Eli5 Help, please my brain hurts. If there is an expanding ring of light from the big bang, what is outside it?

Submitted by ExtremeQuality1682 t3_11cpatj in explainlikeimfive

I'm just assuming that I'm correct in that there is an expanding ring of light, still expanding outward from the big bang. If that assumption is true, then what possibly can be outside that ring? What is the absence of everything, even light? It's not dark, it's not anything? And another tiny brain idea I had was, is time is relative to speed? So if there is not light even, does that mean outside the ring there is no time? Ugh my tiny brain can't take this, please help.

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MOXPEARL25 t1_ja48rnj wrote

The Big Bang is often described as an explosion, but it's important to note that it's not an explosion that occurred in space; rather, it's an explosion of space itself. This means that the Big Bang did not occur at a particular point in space, but rather, it created space itself.

When we talk about an expanding ring of light from the Big Bang, we are referring to the cosmic microwave background radiation (CMB), which is the leftover radiation from the Big Bang. The CMB is often depicted as a "ring" because it is the furthest we can currently observe in the universe, and it is at the "edge" of the observable universe.

As for what is outside the CMB, the truth is that we don't know for sure. It's possible that the universe is infinite, and there is simply more universe beyond what we can observe. It's also possible that the universe is finite and bounded, in which case there may be some sort of boundary beyond the CMB. However, the nature of this boundary, if it exists, is currently unknown.

It's important to keep in mind that when we talk about the universe, we are talking about everything that exists, including space and time. So if there is something "outside" the universe, it is by definition not part of the universe. Therefore, the question of what is outside the universe may not be a meaningful question at all.

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ExtremeQuality1682 OP t1_ja49e5e wrote

You are awesome, I'm not sure I understand entirely, or that anyone does but I understand slightly better. So the big bang did not follow the rules of physics and happened faster than the speed of light then? So there are theoretically dark galaxies that still have not had light reach them yet, and there always will be? Btw thank you in advance, you're awesome.

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MOXPEARL25 t1_ja4ax3e wrote

While it is true that some parts of the universe are currently beyond our observable horizon, this does not necessarily mean that there are dark galaxies that we cannot see. Our ability to observe objects in the universe is limited by the speed of light, which is the fastest anything can travel. The farthest objects we can currently see are the ones whose light has had enough time to reach us since the beginning of the universe.

However, it is possible that there are areas of the universe where light has not yet reached us, and we cannot observe them yet. These regions are commonly referred to as the "unobservable universe." However, it is important to note that this is not the same as a "dark galaxy," which refers to a galaxy that emits very little or no visible light. Dark galaxies are still detectable through other means, such as their gravitational effects on surrounding matter.

Overall, our understanding of the universe is continually evolving, and there is still much we do not know.

So in a nutshell: We can only physically SEE so far. But by other means of measure we can detect certain energies further out into the universe. This one’s we can detect but can’t see are the “dark galaxies”. They still exist but are too far for us too see. And outside that is really unknowable.

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RubyPorto t1_ja4d4ly wrote

>However, it is possible that there are areas of the universe where light has not yet reached us, and we cannot observe them yet.

Depending on the cosmological model you subscribe to, there are instead areas of the universe whose light will never reach us (assuming expansion continues), and we will never be able to observe. And areas where light from the past was able to reach us, but light emitted now will never be able to reach us.

For objects beyond a certain distance, the expansion rate of the universe is such that the distance between us and the object increases at a rate greater than the speed of light, meaning that photons emitted by that object will not reach us in finite time. (This does not mean anything is moving faster than the speed of light, to be clear.)

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ExtremeQuality1682 OP t1_ja4e5a8 wrote

Oh, thank you. That makes it actually make more sense. I'm thinking as there was only 1 big bang. So our light wouldnt reach them, but that doesn't mean there's nothing. Like you said they're light wouldnt reach us either. So there isn't nothing just another universe expanding toward us. Theoretically of course. It was the concept of nothing that had my brain messed up.

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RubyPorto t1_ja4gn19 wrote

I think my comment may not have been clear enough. There was only 1 big bang. There isn't another universe expanding towards us. This is all talking about one universe.

Imagine that the universe is represented by the skin of a balloon (just the 2d skin, not the internal volume). Cover the balloon with dots and pick one to call Earth. As you blow the balloon up, all of the dots will get farther from the earth dot, but the change in distance will be smaller for the near dots than the already far dots. Now imagine there's a speed limit for moving between the dots. If the rate at which the distance to the far dots is increasing is faster than that speed limit, you can never get from the far dots to the Earth dot.

