In the universe, we see many examples of similar objects, but each object is unique. Of all the galaxies, stars, and planets we know, no two are the same, but each has its own unique history, properties, and composition. However, it's a compelling idea that if enough universe could work, eventually the particles in it would be organized in such a way that the same possibility—however unlikely—would occur multiple times at different times. Perhaps, given the concept of an infinite universe, every system we can imagine, including the Earth, may even have an infinite number of copies in which each of us lives.
It was this idea that each of us could have an infinite number of copies somewhere, which gave rise to our modern concept of the multiverse. Maybe we have different versions, where a small decision, an outcome, or even a quantum measurement, leads to a very different outcome. While many people scoff at the idea that the multiverse is fundamentally unscientific – after all, there is no way to see, test, or obtain information about any part of the universe other than our limited observable universe – the truth is that the existence of the multiverse is rooted in science itself. In fact, if only two things were true:
Cosmic inflation, before and after the Great **, occurs as we think it is, and inflation, like all other fields in the universe, is essentially a quantum field, subject to all the quantum rules followed by other quantum theories, so the emergence of the multiverse is an inevitable consequence of these ideas. That's why physicists, despite the opposition of a few, overwhelmingly claim that the multiverse must exist.
A "raisin bread" model of an expanding universe in which relative distances increase as space (dough) expands. The farther any two raisins are from each other, the greater the redshift observed when receiving light. The redshift-distance relationship of the expanding universe has been confirmed by observations and is consistent with what has been known since the 1920s. **NASA WMAP Science Team.
The story begins with the discovery of an expanding universe. As early as the 1920s, the evidence became overwhelming that not only was the large number of spirals and ellipses in the sky actually the entire galaxy itself, but that the farther such a galaxy was determined, the greater the amount of light transferred to a systematic, longer wavelength. While a variety of explanations were initially proposed, they all faded away with richer evidence until only one remained: that the universe itself is undergoing cosmic expansion, like a fermented raisin loaf of bread in which conjugated objects like galaxies (e.g., raisins) are embedded in the expanding universe (e.g., dough).
If the universe is expanding today, and the radiation in it is shifting towards longer wavelengths and lower energies, then that means that in the past, the universe must have been smaller, denser, more uniform, and hotter. As long as any amount of matter and radiation is part of this expanding universe, the idea of a big ** gives rise to three clear and universal **:
A massive cosmic web with galaxies growing, evolving, and aggregating more abundantly over time, a low-energy background of blackbody radiation, left over from the first formation of neutral atoms in the red-hot early universe, and a specific set of ratios for the lightest elements (hydrogen, helium, lithium, and their various isotopes), which exist even in regions where stars never formed.
This fragment from a structural formation simulation, as the universe expands, represents billions of years of gravitational growth in a universe rich in dark matter. Over time, overly dense mass of matter becomes richer and more massive, growing into galaxies, groups of galaxies, and clusters of galaxies, while regions with below-average densities preferentially abandon their matter to denser surrounding regions. **Ralf Kaehler and Tom Abel (Kipac) Oliver Hahn
All three of these prophecies were confirmed by observations, which is why the Great ** has taken hold supremacy as our main theory of the origin of the universe, while all its other competitors have been put on hold. However, the big ** only describes what our universe looked like in its early stages; It does not explain why the universe possesses specific properties that we observe. In physics, if you know the initial conditions of a system and what the rules it follows are, you can be very accurate** — at the limits of your computing power and the uncertainty inherent in the system — how it will arbitrarily develop into the distant future.
Therefore, we can ask an important question: what initial conditions did the Great ** need to have at the beginning to provide us with the universe we now observe? The answer is a bit surprising, but we found out:
There must be a clear (at least about 1000 times) maximum temperature lower than Planck's scale, where the known laws of physics collapse, the universe must be born with density fluctuations of approximately the same magnitude at all scales (a few percentage points smaller than on large scales), the rate of expansion and the total density of matter and energy must be almost perfectly balanced: at least 30 significant figures at the moment of the beginning of the thermo-large **, the same initial conditions – the same temperature, Density and wave spectra – must be present in all locations, even between two locations, and it is impossible for a signal of the speed of light to travel the distance between them in the time elapsed after the large **.
