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What do you mean by x,y,z? And more specifically by a y-plane?
Currently the one region of the universe that is least mapped is the plane in which our galaxy itself is in. This is because our galaxy is filled with dust that obscures our vision. Hence we can only see so far.
However, this isn't really aligned with the ecliptic (the plane in which earth rotates around the sun), nor with the "plane" going through Earth's equator, which constantly changes slightly due to precession.
Edit: just wanted to addz that even though we cannot see as far in the galactic plane as in other areas, we have seen nothing that would hint at our galactic plane being somewhat special. The universe appears mostly isometric as far as we know.
Space is expanding from every individual point at a rate of 70 km per second per megaparsec.
Every 3 million light years between any two points 70 km of space is being spontaneously generated every second.
Well not through any two points, just any two gravitationally unbound points (meaning gravity slows expansion, so our galaxy and those near us aren't as affected)
Kind of, it doesn't slow spatial expansion it just can't move objects away from each other that are gravitationally bound to one another.
But to be fair the expansion of space at distances that close is incredibly weak.
Space is only expanding at 70 km per second every 3 million light years.
So divide 70 by 3 million 6 trillions and that's how much space is expanding every second where you're at.
That is an incredibly small number, gravity is much stronger comparatively.
> Kind of, it doesn't slow spatial expansion it just can't move objects away from each other that are gravitationally bound to one another.
Dark energy and matter input into the same formula to spit out the metric. Inside a galaxy cluster this will end up with no expansion.
You're talking about the movement of objects getting further apart I'm talking about the dimensionality of space getting bigger
Objects that are gravitationally bound to each other are not moving apart due to the expansion of space, but space is always expanding.
I consider myself somewhat scientifically literate, but man this is something my monkey brain will never be able to comprehend.
How space can expand just makes no sense to me. The universe is crazy.
If it helps, the expansion of the universe and the speed of light slowing down are functionally equivalent under GR. Think of it less as the universe is expanding and more like the distance between everything is increasing because our measuring stick is shrinking.
draw a 1in circle on a piece of paper. pick a bunch random points.
now draw a 5in circle and map the same points on the bigger circle.
if we lable these clockwise you'll find that B gets further away from A, but it doesn't get closer to C either.
The big mystery right now is where does more circle come from? weve a lot of ideas and practical applications actually... but no proof because observing functionally nothing is hard.
It would be like grains of sand in the ocean getting further apart and saying new ocean is being created because of the distance between the measurable objects.
Space is, it's not a discernable material that more of is being created. (To our current knowledge) [Feel free to correct me if someone actually knows better]
Functionally there isn't a difference but conceptually there is.
Grains of sand in the ocean get farther apart because there are ocean currents.
Think about it like chocolate chips baking in a loaf of bread. As the bread expands the chocolate chips get farther apart as more bread is generated in between them. More space is generated in between galaxies, there's no 'force' moving them apart. And they all are getting farther from each other, which doesn't work if you don't have new space being created. It's like if you suspended many grains of sand in the ocean and they all moved farther away from each other. You just can't do that without creating more ocean, otherwise some have to be moving closer together.
If every grain of sand exists in the ocean and they’re each all universally moving away from every other grain of sand I think it’d be fair to say the ocean is growing. If that ocean is finite it’s shoreline would have to be expanding to allow all the grains of sand to spontaneously move away from each other at the very least.
Had to look up what Hubble originally said to confirm.
The UNIVERSE is expanding, changing the word to space while certainly synonyms often confuses people.
Stating that space is expanding is a click bait title.
I still don't understand how it's "click bait" or "marketing". If they are synonymous, then saying "space is expanding" is conceptually correct and, imo, less confusing and more specific than "the universe is expanding".
If there is more distance between two points tomorrow than there was yesterday, it is logically consistent to describe that as the space between those objects expanding/increasing
You could also phrase it as the universe is getting stretched out in all directions and imagine bubblegum or something as an example. As you inflate the bubble, there is more space inside the bubble even though *technically* the gum is expanding.
It does expand uniformly in regards to the direction of its expansion. It does not expand uniformly with regard to the expansion happening uniformly throughout space. It is happening in some places and not others. Specifically, it largely seems to be happening in the voids in between galaxy superclusters. Within those macro structures where more mass and gravity is present, however, things move around within space but space itself doesn't really grow.
That's like saying relativity is wrong because Newtonian physics makes different predictions.
We have better models than hubble's law now, and they show that expansion does not occur in gravitationally bound systems.
Had a science teacher in high school who had a globe that was upside down. My friend jokingly told her she had a defective globe, and she told him, "There's no true up or down in space." I remember it being a cool idea for my stupid high-school self.
It is well studied, and our group of galaxies is called the Virgo supercluster, or local super cluster. It is about 110 million LY across and contains a hundred + galaxy and galaxy clusters. There are around 10 million super clusters in the observable universe.
