Universe

How did they "estimate" the size of the universe ? And whats at the end of it ?
Does it just loop back on itself ?

pic is from "the scale of the universe"

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youtu.be/IcxptIJS7kQ?t=33m
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I gotchu guys

That image sucks. Often "universe" actually refers to observable universe. The size of the observable universe is gotten by the expansion rate and the speed of light. It is the farthest an object's light could reach us if it was traveling since the big bang. Thus the observable universe is always changing in size. We are at the center of the observable universe

The rest of the universe extends beyond the observable universe. Since the matter we observe in the observable universe looks homogenous and evenly distributed, we predict the rest of the universe looks the same. So there is no center, are we are quite sure the universe is boundless. Being boundless means it's either infinitely large, or loops back on itself. If it loops back on itself, it means it is curved in a 4th spatial dimension and we should be able to measure it. Measurements have shown no sign of this, but we have no idea how slight the curvature may be, possibly way beyond our capabilities.

I already understood the obversable universe
but thought they where talking about something else here

We could only know the size of the whole universe if we ever detect the geometry. Until then it's considered infinite.

this, it's assumed to just go on and on.

>Measurements have shown no sign of this
Background radiation.

If there was no looping, we wouldn't be able to see the residual glow of the Big Bang since it would have long since passed us.

>passed us
Nope. There is no flow of matter from any origin point.

Exactly.
That's why there is a loop

No... The big bang was an expansion of all space. It could very well have been an infinite space.

Where the big bang got energy for an expansion?

If the universe was infinitely expanding solely in a 3D way, how can we detect the afterglow of the Big Bang?

Everything points to the universe being a 3D space riding a 4D expansion.

Not sure I follow. A 3D space can be infinite. Like a 2D plane is in 3 dimensions. The afterglow takes up the entirety of the infinite 3D space.

>Like a 2D plane is in 3 dimensions.
A 2D plane is only infinite in 3 dimensions when it's curved back on itself. Like on the surface of a sphere.

And to detect the CBR, you need particles from it to impact our detectors.
If the 3D universe was strictly expanding in a 3D way, then the Big Bang would like any other explosion in 3D space.
How do you hear an echo of a regular explosion?
How do you detect an explosion that already happened?

The only way that we can "hear" the Big Bang still is if we're in an "enclosed" space so that we can "hear" an echo of it

everywhere in the universe is still a little "hot" from the big bang and you can see how "hot" by pointing a telescope anywhere and seeing the background radiation.

And what is radiating that heat?
If you say spacetime, then we're on same page. That means looping.

no it doesn't mean looping.

its like taking a frying pan off the stove and measuring 5 minutes later how much residual heat is still left in the pan.

there is no echoing wave of energy bouncing around through looping space-time.

Ok.
Let's break down your analogy
What's your pan in real terms?

What exactly is radiating the CBR?

>A 2D plane is only infinite in 3 dimensions when it's curved back on itself. Like on the surface of a sphere.
Wut...? It can be a flat infinite plane. Also if it's the surface of a sphere, it's not infinite. It's only boundless.

The CBR is photons emitted when matter was expanded enough for them to travel anywhere. Before that it was too dense.

>it's not infinite. It's only boundless.
Sorry, I conflated the two to be the same.

>The CBR is photons emitted when matter was expanded enough for them to travel anywhere.
That happened several billion years ago

Why can we still detect it?

You're perceiving space wrong. There is no center of the universe. The big bang happened everywhere in the universe simultaneously. That is why we see the cbr. The big bang wasn't some location fixed in space spewing out energy to other parts of space, it was the entire universe that was banging.

There is no centre only due to the looping nature of the 3D universe.
You're only saying what I've been saying.

What's the centre of the surface of a sphere?

By saying that the universe is finite and expanding is saying that there is a centre.

>Why can we still detect it?
Because light takes time to travel. The light from 13 billion years ago is only just reaching us now.