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apoeticturtle t1_ja6zmlv wrote

Unfortunately, imagining "nothing" beyond the balloon is where everyone gets lost. Most people, with sense, would easily counter-explain that the balloon could not expand without the "room" to be able to expand. I mean, sure the "thing" expanding also made/caused the actual phenomenon of expansion, but we'll let the philosophers continue haggling over that paradox.

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RubyPorto t1_ja70srv wrote

Every model has limits. The point of the balloon model here is to explain how a cosmologic event horizon can occur.

I agree with you that it's limited as a way to visualize the general idea of the expansion of the universe, since it requires the same essential leap as not using a model (i.e. that the universe isn't expanding into/through anything).

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apoeticturtle t1_ja7n728 wrote

Can you point me to any information on how the idea of this "expanding into nothing" can be conceptualized?

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sofar55 t1_ja9fn4t wrote

Going back to the balloon analogy, the dots are moving away from each other. Without the vertical dimension, the "universe" of the balloon surface is getting bigger, but what is it expanding into? The space between dots is expanding, but where is the space coming from?

In this model, the dots dont understand elastic stretching. In the universe, it's believed that empty space is just expanding and pushing everything apart, but we don't know how.

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RubyPorto t1_ja9asum wrote

I'm not sure I can. Every physical analogy is going to be expanding into a medium.

It's also not really "expanding into nothing." The coordinate plane of space is itself expanding, full stop. It's not expanding into anything (or nothing).

It's a fact that you just have to decide you're ok with, without a relatable model to compare it with.

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apoeticturtle t1_jabgplj wrote

There are many things in my life that I do have to decide if I am OK with, but thankfully not this one. I cannot even imagine "nothing" and having less than nothing (that which lies beyond our Universe's edge) is as mind-boggling as it is speculative. All the energy in our Universe may be just a tiny fraction of all the energy everywhere/when. It seems more likely, to me, that our Universe is a tiny part of something bigger. If not, what a waste of energy and time/space.

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UniversalAdaptor t1_ja4gpx5 wrote

The speed of light only applies to matter and energy. Space is free to expand at any speed, it does not have any limit (that we know of). Yes there are galaxies beyond the cosmic horizon that are still coming into view. Although since galaxies are hundreds of thousands of light years across, it therefore would take that much time for one to come into view. We don't know how big the universe is but we do know it is at least several times bigger than the observable universe.

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sofar55 t1_ja9g013 wrote

Wait, how do we know it's "several times" bigger than the observable? I haven't seen anything to reference the actual size of the entire universe beyond observable.

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turnedonbyadime t1_ja4jqax wrote

You don't understand because this entire concept is wildly far beyond anything humans were ever meant to understand. Maybe the only satisfying answer to this kind of question is coming to peace with the fact that we'll likely never have a satisfying answer.

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ExtremeQuality1682 OP t1_ja57cbl wrote

Ha, explain to my brain like it's 5 how to do that one while you're at it. I'm just ribbing you. My brains the one that's a jerk.

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phunkydroid t1_ja5f0ro wrote

>So the big bang did not follow the rules of physics and happened faster than the speed of light then?

The expansion of space is not limited by the speed of light. That speed applies to things in space, not to space itself.

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Pegajace t1_ja49i2z wrote

>I'm just assuming that I'm correct in that there is an expanding ring of light, still expanding outward from the big bang

There isn’t, because the Big Bang wasn’t an explosion at a specific point in space casting matter into an empty void. It was a rapid growth of space itself that happened everywhere, and the closest thing to an afterglow (the “Cosmic Microwave Background”) can be seen from everywhere coming from every direction.

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ExtremeQuality1682 OP t1_ja49yb7 wrote

That makes my brain hurt even worse lol. The universe expanded faster than light?

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Pegajace t1_ja4apqv wrote

The speed of light is an upper limit on how fast matter, energy, and information can move through space. The expansion of space during the Big Bang (and afterwards at a much slower rate) is something fundamentally different from motion. It’s a “metric expansion,” which doesn’t require anything to move within space and is not limited by the speed of light. It’s not even measured in the same units as speed; speed is distance/time, whereas expansion is (distance/time)/distance, which oddly collapses down to just units of 1/time.

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ExtremeQuality1682 OP t1_ja4bpxl wrote

I so very much appreciate your time. This is unacceptable to not comprehend to my brain. Please elaborate how is Expansion = (distance/time)/distance? I feel if I can understand that I'll "get it"

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extra2002 t1_ja5nv01 wrote

The speed of something moving away is proportional to how far away it is, so the rate is measured as speed/distance. Speed is distance/time, so ...