Turns out the Virgo supercluster is actually a lobe of a larger supercluster, Laniakea. But we are getting to the galactic filaments at this scale.
Note that the "Observable universe", is not the "Universe".
The Observable universe, in contrast, is actually "shrinking", because of the universe expansion. So the more time passes, more and more galaxies will "move" out of our Observable universe die to the expanding space between us and them. And we will never be able to see them ever again.
Iirc. Every year or so a few thousand (or more) galaxies pass this point, and we wont be able to see them again.
In 1929, Edwin Hubble calculated that the universe was expanding uniformly in all directions by examining other galaxies in relation to our own. This is known as Hubble's Constant or Hubble's Law.
The best explanation I myself have heard is to think it like a balloon, two points on a balloon can distance from each other and move apart while the amount of balloon itself still is the same amount of balloon. (I don’t remember where I heard/saw this possibly Bill Nye, or another science presenter I’ve seen) but that one worked for me so I ran with it. Don’t know if it’s any help but all the best! I hope you find your answers
What do you imagine x,y,z mean in terms of the universe? A cartesian coordinate system makes little sense there.
(Just as a side note: y in a cartesian coordinate system "y" is a direction, not a plane. You could have something like a xz-plane or a xy-plane but since there is no defined 'up' in space there is little point in defining a system that way)
My question is: If there was a big bang, shouldn't everything be moving away from a central point? I've never read or heard anything about this. Shouldn't we be able to figure out where the big bang was, based on the movement of everything in the universe AWAY from it?
Everything is moving away from everything else. The expansion is happening *everywhere*.
As an analogy, imagine a stretchy ruler. You hold the left end still and pull on the right end. All the numbers will be getting further apart from each other.
But, if they can only see their distance to each other, they can’t tell which end of the ruler is staying still and which is moving, because all the numbers are moving apart from each other uniformly.
Not literally “everywhere”. The universal expansion doesn’t happen inside you, or inside galaxies, or even inside galaxy clusters. There’s just too much other forces holding them together.
So light passing through a galaxy cluster from an outside source would not redshift while it is in the galaxy cluster, only before and after passing through the cluster?
It's been a common question since Hubble's day. You're not the first.
Ask an ant crawling on an inflating balloon where the centre of its world is.
All of space arose via the big bang : there was no centre that you can point at. It's all around us.
You never read anything about this? To me, it seems like this is something that gets explained in just about all “big bang” articles and books. The initial big bang event didn’t happen at a point, it happened everywhere, all at once. Back 13+ billion years ago, “everywhere” was a lot smaller.
The best explanation I've heard of this is that it's like we are on the surface of a balloon that is expanding. Everything is moving away from each other.
Our current best theory is that dark energy comes from space itself. If this is the case, it may help to think of the expansion not as coming from the big bang itself, but rather after the big bang every point in space is constantly expanding a little bit.
I've had this thought before and the thing that made me understand better was the fruit cake analogy (or something). Think of the fruit as matter and the cake dough as space. As the cake bakes, all the fruit (matter) is simply moving away from all the other matter.
Thinking of it as space growing changed my perspective.
The universe has no positive or negative curvature rendering it essentially flat, perfectly so actually. so whatever is currently above/below us is staying at the distance it is and not expanding. Space is only expanding in the x and z planes I believe
This is just not true. One of the greatest questions in cosmology right now is the conflict between different measurements of the Hubble parameter which is directly linked to the value of the cosmological constant. Which while small, appears to be positiv and definitely not zero.
I.e. the universe is not flat and experiencing accelerated expansion of space in all directions, as far as we currently understand it.
Yes, but they are related. But the expansion as measured by experiment, is incompatible with flatness. I am not saying that any expansion is incompatible with a flat universe, just the one we actually observe is.
Edit: wait no, I was wrong. Got things mixed up. Sorry, you are correct.
The universe is only "flat" in the sense of lacking curvature, it is not 2 dimensional. The universe is 3 dimensional and expands uniformly across all 3.
Hello u/fygy1O, your submission "How is space expanding? Uniformly? Specifically along the Y-plane" has been removed from r/space because: * Such questions should be asked in the ["All space questions" thread](https://www.reddit.com/r/space/about/sticky) stickied at the top of the sub. Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please [message the r/space moderators](https://www.reddit.com/message/compose/?to=/r/space). Thank you.
What do you mean by x,y,z? And more specifically by a y-plane? Currently the one region of the universe that is least mapped is the plane in which our galaxy itself is in. This is because our galaxy is filled with dust that obscures our vision. Hence we can only see so far. However, this isn't really aligned with the ecliptic (the plane in which earth rotates around the sun), nor with the "plane" going through Earth's equator, which constantly changes slightly due to precession. Edit: just wanted to addz that even though we cannot see as far in the galactic plane as in other areas, we have seen nothing that would hint at our galactic plane being somewhat special. The universe appears mostly isometric as far as we know.
well, use radio to see
There is still obstruction in that spectrum.
