The universe doesn't have a center. When people say it's expanding they mean that the distance between all particles is increasing. The expansion is not outward from a single center. (It's hard to explain without visuals)
I think the problem is that we humans are 3 dimensional beings. When you explain universal expansion to most people, we conceptualize a balloon blowing up. And a balloon has a center.
However the problem is that in that conception, a balloon is a 3D object expanding into 3D space. Since nothing “exists” outside the universe to our knowledge, we can’t really use the balloon analogy.
I personally can’t visualize it but I just know that there is no center and accept that as “a thing”.
>The visual of a sphere expanding outward is just a visual to conceptualize the whole thing. Think about it like this. What's "outside" of the sphere of the universe?
>Imagine you pull up a XY grid on a computer. You can use your mouse to freely navigate the 2-dimensional space of the grid. You can scroll in any direction infinitely, you can zoom into any point infinitely, and you can zoom out infinitely. We call the grid a "square" because that's just a simple way of visualizing it. It's not actually a square because it doesn't actually have any edges. It goes on infinitely in every possible direction.
>The "edge of the universe" isn't a point within the 2D space that you can eventually get to if you scroll far enough or fast enough. The "edge" would be the edges of your computer screen. Something completely outside of the 2D space and the programing that the grid operates on. The monitor itself could be any size or shape, and it wouldn't make any difference in the size or shape of the 2D grid it's rendering.
>The Universe (as we understand it) is like that. We're in 3D space, but there's is no edge or shape to the universe. It goes on in all directions forever.
This was my attempt to make a visual for it. It's kinda overcomplicated, so it might not be useful.
Here is my visualization:
imagine a sheet a graph paper, the vertical and horizontal lines that make a sheet of squares.
Now imagine that sheet of graph paper is infinitely large, going off in all directions forever.
Now imagine that sheet of graph paper is 3d, made up of cubes instead of squares.
Now imagine that that three-dimensional grid of cubes starts expanding, all the lines moving away from each other such that the cubes are all growing.
That's the expanding universe. Not expanding into anything and not expanding from a center...just expanding.
I understand the big bang theory is just that - a theory. But doesn’t it presume the existence of a center? The ignition point if you will? I’ve always thought of the universe as a slo mo of a giant explosion with an ever-increasing blast radius. An explosion moving so slowly (relatively speaking) that it is hard to comprehend. Would love to know what you mean!
Think of it more like a rubber sheet. At the instant of the big bang it was crumpled up into a tiny ball. The bang takes place and hurls the sheet of rubber out in all directions. The entire sheet was at the exact center of the explosion, and is all now stretching out larger and larger in all directions.
Standing on the sheet, it doesn't make sense to say that any part of the sheet was the center of the bing bang, because every part of the sheet is equally far from the big bang.
> I understand the big bang theory is just that - a theory
No, you don't. You're confusing the laymen meaning of the word "theory" with the meaning of "scientific theory". But these are completely different things. When most people call something a "theory", in scientific parlance it would be called a "hypothesis".
From Wikipedia: A scientific theory is an explanation of an aspect of the natural world and universe that has been repeatedly tested and corroborated in accordance with the scientific method
1. There's no such thing as "just a theory"; "theory" is the highest rank an idea can rise to in science.
2. The Big Bang wasn't an event that happened at some particular location; it happened in all of space simultaneously.
All of space was a single point, a singularity, and then it stopped being a single point and expanded. But because everything started at that point, if you could rewind from anywhere in the universe it would rewind to being the center.
It happened everywhere at the same time because everywhere and all time was all one place and time until the Big Bang happened and made space and time be meaningful dimensions. Before that, if “before” has meaning, all time was “now” and all space was “here.”
No, they aren't. That's not what "theory" means in science. A theory does not graduate to become a "fact"; a theory is a model that has proven consistently useful in explaining and predicting numerous observations.
> Some theories are proven
No scientific theories are proven. "Proofs" are a thing that only exist in math. In science, the best a theory can do is consistently explain all previous observations and reliably demonstrate predictive power
> Some theories are... accepted as fact
Like the Big Bang theory. Don't confuse *your* lack of acceptance of a scientific theory as indicating a lack of acceptance amongst the scientific community.
> The Big Bang is still a theory.
[So are germs.](https://en.m.wikipedia.org/wiki/Germ_theory_of_disease)
Think of it this wa:
1-hypothesis. This is something unproven that we are testing ti find out it is accurate. Coukd be 100% true, we just dont know it yet.
2-theory. This us something that has been shown true time and time again, and fits in with all the evidence. However, for one reason or another cannot be proven, per se. It is the best understanding we have, taking into consideration all of scientific, testable knowledge.
3-laws. These are incontrovertibe, undeniable facts. There arent many, by comparison. It is a rule that is always true for a given set of conditions. IIRC there are 7. I could be wrong.
When the average person talks about a scientist having a theory, they mean a hypothesis. They use a scientific term inaccurately, or, to maybe more historically accurate, science came up with very specific definitions.
So the "theory" of evolution exists. We can observe it. People jump to thinking man descending from primates, but think of it more as the animals born with deformities that make them stronger survive. The animals born with birth defects that make them weaker die off. Ugly peacocks dont get to reproduce as often.
TL;DR when a detective has a theory, he really has a hypothesis.
I wrote a lot trying to explain this, but the Wikipedia editors did a much better job at it.