You're implying that your position has been static compared to the "origin" of the Big Bang

>By saying that the universe is finite and expanding is saying that there is a centre.

where is the center on the surface of an expanding sphere? Every point has equal claim to being the "center" as it is for our 3D expanding space... There is no center.

No. That's just one possibility. It could be the universe was just a small flat plane 1m×1m. Then the big bang happened and now that sheet is 10^29 lightyears across. The original stuff from the big bang was stretched with it, which is why it is everywhere present. Could be a sphere,saddle, or plane. We don't know yet.

That's EXACTLY what I'm saying.

How are we disagreeing

No origin. It encompassed all of space. Our view of the CMB is unique to us, just like our observable universe.

>The original stuff from the big bang was stretched with it, which is why it is everywhere present.
Then how are we detecting CBR?
It's being emitted omnidirectionally.
If the universe is just an expanded 3D space, then how are we getting emissions equally from the opposite direction of the expansion?
How is every galaxy moving away equally regardless of direction?

You keep saying what I'm saying but when I put a point on it, you disagree.

If you don't have an origin, then you have to admit that the universe is the 3D equivalent of the 2D space on an expanding balloon.

No... That's a possibility, but it can also be the equivalent of a flat infinite 2D plane.

Because it happened everywhere in that 3D space, infinite or not.

>Because it happened everywhere in that 3D space, infinite or not.
So.. You and I and the Sun and the Earth are all emitting CBR?

If everywhere in that 3D space is emitting that radiation, so must we be

We are emitting radiation. It will eventually be redshifted to microwave, yes. The light that is fully redshifted by now is all very old light, and that's what the CMB is. The patterns we see in the CMB are features billions of light-years away, and were formed in the early universe.

quick answer: gravity
short explanation: youtu.be/IcxptIJS7kQ?t=33m
long explanation: youtu.be/IcxptIJS7kQ?t=24m40s

>Since the matter we observe in the observable universe looks homogenous and evenly distributed, we predict the rest of the universe looks the same.
>im alive today so i'll be alive forever

feel free to share with us how this sudden change occurs that you are suggesting

>That happened several billion years ago

>Why can we still detect it?

Because speed of light is finite and by looking through a telescope we are also literally looking into the past.

>So.. You and I and the Sun and the Earth are all emitting CBR?

We are not currently, but the plasma that became us did emit it 13 billion years ago. Someone looking in our direction from 13 billion light years away would see it.

>that pic
>we're not at the center of the universe
I thought any observer will see the universe as if they were at the center?

You are both right if we can see the CBR be directional.

Things closer to us after the Big Bang should emit more CBR than bodies farther away

But that's not true.
CBR is a blanket radiation.
There is no direction. No blue or red shift.

How do you explain that?

If you believe that there is no curving of space-time, then how is there no direction in the CBR?

you know, we can predict things without being fallacious.

That wasnt me. Anyways, he's right.

Take a balloon and pop it. Strech out what's left over. Planes, saddles,spheres, etc can be morphed into each other. Theyre topologically equivalent. What matters here is that the big bang was the entire universe, whatever that shape is. What we see isn't from some place from far away, presumably, the cmb would be more or less the same no matter where you view it. If there was really a center in the 3d topolgy, the center would most likely look different but we don't think it is therfore there's no center. You could argue the center of the universe is the center of the sphere but that would be wrong since by definition, the universe is only the surface. In gr, there is no need for spatial dimensions beyond 3 to describe the topology. Again, it could be the case that the universe loops on itself and theres been studies that try to look for mirroring of galaxies but none have been found. At this time, we believe the universe is almost completely flat. Well have to wait for space Columbus to show us otherwise.

No. The cbm is a snapshot of the universe when it was still very small and billions of years younger. The cmb we measure is very specific red shifted light. It'll be billions more years before the light being emitted now would cool to the point we see it in the cmb, at which point the cmb would look different than it does now. Again, the expansion of the universe is expansion of space itself, not the movement of things in space. If the expansion were due to things moving in space but not space itself, then we would see a center, but that's not the case, so no center.