The total entropy of the universe must have been much lower than it is today, trillions of times lower.
If these three different regions of space never had time to heat up, share information, or transmit signals to each other, then why are they all the same temperature? This is one of the problems with the big ** initial condition; How is it possible for these areas to all get the same temperature unless they start somehow? **e. siegel/beyond the galaxy
Whenever we have the question of initial conditions – basically, why our system starts the way it has to start – we have only two options. We can appeal to the unknowable and say that it is so, because this is the only possible way for it (i.e., Lady Gaga's interpretation, which says that it was simply "born this way"), and we cannot know anything further. However, we can also try a scientific approach: we can try to find a mechanism to build and create the conditions that we know we need to have. The second way is what physicists call "appealing to dynamics", where the mechanism we design must do three important things.
It must reproduce every success produced by the model it is trying to replace – in this case the popular big **. These early building blocks had to come from whatever mechanism we came up with.
It must explain the key observational fact that the big ** cannot explain: the initial conditions under which the universe began. These questions, those that cannot be explained in the universe, must be explained by any novel ideas.
It must make new things that are different from the original (big) theories, and in these must lead to some degree of observable, testable, and or measurable results.
The only idea we have that meets these three criteria is the theory of cosmic inflation, which is now with unprecedented success on all three fronts.
The exponential expansion that occurs during inflation is so powerful because it is relentless. Every 10 -35 seconds (or so), the volume of any particular area of space doubles in each direction, resulting in any dilution of particles or radiation, and causing any curvature to quickly become indistinguishable from flat. After just a few hundred doublings, i.e. 10 -32 seconds, fluctuations that were initially smaller than Planck's scale will now be stretched to be larger than the currently observable universe. **e. siegel （l）;ned wright'S cosmology tutorial (R) (English).
Inflation basically says that the universe was in a state before it was hot, dense, full of matter and radiation, and it was dominated by a massive amount of energy inherent in space itself: some kind of field or vacuum energy. It's just that, unlike today's dark energy, which had a very small energy density (equivalent to about one proton per cubic meter of space), the energy density during expansion was enormous: about 1025 was several times greater than today's dark energy density. According to Einstein's general theory of relativity, it is the energy density that determines the rate of expansion, which means that during inflation, the rate of expansion is not only incredibly large, but also relentless: as space continues to expand, the rate of expansion remains large.
This is very different from the universe we are familiar with today. In a universe where matter and radiation are constantly expanding, the volume increases, while the number of particles remains the same, so the density decreases. Since energy density is related to the rate of expansion, the rate of expansion of the universe slows down over time.
However, if the energy density is an intrinsic form of the space itself, then the energy density will remain the same over time and the rate of expansion will remain the same. The result is what we know as exponential inflation, in a very short period of time, the size of the universe doubled, after that time, it doubled again, and so on. In a very short period of time – a fraction of a second – a region that was initially smaller than the smallest subatomic particle can be stretched to be larger than the entire visible universe today.
In the top panel, our modern universe has the same properties everywhere (including temperature) because they originate in regions with the same properties. In the middle panel, the space that could have had any arbitrary curvature is inflated to the point where we cannot observe any curvature today, solving the flatness problem. In the bottom plate, the original high-energy relics were inflated and taken away, providing a solution to the problem of high-energy relics. This is how inflation solves the three major problems that the big ** itself cannot explain. **e. siegel/beyond the galaxy
During inflation, the universe – whatever properties it had at the beginning of inflation – is stretched to a gigantic scale. This accomplishes a ton of things in the process, including:
Stretching the observable universe, whatever its initial curvature, cannot be distinguished from flatness, taking any initial conditions that exist in the region that begins to expand, and stretching them so that they are now uniform throughout the visible universe, before inflation, taking any quanta present in that region, and quickly driving them into each other to arbitrarily low densities, creating tiny quantum fluctuations, and extending them throughout the universe, so that they are almost identical on all distance scales, But on a smaller scale (when inflation is coming to an end) the amplitude is slightly smaller, converting all "inflationary" field energy into matter and radiation, but only allowing matter and radiation to reach a maximum temperature that is still well below the Planck scale (but comparable to the inflation energy scale) and producing a spectrum of density and temperature fluctuations that exist on a larger scale than the cosmic horizon and are everywhere adiabatic (constant entropy) rather than isothermal (constant temperature).