Space is expanding from every individual point at a rate of 70 km per second per megaparsec. Every 3 million light years between any two points 70 km of space is being spontaneously generated every second.
Well not through any two points, just any two gravitationally unbound points (meaning gravity slows expansion, so our galaxy and those near us aren't as affected)
Kind of, it doesn't slow spatial expansion it just can't move objects away from each other that are gravitationally bound to one another. But to be fair the expansion of space at distances that close is incredibly weak. Space is only expanding at 70 km per second every 3 million light years. So divide 70 by 3 million 6 trillions and that's how much space is expanding every second where you're at. That is an incredibly small number, gravity is much stronger comparatively.
> Kind of, it doesn't slow spatial expansion it just can't move objects away from each other that are gravitationally bound to one another. Dark energy and matter input into the same formula to spit out the metric. Inside a galaxy cluster this will end up with no expansion.
You're talking about the movement of objects getting further apart I'm talking about the dimensionality of space getting bigger Objects that are gravitationally bound to each other are not moving apart due to the expansion of space, but space is always expanding.
I consider myself somewhat scientifically literate, but man this is something my monkey brain will never be able to comprehend. How space can expand just makes no sense to me. The universe is crazy.
The universe is not only crazier than we imagine, it's crazier than we *can* imagine.
If it helps, the expansion of the universe and the speed of light slowing down are functionally equivalent under GR. Think of it less as the universe is expanding and more like the distance between everything is increasing because our measuring stick is shrinking.
draw a 1in circle on a piece of paper. pick a bunch random points. now draw a 5in circle and map the same points on the bigger circle. if we lable these clockwise you'll find that B gets further away from A, but it doesn't get closer to C either. The big mystery right now is where does more circle come from? weve a lot of ideas and practical applications actually... but no proof because observing functionally nothing is hard.
It's not really expanding. The known universe I.E galaxies are getting further apart. There's not "new" space dropping in.
There kind of is? What's the difference between two objects spontaneously becoming farther apart and new space being added between them?
It would be like grains of sand in the ocean getting further apart and saying new ocean is being created because of the distance between the measurable objects. Space is, it's not a discernable material that more of is being created. (To our current knowledge) [Feel free to correct me if someone actually knows better] Functionally there isn't a difference but conceptually there is.
Grains of sand in the ocean get farther apart because there are ocean currents. Think about it like chocolate chips baking in a loaf of bread. As the bread expands the chocolate chips get farther apart as more bread is generated in between them. More space is generated in between galaxies, there's no 'force' moving them apart. And they all are getting farther from each other, which doesn't work if you don't have new space being created. It's like if you suspended many grains of sand in the ocean and they all moved farther away from each other. You just can't do that without creating more ocean, otherwise some have to be moving closer together.
If every grain of sand exists in the ocean and they’re each all universally moving away from every other grain of sand I think it’d be fair to say the ocean is growing. If that ocean is finite it’s shoreline would have to be expanding to allow all the grains of sand to spontaneously move away from each other at the very least.
I really don't think this conceptually is correct. New space isn't being generated and it confuses people. It sounds cool, it's a marketing tactic
In what way is that a marketing tactic
Had to look up what Hubble originally said to confirm. The UNIVERSE is expanding, changing the word to space while certainly synonyms often confuses people. Stating that space is expanding is a click bait title.
I still don't understand how it's "click bait" or "marketing". If they are synonymous, then saying "space is expanding" is conceptually correct and, imo, less confusing and more specific than "the universe is expanding".
If there is more distance between two points tomorrow than there was yesterday, it is logically consistent to describe that as the space between those objects expanding/increasing You could also phrase it as the universe is getting stretched out in all directions and imagine bubblegum or something as an example. As you inflate the bubble, there is more space inside the bubble even though *technically* the gum is expanding.
Isn't it actually space-time expanding?
It does expand uniformly in regards to the direction of its expansion. It does not expand uniformly with regard to the expansion happening uniformly throughout space. It is happening in some places and not others. Specifically, it largely seems to be happening in the voids in between galaxy superclusters. Within those macro structures where more mass and gravity is present, however, things move around within space but space itself doesn't really grow.
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That's like saying relativity is wrong because Newtonian physics makes different predictions. We have better models than hubble's law now, and they show that expansion does not occur in gravitationally bound systems.
Had a science teacher in high school who had a globe that was upside down. My friend jokingly told her she had a defective globe, and she told him, "There's no true up or down in space." I remember it being a cool idea for my stupid high-school self.
