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Nwadamor t1_iwmafzn wrote

What is space "expanding" into?

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theCumCatcher t1_iwmbql7 wrote

Itself. It's not expanding into anything there's just more of it all the time.

There's nothing outside of the universe.

If there was we would need to change our definition of universe.

The Big bang wasn't an explosion in space it was an explosion of space.

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Nwadamor t1_iwmc3t6 wrote

What do you mean expanding into itself. You are saying more space is being "created"?

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warblingContinues t1_iwmgqh8 wrote

It means that the overall volume of space is increasing over time. There isn’t anything that the inverse sits in or expands into. We make measurements of how far things are from us in the universe and these objects get farther away in a manner not due to, say, moving through space. We deduce that the volume of space itself is increasing.

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Nwadamor t1_iwmh07n wrote

Cool. But where is the extra volume coming from?

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ashara_zavros t1_iwmmagr wrote

There’s no Conservation of Volume law in physics, mate: the volume doesn’t come from anywhere.

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theCumCatcher t1_iwnb4ep wrote

why does it have to come from anywhere?

okay...maybe it'd be simpler to explain it mathematically.

it's like the coordinate system is changing so there are more points, all the time.

there are more grid squares every time we look.

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Clearlybeerly t1_iwnm15n wrote

>We deduce that the volume of space itself is increasing.

so if there's no "outside" of the universe, what exactly is expanding "space", and what is this "non-space" it is expanding into and the universe?

Is it a balloon within a balloon, where the inner balloon is space, the outer ballon is the universe, except the other ballon is infinitely big, but the inner balloon called "space" is not infinitely big? If so, what is outside of space, as opposed to the universe, because the universe is not the same as space.

Or is space expanding into space, and you just have infinite balloons all the way down?

Just made me think - if space is expanding, are the molecules within by body expanding? If I lived for 20 million years, would I be a 7'10" man instead of my 4'11" height and so then in 20 million years I can finally get into the NBA?

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Ape_Togetha_Strong t1_iwnnet8 wrote

Why do you feel that space has to expand "into" something? "Into" requires some sort of spacial relationship. If there was something for space to "expand into" then that would just be space.

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Clearlybeerly t1_iwnnt0x wrote

So what does it mean when it is said that "space is expanding"? Is that misnomer?

How can space expand if it isn't expanding?

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Ape_Togetha_Strong t1_iwno8l3 wrote

I didn't say that it doesn't expand. I asked why you feel that there has to be something for it to expand into for it to expand.

Expand is just the best word we have for what space does, it doesn't mean it has to be exactly like other sorts of expansion you can think of.

Space is expanding. Space is not expanding into anything. The distances between things are just getting bigger.

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nivlark t1_iwnsmrq wrote

"Expand" is simply the closest English word to describe a particular behaviour we observe in distant objects.

For a more precise description, you need to turn to mathematics: an expanding space is one where the "metric tensor" - the mathematical object in general relativity that tells you how to calculate the distance between two points in curved spacetime - is time-dependant.

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Clearlybeerly t1_iwoaqmb wrote

OK, thanks. I looked up metric tensor on wiki and looked up other hyperlinks in the metric tensor entry, and I have a very, very vague understanding, but it sure does help me understand, because while I have a vague understanding, what it mainly does is allow me to cut away the extraneous. So very cool, thank you.

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ShortysTRM t1_iwo7t7j wrote

From what I can tell, these people keep referring to any type of known matter existing anywhere in any amount as "space," ignoring the infinite void that you and I and everyone else seem to be wondering about. I think they're saying that all matter in the void is expanding outwardly from one singular point, not that there isn't an endless expanse of nothingness for it to expand into. I don't know this for sure, but the ones who do seem to be ignoring the entire concept of "yes, the paint is expanding onto the blank canvas, but how big is the canvas, and does it ever end?"

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clintontg t1_iwob1w7 wrote

Space isn't matter, it is what matter exists inside of. And the space is expanding in all directions simultaneously, irrespective of a single point. An analogy would be like zooming in on the cartesian coordinate system and seeing more points appearing between the grid lines. So the distance between "1" and "2" increase despite our ruler staying the same length.

As for what space is expanding into, it's a bit of semantics and a bit of scientific definitions/limitations. There is no proof of there being more than 3 spacial dimensions and the universe is defined as the thing containing all of the space, matter, and energy in existence. So as far as we can see there is no "outside" of the universe. It's an all encompassing, self contained thing.

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boraras t1_iwo36wz wrote

Is it like the "CSI enhance" feature but in reverse? Like you can keep zooming out indefinitely and see more of what was already there?

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Vietoris t1_iwpdr99 wrote

When we say that space "expands" you probably imagine in your head watching something that grows in front of you. For example, you inflate a balloon and watch it expand, and you imagine that what is inside this balloon represents the universe that is expanding into the ambiant space where you are.

This is the wrong way to look at things, because it relies on that notion of "ambiant space"

Instead, imagine that you are Pac-Man, living in the Pacman world. For the sake of the example, let's say that the Pac-Man screen is 10m wide. For you the the world is finite and is exactly 100m^2. But more importantly, if you walk straight in the horizontal direction, you will get back to where you started after 10m. Same thing if you walk straight in the vertical direction (that's the main feature of the PacMan world). For Pac Man, there is absolutely nothing outside this 100m^2 of land. There is no "ambiant space" where this 100m^2 land sits in. There are no "exterior wall" walls in the Pac-Man universe.

Now, imagine that by some mechanism, the ground of the universe is getting bigger. The mechanism itself is not important, but you can imagine that the ground of the Pac-Man world is made of metal, and that you are applying heat to that metal (and metal expands when it's getting hotter). The metal will expand a little bit, by 10% in each direction for example. Now the world, is no longer 100m^2 but is 121m^2 . Now you have to walk 11m in the horizontal direction to get back where you started.

And yet, the Pac-Man universe didn't expand into an already existing piece of land. As there are no "borders" to th Pac Man universe, you cannot consider that the borders have moved further. It's just the ground that you are walking on that gets bigger.

This is the picture that you should keep in mind when imagining the universe expanding. Not as an outside observer, but as someone inside. "Expanding" just means that there is more space to cover to get from point A to point B.

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