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The best-fit model to observational data is a spatially flat and, consequently, spatially infinite universe. It is spatially endless today and was always spatially infinite in the past.
The “initial singularity” is not part of the Universe. It is a moment, a point in time that does not exist; only subsequent points do. There are points in time arbitrarily close to the singularity. The closer a point in time is to the singularity, the denser and hotter the Universe is. But still infinite.
Yes, things that are far apart today would have been very close in the early Universe. But that does not mean that they originate from a single point. They were very close, and no matter how great a distance you name or how early in the Universe you go, you will always find things that are farther apart than that distance.
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hings would be different if we lived in a positive curvature, spatially closed Universe. Such a universe would have a finite volume; earlier in its history, it would have had a smaller volume. Extremely close to the singularity, its volume would have been minimal. But even in this case, the singularity is not part of the Universe. This is hypothetical; there are no indications that we live in a spatially closed universe and plenty of indications that we don’t.
observed or detected but can be inferred from gravitational effects.
- Scientists don’t know why.
- A day on Venus is longer than a year on Venus, meaning that Venus rotates on its axis much more slowly than it orbits the sun.
- There are more stars in the Universe than grains of sand on all the beaches on Earth.
- The largest known structure in the Universe is a cluster of galaxies called the Hercules-Corona Borealis Great Wall, which is 10 billion light-years away and over 10 billion light-years long.
- The Universe is estimated to be around 13.8 billion years old. Still, due to the effects of time dilation, some regions may be older or younger than others.
- If you fell into a black hole, spag certification would cause you to be stretched out into a long, thin strand of matter. The Universe is mainly made up of dark matter and dark energy, which cannot be directly
- There are more atoms in a single grain of sand than there are grains of sand on Earth.
- According to theories such as string theory and the many-worlds interpretation of quantum mechanics, there may be parallel universes or multiple dimensions of reality that we cannot directly observe or interact with.
- I don’t know what existed before the Big Bang, if anything. Of course, this doesn’t stop people from speculating and sounding like they know.
- There is good evidence for the Big Bang as it is left lying around in the Universe and what that stuff is doing. We can be confident that the Universe was once extraordinarily compressed and highly energetic and that after the Big Bang, the Universe developed in a way consistent with known physics. This shouldn’t be a surprise because “known physics” is modeled on the observed Universe.
- The problem is that physics gets confusing when you try to work back and forth in time to get to the instant of the Big Bang. When physicists find they are in this kind of muddle, the usual strategy is to gather data and then find equations and models that match the data. Unfortunately, all the data available comes from this Universe and the time after the Big Bang. We’re stuck! It’s like trying to build a car using a cake recipe or something. If we had just one reliable observation from before the Big Bang (if there was anything) or another universe (if there is any), that would be incredibly illuminating and provide enormous guidance to physics. Still, there appears to be nothing available, and there is probably no hope of ever getting any of the data we require.
In this situation, physicists have to make stuff up. They don’t make up random stories (like a giant tortoise vomited up the Universe) but try to form models consistent with what they think are more profound underlying principles of physics. Unfortunately, no one knows what these profound underlying principles are, either. We have to guess that, too.
- The Universe from nothing is one such idea. Or, more correctly, one “group” of ideas: most of these speculations come in multiple versions and may overlap with other speculative models. The general idea is there is a background vacuum realm that is even more empty than empty. It doesn’t even have unique dimensions and maybe not even time. This is impossible to visualize; you have to believe it or not. What this proto-space does have—or is assumed to have—is quantum fluctuations, a little like the quantum fluctuations in the “empty” space in our Universe that can produce random particles. Here and there, now and then—whatever that means in a realm with no space and maybe no time—quantum fluctuations create a tiny bit of real space. If this bit of space is too small, it might just disappear, but if it has a critical size, it grows in a kind of wild runaway process into a universe, aka a Big Bang. The energy of the Big Bang is provided by the gravitational potential energy of the new space itself (I believe).
- Is there any evidence for this? Nothing, or almost nothing. There is just one key bit of evidence: our Universe has not been around forever; it, or at least the current form of it, did start somehow, about 14 billion years ago.