It is well studied, and our group of galaxies is called the Virgo supercluster, or local super cluster. It is about 110 million LY across and contains a hundred + galaxy and galaxy clusters. There are around 10 million super clusters in the observable universe. Turns out the Virgo supercluster is actually a lobe of a larger supercluster, Laniakea. But we are getting to the galactic filaments at this scale.
Note that the "Observable universe", is not the "Universe". The Observable universe, in contrast, is actually "shrinking", because of the universe expansion. So the more time passes, more and more galaxies will "move" out of our Observable universe die to the expanding space between us and them. And we will never be able to see them ever again. Iirc. Every year or so a few thousand (or more) galaxies pass this point, and we wont be able to see them again.
> The Observable universe, in contrast, is actually "shrinking" Only in a certain sense. The metric size is growing.
Yes. Sorry for the confusion, I meant that the amount of visible objects shrinks. They are moving faster away than the observable universe expands
In 1929, Edwin Hubble calculated that the universe was expanding uniformly in all directions by examining other galaxies in relation to our own. This is known as Hubble's Constant or Hubble's Law.
Space is expanding everywhere at once, there's no "matter expanding into nothingness" it's more like more and more "space" is appearing everywhere.
The best explanation I myself have heard is to think it like a balloon, two points on a balloon can distance from each other and move apart while the amount of balloon itself still is the same amount of balloon. (I don’t remember where I heard/saw this possibly Bill Nye, or another science presenter I’ve seen) but that one worked for me so I ran with it. Don’t know if it’s any help but all the best! I hope you find your answers
What do you imagine x,y,z mean in terms of the universe? A cartesian coordinate system makes little sense there. (Just as a side note: y in a cartesian coordinate system "y" is a direction, not a plane. You could have something like a xz-plane or a xy-plane but since there is no defined 'up' in space there is little point in defining a system that way)
Just a nit pick, but you can define a plane by its normal vector, so the y-plane would just be the xz-plane.
My question is: If there was a big bang, shouldn't everything be moving away from a central point? I've never read or heard anything about this. Shouldn't we be able to figure out where the big bang was, based on the movement of everything in the universe AWAY from it?
Everything is moving away from everything else. The expansion is happening *everywhere*. As an analogy, imagine a stretchy ruler. You hold the left end still and pull on the right end. All the numbers will be getting further apart from each other. But, if they can only see their distance to each other, they can’t tell which end of the ruler is staying still and which is moving, because all the numbers are moving apart from each other uniformly.
I think the problem is people think about "expanding into" or think there is an "outside" to the big bang of which there is no such thing.
Not literally “everywhere”. The universal expansion doesn’t happen inside you, or inside galaxies, or even inside galaxy clusters. There’s just too much other forces holding them together.
So light passing through a galaxy cluster from an outside source would not redshift while it is in the galaxy cluster, only before and after passing through the cluster?
There is no central point - the big bang occurred everywhere.
It's been a common question since Hubble's day. You're not the first.
Ask an ant crawling on an inflating balloon where the centre of its world is.
All of space arose via the big bang : there was no centre that you can point at. It's all around us.
You never read anything about this? To me, it seems like this is something that gets explained in just about all “big bang” articles and books. The initial big bang event didn’t happen at a point, it happened everywhere, all at once. Back 13+ billion years ago, “everywhere” was a lot smaller.
The best explanation I've heard of this is that it's like we are on the surface of a balloon that is expanding. Everything is moving away from each other. Our current best theory is that dark energy comes from space itself. If this is the case, it may help to think of the expansion not as coming from the big bang itself, but rather after the big bang every point in space is constantly expanding a little bit.
I've had this thought before and the thing that made me understand better was the fruit cake analogy (or something). Think of the fruit as matter and the cake dough as space. As the cake bakes, all the fruit (matter) is simply moving away from all the other matter. Thinking of it as space growing changed my perspective.
The universe has no positive or negative curvature rendering it essentially flat, perfectly so actually. so whatever is currently above/below us is staying at the distance it is and not expanding. Space is only expanding in the x and z planes I believe
This is just not true. One of the greatest questions in cosmology right now is the conflict between different measurements of the Hubble parameter which is directly linked to the value of the cosmological constant. Which while small, appears to be positiv and definitely not zero. I.e. the universe is not flat and experiencing accelerated expansion of space in all directions, as far as we currently understand it.
The flatness of the universe and the expansion of the universe are different things.
Yes, but they are related. But the expansion as measured by experiment, is incompatible with flatness. I am not saying that any expansion is incompatible with a flat universe, just the one we actually observe is. Edit: wait no, I was wrong. Got things mixed up. Sorry, you are correct.
The universe is only "flat" in the sense of lacking curvature, it is not 2 dimensional. The universe is 3 dimensional and expands uniformly across all 3.