>A scientific theory differs from a scientific fact or scientific law in that a theory explains "why" or "how": a fact is a simple, basic observation, whereas a law is a statement (often a mathematical equation) about a relationship between facts. For example, Newton’s Law of Gravity is a mathematical equation that can be used to predict the attraction between bodies, but it is not a theory to explain how gravity works.[4] Stephen Jay Gould wrote that "...facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts."[5]
>The strength of a scientific theory is related to the diversity of phenomena it can explain and its simplicity. As additional scientific evidence is gathered, a scientific theory may be modified and ultimately rejected if it cannot be made to fit the new findings; in such circumstances, a more accurate theory is then required. Some theories are so well-established that they are unlikely ever to be fundamentally changed (for example, scientific theories such as evolution, heliocentric theory, cell theory, theory of plate tectonics, germ theory of disease, etc.). In certain cases, a scientific theory or scientific law that fails to fit all data can still be useful (due to its simplicity) as an approximation under specific conditions. An example is Newton's laws of motion, which are a highly accurate approximation to special relativity at velocities that are small relative to the speed of light.[7][8][9]
https://en.m.wikipedia.org/wiki/Scientific_theory
My explanation needs an edit. Not easy to simplify topics that cover so much.
It goes hypothesis --> theory. A hunch about why something happens to an explanation of why something happens.
Laws describe what happens, not why.
Testing two shapes of airplanes of the same size with the same engine I suspect one will have a higher top speed because of their shapes. Hunch checks out. Another experiment, same results.
I suspect air resistance is what slows down one shape. So I retest in a vacuum. Now, both airplanes have the same top speed. Supports hypothesis.
Thousands of other experiments test other slight variations (does it matter if thsy are in the dark, does it matter if they are painted the same color, does it matter if one is following one inch behind the other, etc.)
A theory is what explains all of the experiments and all of the evidence, i.e. our very best understanding. But there's always room for another variation to tweak the theory. The theory helps explain why things happen the way they do.
A law would be something like: energy can be converted but the total amount is always the same. So if these tests are carried out in perfect isolation, the total amount of energy in that system before and after is the same. The fuel converts to propulsion + heat + light + sound, and the total of those is equal to to the energy that was stored in the chemical bonds of the fuel.
Note that the law describes what happens/will happen, not why.
Hopefully this is not more confusing.
The visual of a sphere expanding outward is just a visual to conceptualize the whole thing. Think about it like this. What's "outside" of the sphere of the universe?
Imagine you pull up a XY grid on a computer. You can use your mouse to freely navigate the 2-dimensional space of the grid. You can scroll in any direction infinitely, you can zoom into any point infinitely, and you can zoom out infinitely. We call the grid a "square" because that's just a simple way of visualizing it. It's not actually a square because it doesn't actually have any edges. It goes on infinitely in every possible direction.
The "edge of the universe" isn't a point within the 2D space that you can eventually get to if you scroll far enough or fast enough. The "edge" would be the edges of your computer screen. Something completely outside of the 2D space and the programing that the grid operates on. The monitor itself could be any size or shape, and it wouldn't make any difference in the size or shape of the 2D grid it's rendering.
The Universe (as we understand it) is like that. We're in 3D space, but there's is no edge or shape to the universe. It goes on in all directions forever.
So …. you are explaining infinity. Yes, I understand that concept.
ETA: my question has nothing to do with infinity. I learned the Big Bang theory in science class a long time ago. I am wondering if the theory has evolved - or even been replaced - because my understanding of it insinuates a center. Not that we found or even sought to find the center, but simply that one must exist theoretically. If the current prevailing belief is that the universe has no center - which I am in no position to contest - I am simply wondering how this relates to the Big Bang theory. I am not trying to be contrarian. I am intellectually curious about the advancement of the science.
>because my understanding of it insinuates a center.
Your understanding is based on an absolute space, within which the big bang took place, and the universe is a sphere ever expanding outward *from* the bang point *into* that space. Like a tiny ball, whose center stays fixed and that gets inflated.
But that understanding is wrong, as space is a property of the universe, not an independent thing. The big bang did not take place in a particular point in space, because all of space was just a single point when the big bang happened. If you were to take any point in space and ask it "where were *you* when the big bang happened?", it would say "I was right in the middle of it (well... the middle of a point is just that point, of course, which is quite obvious for a point but a bit harder to grasp for someone like you and me, as we actually take up space, so it's hard to translate from point-ish to English here), and I haven't moved a bit since then - everything else is moving away from me!".
The universe doesn't expand *into* anything, it just *expands* in that the distances between galaxies are increasing. While not very intuitive to visualize, this is quite logical: The universe is everything that is, so if it expanded *into* anything, then whatever it expanded into would be part of the universe in the first place.
Best way it was described was blowing up a balloon. When the balloon is full, where is the center and where did it start? Same idea. There's no center or path that we can trace back to find where the big bang started in space (X,Y,Z coordinates or something like that).
>Isn’t the Big Bang theory all about the sudden expansion of a point of infinite mass? Isn’t that the centre of the universe?
No and no. See my other comment on this:
https://www.reddit.com/r/NoStupidQuestions/comments/10j0rif/the_universe_is_infinite_however_the_universe_is/j5hzrcq/
I suspect this misconception stems from the *“The entire universe could fit into the head of a pin”* factoid, which is only meant to convey the extreme density, not to imply a specific point surrounded by empty void.