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Junker-king t1_ja4tqbb wrote

yes and no, there is actually a specified timeline of the universe's expansion down to the minute and even the second(or less than second lol). let me see if i can find the one that I was taught on... ok, so on second thought... Obviously I can't just upload a book to reddit, but the graphic and explanation in this link is similar enough to my understanding that i'm trusting it to teach you. https://www.physicsoftheuniverse.com/topics_bigbang_timeline.html

basically, it cannot be said that the universe expanded at the speed of light for multiple reasons:

one being the universe didn't expand, it is currently expanding. It never stopped, we can measure it right now if we wanted to and if we were rich enough. I had to specify that first because if I didn't I would be allowing you to be misled.

two, being it entirely depends on which distance away from us (or Planck's constant, which was the very beginning of the very beginning, meaning it is currently impossible for us to measure anything before it occurred because it was the beginning of time as we know it) and at what point in time you are measuring. If we measured a galaxy next to us right now, it would not be expanding away from us at the speed of light because the distance between us is way smaller, but if we were to measure a galaxy on the other-side of the universe it would most likely be expanding away from us past the speed of light because the distance is *impossible to comprehend*. Keep in mind speed is just distance/time, and so is unfortunately not very helpful in this specific example... i'm actually pretty unwell rn so if this explanation makes absolutely zero sense, I sincerely apologize, I tried my best and if you have further questions I will try my best again to clarify.

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ExtremeQuality1682 OP t1_ja5749n wrote

Your time is very much appreciated. Get some rest if you can. Thanks.

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sofar55 t1_jaabfm8 wrote

Another explanation is that the more space between 2 galaxies, the more that space expands. Say you have 12 ft of rope. Every 5 minutes is expands by 1 in per foot. After the first cycle you have 13 ft of rope After the 2nd, 14ft 1in After the 3rd, 15ft ~3in The longer the rope, the faster it expands.

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Farnsworthson t1_ja4fu3q wrote

The thing is - from the perspective of the unverse as it is now, the Big Bang happened everywhere all at once. You are right where it happened - but then, so is absolutely everything else as well. And all of it was packed incredibly close together* at the time. There's no "expanding ring of light" - the light started from everywhere, heading off in all possible directions, and is still going, just moving between places that were all close together at the time. Some of the light started off in your living room, and is still heading outward; but plenty of light from other places is reaching us from every direction as well.

2D analogy. Imagine the surface of a balloon. It's an incredibly small balloon when it's not inflated, but it's also incredibly stretchy. Suddenly, it starts growing - and as it does, thanks to the marvels of thought experiments, as each point of the surface starts to stretch, lots of sparkly light goes shooting off from that point in all directions along the surface. But the whole balloon is stretching, so the light is coming from everywhere, going everywhere. A couple of hours later (or maybe 14 billion years) the balloon is still getting bigger, and its whole surface is still chock full of sparkly light heading in every direction. There's no "expanding ring" - the light started out everywhere, heading everywhere.

Put back in the context of the universe, that's what we see - the Cosmic Microwave Background. Light from all over the place, that just happens to be passing here right now.

*"Incredibly close together" is as far back as we can go. There's a point where everything is so close together that our current models of the way the universe works simply break down. What happens before that is, basically, currently unknowable.

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ExtremeQuality1682 OP t1_ja4gajz wrote

Thanks. Good news Cubert, that helps tremendously 😁. You're name is the bee knees btw. Whimmy wham wham wazzle

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Mammoth-Mud-9609 t1_ja4bjo8 wrote

A complete vacuum or possibly if you go far enough another universe expanding out towards us. https://youtu.be/t80qywmnADM

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ExtremeQuality1682 OP t1_ja4cbap wrote

Yeah, what he was describing was what got me down the rabbit hole. We can never know if ours is the only big bang. Not that we can theoretically never know. We literally can never know.

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UniversalAdaptor t1_ja4hvqd wrote

The CMB is not a ring, it is everywhere and can be seen in every direction. It fills the whole universe like water fills the whole ocean. The CMB comes from the time of the early universe, when the universe more dense and every part of space was filled with hot glowing matter. As the universe expanded the matter cooled off and stopped glowing but the light from that glow continues to spread in all directions.

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Ansuz07 t1_ja4930m wrote

>I'm just assuming that I'm correct in that there is an expanding ring of light

Its not just light. Its everything - light, matter, space, time. Everything was created in the Big Bang.