>Take a balloon and pop it.
Yes.
That's what I've been saying.
Pop a 4D balloon

You can't have a strict 3D space without a center.

>If you believe that there is no curving of space-time, then how is there no direction in the CBR?

because big bang happened everywhere at once

you already know that surface of a sphere can expand uniformly with no center of expansion on the surface

now you just need to realize that a sphere with infinite diameter (a plane, really) can expand just the same, too

>You can't have a strict 3D space without a center.

You can if it is infinite

>Again, the expansion of the universe is expansion of space itself, not the movement of things in space.
Hmm... So you're saying.. It's like ink on the surface of a balloon. The ink isn't moving, it's the medium it's grounded on.

Sounds a whole like a 3D universe grounded on a 4D reality.

You're just describing what's happening without saying what's happening?

>My boat is sitting on the water and is moving away, but there is NO current. It's just that there is more water between me and the boat. There is NO current, just more water.

We all know that's bullshit.

A flatlander will say that the 3D space is impossible and that their 2D realm is just infinite instead.

It's a weak way out that prefers the totality human experience over the possibility that we're just a part of something larger.

Your argument is the EXACT same as a person saying that "Well everyone else isn't immortal, but I haven't died yet, so I am immortal"

Now we're getting somewhere.

Take a deflated balloon and mark dots on it. This was the universe pre big bang. Now blow the balloon up. The dots get further and further apart. That's the universe now. The cmb is the balloon just after it started blowing up. The surface has no center. With respect to the expansion. It's equal in all directions and in magnitude. There could be a 4d space that the universe is embedded in bUT current models don't necessitate it. Then there's also the question of whether or not the 4d is embedded in 5d and so on, so the recursiveness is unappealing and irrelevant at this point in the development of the theory.

Not true, because if 2d was embedded in 3d, then 3d objects intersecting the 2d space would disappear and reappear while rotating. It would be easy if something outside our 3d came and said here we are! But we haven't seen any evidence of higher dimensional interactions except for some models that predict gravity is bleeding out. We're not closed to the possibility, and it hasn't been disproved, it just hasnt been observed.

How do you figure a lack of centre in a strict 3D universe?

To compare to a 2D example, you're saying that the universe is an expanding sheet.
A series of dots on that strict 2D sheet can indeed extrapolate where the center used to be.
Only a 2D plane on a 3D sphere cannot detect a center.

And fuck off with the "infinite 2D plane" shit.

If the universe was truly infinite, then the sky would be uniformly infinitely bright at all times. Because there are an infinite amount of stars and if even each star contributes 0.0000000000001% of full daylight, then an infinite universe would exceed that by, guess what, an infinite amount.

Dark matter.

Also, why isn't the sky infinitely bright if there are an infinite amount of stars?

I thought the universe was spirit science spirals and shit

There was no center. The dots were sPread all over the deflated balloon remember? All you would find by extraplating is that the dots used to be much closer together, which is what we observe with the cmb.

The question about bright skies is actually very good. The answer is that while the light travels, the space is stretching. Light further away than abut 100 light years have actually traveled much further than 100 light years so the light is significantly less bright. This is one of the primary reasons the argument for expanding space works in the first place. There was a lot of discussion about it when hubble first posted his findings.

>The dots were sPread all over the deflated balloon remember?
Again, you're using the metaphor of the 2D space drawn on a 3D background to argue that our 3D space has no 4D background.
Do you see how that may not seem like a sound argument?

And if the universe is infinite and expanding, shouldn't there at least be a level where the number of photons are infinite?
Just because photons become red shifted, it doesn't mean they disappear, right?

If there are infinite stars, then every single aspect of the universe should be populated by an infinite number of photons.

Infinity opens up so many problems.
It's much simpler to assume a boundless universe rather an infinite one.