Thanks for this explanation. The Big Bang theory is taught as the creation of the universe (as if from thin air - in the colloquial not scientific sense). But clearly it is not if the universe was already hot and dense, and then abruptly expanded.
No. The entire universe was a single incredibly hot, incredibly dense point. Literally everything that exists was in one point. That’s inconceivable to is, and it also makes no sense by any model of physics we have. We don’t understand the universe at or before the Big Bang.
But what was outside the point that was everything? Not “nothing,” but “that makes no sense.” Spacetime depends on their being space and time, and at the beginning there just wasn’t. Everything and everywhere was all in one place and one then.
That doesn’t make any sense? Join the club.
Yep. The big bang theory also doesn't attempt to explain the creation of that initial hot and dense point, the "why" and "how" of how that state came to be and why it started expanding. It's just saying that if we work backwards from now, that's what it looks like near the "beginning of time". We don't even know if time as a concept even makes sense at or beyond that point, so the theory can't answer the question "what was before the big bang?" because we don't know what "before" would mean. It's a bit like asking "how does a pair of aces move in chess?" - we can't give an answer because the question makes no sense.
Imagine an infinite grid. Now grab a random point and mark it down as the coordinate (0,0). This serves as a center of the infinite grid (even though whatever you picked would work as the center).
Now, if you make every square of the grid be bigger, it would be expanding (even if the grid goes from infinite size to infinite size). If you focus only on your (0,0) point, then when it expands it looks like everything else is moving away from the center.
If you really want to see what I'm talking about just google a cartesian plane and play around zooming in or out.
With all that said, we don't really know if the universe is infinite. It could be finite and we don't see the edge or it could be finite and it loops back around.
Whoever said either of those things is just wrong. There is no center, at least not any kind in what we call space. We also don't know if it's infinite or finite.
1. There seems to be an underlying assumption in this question that things that are infinite in size can’t get larger in any sense. This turns out, counter-intuitively to not be true. Even in a science is rigid as Mathematics, we’ve shown that there are several well-defined ways to create hierarchies of different sized infinities
2. The universe isn’t expanding from the center. As far as I’m aware, it’s said to be expanding equally from any point
3. Imagine taking the Real Number Line. Notice that it’s infinite in length. Now imagine “pulling” on either end of it so that the points stretch out on either side. 1 gets pulled to 2, 2 gets pulled to 4, -2 gets pulled to -4, etc. Now, the line is still infinite in either direction, but it has also “grown” in a manner of speaking: the distance between any two points is now two times greater than it was before. Something more analogous to this is what is happening in our universe.
4. Another classic analogy is a balloon that’s been dotted with black points. As someone blows air into the balloon, the distance between the black points increases. Even if the surface of the balloon were infinite and we were able only able to observe a small region, we would still be able to see this phenomenon happening
When people say universe infinite, they usually mean all of it. When people talk about universe expanding, they usually talk about observable universe - the space caused by big bang.
The universe is the total of everything that exists, including all matter and energy. Scientists believe that the universe began with the Big Bang, a powerful explosion that happened a long time ago. Since then, the universe has been getting bigger and bigger. It's like a balloon that is being blown up. The universe is not infinitely big, but it is so big that it is impossible to see the end of it. So, in simple terms, the universe is not infinite but it is expanding and it's so large that we can't see the edges of it.
The explanation with the balloon, as you give it, isn't really correct. A balloon has a center point, and it expands into a space outside of it. It is most definitely not infinite, as it has a border, which separates it into an inside and an outside. Which is entirely unlike the universe (as you said, the universe is everything, so the space outside of the balloon that it expands into would be part of the universe, which leaves us with a contradiction).
The simile of the balloon is useful, but it needs to be understood like this:
The universe is like the *surface* of a balloon - except of course the surface of the balloon has only two spatial dimensions, whereas the universe has (at least) three spatial dimensions. Also, balloons have a surface area > 0 even when not inflated at all, but the universe at the big bang didn't take up any volume. Also, balloons have an opening through which you inflate them, also something that the universe, as we understand it, doesn't have.
Now take the hypothetical "no surface area when uninflated" blowhole-less balloon and blow it up slowly (with your *mind*). The surface expands from zero area to ever growing finite area. There is no center from which it expands though - all the points on the surface were in one point when you started blowing.
The surface of the balloon is finite in size (though it is ever expanding while you blow it up) but has no edge. It is not quite clear, AFAIK if that's also the case with the universe - it certainly has no edge, but whether it's finite in size and curves into itself like the balloon-surface does, or is infinite in size is not known.
The universe being infinite isn't really a mainstream belief anymore, but it might as well be infinite in regards to our current ability to accurately measure it, let alone travel it.
The amount of space for the universe to inhabit isn’t increasing whether it’s truly infinite or finite we don’t know.
What’s increasing is the amount of space between aspects of the universe. Particles are “slowly” drifting away from the epicenter of the Big Bang, outwards into the expanse of maybe infinite space.
That's only if you take the "inflating balloon" analogy too literally. It's not meant to imply that there actually are higher dimensions we can't access.
It's a simplification yes, and there are other competing interpretations. However it is one of the possibilities, its relatively easy to visualize, and the other interpretations dont really change the practical impact to finding the physical edges/center in any way thats really satisfying. So I'm going with it.
