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Comments
erkynator OP t1_ixedg74 wrote
Far point. But just something is really really really big, doesn’t mean it’s infinite. I appreciate it sounds like a silly question, but I’m genuinely interest in people’s thoughts. If you traveled for long enough, on a completely linear path, what would happen? Where is Prof Brian Cox when you need him?!
FowlOnTheHill t1_ixef850 wrote
There are no linear paths in space :)
Different-Brain-9210 t1_ixeilws wrote
Space is (as far as we can see) expanding in a way, that distance to objects far enough is increasing faster than speed of light. And the expansion is accelerating (as far as we can see). So no matter how fast you travelled, you'd still see the fartherst objects disappearing from your sight (light from them being red-shifted more and more towards infinitely long wavelengths), rather than getting closer.
ferrel_hadley t1_ixecxmb wrote
>The idea that space is infinite makes no sense to me
Your intuition evolved as a primate on the African veldt. It views the world at speeds of a few 10s of kmh and distances of a few kilometres at best. The visible Universe alone's size is so far beyond comprehension of intuition there is no point to it, we cannot use intuition to think about the nearest star to our solar system, let alone distant galaxies.
To think about the size and shape of the Universe requires years of slowly building up the knowledge to think abstractly about physics and distance.
I do not wish to discourage you but point out this is but the first step on a long journey.
erkynator OP t1_ixefaw5 wrote
I understand the concept of theoretical physics. But at the same time I do live a big lump of rock, and the model of “balls in a box” is logical when you consider earth, moons, stars etc. Always happy to educated, talked down to no so much.
Embarrassed_Aside_76 t1_ixei0tg wrote
If you haven't already I would suggest reading Stephen Hawkins book "a brief history of time" as it tackles a lot of these concepts
If you don't have any advanced physics qualifications or mathematics (I only say this because most people don't) it's quite information dense, so you'll want to chunk it up. I hugely recommend when I found it hard to grasp the points to watch some YouTube videos about it. Especially with things like additional dementions, YouTube was unreal for helping me visualise things better.
The concepts get progressively more challenging as the book progressed I found, but it's informative throughout.
FowlOnTheHill t1_ixew5yr wrote
I second YouTube as an excellent resource:
Check out: Melodysheep, Kurzgesagt, Veritasium
They all have good easy to understand videos.
People like PBS space time but I think it’s very technical and easy to lose track.
Read any book by Carlo rovelli. “7 brief lessons in physics” is a good one to start with. “Reality is not what it seems” is also good if you liked the previous one.
Hk-Neowizard t1_ixed4xs wrote
Space might be finite, we don't know, and can't know, since the observable space is all we can talk about in any certain matter (i.e the region of space that we can see or interact with, given the limitation of the speed of light). The observable space is finite.
However infinite space could exist, without there being something "outside" space. It doesn't have to have an edge. That's easy if you consider curved in a higher dimension.
Take the 2D case for simplicity. A 2D creature living on a sheet of A4 paper can't see height, only width and depth. If you roll that sheet into a cylinder, "space" is still finite, but has no edge. You could travel along the circumference forever.
So finite space with no edge is easy, and in fact likely given some observations we made (which are a bit over my head, TBH)
WictImov t1_ixek2zw wrote
The closed loop model is a different animal, it would suggest you could end back at your starting point if you travel in one direction far enough (just like going around the world in an airplane). While possible, I am unaware of any evidence that leads us in that direction. I would say the cosmic microwave background suggests otherwise.
thiswilldefend t1_ixeedlo wrote
i used to think of this all the same when i was younger... one of the things that came to my mind back then was there actually being an edge and thinking if there is NOTHING on the other side of this edge nothing can not have a clearly drawn line between existing and not existing... so my next thought was that the universe was actually growing (expanding) and getting bigger and bigger and bigger... and the bigger it gets the faster it spreads... and i thought well then this is interesting.. what is the speed of existence??
prototype_27 t1_ixeecp0 wrote
Nobody can tell with total certainty, however, experts now tend to think it is finite, unlike decades ago when “infinite” was the consensus.
Funkybeatzzz t1_ixebiyo wrote
There’s no edge if you consider the universal plane is on the surface of an expanding “bubble” or “donut”
erkynator OP t1_ixedlsj wrote
Can you please expand on that? No pun intended.
Funkybeatzzz t1_ixee9ov wrote
Google Bubble Universe Theory
Oriana_xx t1_ixefs1g wrote
we dont know whats beyond what we can see, maybe the every piece of matter the universe connected to our observable universe is just the result of one big bang, and that so unimaginably far away another big bang happened, then once that universe is out of energy, everything there slowly falls back into one point, making the next big bang, or it could just be ours, its big, unlikely infinite, but big enough to be impossible to explore even if you lived forever
idiggory t1_ixejhfs wrote
The problem is that you're framing this in fundamentally impossible ways.