In the end, this completes all three things we need to consider replacing the old theory with a new one. Inflation reproduces the success of non-inflationary thermal hyper**, provides a mechanism to explain the initial conditions of large**, and makes a series of new ** that are different from the onset of non-inflation. From the 1990s to the present day, inflation scenarios are consistent with observations and different from non-inflationary hot ones.
During the expansion of the universe, the quantum fluctuations inherent in space extend throughout the universe, creating density fluctuations imprinted in the cosmic microwave background, which in turn give rise to stars, galaxies, and other large structures in the universe today. This is our best description of the behavior of the entire universe, with inflation preceding and setting the big **. Unfortunately, we only have access to information within the cosmic horizon, which is all part of the same part of a region where inflation ended about 13.8 billion years ago. **e. siegel;ESA, Planck and the Department of Energy, NASA, the National Academy of Sciences, the CMB Research Interagency Working Group.
Based on the properties that the universe possesses as we observe it today, in order to reproduce what we see, a minimum inflation had to occur in the past. This further means that inflation must meet certain conditions in order to succeed: those conditions that lead to those **and after-the-fact** that we have just mentioned. Perhaps the simplest and most understandable way to simulate inflation is to think of it as a hill that expands as long as you stay on top of it, but once you roll into the valley below, the inflation ends and converts its energy into matter and radiation.
If you do this, you'll find that your hill can have certain shapes, or what physicists call "potential energy," that succeeds in these areas, while others don't have it at all. The key to getting the required amount of inflation has to do with the top of the mountain: it needs to maintain a sufficiently flat shape over a sufficiently large area. In simple terms, if you think of the inflation field as a ball on top of a hill that needs to roll slowly for most of the time of inflation, it picks up speed and rolls quickly only when it enters the valley, and that's what ends inflation. As scientists, we have quantified how slow inflation needs to be, which allows us to understand the shape needed for this potential. As long as the top is flat enough, inflation can serve as a viable solution for the beginning of our universe.
When the expansion of the universe occurs, there is a lot of energy inherent in space because it is located at the top of this mountain. When the ball rolls into the valley, the energy is converted into particles. This not only provides a mechanism to not only set up a hot large, but also to solve the problems associated with it and make new ones. e. siegel/beyond the galaxy
So, where does the idea of the multiverse come into play? It has to do with one way that we can't take the analogy of the ball and the mountain too seriously: in fact, it's a purely classical view of things. At least as we understand it, the universe is not purely classical, but quantum in nature. This means that inflation, like all fields as we know it, should also be a quantum field by its very nature. The quantum nature of the field tells us that many of its properties cannot be precisely determined, but rather have probability distributions. And, as with all transient quantum systems, the longer the elapsed time, the greater the dispersion of the probability distribution.
In other words, inflation is not rolling a dotted ball down a hill. Instead, what really rolls down the hill is the quantum probability wave function, which is able to take a variety of permissible values.
But as the ball rolls along the hill, the universe is experiencing cosmic expansion, which means it expands exponentially in all three dimensions. If we take a cube of 1 1 1 1 and call it "our universe", then we can see that this cube expands during expansion. If the cube takes some very little time to double in size, then it becomes a 2 2 2 cube, which takes 8 original cubes to fill. Let the same amount of time pass and it becomes a 4 4 4 cube that requires 64 original cubes to fill. Let time pass again, it is an 8 x 8 x 8 cube with a volume of 512. After about 100 "multiplications", we will have a universe of about 10 of 90 of which the original cube, or a universe of the same coefficient of volume expansion: 1090
If inflation is a quantum field, then the field value spreads over time, and different regions of space implement the field value differently. In many areas, the game value will end at the bottom, ending inflation, but in many more areas, inflation will continue as long as the ball remains in the flat part of the hill, where it can remain arbitrarily into the distant future. **e. siegel/beyond the galaxy
This is where the problem arises. If inflation is a quantum field that spreads over time, what happens when a "quantum ball" on the top of a mountain rolls slowly along the flat part of the summit?