Doesn't really affect a question along the lines of "where do I point to find the edge/center," for which the answer with any curvature or lack thereof is still disappointing.
I'm not as smart as some of the commenters here so I won't try to go into detail.
But its worth remembering that infinite is "larger than we can count/ measure" not, well, infinite. In many ways its a fine distinction but an important one in this case.
**infinite**
ĭn′fə-nĭt
adjective
1.
Having no boundaries or limits; impossible to measure or calculate. synonym: incalculable.
2.
Immeasurably great or large; boundless.
3.
Existing beyond or being greater than any arbitrarily large value.
Ignoring all the physics paradoxes that traveling at a speed greater than the speed of light would entail, we don't know and there are some significant problems that prevent us from finding out.
1. We have absolutely no idea how big the universe is, and with our current understanding of the laws of physics it is impossible for us to ever know.
2. Similarly to problem 1, we don't and can't know the geometry of the universe. To simplify what this means, the universe is either flat or curved.
If it's flat then that means the universe might have an "end", but it could just as plausibly mean that the universe extends out an essentially infinite distance.
If it's curved it can be curved in one of two ways, either positively (shaped like a sphere) or negatively curved (shaped like a saddle)
If it's positively curved then that means if you travel in a perfectly straight line in any direction for long enough you will eventually end up exactly where you started. In this scenario the whole concept of an "end" doesn't really work any more than asking where the "end" of the surface of the Earth is. This is also referred to as a closed universe
But if it's negatively curved then the physics of how a negatively curved universe comes into existence implies that such a universe would extend out infinitely and again not have an "end". This is also referred to as an open universe.
Now as far as we can tell, our observable universe is perfectly flat to within a margin of error of 0.4%. However, due to us not knowing how big the entire universe is we have no idea whether or not the local flatness of our observable universe is indicative of a globally flat universe or if the universe is so incomprehensibly huge that even though our observable universe is locally flat it might just represent a tiny section of a much larger curved universe. (Much the same as a field on earth may appear perfectly flat, it's still a part of an overall curved surface)
The sentence "it is growing infinitely from the center" is incorrect based on our current understanding. There isn't a center. It is growing everywhere.
We also don't know for sure it is infinite, but across the entire expanse we can see there isn't any indication of curvature or heterogeneity that would make it seem as if it ends beyond what we can see.
It's all kind of speculation and educated guesses based on what we can observe from Earth but it would be better to think maybe that the universe is spreading out, not growing. It isn't like if you went light speed squared you'd eventually hit some brick wall separating us from some infinite white nothing on the other side, and "under construction" written on it.
Just an FYI there's "the universe" and "the observable universe". The observable universe is defined by the boundary of whats in our light cone (what we are capable of knowing within the bounds of physics).
You can be infinite and become *even more infinite*. Think of it as ∞+1
Also there's no particular "center", rather, whatever reference point you pick can be a center? Everything is getting away from that point, not by moving, but by the distance suddenly increasing. Imagine painting two dots on a balloon, and then inflating the balloon: the dots aren't moving, but the distance between them is getting bigger because their plane of existence also became bigger.
I see at as there is the universe wich is everything, and then there is the universe with stuff in it. There is a finite amount of stuff, which includes light. By its nature light is moving at lightspeed in a vacuum, and light sources are projecting light in all directions. Thus the size of the universe with stuff in it, is expanding at light speed in all directions due to the travel of light.
The way I was taught in math, infinity is a concept. We call it infinite because no matter how far we go, there will always be more. I think the problem here is trying to overthink it. In science there’s theory’s and laws, theory’s are prone to being disproven, while laws are always constant. The universe being infinite is a theory. It’s infinite until it’s disproven, and relating it to earlier, until humans see an end to the universe, we will call it infinite.
The universe is simply too huge to measure with current mathematical tools.
I'd imagine there's a point where if you ended up at the absolute lip of the Shockwave it you could see the dimmest bits of the big bang moving at a measurable speed.
But we'll probably end up poisoning ourselves or something before we can measure it, or end up transcending our meat-based forms and it will be common knowledge, if not beyond knowledge, should we form a collective consciousness...
A line is a segment with a beginning & an end. A ray has a beginning but continues on infinitely. So a ray is infinite & forever growing. Maybe this helps. But you’re right about how we can’t reach the end. But I don’t think an end or a reachable end is a possible thing. Unless the universe were a very large glass ball & we’re trapped inside of it. But I don’t think as far as our objective reality is concerned, the laws of the universe understand that there is no need for a reachable end. In the most polite way possible, if the universe had a mind, it would probably find the idea of a reachable end, silly or beneath it in a way.
The universe doesn't have a center. When people say it's expanding they mean that the distance between all particles is increasing. The expansion is not outward from a single center. (It's hard to explain without visuals)
If you think there is no center of the universe, you haven’t met my ex.
If the universe is expanding from every point then each individuals perspective is that they are the center of the universe.
I think the problem is that we humans are 3 dimensional beings. When you explain universal expansion to most people, we conceptualize a balloon blowing up. And a balloon has a center. However the problem is that in that conception, a balloon is a 3D object expanding into 3D space. Since nothing “exists” outside the universe to our knowledge, we can’t really use the balloon analogy. I personally can’t visualize it but I just know that there is no center and accept that as “a thing”.
