, it expands and spreads at a dizzying pace.
Einstein, despite being stubborn, was also a humble person who knew how to admit his mistakes. If he had only chosen the first option, he could have predicted the expansion of the universe by himself and would not have had to add this strange force of repulsion to his beautiful theory. "This is the biggest mistake of my life," admitted Einstein sadly, immediately removing him from the equation. This story could end here, but science is much more fascinating than anything we can imagine...
Back to Einstein
Even if our universe is expanding and the galaxies are moving away from each other, there is a strong effect of the gravitational forces between the galaxies. These gravitational forces are opposite in direction to the motion of the galaxies, and therefore should constantly slow down their speed.
We will return to the previous example of an object that does not fall, but this time we will choose the first option - someone threw it at great speed and it still rises following the throw. Even if you throw a ball as high as you can - its speed will decrease all the time due to the Earth's pull, and in most cases the ball will finally stop and fall back (unless you throw it at a speed of a little more than forty thousand kilometers per hour, then it will manage to escape from the Earth's gravity) .
For years, astronomers were looking for evidence to confirm the speed of galaxies, but in 1998 everyone was completely shocked by one of the strangest discoveries of all time: not only that the galaxies are not slowing down, but they are speeding up! That is, they are running away from each other at a speed that is increasing all the time! It turns out that our universe is spreading and expanding at a tremendous rate.
Since then, scientists have been trying to explain this strange acceleration with all kinds of different theories. In order for the galaxies to accelerate away from each other, a tremendous force of repulsion is needed to overcome the force of attraction between them. Perhaps you have heard of such a power by chance?
Well, in a reality that surpasses all imagination, many physicists today believe that "Einstein's big mistake" is exactly what they are looking for! The same force of repulsion that Einstein added indiscriminately to his equations and then caused him embarrassment - is exactly suitable for the new researchers. I wonder what Einstein would have thought about it...
So how does this story end? Right now no one really knows. The best scientists in the world are sitting at this moment and trying to fulfill Einstein's great dream - to understand our universe. Will it ever happen? Are our brains smart enough for this? We promise to update you when there are interesting developments.
The article was published in the October 2014 issue of Young Galileo
Want to read more? To receive a young Galileo magazine as a gift
More of the topic in Hayadan:
- A victory for Einstein after two stars put the theory of relativity to the test
- Did Einstein's first wife secretly compose the theory of relativity with him?
- Is it possible to sense the lengthening of time from Einstein's theory of aberrations?
16 תגובות
It is true that the galaxies are moving away from each other, but the Andromeda galaxy is actually approaching our Milky Way and a collision with it is inevitable.
The biggest mistake of science in general is that the manipulation is done on something external.
This is why we cannot treat the results objectively.
The truth is that there is no such thing as objective, but if we could carry out (what we were, this is happening, this paradigm began) manipulations, changes, refinement and self-investigation, then we could reach results that would be different each time, but also closer to the truth.
why? Because the more we know or rather get to the root of the matter, the closer we will be to the truth.
And this root will not be achieved except by changing man.
fun to read
Shmulik,
By and large, yes. The difference between quantum and classical geometry is that quantum geometry fluctuates and suffers from uncertainty. Of course, this small detail sometimes causes completely different physical behaviors, just as uncertainty in a particle's position turns all classical physics upside down and brings us to quantum phenomena. One should be careful in using the term "gravitational waves" because gravitational waves are a completely classical phenomenon, like electromagnetic waves. The quantization is that these waves can also be understood as particles (gravitons) and not only as disturbances moving in a vacuum. Like the difference between electromagnetic waves in classical theory and photons in quantum mechanics.
I haven't read the "elegant universe", but it is likely that these things are mentioned there, perhaps in a much clearer way than I can describe.
albentezo,
thank you very much for your answer. I will read it several times to understand the answer better 🙂
If I understand correctly, those fluctuations (gravitational waves?) that are supposed to occur when we examine a region of space with great precision in a short time domain, as a result of the uncertainties, which we have not yet noticed, are they the breaking point between quantum mechanics and relativity?
If I'm not mistaken, Brian Greene wrote something about it in the elegant universe
Shmulik,
I wrote you a reply but it has not been published yet. I don't know why. Hope the editor will release it soon.
Hello Shmulik,
Both questions you asked are good, and although they have answers, they are difficult and I am not so optimistic about my ability to convey physical intuition to you. I hope I will be somewhat successful.
1. Let's start with the second question. We will actually look, as you expected me to do, at electromagnetic interactions. Two charged particles are sitting and the electric force between them is manifested in the fact that they throw photons at each other, which transfer momentum between them. Let's look at a one-dimensional problem. You are asking how attraction is possible - that is, if I throw a photon at you, it must transfer momentum to you in the opposite direction from me, and therefore repel you. This error arises from using classical intuition for a quantum problem. True in quantum mechanics, position and momentum are not interchangeable, meaning we cannot know both at the same time. Suppose we know the momentum of the two particles before the interaction. So we don't know what their position is relative to each other and it cannot be said that a path between them must transfer momentum in one direction or another. Another way of saying the same thing is that a virtual photon passing between the particles is not bound to a classical physical trajectory (it is not even bound to comply with the equations of motion of a photon) and therefore there is no obstacle for it to transfer attractive or repulsive momentum. If you know the language of Feynman diagrams, this might make it easier for you. If you draw a diagram of two charged particles exchanging a photon between them, you will see that the photon between them can have any possible momentum. I know the explanation is a bit more mathematical than physical, but the bottom line is - the virtual particles transferred between the charges are not committed to a classical trajectory and therefore do not have to have momentum pointing from the first particle to the second. Hope that clears it up a bit.