Can someone explain how the universe is 2D?

nope, i never said there was no 4d background. I just said it's not necessary.

Also, i never said the universe was infinite.

2d
2 digits
2s

I'm going to jump in on this and try to shift some perspectives, if I may.

Why do we assume that the universe that we are not observing stays the same while unobserved?

We can only observe a fraction of the universe at a time, due to the periscopic nature of our own perceptual apparatus.

We cannot simultaneously observe what is in front of us, behind, above, below, and to the left and right. Unless of course you believe that the entire universe can be observed within one particular scope (the looping phenomenon discussed earlier).

However, if this were the case, we would have to consider whether or not the "observing" entity was even contained within the system being observed.

This is more of a philosophical question than a scientific one, unless quantum theory is the better solution to such a question.

However, I must ask, out of genuine curiosity, why would we ever assume that we could observe the entire observable universe, at once?

How can you have an omnidirectional CBR without an infinite universe AND no 4D background

You sound like you're just taking no position in order to always be right

they used muh dick to estimate it because they know it cant be larger than it.

>why would we ever assume that we could observe the entire observable universe
Because by definition what we see is the observable universe.
Maybe there is more out there but it doesn't matter because we can't see it.

The bottom line of science is that if we can't observe something, it doesn't exist and it doesn't matter even if it does.

So by that logic, when a parent plays peek-a-boo with their child (the observer in this case), once the parents face disappears from the child's perception, it no longer exists, and no longer has any matter or merit?

On a more relatable level, sitting in front of a computer screen, and the immediate background is all that exists? All else that we "remember" to have existed at a previous time, no longer does?

I am honestly having a hard time grasping this concept. I constantly run into this type of argument. It's solipsistic at its roots. Only what I can observe exists. That's a very lonely view of the world.

So, tell me, once we stop observing, do things not go on?

When I say "observable" I don't mean "can be seen with visible light"

I mean "has no connection to anything".
That parent's face in a game of peekaboo has lots of observable aspects. Like arms that lead up to a central mass. And if you ignore the past entirely, the face behind those hands will exert a gravitational profile on the matter around it.

Yes, current technology couldn't possible detect that face, but the means to detect it is possible.

That's how Neptune was discovered. It's gravitational mass was detected through it's non-visible interaction with other bodies.

I agree with you there.

However, when an object attracts our attention, whether through direct or indirect observation, should the notion that "everything else" falls out of our "attention span" be considered as a factor?

I find it odd and rather unimaginable to picture the entire universe, unless I, the observer, was somehow completely "outside" or "removed" from the entire universe.

At that point I would need to be skeptical of the reality of the situation and whether or not that was actually possible, because to me, it seems highly unlikely.

To feel as though I am able to manipulate and observe a universe that I am not actually a part of seems to be contradicting to me.

I'll try to explain it one more time.

Consider a 2d shape. any 2d shape. This is the universe pre-big bang. Does the shape have a center? maybe. if it 's a flat square of finite or infinite size, it would have a center, doesn't matter. now, the big bang "starts" and shit fills up the square including the center. now the square starts getting bigger. the shit in the center of the squre is stretched out ,the shit at the corners is stretched out, shit everywhere is stretched out. the big bang did not originate from the center of this square and radiate outwards, the big bang was the entire square. it should be clear from this example that whether or not there's a geometric center has nothing to do with whether there's a center to the big bang, which is what we've been talking about. the big bang is everywhere in the universe simultaneously, as previously stated.

Because the light from most of the stars hasn't reached us yet

>And fuck off with the "infinite 2D plane" shit.
>If the universe was truly infinite, then the sky would be uniformly infinitely bright at all times. Because there are an infinite amount of stars and if even each star contributes 0.0000000000001% of full daylight, then an infinite universe would exceed that by, guess what, an infinite amount.