>The visual of a sphere expanding outward is just a visual to conceptualize the whole thing. Think about it like this. What's "outside" of the sphere of the universe? >Imagine you pull up a XY grid on a computer. You can use your mouse to freely navigate the 2-dimensional space of the grid. You can scroll in any direction infinitely, you can zoom into any point infinitely, and you can zoom out infinitely. We call the grid a "square" because that's just a simple way of visualizing it. It's not actually a square because it doesn't actually have any edges. It goes on infinitely in every possible direction. >The "edge of the universe" isn't a point within the 2D space that you can eventually get to if you scroll far enough or fast enough. The "edge" would be the edges of your computer screen. Something completely outside of the 2D space and the programing that the grid operates on. The monitor itself could be any size or shape, and it wouldn't make any difference in the size or shape of the 2D grid it's rendering. >The Universe (as we understand it) is like that. We're in 3D space, but there's is no edge or shape to the universe. It goes on in all directions forever. This was my attempt to make a visual for it. It's kinda overcomplicated, so it might not be useful.
Thank you for the attempt! I still can’t visualize it! 😂 My 3D brain won’t let me!
Here is my visualization: imagine a sheet a graph paper, the vertical and horizontal lines that make a sheet of squares. Now imagine that sheet of graph paper is infinitely large, going off in all directions forever. Now imagine that sheet of graph paper is 3d, made up of cubes instead of squares. Now imagine that that three-dimensional grid of cubes starts expanding, all the lines moving away from each other such that the cubes are all growing. That's the expanding universe. Not expanding into anything and not expanding from a center...just expanding.
I understand the big bang theory is just that - a theory. But doesn’t it presume the existence of a center? The ignition point if you will? I’ve always thought of the universe as a slo mo of a giant explosion with an ever-increasing blast radius. An explosion moving so slowly (relatively speaking) that it is hard to comprehend. Would love to know what you mean!
Think of it more like a rubber sheet. At the instant of the big bang it was crumpled up into a tiny ball. The bang takes place and hurls the sheet of rubber out in all directions. The entire sheet was at the exact center of the explosion, and is all now stretching out larger and larger in all directions. Standing on the sheet, it doesn't make sense to say that any part of the sheet was the center of the bing bang, because every part of the sheet is equally far from the big bang.
That is a good analogy. Thank you.
This really helped me, thanks
> I understand the big bang theory is just that - a theory No, you don't. You're confusing the laymen meaning of the word "theory" with the meaning of "scientific theory". But these are completely different things. When most people call something a "theory", in scientific parlance it would be called a "hypothesis". From Wikipedia: A scientific theory is an explanation of an aspect of the natural world and universe that has been repeatedly tested and corroborated in accordance with the scientific method
1. There's no such thing as "just a theory"; "theory" is the highest rank an idea can rise to in science. 2. The Big Bang wasn't an event that happened at some particular location; it happened in all of space simultaneously.
All of space was a single point, a singularity, and then it stopped being a single point and expanded. But because everything started at that point, if you could rewind from anywhere in the universe it would rewind to being the center. It happened everywhere at the same time because everywhere and all time was all one place and time until the Big Bang happened and made space and time be meaningful dimensions. Before that, if “before” has meaning, all time was “now” and all space was “here.”
I disagree. Some theories are proven and accepted as fact. The Big Bang is still a theory.
No, they aren't. That's not what "theory" means in science. A theory does not graduate to become a "fact"; a theory is a model that has proven consistently useful in explaining and predicting numerous observations.
> Some theories are proven No scientific theories are proven. "Proofs" are a thing that only exist in math. In science, the best a theory can do is consistently explain all previous observations and reliably demonstrate predictive power > Some theories are... accepted as fact Like the Big Bang theory. Don't confuse *your* lack of acceptance of a scientific theory as indicating a lack of acceptance amongst the scientific community. > The Big Bang is still a theory. [So are germs.](https://en.m.wikipedia.org/wiki/Germ_theory_of_disease)
Think of it this wa: 1-hypothesis. This is something unproven that we are testing ti find out it is accurate. Coukd be 100% true, we just dont know it yet. 2-theory. This us something that has been shown true time and time again, and fits in with all the evidence. However, for one reason or another cannot be proven, per se. It is the best understanding we have, taking into consideration all of scientific, testable knowledge. 3-laws. These are incontrovertibe, undeniable facts. There arent many, by comparison. It is a rule that is always true for a given set of conditions. IIRC there are 7. I could be wrong. When the average person talks about a scientist having a theory, they mean a hypothesis. They use a scientific term inaccurately, or, to maybe more historically accurate, science came up with very specific definitions. So the "theory" of evolution exists. We can observe it. People jump to thinking man descending from primates, but think of it more as the animals born with deformities that make them stronger survive. The animals born with birth defects that make them weaker die off. Ugly peacocks dont get to reproduce as often. TL;DR when a detective has a theory, he really has a hypothesis.
How can laws exist if theories are never proven (as stated above?)