>then what possibly can be outside that ring?

That is like asking what is north of the North Pole. Nothing - in the truest sense of that word - because everything in existence was created in the Big Bang (as far as we know). There isn't even space for the nothing to exist in - space is part of the Big Bang too.

>So if there is not light even, does that mean outside the ring there is no time?

Correct - no space, no time, nothing.

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ExtremeQuality1682 OP t1_ja49s8t wrote

This just isn't something my brain can comprehend, I guess. What is the absence of everything, how does that react with something then?

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Ansuz07 t1_ja4a348 wrote

It isn't something that anyone can comprehend. Nothing is not a concept that we are capable of understanding.

We don't really know how nothing interacts with the universe, as we are unable to observe this occurring (if it occurs at all).

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ExtremeQuality1682 OP t1_ja4ahfg wrote

I'm honestly glad I'm dumb, I can't comprehend how people like Einstein could ever even sleep. My brain does not compute incomprehensible.

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cshaiku t1_ja4b4r4 wrote

Some say, that space and time are simply two sides of the same coin.

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ExtremeQuality1682 OP t1_ja4cwx1 wrote

Someone said below it's different, it's an expansion which is (distance/time)/distance. Which would make everything kinda make sense but I'm awaiting a better explanation of that cause my brain can't grasp it. Is there time outside the ring, or if that explanation is true, there is not distance but only time?

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Frednotbob t1_ja4k3j0 wrote

It's more like, there is neither without the other. You can't move in space without moving in time, and vice versa.

So, my slightly-headache-inducing answer: if the universe is infinite in size, then the ring is traveling through space-time just like we are. If space is finite, then the ring just hasn't reached the 'boundary' of whatever spacetime object we're contained in (what happens when it gets there is a question I'll happily leave to philosophers and quantum physicists).

In either case, there must be space for the ring to occupy while it travels, which necessitates the existence of time outside the ring.

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Junker-king t1_ja4umjz wrote

Wonderful explanation, especially the very last part! Summarized very succinctly!

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BobFX t1_ja56f7j wrote

There is a solid wall of nothingness at the edge of the universe. It took years after inventing numbers for man to invent zero. So absolute nothingness is literally impossible to imagine. It is like trying to imagine a 4th direction in space except there are no directions at all. It is not empty space filled with nothing, it is nothing absolute.

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Person012345 t1_ja5bf4y wrote

Looking out into space is like looking back in time. Look 100 million light years away and you'll see what was happening over there 100 million years ago. Well, if you look far enough, you'll see what was happening 13.8 billion years ago. But at that point, it's just an opaque mass of radiation that we can't "see through" because this represents the birth of the universe, the big bang. What was happening 13.8 billion years ago, no matter which direction you look, was that the universe was being born. This is why it's a "ring".

This is called the observable universe and to be clear, I'm pretty sure current technology does not allow us to look that far. But this is what you would see.

As for what is "outside" it, our current understanding of physics can only extrapolate back to 1 planck time after the big bang. What was going on before that, in the moment of the big bang and any hypothetical "before", nobody can tell you. It's a singularity, it's where mathematical values reach infinity, and we don't really understand what happens when values reach infinity in real life. It's why people say we don't know what happens "inside" a black hole, it's the same problem.

Ultimately your question is one and the same as "what was before the big bang". My personal preferred idea is that space and time itself didn't exist before the big bang, therefore the very concept of "before" the big bang is nonsensical. So then what is "outside the universe", as far as I'm concerned it may well be a nothing beyond what you can even comprehend, a "place" in which space and time simply doesn't exist. Or it could be a gazillion pink elephants having a tea party. It's likely we will never know for sure.

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icpooreman t1_ja60943 wrote

The big bang happened everywhere. We can only see as far into the past as the radiation from that event will let us.

Pretend you’re at a fixed point inside a very smoky half filled balloon. Then somebody starts filling the balloon with clear air and now you can start seeing stuff as the smoke disappates. But you can never really see what the inside of the balloon was like before or during the smoky period.

And the balloon just keeps expanding at an accelerating rate.

And also the balloon may be infinite / may have always been infinite / but you don’t know because you can’t see further back than the smoky period. You’ve never seen an edge, the smoke was the edge, was the smoke infinite? And the only thing you have to figure it out is math that you know is wrong.

Basically there may not be an edge. The big bang happened and we can’t see an edge in any direction. Just more places that experienced the big bang just like we did.

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