No, fuck you.
Universe = infinite
Observable universe = finite

Those two things are not even remotely similar

>infinitely bright skies
That's an argument against a static universe with an infinite history, but luckily we live in a non-static universe with a finite history (and a finite speed of light)

A fundamental tenet of empirical philosophy is that the universe keeps existing whether you're looking at it or not. Human attention spans have no particular bearing, only the exchange of matter and energy between objects.

>If the universe was truly infinite, then the sky would be uniformly infinitely bright at all times.

Only true for an infinitely old universe. Certainly not for our universe.

technically everyone is at the center of their own visible universe

No center? how? Also your example of baloon, when you fill it with air it stretches (ideally) in all directions equally in respect to the center of the baloon inside.

surely if the universe was finite, then the CMB would all have been absorbed by matter as it looped around infinitely?

my question is how the fuck does one measure the curvature of space-time?

with a very very accurate straightedge

See this is the issue that, in my opinion, people of science fail to seriously consider.

Our understanding of the universe is almost entirely dependent upon our ability to perceive it. I think it would be difficult to argue this point, it's like asking a blind man to describe what a tree would "look" like from a perspective other than his own.

But why do most modern scientists dismiss our own methods of perception? As if the universe only behaves in ways that we perceive it to, and there is no other possibility.

Just imagine the implications of the possibility that our perception of a system, and a perception alone, can vastly alter the observed system itself, without any formidable manipulation.

It would literally turn science upside down and render all experimentally determined "facts" as a mere consequence of the circumstantial perceptions of the observer.

Makes the universe seem a lot smaller than what most make it out to be.

All of space is expanding, every location is equally far away from the origin of expansion

Everywhere is the centre

Like I said last night, the universe is represented by the surface of the balloon. The center of the balloon is not the surface, therfore it's not part of the universe.

There's no evidence that our perception vastly alters the universe. At the end of the day, our perception is all we have. Historically, it has been one of the main reasons it's taken us this long to discover what we have. It would be much easier if 10th dimensional beings just came and verified/refuted our perception. Until that day, we keep going on.

>they
Professor Einstein was the first to do it,
there was no "they", faggot.

I wouldn't agree with the notion that the universe is boundless. If there is a set amount off matter in the universe at the point of origin (the big bang), then the universe can only exist as far out as the matter is distributed. And if we assume that the universe is infinitely large, then 2 things must be accepted without question. 1.) There is infinite matter in the universe and 2.) The matter in the universe does not take up the whole space of the universe. Both of these upset a variety of physics laws.

>If there is a set amount off matter in the universe
There would be a set amount of matter in a hyperspherical universe. Still boundless, it just loops back on itself.
>at the point of origin (the big bang), then the universe can only exist as far out as the matter is distributed.
Very incorrect interpretation of the big bang. The big bang wasn't an explosion from a point.
>1.) There is infinite matter in the universe
Yep, very possible. If the universe has no higher dimensional curvature, then this is the reality.
>2.) The matter in the universe does not take up the whole space of the universe.
Nah, an impossibility from every model of the universe.

>no mention of inflation in the entire thread

/sci, I am disappointed in you

>pic related, universes looking somewhat like this are generically predicted by inflation

I've only seen Hubble's name posted once, and no mention of the cosmological constant.

This is a popsci thread for idiots that watch science shows on TV and think they can visualise the Uniiverse. It's an idiot thread, basically.

Yeah one thought is that the further towards the outer edge of the universe you get, the more spatial geometry begins to behave in a non euclidian manner. I.e. is you extended a line on and on through the universe, eventually it would stop behaving like a straight line and start to curve in some way.

Careful saying "edge." It's true the further you go the more it will deviate from euclidean geometry, but there is nothing to suggest that it will be anything significant within the bounds of the entire observable universe. We may never detect it.

>This is a popsci thread for idiots that watch science shows on TV and think they can visualise the Uniiverse. It's an idiot thread, basically.
I thought this is all this board was about.

What are you on about? The central argument in the thread is inflation of space vs. Inflation of distribution of matter in a static universe.