The universe is a system which is everything. All of spacetime as we are able to understand it is a part of the universe. And all of those parts we understand in relationship with other parts. The fabric of spacetime itself is relational to what exists.
So if the universe is finite, there may be points in space/time where no matter or energy is affected by anything, whatsoever, in certain four-dimensional directions. If you could stand on the exact edge of the universe, for one infinitesimally small moment of time, there would be nothing before your eyes. Truly nothing - no matter or energy which your senses or whatever tools you have could detect. For an infinitesimally small moment of time, there would be nothing "in front" of you. Which would then be utterly changed one infinitesimally small moment later, when energy had emitted into that space.
(Of course, the universe may also be curved, so even this might not be true, even if finite. There might be no "edge" even in this idea of an edge).
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Let me put it another way. We often think about the big bang as a central point from which matter/energy exploded from into space. Except that's not true. The big bang happened where I am. Where you are. Where someone 14 billion lightyears away is, if such a person exists.
The big bang wasn't an explosion into spacetime. It's the release of energy which created spacetime, because spacetime itself is an emergent property of the big bang. It's created by different forces which emerged following the big bang which influenced how the system was being expressed. Spacetime as we understand it did not exist "before" the big bang, because there was no "before" temporally speaking. For all we know, there's no before in terms of logical causation, either.
sjiveru t1_ixecvy0 wrote
As I understand it, the jury is still out. A lot of people have done a lot of math about it, but we still lack some empirical data to check that math against. There's a number of possible options that are consistent with current observations.
> The idea that space is infinite makes no sense to me as even the physical “space” between planets, stars etc is still “something” and according to the Law of Conservation of Mass, matter cannot be created or destroyed.
That space is, I suppose, "something" in a sense, but it certainly isn't matter. It's just location. (And matter can be created and destroyed; it's just converted to or from energy when that happens. This is what E=mc^2 is about. But the expansion of the universe is creating neither matter nor energy - just locations for it to be in.)
> BUT if space is finite, that suggests if you were able to travel for sufficient time, you would eventually reach the end/edge, which surely suggests it is contained within something. If this is true what/who is outside “the box”?
Not necessarily. The two-dimensional surface of a three-dimensional sphere has no edge. Our three-dimensional universe could be arranged in some four-dimensional way such that it has no edge.
In any case, since it's impossible to observe what's outside the universe (by definition of 'the universe'), science can simply say nothing at all about the outside of it.
WictImov t1_ixekc14 wrote
When science has no answers, we turn to God(s).
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[deleted] t1_ixegb9a wrote
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010011100000 t1_ixegpvf wrote
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We don't know. All observations and theories are consistent with either option
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The law of conservation of mass (which doesn't even hold anyways) has nothing to do with this. There's no mass or energy associated with just space itself. And it's not being created so it doesn't matter
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Space being finite doesn't mean that if you were to travel forever you would eventually reach the edge. The surface of the earth is finite but there's no edge
space-ModTeam t1_ixeguoh wrote
Hello u/erkynator, your submission "Is space infinite or finite?" has been removed from r/space because:
- Such questions should be asked in the "All space questions" thread 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. Thank you.
Embarrassed_Aside_76 t1_ixegxne wrote
In reality, the universe that we can observe is expanding significantly faster than we can travel, even if we could go much faster than now.
Even if you imagine the universe is not infinite, it's functionally infinite from our perspective.
There are conflicting models of how we can have an infinite universe, that is also expanding (that bit always hurts my brain). So we don't know this for sure.
Essentially to quote the brilliant Douglas Murray "space is big. You just won't believe how vastly, hugely, mind boggingly big is. I mean, you may think it's a long way down the road to the chemists but that's peanuts to space"
[deleted] t1_ixehlsc wrote
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WictImov t1_ixej9vc wrote
If you get to the edge, you would find Milliways.
Since the universe is [still] expanding, then no matter how far you travel (limited by the speed of light) you would never reach the edge. The rate of expansion is estimated* to be 73 million kilometres per second per megaparsec. Both parts of that number are important because the expansion is not at the edges but throughout the universe. Don't think of the expansion as a ripple in water that travels outward from a point, but rather an elastic band that stretches everywhere along its length.
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* Yes, I know about the discrepency with the 67.5 kilometres per second per megaparsec estimate but that is too much detail for here.
staticminor t1_ixeb6qc wrote
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is google broken at your house?
