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?
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Since atoms are made of discreet particles, ( protons and neutrons ) as space expands does the space in an atomic nucleus between the particles increase or does the strong and weak forces negate the expansion and the distance stays the same?
Since atoms are made of discreet particles, ( protons and neutrons ) as space expands does the space in an atomic nucleus between the particles increase or does the strong and weak forces negate the expansion and the distance stays the same?
This is a great question. I’d like to add: our perception of TIME is essentially a perception of this space increasing. There’s no more fundamental change than that.
So when we say there is increasing “space” between, among, and within atoms, we are ALSO saying “time has passed”. AKA space = time.
Now, I wonder whether the physical measurement of an increase in space is real? If everything is increasing, how can we say that something is increasing at all? If the increase is limitless, is time limitless? Is limitless expansion actually possible? If not, does time stop and/or proceed backwards?
Is it actually an expansion, or is it just the passage of TIME that makes our instruments perceive an expansion?
This is a great question. I’d like to add: our perception of TIME is essentially a perception of this space increasing. There’s no more fundamental change than that.
So when we say there is increasing “space” between, among, and within atoms, we are ALSO saying “time has passed”. AKA space = time.
Now, I wonder whether the physical measurement of an increase in space is real? If everything is increasing, how can we say that something is increasing at all? If the increase is limitless, is time limitless? Is limitless expansion actually possible? If not, does time stop and/or proceed backwards?
Is it actually an expansion, or is it just the passage of TIME that makes our instruments perceive an expansion?
> At first I thought it just meant more matter is getting created on the outer areas of the universe or something
The expansion of space has nothing to do with creating matter or energy. Matter and energy cannot be created or destroyed so however much the Universe had when it was created is how much it will have forever. It may change forms, but the total amount of matter and energy will remain constant due to conservation laws. This is an oversimplification, but the expansion of space is the empty space between matter and energy getting larger. However, it’s a function of distance so it doesn’t effect atoms because the other forces are stronger at those scales.
> But it’s moreso space in the spacial sense is expanding between everything, like a balloon being inflated.
The problem is you’re looking at the expansion of space in isolation. You have to consider all the forces acting on an object, how strong they are, and how their strength changes with distance. This gets you the net force and will tell you if an object should stay clumped together or get ripped apart. The latter only occurs on very large distance scales because the expansion of space increases very slowly and requires millions of lights years to create a noticeable cumulative effect. Below that scale (galaxy clusters and below) the other forces win out and hold everything together. Here’s an easy dividing line:
Galaxy cluster and below: The fundamental forces win and anything bound by them will remain bound forever. Gravity holds everything together on these scales. Below the limit of self-gravitation, the electromagnetic force holds things together (roughly between human-sized scales and individual atoms. While the electromagnetic force holds individual atoms together, the protons and neutrons in every atomic nucleus is held together by the strong force. All these forces are strong enough to counter the expansion of space at these scales.
Clusters of galaxy clusters and above: The expansion of space is stronger than the fundamental forces so these objects will recede at an accelerating rate until one day they leave the observable Universe as seen from Earth. Notice how this scale involves many millions of billions of light years. It takes large distances for the expansion of space to create a noticeable, cumulative effect because it grows very slowly with distance.
> how is there a limit to the space between atoms?
The expansion of space isn’t a factor at atomic distance scales. Atoms have a preferred distance because of the strong force and electromagnetic forces. The EM force causes atoms to bind together. If they get too close, the strong force will repel them away. The strong force is only attractive at the scale of an atomic nucleus. Beyond that it actually pushes other nuclei away to prevent multiple nuclei from merging together. Since there’s an attractive and repulsive force, there’s a sweet spot where the forces cancel out and that creates the preferred distance for atom. Above this distance and the EM force will attract two atoms so they get closer. Below this distance the strong force will push them away.
Atoms can get closer if there’s enough mass. This is of course due to gravity which is attractive and only acts towards the center of mass. However, gravity is many orders of magnitude weaker than the other forces, so you need A LOT of mass to over come them. That’s why stars can only form when massive amounts of gas come together and initiate stellar fusion. There’s a minimum mass required for gravity’s crushing force to overcome the repulsive effect of the strong and EM forces (protons repel protons and electrons repel electrons due to having the same charge.)