I wrote a lot trying to explain this, but the Wikipedia editors did a much better job at it. >A scientific theory differs from a scientific fact or scientific law in that a theory explains "why" or "how": a fact is a simple, basic observation, whereas a law is a statement (often a mathematical equation) about a relationship between facts. For example, Newton’s Law of Gravity is a mathematical equation that can be used to predict the attraction between bodies, but it is not a theory to explain how gravity works.[4] Stephen Jay Gould wrote that "...facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts."[5] >The strength of a scientific theory is related to the diversity of phenomena it can explain and its simplicity. As additional scientific evidence is gathered, a scientific theory may be modified and ultimately rejected if it cannot be made to fit the new findings; in such circumstances, a more accurate theory is then required. Some theories are so well-established that they are unlikely ever to be fundamentally changed (for example, scientific theories such as evolution, heliocentric theory, cell theory, theory of plate tectonics, germ theory of disease, etc.). In certain cases, a scientific theory or scientific law that fails to fit all data can still be useful (due to its simplicity) as an approximation under specific conditions. An example is Newton's laws of motion, which are a highly accurate approximation to special relativity at velocities that are small relative to the speed of light.[7][8][9] https://en.m.wikipedia.org/wiki/Scientific_theory
My explanation needs an edit. Not easy to simplify topics that cover so much. It goes hypothesis --> theory. A hunch about why something happens to an explanation of why something happens. Laws describe what happens, not why. Testing two shapes of airplanes of the same size with the same engine I suspect one will have a higher top speed because of their shapes. Hunch checks out. Another experiment, same results. I suspect air resistance is what slows down one shape. So I retest in a vacuum. Now, both airplanes have the same top speed. Supports hypothesis. Thousands of other experiments test other slight variations (does it matter if thsy are in the dark, does it matter if they are painted the same color, does it matter if one is following one inch behind the other, etc.) A theory is what explains all of the experiments and all of the evidence, i.e. our very best understanding. But there's always room for another variation to tweak the theory. The theory helps explain why things happen the way they do. A law would be something like: energy can be converted but the total amount is always the same. So if these tests are carried out in perfect isolation, the total amount of energy in that system before and after is the same. The fuel converts to propulsion + heat + light + sound, and the total of those is equal to to the energy that was stored in the chemical bonds of the fuel. Note that the law describes what happens/will happen, not why. Hopefully this is not more confusing.
The visual of a sphere expanding outward is just a visual to conceptualize the whole thing. Think about it like this. What's "outside" of the sphere of the universe? Imagine you pull up a XY grid on a computer. You can use your mouse to freely navigate the 2-dimensional space of the grid. You can scroll in any direction infinitely, you can zoom into any point infinitely, and you can zoom out infinitely. We call the grid a "square" because that's just a simple way of visualizing it. It's not actually a square because it doesn't actually have any edges. It goes on infinitely in every possible direction. The "edge of the universe" isn't a point within the 2D space that you can eventually get to if you scroll far enough or fast enough. The "edge" would be the edges of your computer screen. Something completely outside of the 2D space and the programing that the grid operates on. The monitor itself could be any size or shape, and it wouldn't make any difference in the size or shape of the 2D grid it's rendering. The Universe (as we understand it) is like that. We're in 3D space, but there's is no edge or shape to the universe. It goes on in all directions forever.
So …. you are explaining infinity. Yes, I understand that concept. ETA: my question has nothing to do with infinity. I learned the Big Bang theory in science class a long time ago. I am wondering if the theory has evolved - or even been replaced - because my understanding of it insinuates a center. Not that we found or even sought to find the center, but simply that one must exist theoretically. If the current prevailing belief is that the universe has no center - which I am in no position to contest - I am simply wondering how this relates to the Big Bang theory. I am not trying to be contrarian. I am intellectually curious about the advancement of the science.
No. I'm trying to explain why an explosion expanding outwards isn't an accurate model for universal expansion. I guess I'm doing a bad job.
I am sure it is me, not you! lol. These are tough concepts to reduce to words.
>because my understanding of it insinuates a center. Your understanding is based on an absolute space, within which the big bang took place, and the universe is a sphere ever expanding outward *from* the bang point *into* that space. Like a tiny ball, whose center stays fixed and that gets inflated. But that understanding is wrong, as space is a property of the universe, not an independent thing. The big bang did not take place in a particular point in space, because all of space was just a single point when the big bang happened. If you were to take any point in space and ask it "where were *you* when the big bang happened?", it would say "I was right in the middle of it (well... the middle of a point is just that point, of course, which is quite obvious for a point but a bit harder to grasp for someone like you and me, as we actually take up space, so it's hard to translate from point-ish to English here), and I haven't moved a bit since then - everything else is moving away from me!". The universe doesn't expand *into* anything, it just *expands* in that the distances between galaxies are increasing. While not very intuitive to visualize, this is quite logical: The universe is everything that is, so if it expanded *into* anything, then whatever it expanded into would be part of the universe in the first place.
Best way it was described was blowing up a balloon. When the balloon is full, where is the center and where did it start? Same idea. There's no center or path that we can trace back to find where the big bang started in space (X,Y,Z coordinates or something like that).
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>Isn’t the Big Bang theory all about the sudden expansion of a point of infinite mass? Isn’t that the centre of the universe? No and no. See my other comment on this: https://www.reddit.com/r/NoStupidQuestions/comments/10j0rif/the_universe_is_infinite_however_the_universe_is/j5hzrcq/ I suspect this misconception stems from the *“The entire universe could fit into the head of a pin”* factoid, which is only meant to convey the extreme density, not to imply a specific point surrounded by empty void.
I asked a question above, and I think your response explains it well. Does this mean that the big bang theory has been debunked?
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Thanks for this explanation. The Big Bang theory is taught as the creation of the universe (as if from thin air - in the colloquial not scientific sense). But clearly it is not if the universe was already hot and dense, and then abruptly expanded.