- This is just one model out of many. It has a bit of inner logic, but it has no objective evidence and isn’t even thoroughly worked out. No one has seen the proto-vacuum; it is highly speculative. We know that the Universe exists, and we guess there is some cause, even if it is just a random fluctuation. Hopefully, someday, someone will develop a model that fits all known observations and is internally self-consistent. Plus, it is simple enough and doesn’t have too many arbitrary elements, but we aren’t there yet. We have a bunch of partially worked-through speculations and physicists chatting about them in their
- But ‘nothing’ is a subtle and complex idea, and the naïve (new, inexperienced) views of it that you or I may have are also naïve in the sense of over-simplistic or just plain wrong. But we can still say quite a bit about nothing, and in particular, that some people think might have been the start of things. And to look at that, let’s
- IT pro, part-time physicist — patreon.com/vttoth
“Before the Big Bang, there was nothing” is a syntactically correct but meaningless, just like the sentence, “North of the North Pole, there is nothing”. The latter sentence implies that there is a location north of the North Pole that contains emptiness when, in fact, “north of the North Pole” is not a valid concept. Same goes for “before the Big Bang”.
- Well, at least in the standard Big Bang cosmology. There are alternatives (e.g., bouncing cosmologies, eternal inflation) in which the Big Bang is not a singularity, just a moment when the Universe was hot and dense. It was preceded by something like a pre-inflationary state (in the case of eternal inflation) or a contracting phase (in the case of a “bounce”). But in these cases, “before the Big Bang,” there were lots of things—an entire universe, in fact, quite different from our own but full of
However, those models also predict that the Universe’s expansion rate should slow down as the overall mass density decreases when, in fact, our observations show that this expansion is accelerating. The models also predict a more homogeneous universe than we have been able to observe. Lastly, observations of galaxies lead to conclusions that the gravitation observed is more significant than can be accounted for by observable matter. And we’re talking about orders of magnitude differences, not statistical error.
This leads to the conclusion that there’s more to what we thought was the “observable” Universe than we can observe and that something other than the four classical fundamental forces governs the expansion universe. That supposed something is dark energy, which we have found evidence to support in the cosmological background radiation of the Universe.
Models using dark energy as the driver of universal expansion, while they predict a rapid expansion overcoming gravity beginning somewhere around what we classically know as t=0 and also faithfully follow the currently observed acceleration of the expansion, do not predict a convergence of all matter to a zero-volume space at that point. Instead, they show that at what we might call t=0 (the point just before expansion ballooned), the Universe already had a nonzero volume and asymptotically approaches a zero volume as t continues arbitrarily far before t=0, which effectively means there may never have been “nothing.”
- On top of that, because we can’t determine a definite point of zero volume, it’s not correct to say that the Universe was ever small; it was, at one point, merely very dense, so much so that before the Planck Epoch, all models of what the Universe was like broke down because the Universe was so hot that nothing but energy itself could exist, and at least so dense that multiple instances of whatever makes up the Universe at the very lowest level would be crammed into a space smaller than we would ever be able to measure reliably. The Universe could still have been effectively infinite in volume; there’s just more in a unit volume of the Universe at this state than we can measure. So, before this time, any expansion would appear to result in the creation of something from nothing. It doesn’t; it simply results in more energy than we can measure being emitted from a smaller volume than we can measure.
- In addition, our inability to observe anything for which light has not yet reached us means we can’t see all of the Universe, and we may never know if parts of it are expanding away from us faster than light can travel. So, we don’t know how big the Universe is now, so we can’t do more than take an extraordinarily wild guess. How much matter exists in the entire Universe?
- At any rate, we can’t do more than theorize about what the Universe might have looked like at or near t = 0. Before the end of the Grand Unification Epoch at 1E-36 seconds, the properties that define matter and even energy as we know it are meaningless, so no tool we could ever conceive of could exist within the Universe to observe it before this time.
- It’s also believed impossible to simulate the creation of the Universe at any smaller scale within our Universe (because the Universe is spacetime, so anything we can observe happens inside our already-existing spacetime) or to leave our Universe and observe it from outside. So, it’s possible, and maybe likely, that we will never really know what the very early Universe was like and thus its origins.
- We don’t know what existed before the Big Bang if anything. Of course, this doesn’t stop people from speculating and sounding like they know.