> At first I thought it just meant more matter is getting created on the outer areas of the universe or something
The expansion of space has nothing to do with creating matter or energy. Matter and energy cannot be created or destroyed so however much the Universe had when it was created is how much it will have forever. It may change forms, but the total amount of matter and energy will remain constant due to conservation laws. This is an oversimplification, but the expansion of space is the empty space between matter and energy getting larger. However, it’s a function of distance so it doesn’t effect atoms because the other forces are stronger at those scales.
> But it’s moreso space in the spacial sense is expanding between everything, like a balloon being inflated.
The problem is you’re looking at the expansion of space in isolation. You have to consider all the forces acting on an object, how strong they are, and how their strength changes with distance. This gets you the net force and will tell you if an object should stay clumped together or get ripped apart. The latter only occurs on very large distance scales because the expansion of space increases very slowly and requires millions of lights years to create a noticeable cumulative effect. Below that scale (galaxy clusters and below) the other forces win out and hold everything together. Here’s an easy dividing line:
Galaxy cluster and below: The fundamental forces win and anything bound by them will remain bound forever. Gravity holds everything together on these scales. Below the limit of self-gravitation, the electromagnetic force holds things together (roughly between human-sized scales and individual atoms. While the electromagnetic force holds individual atoms together, the protons and neutrons in every atomic nucleus is held together by the strong force. All these forces are strong enough to counter the expansion of space at these scales.
Clusters of galaxy clusters and above: The expansion of space is stronger than the fundamental forces so these objects will recede at an accelerating rate until one day they leave the observable Universe as seen from Earth. Notice how this scale involves many millions of billions of light years. It takes large distances for the expansion of space to create a noticeable, cumulative effect because it grows very slowly with distance.
> how is there a limit to the space between atoms?
The expansion of space isn’t a factor at atomic distance scales. Atoms have a preferred distance because of the strong force and electromagnetic forces. The EM force causes atoms to bind together. If they get too close, the strong force will repel them away. The strong force is only attractive at the scale of an atomic nucleus. Beyond that it actually pushes other nuclei away to prevent multiple nuclei from merging together. Since there’s an attractive and repulsive force, there’s a sweet spot where the forces cancel out and that creates the preferred distance for atom. Above this distance and the EM force will attract two atoms so they get closer. Below this distance the strong force will push them away.
Atoms can get closer if there’s enough mass. This is of course due to gravity which is attractive and only acts towards the center of mass. However, gravity is many orders of magnitude weaker than the other forces, so you need A LOT of mass to over come them. That’s why stars can only form when massive amounts of gas come together and initiate stellar fusion. There’s a minimum mass required for gravity’s crushing force to overcome the repulsive effect of the strong and EM forces (protons repel protons and electrons repel electrons due to having the same charge.)
Because the atoms repel each other. There’s little bits called electrons that push each other away very strongly at close distances.
If you do push them together hard enough, boom- that’s nuclear fusion. You’ve created a new, bigger element. In other words two pieces of matter cannot occupy the same space at same time.
If you’re still curious I recommend reading into this https://en.m.wikipedia.org/wiki/Intermolecular_force
I don’t understand the exact problem you want to understand – but yes, there very likely was something before the big bang. The universe didn’t just pop out of nothing (do not mix it up with “out of nowhere”, this is possible).
Space is relative, and I mean this in a very absolute sense, like time. Time is just the relation of processes: It takes you twice the time to count to 10 than it takes you to count to 5. There is probably nothing more than this concept, that some processes are faster than others, meaning quantum mechanically “more likely to happen next”. And there you go with the connection between energy, space and time.
So space is just something you can measure, for e.g. by the time it takes light “to process through from A to B”.
It doesn’t matter if the space is finite or infinite between two things. All that matters is the relation of that space to other measured spaces, the speed of light and so on. In fact the space between two atoms can be infinite, but how would you know if you are infinite yourself? This is all normalized by the speed of light (or any other thing that you define as “1”, e.g. a foot).
By the way:
Very likely (in my opinion) is that the universe does not expand “by itself”, but that the expansion is simply a property of the matter in the universe. This is why it expanded so fast in the beginning out of that dense matter. You can also see this behaviour when falling into a black hole, which is more or less equivalent to an instantanious start of expansion of the space around you. Probably the big bang was just the formation of a black hole (that is called black hole cosmology).
By the way II:
There is a nice theory, that all fundamental particles (like an electron) are black holes themselves. Maybe it is a whole universe itself! So there isn’t much more than nested black holes at all to build the whole universe. Does this expand your imagination of infinite/finite things?
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