The answer is that the part of the wave function that is closer to the end of the valley of the hill is more likely to roll into the valley itself. In these areas, the inflation is likely to end quickly, and then the field energy will be converted into matter and radiation, and with it, what we know as a hot **. This region may form irregularly at the boundary, but some regions seem to describe a part of the observable universe that we can see and enter. As long as enough inflation occurs to reproduce the observational successes we see in the universe, it seems like a good description of our own cosmic history.
But what about the flatter parts of the wave function that are closer to the top of the mountain? The inflation there has lasted much longer, and these are the areas that we can consider "outside" the areas where inflation ended quickly. What this means, in terms of:
Inflation is over, and with it comes the blazing big **, compared to those countries where inflation continues to grow, even if it ends elsewhere?
Whenever inflation occurs (the blue cube), it creates exponentially more areas of space with each step forward in time. Even if there are many cubes of inflation ending (red x), inflation will continue into the future in many more areas. The fact that inflation never ends anywhere makes inflation "eternal" once it starts is also part of our modern concept of the multiverse (regions with red X's describe separate, disconnected universes). e. siegel/beyond the galaxy
When you figure out the math to get enough expansion before the hot big ** happens, that's what science tells us the multiverse is almost inevitable. We must require the universe to undergo enough expansion for our universe to exist with the properties we observe it to have. We also know that inflation must have persisted much longer outside of the regions where it ended.
Now let's ask the big question, "What is the relative size of these regions?" If we compare the following regions:
In areas where inflation ends at a certain time, and after that period of time, where inflation is still not over, we find that the latter region where inflation continues is growing exponentially (and is still growing over time) compared to areas where inflation ends and the hot ** that comes with it. Moreover, this scale gap continues to worsen over time. Even if there are countless regions that end inflation, there will be even larger and infinite regions that persist. In addition, the various areas where it ends – where the heat is large ** – will be further separated by more expansive areas of space by being decisively opened.
To put it simply, if every hot big ** takes place in a "bubble" universe, then these bubbles will never collide. As time goes by, what we end up with is more and more disconnected bubbles, all separated by an eternally expanding space.
While many independent universes are created in expanding space-time, expansion never ends anywhere immediately, but only in different, separate regions separated by space that continues to expand. This is the scientific motivation for the multiverse, and why no two universes collide. The universe doesn't expand into anything; It itself is expanding. **ozytive public domain.
This is the nature of the multiverse and why scientists accept its existence as the default position. We have overwhelming evidence that the big ** is hot, and that the big ** begins with a series of conditions that have no factual explanation. If we add an explanation – cosmic inflation – then creating and triggering the big expansion space-time will make a new set of its own. Many of these are confirmed by observations, but others that are not observable are still consequences of inflation.
One of them is the existence of countless universes, each disconnected region with its own thermal mega**, and when you put them together, they make up the multiverse as we know it. This doesn't necessarily mean that different universes have different rules, laws, or fundamental constants, or that all the possible quantum outcomes you can imagine are happening in other areas of the multiverse. This doesn't even necessarily mean that the multiverse is physically real, as it's a ** that we can't verify, verify, or falsify. However, what if:
The inflation theory is a good theory, the data shows that it is, our universe is quantum in nature, all the evidence suggests that it is, and then the multiverse is almost inevitable. You may not like it, and you may really not like the way some physicists abuse this idea, but until a better, viable alternative to inflation emerges—until this alternative can clear the three theoretical hurdles that inflation has removed—the multiverse is here to stay.
**10,000 Fans Incentive Plan