2. Gravitons and the curvature of space are one. If you thought the previous answer was more math than physics, wait for what is going to come now.
In general relativity, gravity is geometry. It is determined according to a tensor (which is a mathematical structure that contains a number of numbers that are related in a certain way) called the metric tensor. The tensor contains the information about the geometry and it is the geometry that creates the illusion of the gravitational force. When quantizing, the matrix tensor becomes a field. That is, just as in field theory (the modern version of quantum mechanics) electrons, gluons, photons, quarks, etc. are described by a field which is found throughout space and at the peaks of which we call particles, so is the trap. In quantum gravity the matrix is a field with spin 2 (the spin can be easily found from considerations of behavior under symmetry) and we also refer to its quanta as particles - the gravitons.
There is a difference between the two descriptions - obviously, just as there is a difference between classical and quantum electromagnetism. If there was no difference, we would not be interested in finding a quantum theory of gravity. But in terms of intuition, I don't think a sharp distinction should be made as you say. In classical physics it is clear that the metric is an expression of geometry and that geometry produces an illusion of force. In quantum physics, this interpretation can still be used. It is still possible to think of the field we defined as something that defines geometry (it maintains the same properties and the same equations) and therefore here too all the interactions it creates are geometric. The difference is that in the classical problem there is a solution to the equations and that's it. All the particles always obey him and that's it. That is, the geometry is fixed and there is no such thing as a particle going against the geometry. In the quantum problem this is not the case - our trap - the spin 2 particle is itself a quantum field and as such it fluctuates. We also said that virtual particles don't have to obey the usual equations of motion at all, so in the quantum problem there may be an unruly graviton that would seemingly break the geometry. That is, it is certainly possible to give quantum gravity an interpretation of geometry, but it will be a geometry that makes fluctuations - quantum geometry. Think of a triangle whose sides suffer from uncertainty. Or a shape where there is a finite chance that two parallel lines will momentarily meet. I think these are the best heuristic explanations I can give without going into the mathematics of the problems.
albentezo,
Sorry for the jump but I would love to hear your opinion regarding my question.
I know we don't have a neat quantum laundry theory, but if gravitons exist:
Does their very existence make the theory of relativity's explanation that attraction is caused by curvature unnecessary?
Alternatively, how exactly are the gravitons supposed to produce attraction? A photon, which collides with an atom, and is not absorbed by it, adds momentum to the atom and moves it, so how should the attraction occur?
I suppose I could ask the same question about electromagnetic attraction except that in this case there is a successful theory that claims that attraction is not a force.
Thanks!
I was glad to hear that Shmulik 🙂
Joseph.
Regarding the black hole. If I am not mistaken, you mean the article that does not claim that black holes are not created, it is difficult to deny that black holes exist because their existence is monitored. The article I am referring to excludes the possibility of a black hole being formed from the gravitational collapse of a sun with too much mass, i.e. it does not rule out the formation of black holes in other ways.
Regarding theories about distant cosmology (including the big bang) they also seem dubious to me because our ability to measure distant objects in place and time is very small.
Thanks Uri, I enjoyed the movie
albentezo,
I'm going to do Yehuda and ask a question I've already asked here, but for me the reason is that I forgot the explanation given to me (I think by Zvi) and not because I hope to hear *this time* the answer that came to me.
If gravitons exist:
Is the theory of relativity's explanation that attraction is caused by the curvature of space incorrect?
How exactly are the gravitons supposed to produce attraction? A photon, which collides with an atom, and is not absorbed by it, adds momentum to the atom and moves it. I understand we don't have quantum gravity but is there any idea of the attraction mechanism?
At the time I was wondering about the mechanism by which the graviton (if it exists) escapes from a black hole and happily there is an answer to that (not that I fully understand it)
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980601a.html
Mario claims that Einstein never said "this is the biggest mistake of my life", and it is an invention of the comedian Gamov from the Alfer Beita Gamov trio.
Joseph
I agree with you.
Be prepared for some commenters to attack you just for expressing these ideas and sometimes in a mean way. Fingers crossed for you in your difficult times!
All the best
Sabdarmish Yehuda
At the moment, a black hole is forming in the examination by Professor Mercini from the USA, who is rejected by the majority, but I have not seen a relevant article.
Thus the Big Bang may be in danger as it too began at the singularity. Therefore, the issue of whether the universe is expanding is a bit open, although it is likely that the majority here will open up a bit about the nonsense. True: a lot of evidence for the expanding universe has been collected. Mainly: Hubble, the observation of the curvature of space, the Friedman equations, the noise from the big bang collected by the COBE satellite.
The subject of the uniformity of the gravity formula for large distances is also unclear, since at the moment the introduction of dark matter is required to offset the evidence and observations. The introduction of dark matter and the motion of the visible stars is fine for us. It is very possible that gravity changes depending on the distance and this also affects how we see the universe, compared to what is really happening there.
I would like to recommend a wonderful episode about Albert Einstein:
https://www.youtube.com/watch?v=n-YWVOG_L4M