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there is not physical "space" between planets. It's a vacuum. It's literal empty nothingness aside from infinitesimally small space dust floating around.
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There is no "edge", we're not in a box, it's infinitely expanding until the heat death of the universe
4)that's our best understanding, we literally have no way of knowing for sure
Swoshu t1_ixedy4v wrote
please try your best to stop being cringe. please.
erkynator OP t1_ixecqs9 wrote
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Nope, Google isn’t based in my house, it’s head office is in California. I live in the UK. And having used it about 5 minutes ago, please don’t be concerned, it still works.
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Oh dear. Yes space is a “near perfect vacuum”. Since you seem to have problems with Google, I’ve provided a helpful link What is Outer Space?
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If it’s expanding is that because the quantity of matter is increasing (in conflict with the above law) or because things are getting bigger? I know my belly is growing with age, but I’m pretty sure earth is roughly the same size as when I started typing.
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I’ll take that as a “NFI”.
Thank you for your contribution!
Hk-Neowizard t1_ixediux wrote
- Space is expanding in the sense that the volume between every two particles (or more reasonably astronomical bodies) is growing. Imagine a grid on a paper. Every intersection is a particle. Now, "zoom in" on one "particle" - look at the distances between all particles compared to before, that's how space is expanding
erkynator OP t1_ixeef37 wrote
Hmm. So does that mean the forces that keep particles “together” is getting weaker? Why are they distancing themselves from one another? Is the end game in sight when they no longer have any remaining bond and go there separate ways? Sounds like a friends marriage!
Hk-Neowizard t1_ixetrw6 wrote
Forces aren't getting weaker, exactly. They're just made to act across a larger gap.
One way to thing about it, is to imagine that every point in space "splits" into multiple points all around it (if space is a 3D grid, then every point "splits" into 3X3X3 points centered around the original point). This of course is wrong since space isn't a "thing" that can split, but it's a way to help our limited brains internalize the concept and develop an intuition around it.
Another way to think about it, is to consider force carriers. The photon, for instance, is the carrier for the electromagnetic force. The gluon is the carrier for the strong force, etc. If you're comfortable with the notion of force carriers, you can imagine these carriers are "slowing down". This is a bit more wrong than the previous analogy, because an expanding space mean that not only do "forces take longer to reach" from one particle to another, it also means the force a particle exerts on another is weaker. The analogy, however, helps give a new perspective on the concept of expanding space, so it's worth playing with.
It's important to note that the expanding space isn't really measurable on small scales yet, and won't be for MANY MANY years. The rate at which space is added between two points is proportional to the distance between those two points (again, consider the "splitting space" analogy, the more space, the more "splits" per unit of time), and anything smaller than intergalactic scales is so slow, that the standard-model forces (strong, weak, EM and gravity) all counteract it completely. Only in the vast nothingness of intergalactic space is there enough space and little-enough of anything else for this expansion to be the dominating affect. For now... (if the expansion of space is indeed accelerating)
Ape_Togetha_Strong t1_ixf80y4 wrote
> It's important to note that the expanding space isn't really measurable on small scales yet, and won't be for MANY MANY years.
The rate of expansion of the universe isn't increasing. It will never increase the space between particles on small scales. That's not what is meant by "the expansion of the universe is accelerating".
Hk-Neowizard t1_ixgms2g wrote
You're right. It seems I mixed in the concepts behind the Big Rip speculative theory with accepted theories around the expansion and dark energy. I have to go revisit those topic now to separate facts from far-fetched conjecture.
Thank you.
Resident_Smoothbrain t1_ixegbx3 wrote
It is less that they are being pushed away from each other, but that all the matter in the universe exploded from a single point a long time ago and is still expanding at that same speed according to Newton's first law (nothing to stop it, so it will stay at the same velocity). The particles are just moving at different speeds/velocities and so are expanding away from each other.
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Think of two cars starting a race. One is a very fast car, and the other is a slow car. When they start the race, they are very close to one another, but slowly, the distance between them increases. The big bang is the start of the race, and the cars are the particles.
The particles in any particular celestial object, however, are not distancing themselves from each other. The molecules on earth all hold themselves together and are moving as a single, very large particle moving away from everything else.
Hk-Neowizard t1_ixeooww wrote
The expansion of space is not the inertia from the big bang. If that were the case it would be slowing down, which evidence doesn't seem to support.
In fact, the expansion is likely accelerating and at a far distant future even the space between protons will expand faster than the strong force can pull them back in.
heart_seizures t1_ixeb49j wrote
for our intents and purposes, it's infinite. it's billions of light years big, and there's still so much we don't know about the nature of our universe. I'm not sure if anyone knows.