Excellent evidence for the Big Bang exists in what is left lying around in the Universe and what that stuff is doing. We can be confident that the Universe was once extremely compressed and energetic and that it developed in a way consistent with known physics after the Big Bang. This shouldn’t be a surprise because “known physics” is modeled on the observed Universe.
- The problem is that physics gets confusing when you try to work back and forth in time to get to the instant of the Big Bang. When physicists find they are in this kind of muddle, the usual strategy is to gather data and then find equations and models that match the data. Unfortunately, all the available data comes from this Universe and the period after the Big Bang. We’re stuck! It’s like trying to build a car using a cake recipe or something. If we had just one reliable observation from before the Big Bang (if there was anything) or another universe (if there is any), that would be incredibly illuminating and provide enormous guidance to physics. Still, there appears to be nothing available, and there is probably no hope of ever getting any of the data we require.
- In this situation, physicists have to make stuff up. They don’t make up random stories (like a giant tortoise or something vomited up the Universe) but try to form models consistent with what they think are more profound underlying principles of physics. Unfortunately, no one knows these more profound underlying physics principles either. We have to guess that, too.
- The Universe from nothing is one such idea. Or, more correctly, one “group” of ideas: most of these speculations come in multiple versions and may overlap with other speculative models. The general idea is that a background vacuum realm is even more empty than space. It doesn’t even have unique dimensions and maybe not even time. This is impossible to visualize; you have to believe it or not. What this proto-space does have—or is assumed to have—is quantum fluctuations, a little like the quantum fluctuations in the “empty” space in our Universe that can produce random particles. Here and there, now and then—whatever that means in a realm with no space and maybe no time—quantum fluctuations create a tiny bit of real space. If this bit of space is too tiny, it might just disappear, but if it has a critical size, it grows in a kind of wild runaway process into a universe, aka a Big Bang. The energy of the Big Bang is provided by the gravitational potential energy of the new space itself (I believe).
- Is there any evidence for this? Nothing, or almost nothing. There is just one key bit of evidence: our Universe has not been around forever; it, or at least the current form of it, did start somehow, about 14 billion years ago.
- This is just one possible model out of many. It has some inner logic but no objective evidence and hasn’t been thoroughly worked out. No one has seen the proto-vacuum; it is highly speculative. We know that the Universe exists, and we guess there is some kind of cause, even if it is just a random fluctuation. Hopefully, someday, one will develop a model that fits all known observations and is internally self-consistent. Plus, it is simple enough and doesn’t have too many arbitrary elements, but we aren’t there yet. We have a bunch of partially worked-through speculations and physicists chatting about them in their tea rooms.
- This simple trick can save Amazon tons of money, but most Prime members ignore it.
- I’ve been asked to answer, so I’ll enter the fray here! And, at the risk of sounding flip or insulting, let me start by pointing out that for most readers… “You don’t know nothing.” Neither do I, really; I’ve just brushed the surface of the subject.
- But ‘nothing’ is a subtle and complex idea, and the naïve (new, inexperienced) views of it that you or I may have are also naïve in the sense of over-simplistic or just plain wrong. But we can still say quite a bit about nothing, particularly nothing that some people think might have been the start of things. And to look at that, let’s
- Well, at least in the standard Big Bang cosmology. There are alternatives (e.g., bouncing cosmologies, eternal inflation) in which the Big Bang is not a singularity, just a moment when the Universe was very hot and dense. It was preceded by something like a pre-inflationary state (in the case of eternal inflation) or a contracting phase (with a “bounce”). But in these cases, “before the Big Bang,” there were many things—an entire universe quite different from our own but full of “stuff” nonetheless. Not “nothing”.
- Most of the answers are wrong about one thing. The most recent theories about the Universe’s origin, incorporating dark energy and the acceleration of the Universe’s expansion, indicate that there was something before the classical t=0, about 13.7 billion years ago. Classical models of the Big Bang assume that the Universe’s initial expansion was governed by mass density, or equivalently, “observable energy density,” those models show spacetime converging to a single point at t = 0.
- However, those models also predict that the Universe’s expansion rate should slow down as the overall mass density decreases when, in fact, our observations show that this expansion is accelerating. The models also predict a more homogeneous universe than we have been able to observe. Lastly, observations of galaxies lead to conclusions that the gravitation observed is more significant than can be accounted for by observable matter. And we’re talking about orders of magnitude differences, not statistical error.
