I recently learned what it really means when people say space is constantly expanding. At first I thought it just meant more matter is getting created on the outer areas of the universe or something. But it’s moreso space in the spacial sense is expanding between everything, like a balloon being inflated. This opened up a realm of stuff I hadn’t thought about, with my brain struggling to comprehend how there is finite ‘space’ in that sense. Like how does existence itself have a limit to size? For distance as a concept to exist, the space between atoms has to be finite, and doesn’t break down infinitely. But my brain can’t comprehend this, similar to how it can’t comprehend there being nothing before the big bang. It obviously can’t be infinite because there’d be no existsnce as we know it, but how can it be finite and exist at all?
I guess the question is, how is there a limit to the space between atoms?
In: 127
I’m a little unclear on what exactly you’re asking, but to start with something fundamental:
>For distance as a concept to exist, the space between atoms has to be finite
This is not quite accurate. You can define distance without reference to the space between atoms. Indeed, a meter is formally defined as the length of the path travelled by light in a vacuum in 1/299792458 second. The speed of light in a vacuum is constant and does not increase along with the expansion of the universe.
As to the “limit” on the space between atoms, there really isn’t one. Atoms can be squeezed together, but it does take energy to do so because you need to overcome the electromagnetic repulsion between similarly charged particles. You can also pull atoms apart, but if they’re too far apart they can’t interact to make molecules because they’re out of range of the electromagnetic force.
I’m a little unclear on what exactly you’re asking, but to start with something fundamental:
>For distance as a concept to exist, the space between atoms has to be finite
This is not quite accurate. You can define distance without reference to the space between atoms. Indeed, a meter is formally defined as the length of the path travelled by light in a vacuum in 1/299792458 second. The speed of light in a vacuum is constant and does not increase along with the expansion of the universe.
As to the “limit” on the space between atoms, there really isn’t one. Atoms can be squeezed together, but it does take energy to do so because you need to overcome the electromagnetic repulsion between similarly charged particles. You can also pull atoms apart, but if they’re too far apart they can’t interact to make molecules because they’re out of range of the electromagnetic force.
>Has to be finite
>Doesn’t break down infinitely
These are not the same. You can infinitely subdivide a finite quantity. Infinite infinitesimals can be a regular, finite size.
>Has to be finite
>Doesn’t break down infinitely
These are not the same. You can infinitely subdivide a finite quantity. Infinite infinitesimals can be a regular, finite size.
Nobody really knows. The main theory at the moment is that yes, everywhere is constantly getting more space, and thus every pair of atoms is becoming ever so slightly further apart constantly. Like, if there’s a pair of atoms floating in space somewhere now one kilometre apart from each other, then in two minutes they’ll be like… *does back of the napkin math* about five quadrillionths of a metre further away from each other because more space will have become in between them.
For atoms that are bound into structures here in the solar system, the forces that bind them will ensure that the atoms stay in the distances they used to – they’ll keep falling into their spots of matching attraction and repulsion.
As for why the Universe has finite size now – it’s only been expanding at a finite rate for a finite time, right? Scientists say that this rate has changed with time and it’s now faster than it used to be. We don’t know what will happen eventually. It’s not out of the question that the rate will change to a negative one and space will start shrinking. It’s not out of the question that time itself will end eventually. If none of these happen, then for any distance you can name, the span of the universe will exceed it eventually.
Nobody really knows. The main theory at the moment is that yes, everywhere is constantly getting more space, and thus every pair of atoms is becoming ever so slightly further apart constantly. Like, if there’s a pair of atoms floating in space somewhere now one kilometre apart from each other, then in two minutes they’ll be like… *does back of the napkin math* about five quadrillionths of a metre further away from each other because more space will have become in between them.
For atoms that are bound into structures here in the solar system, the forces that bind them will ensure that the atoms stay in the distances they used to – they’ll keep falling into their spots of matching attraction and repulsion.
As for why the Universe has finite size now – it’s only been expanding at a finite rate for a finite time, right? Scientists say that this rate has changed with time and it’s now faster than it used to be. We don’t know what will happen eventually. It’s not out of the question that the rate will change to a negative one and space will start shrinking. It’s not out of the question that time itself will end eventually. If none of these happen, then for any distance you can name, the span of the universe will exceed it eventually.
this whole question isnt in the realm of eli5, so ill give a corresponding answer to the core of your question: distance can’t be broken down infinitely (like the zeno of elea riddle). there is an absolute smallest distance and thats the plank length ℓP
this whole question isnt in the realm of eli5, so ill give a corresponding answer to the core of your question: distance can’t be broken down infinitely (like the zeno of elea riddle). there is an absolute smallest distance and thats the plank length ℓP
what is expanding is space itself, not the distance between atoms. on a small scale, atoms are bound together by what is known as the electromagnetic and “strong” force. on a large scale, structures (people, planets, stars, galaxies, etc.) are considerably affected by each other’s gravity and are not going anywhere or expanding.
for example, the milky way galaxy we live in is not getting any bigger, nor is anything inside going anywhere from each other. gravity holds everything together. however, a galaxy that’s a billion light-years away isn’t affected by gravity from the milky way and is free to flow away with the expansion of space.
if you take your example of the universe as a balloon, imagine that you draw dots on the balloon representing the galaxies. when you inflate it, imagine the dots itself aren’t getting any bigger (they actually do on a balloon but you get the idea), but the space between dots are.
so why don’t the structure that makes up space rip apart due to such enormous expansion? we don’t technically know for sure if it won’t. some say it will rip apart one day in the future in an event called the “Big Rip”. others say space is not made out of anything, and it’s more of a concept of how far away things are relative to each other than a physical thing. there are many opinions and arguments on this, but they’re not much better than hypotheses at this point.
what is expanding is space itself, not the distance between atoms. on a small scale, atoms are bound together by what is known as the electromagnetic and “strong” force. on a large scale, structures (people, planets, stars, galaxies, etc.) are considerably affected by each other’s gravity and are not going anywhere or expanding.
for example, the milky way galaxy we live in is not getting any bigger, nor is anything inside going anywhere from each other. gravity holds everything together. however, a galaxy that’s a billion light-years away isn’t affected by gravity from the milky way and is free to flow away with the expansion of space.
if you take your example of the universe as a balloon, imagine that you draw dots on the balloon representing the galaxies. when you inflate it, imagine the dots itself aren’t getting any bigger (they actually do on a balloon but you get the idea), but the space between dots are.
so why don’t the structure that makes up space rip apart due to such enormous expansion? we don’t technically know for sure if it won’t. some say it will rip apart one day in the future in an event called the “Big Rip”. others say space is not made out of anything, and it’s more of a concept of how far away things are relative to each other than a physical thing. there are many opinions and arguments on this, but they’re not much better than hypotheses at this point.
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