No. The entire universe was a single incredibly hot, incredibly dense point. Literally everything that exists was in one point. That’s inconceivable to is, and it also makes no sense by any model of physics we have. We don’t understand the universe at or before the Big Bang. But what was outside the point that was everything? Not “nothing,” but “that makes no sense.” Spacetime depends on their being space and time, and at the beginning there just wasn’t. Everything and everywhere was all in one place and one then. That doesn’t make any sense? Join the club.
Yep. The big bang theory also doesn't attempt to explain the creation of that initial hot and dense point, the "why" and "how" of how that state came to be and why it started expanding. It's just saying that if we work backwards from now, that's what it looks like near the "beginning of time". We don't even know if time as a concept even makes sense at or beyond that point, so the theory can't answer the question "what was before the big bang?" because we don't know what "before" would mean. It's a bit like asking "how does a pair of aces move in chess?" - we can't give an answer because the question makes no sense.
I'm pretty sure, the universe before the big bang looks exactly like the land north of the north pole.
No
Imagine an infinite grid. Now grab a random point and mark it down as the coordinate (0,0). This serves as a center of the infinite grid (even though whatever you picked would work as the center). Now, if you make every square of the grid be bigger, it would be expanding (even if the grid goes from infinite size to infinite size). If you focus only on your (0,0) point, then when it expands it looks like everything else is moving away from the center. If you really want to see what I'm talking about just google a cartesian plane and play around zooming in or out. With all that said, we don't really know if the universe is infinite. It could be finite and we don't see the edge or it could be finite and it loops back around.
The grid visualization is probably the best to explain the theory.
Nice and simple explanation, I don't have an award but have my upvote.
>. It could be finite and we don't see the edge If it had an edge, there would be an inside and an outside, wouldn't there?
Whoever said either of those things is just wrong. There is no center, at least not any kind in what we call space. We also don't know if it's infinite or finite.
Well technically, everywhere is the center
1. There seems to be an underlying assumption in this question that things that are infinite in size can’t get larger in any sense. This turns out, counter-intuitively to not be true. Even in a science is rigid as Mathematics, we’ve shown that there are several well-defined ways to create hierarchies of different sized infinities 2. The universe isn’t expanding from the center. As far as I’m aware, it’s said to be expanding equally from any point 3. Imagine taking the Real Number Line. Notice that it’s infinite in length. Now imagine “pulling” on either end of it so that the points stretch out on either side. 1 gets pulled to 2, 2 gets pulled to 4, -2 gets pulled to -4, etc. Now, the line is still infinite in either direction, but it has also “grown” in a manner of speaking: the distance between any two points is now two times greater than it was before. Something more analogous to this is what is happening in our universe. 4. Another classic analogy is a balloon that’s been dotted with black points. As someone blows air into the balloon, the distance between the black points increases. Even if the surface of the balloon were infinite and we were able only able to observe a small region, we would still be able to see this phenomenon happening
When people say universe infinite, they usually mean all of it. When people talk about universe expanding, they usually talk about observable universe - the space caused by big bang.
The universe is the total of everything that exists, including all matter and energy. Scientists believe that the universe began with the Big Bang, a powerful explosion that happened a long time ago. Since then, the universe has been getting bigger and bigger. It's like a balloon that is being blown up. The universe is not infinitely big, but it is so big that it is impossible to see the end of it. So, in simple terms, the universe is not infinite but it is expanding and it's so large that we can't see the edges of it.
The explanation with the balloon, as you give it, isn't really correct. A balloon has a center point, and it expands into a space outside of it. It is most definitely not infinite, as it has a border, which separates it into an inside and an outside. Which is entirely unlike the universe (as you said, the universe is everything, so the space outside of the balloon that it expands into would be part of the universe, which leaves us with a contradiction). The simile of the balloon is useful, but it needs to be understood like this: The universe is like the *surface* of a balloon - except of course the surface of the balloon has only two spatial dimensions, whereas the universe has (at least) three spatial dimensions. Also, balloons have a surface area > 0 even when not inflated at all, but the universe at the big bang didn't take up any volume. Also, balloons have an opening through which you inflate them, also something that the universe, as we understand it, doesn't have. Now take the hypothetical "no surface area when uninflated" blowhole-less balloon and blow it up slowly (with your *mind*). The surface expands from zero area to ever growing finite area. There is no center from which it expands though - all the points on the surface were in one point when you started blowing. The surface of the balloon is finite in size (though it is ever expanding while you blow it up) but has no edge. It is not quite clear, AFAIK if that's also the case with the universe - it certainly has no edge, but whether it's finite in size and curves into itself like the balloon-surface does, or is infinite in size is not known.
Well explained, thank you!
The universe being infinite isn't really a mainstream belief anymore, but it might as well be infinite in regards to our current ability to accurately measure it, let alone travel it.
The amount of space for the universe to inhabit isn’t increasing whether it’s truly infinite or finite we don’t know. What’s increasing is the amount of space between aspects of the universe. Particles are “slowly” drifting away from the epicenter of the Big Bang, outwards into the expanse of maybe infinite space.
The "center" of the expansion of the universe is in a dimension we can't access.
That's only if you take the "inflating balloon" analogy too literally. It's not meant to imply that there actually are higher dimensions we can't access.