- This leads to the conclusion that there’s more to what we thought was the “observable” Universe than we can observe and that something other than the four classical fundamental forces governs the expansion universe. That supposed something is referred to as dark energy, which we have found evidence to support in the cosmological background radiation of the Universe.
- Models using dark energy as the driver of universal expansion, while they predict a rapid expansion overcoming gravity beginning somewhere around what we classically know as t=0 and also faithfully follow the currently observed acceleration of the expansion, do not predict a convergence of all matter to a zero-volume space at that point. Instead, they show that at what we might call t=0 (the point just before expansion ballooned), the Universe already had a nonzero volume and asymptotically approaches a zero volume as t continues arbitrarily far before t=0, which effectively means there may never have been “nothing.”
- On top of that, because we can’t determine a definite point of zero volume, it’s not necessarily correct to say that the Universe was ever microscopic; it was, at one point, merely very dense, so much so that before the Planck Epoch, all models of what the Universe was like broke down because the Universe was so hot that nothing but energy itself could exist, and at least so dense that multiple instances of whatever makes up the Universe at the very lowest level would be crammed into a space smaller than we would ever be able to measure reliably. The Universe could still have been effectively infinite in volume; there’s just more in a unit volume of the Universe at this state than we can measure. So, before this time, any expansion would appear to result in the creation of something from nothing. It doesn’t; it simply results in more energy than we can measure being emitted from a smaller volume than we can measure. In addition, our inability to observe anything for which light has not yet reached us means we can’t see all of the Universe, and we may never be able to see it if parts of it are expanding away from us faster than light can travel. So, we don’t know how big the Universe is now, so we can’t do more than take an extraordinarily wild guess about how much matter is in the Universe.
- At any rate, we can’t do more than theorize about what the Universe might have looked like at or near t = 0. Before the end of the Grand Unification Epoch at 1E-36 seconds, the properties that define matter and even energy as we know it are meaningless, so no tool we could ever conceive of could exist within the Universe to observe it before this time.
- It’s also believed impossible to simulate the creation of the Universe at any smaller scale within our Universe (because the Universe is spacetime, so anything we can observe happens inside our already-existing spacetime) or to leave our Universe and observe it from outside. So, it’s possible, and maybe likely, that we will never really know what the very early Universe was like and thus its origins.
- Is Andrei Linde’s chaotic inflation theory compatible with our observable Universe, which appears flat and possibly infinite?
- Chaotic inflation is usually taken as implying eternal inflation. The Penrose diagram for an eternally expanding (inflating) Universe (very similar to the old Steady State model, in some ways) looks like the lower half of a diamond, where the flat top is the infinite future and the lower vertex is the endless past.
- Spacetime. (In reality, this space should be Hubble expanding, but let’s pretend the expansion halts immediately so we can model it quickly.). These universes, embedded within the eternal inflation Penrose diagram, form finite-sized diamonds (squares tipped over at 45 degrees). They get smaller as you move up the diagram due to the scaling, and there would be an infinite number of them. But here is the surprise: each Minkowskian Universe models a static, infinitely large flat universe with an infinite past and an infinite future
- Quantum physics begins when we take some equations from classical physics, play with them a little, and come up with equations that have, besides the classical solutions, solutions that make no sense in a classical context. And then we say that these solutions nonetheless describe reality.
- Remember that famous line from The Matrix: “There is no spoon”? It’s really like that. There is no (classical) electron path. There is no electron position. Or momentum
- If protons have no charge in an atom, how do they stay in the nucleus and ‘stick’ the protons together?
- Indeed, neutrons do not participate in interactions based on electromagnetic force since they have no charge. However, the strong nuclear force affects them (or the quarks that comprise them). That’s the force that holds protons and neutrons together in nuclei, and in non-radioactive (stable) atoms, it’s decidedly more substantial than the EM repulsion the protons produce on one another. Even when the EM force “fluctuates up” and the strong force “fluctuates down,” the strong force still wins. In heavier, radioactive atoms, those fluctuations can cause the EM force to win momentarily, and those protons fly apart—that’s why radioactive atoms decay occasionally.
- So, you don’t usually get taught about separate forces in high school. Gravity and electromagnetism are the “common forces” that affect our day-to-day lives, but the strong and weak nuclear forces are also essential. They operate on very short distances.
- Einstein’s now-widely accepted photon theory, a precursor to his general relativity theory, states that light is packaged into “quanta” that have particle-like properties (later experiments would show a “wave-particle duality” of light and certain other tiny massive particles). In the case of collisions with matter, light tends to behave more particle-like. We know that the atoms that makeup matter have a lot of space due to electromagnetic forces separating atomic nuclei from each other. When light encounters a solid material, a nonzero amount of it will pass right through (though that amount may not be detectable by the human eye). The amount that passes through depends on the density of the material; the more tightly the atoms of the material are packed, the less likely a photon will get through without collisions.
- A half-silvered mirror places a thin, translucent layer of a typically highly reflective material like metal over a usually transparent material like glass. While glass is relatively high-density, the properties of the silica material it’s made of allow for the transmission of light by capturing and releasing photons along the same vector (or very near so), so it slows but does not stop or scatter visible light (glass does block UV, but that’s another question). The silver, however, will reflect light, capturing and releasing it at a very high” refraction angle” compared to glass’s very low one. So, whether the photon is reflected by the silver or refracted through the mirror’s glass depends on what that photon hits first: silver or silica. The principles behind quantum theory state that it is impossible to predict precisely what material each photon will hit first, and thus, it is a fundamentally random event; we can use probability and the Law of Large Numbers to predict percentages of light reflection and transmission, but tracing any single photon’s path through spacetime is impossible.
- [t might not be the most satisfying explanation, but it is the honest answer. According to the most up-to-date and most
- The vital lesson to remember is that the initial singularity is a moment in time that is not part of this Universe; only subsequent moments are like the set of all real numbers greater than 0. This set includes.
- There is excellent evidence for the Big Bang in the form of what is left lying around in the Universe and what that stuff is doing. We can be confident that the Universe was once highly compressed and extremely energetic and that after the Big Bang, the Universe developed in a way consistent with known physics. This shouldn’t be a surprise because “known physics” is modeled on the observed Universe.
- The problem is that physics gets confusing when you try to work back and forth in time to get to the instant of the Big Bang. When physicists find they are in this kind of muddle, the usual strategy is to gather data and then find equations and models that match the data. Unfortunately, all the available data comes from this Universe and the period after the Big Bang. We’re stuck! It’s like trying to build a car using a cake recipe or something. If we had just one reliable observation from before the Big Bang (if there was anything) or another universe (if there is any), that would be incredibly illuminating and provide enormous guidance to physics. Still, there appears to be nothing available, and there is probably no hope of ever getting any of the data we require.
- In this situation, physicists have to make stuff up. They don’t make up random stories (like a giant tortoise or something vomited up the Universe) but try to form models consistent with what they think are more profound underlying principles of physics. Unfortunately, no one knows these more profound underlying physics principles either. We have to guess that, too.
- The Universe from nothing is one such idea. Or, more correctly, one “group” of ideas: most of these speculations come in multiple versions and may overlap with other speculative models. The general idea is that a background vacuum realm is even more empty than space. It doesn’t even have SPECIAL dimensions and maybe not even time. This is impossible; you have to believe it, kind of or not. What this proto-space does have—or is assumed to have—is quantum fluctuations, a little like the quantum fluctuations in the “empty” space in our Universe that can produce random particles. Here-and-there, every now-and-then—whatever that means in realm with no space and maybe no time—a tiny little of real space is created by quantum fluctuations. If this bit of space is too small, it might just disappear, but if it has a critical size, it grows in a kind of wild runaway process into a universe, aka a Big Bang. The energy of the Big Bang is provided by the gravitational potential energy of the new space itself (I believe).
- Is there any evidence for this? Nothing, or almost nothing. There is just one key bit of evidence: our Universe has not been around forever; it, or at least the current form of it, did start somehow, about 14 billion years ago.
- This is just one model out of many. It has a bit of inner logic, but it has no objective evidence and hasn’t even been thoroughly worked out. No one has seen the proto-vacuum; it is highly speculative. We know the Universe exists and guess there is some cause, even if it is just a random fluctuation. Hopefully, someday, someone will come up with a model that fits all known observations and is internally self-consistent, plus it is simple enough and doesn’t have too many arbitrary elements, but we aren’t there yet.