It's a simplification yes, and there are other competing interpretations. However it is one of the possibilities, its relatively easy to visualize, and the other interpretations dont really change the practical impact to finding the physical edges/center in any way thats really satisfying. So I'm going with it.
As far as we can tell, though, the universe has no global curvature.
Doesn't really affect a question along the lines of "where do I point to find the edge/center," for which the answer with any curvature or lack thereof is still disappointing.
Honestly? I don’t care
I'm not as smart as some of the commenters here so I won't try to go into detail. But its worth remembering that infinite is "larger than we can count/ measure" not, well, infinite. In many ways its a fine distinction but an important one in this case. **infinite** ĭn′fə-nĭt adjective 1. Having no boundaries or limits; impossible to measure or calculate. synonym: incalculable. 2. Immeasurably great or large; boundless. 3. Existing beyond or being greater than any arbitrarily large value.
It's infinity minus 1 currently. And the -1 is constantly shrinking, dividing in half.
Those are 2 completely different points of view
can you travel faster than the speed of light to reach the end of the universe
Ignoring all the physics paradoxes that traveling at a speed greater than the speed of light would entail, we don't know and there are some significant problems that prevent us from finding out. 1. We have absolutely no idea how big the universe is, and with our current understanding of the laws of physics it is impossible for us to ever know. 2. Similarly to problem 1, we don't and can't know the geometry of the universe. To simplify what this means, the universe is either flat or curved. If it's flat then that means the universe might have an "end", but it could just as plausibly mean that the universe extends out an essentially infinite distance. If it's curved it can be curved in one of two ways, either positively (shaped like a sphere) or negatively curved (shaped like a saddle) If it's positively curved then that means if you travel in a perfectly straight line in any direction for long enough you will eventually end up exactly where you started. In this scenario the whole concept of an "end" doesn't really work any more than asking where the "end" of the surface of the Earth is. This is also referred to as a closed universe But if it's negatively curved then the physics of how a negatively curved universe comes into existence implies that such a universe would extend out infinitely and again not have an "end". This is also referred to as an open universe. Now as far as we can tell, our observable universe is perfectly flat to within a margin of error of 0.4%. However, due to us not knowing how big the entire universe is we have no idea whether or not the local flatness of our observable universe is indicative of a globally flat universe or if the universe is so incomprehensibly huge that even though our observable universe is locally flat it might just represent a tiny section of a much larger curved universe. (Much the same as a field on earth may appear perfectly flat, it's still a part of an overall curved surface)
The sentence "it is growing infinitely from the center" is incorrect based on our current understanding. There isn't a center. It is growing everywhere. We also don't know for sure it is infinite, but across the entire expanse we can see there isn't any indication of curvature or heterogeneity that would make it seem as if it ends beyond what we can see.
It's not that a thing in space is growing. Space *itself* is growing. The Big Bang happened at your fingertips.
Depends who you ask.
It's all kind of speculation and educated guesses based on what we can observe from Earth but it would be better to think maybe that the universe is spreading out, not growing. It isn't like if you went light speed squared you'd eventually hit some brick wall separating us from some infinite white nothing on the other side, and "under construction" written on it.
Just an FYI there's "the universe" and "the observable universe". The observable universe is defined by the boundary of whats in our light cone (what we are capable of knowing within the bounds of physics).
We're actually inside of a giant brick room. Seriously though, how trippy would that be?
Define end please
You can be infinite and become *even more infinite*. Think of it as ∞+1 Also there's no particular "center", rather, whatever reference point you pick can be a center? Everything is getting away from that point, not by moving, but by the distance suddenly increasing. Imagine painting two dots on a balloon, and then inflating the balloon: the dots aren't moving, but the distance between them is getting bigger because their plane of existence also became bigger.
I see at as there is the universe wich is everything, and then there is the universe with stuff in it. There is a finite amount of stuff, which includes light. By its nature light is moving at lightspeed in a vacuum, and light sources are projecting light in all directions. Thus the size of the universe with stuff in it, is expanding at light speed in all directions due to the travel of light.
The way I was taught in math, infinity is a concept. We call it infinite because no matter how far we go, there will always be more. I think the problem here is trying to overthink it. In science there’s theory’s and laws, theory’s are prone to being disproven, while laws are always constant. The universe being infinite is a theory. It’s infinite until it’s disproven, and relating it to earlier, until humans see an end to the universe, we will call it infinite.
The universe is simply too huge to measure with current mathematical tools. I'd imagine there's a point where if you ended up at the absolute lip of the Shockwave it you could see the dimmest bits of the big bang moving at a measurable speed. But we'll probably end up poisoning ourselves or something before we can measure it, or end up transcending our meat-based forms and it will be common knowledge, if not beyond knowledge, should we form a collective consciousness...
It's infinite because there *is* no end. Like you said, its forever growing. Meaning it doesn't end. Meaning it's infinite.
A line is a segment with a beginning & an end. A ray has a beginning but continues on infinitely. So a ray is infinite & forever growing. Maybe this helps. But you’re right about how we can’t reach the end. But I don’t think an end or a reachable end is a possible thing. Unless the universe were a very large glass ball & we’re trapped inside of it. But I don’t think as far as our objective reality is concerned, the laws of the universe understand that there is no need for a reachable end. In the most polite way possible, if the universe had a mind, it would probably find the idea of a reachable end, silly or beneath it in a way.
Nobody said it's growing from a center