Discussion Title: Does the multiverse exist?

1. The multiverse does exist.
1.1. Pro: Since it can't be disproven, there's no reason to rule it out.
1.1.1. Con: There's no evidence of it now, we can't say it can exist without it.
1.1.1.1. Pro: Testability and explanatory power are two intrinsic tenets of science. Disregarding them to make us think a multiverse possible takes us to finding the truth \(plus, doing this becomes [dangerous](https://academic.oup.com/astrogeo/article/49/2/2.33/246813) to scientific credibility, which only worsens our ability of getting evidence\).
1.1.1.2. Pro: We don't even understand our own universe and its origins \(like why did the big bang occur?\). Without this hindsight, then there's no understanding about other universes possibly existing.
1.1.1.3. Con: Just because we can't see it, doesn't mean it's not there.
1.2. Pro: If the big bang started our universe, it probably was part of a chain reaction of other universes too \(called [bubble universe](https://www.dailymail.co.uk/sciencetech/article-2698010/Are-living-multiverse-Researchers-claim-universe-one-bubble-frothy-sea-bubbles.html)\).
1.2.1. Pro: Researchers [argue that](https://www.dailymail.co.uk/sciencetech/article-2698010/Are-living-multiverse-Researchers-claim-universe-one-bubble-frothy-sea-bubbles.html) this means that our universe is just ''one bubble in a frothy sea of bubbles.''
1.2.2. Pro: The multiverse is likely able to be explored, but since we're not able to go between them \(due to the black hole [cutting off](https://youtu.be/9P6rdqiybaw?t=182) the other side, which we would travel to\), we won't be able to visit and see them.
1.3. Pro: There are fluctuations in the [cosmic microwave background \(CMB\)](https://phys.org/news/2010-12-scientists-evidence-universes.html) that may signify that this universe collided with other universes in the past.
1.3.1. Pro: In a [recent study](https://phys.org/news/2010-12-scientists-evidence-universes.html) on pre-big bang, researchers discovered 4 statistically unlikely circular patterns that they think are 'bruises' when out universe bumped into other universes.
1.4. Con: We don't see evidence for ['nested' universes](http://www.bbc.com/earth/story/20160318-why-there-might-be-many-more-universes-besides-our-own), so those multiverses don't exist.
1.4.1. Pro: The idea of a 'nested' universes version of a multiverse is [fundamentally untestable](https://www.forbes.com/sites/startswithabang/2019/03/15/this-is-why-the-multiverse-must-exist/#7832e01b6d08), as it requires looking for evidence of something that exists outside our visible universe and leaves no trace within it.
1.4.2. Con: Due to the ability to make predictions, we don't need evidence to know that they can exist, just logic \(like math and science\). Only after we solidify our understanding to belief it could exist can we find evidence for it. Right now, it's possible it can exist, so likely it does and we'll hopefully see evidence for it one day when we look in the right direction and spot it.
1.4.2.1. Pro: Decades before we directly detected [gravitational waves](https://www.forbes.com/sites/startswithabang/2019/03/15/this-is-why-the-multiverse-must-exist/#7832e01b6d08) and [Higgs bosons](https://www.newscientist.com/article/dn22008-a-brief-history-of-a-boson-timeline-of-higgs/), we knew that they must exist, because we observed their effects and formulated their mechanisms. This shows that we don't always need hard evidence to know that something is true.
1.4.3. Con: This may simply be because we currently lack the technology to gather evidence.
1.4.3.1. Pro: Modern telescopes can [only see things within a limited radius](https://www.economist.com/news/science-brief/21660968-our-second-brief-scientific-mysteries-we-ask-whether-world-might-make-more-sense). There might an infinity number of universes outside this radius that we simply can not see yet
1.4.4. Con: Maybe we can't see it, because we're in a simulation. If we knew we are in a simulation and see how it runs, we may be able to see the nested layers within it. However, we can't know that right now, because without solving the simulation hypothesis, we can't find out if this is true or not.
1.5. Con: The universe keeps expanding without stopping \(like bumping into something\), it's likely that there's nothing, no other universes, out there.
1.5.1. Con: If the universe keeps on expanding, its temperature will eventually reach absolute zero, however that shouldn't be possible according to [quantum uncertainty](https://www.theguardian.com/science/2013/nov/10/what-is-heisenbergs-uncertainty-principle), so something must happen to make that stop. That something could be our universe colliding with other universes.
1.5.2. Con: It may be possible that when the universe was young, it bumped into and pushed the other universes away. Now, there's nothing to run into, but it doesn't mean they aren't there, as they might just be further away than we can't touch them anymore.
1.6. Con: It's likely that we don't live in a black hole, as new material gets injected into our universe all the time \(what's in the universe now is what we started with\).
1.6.1. Con: Some physicists [disagree](https://www.nationalgeographic.com/news/2014/2/140218-black-hole-blast-explains-big-bang/), arguing that we may live inside a black hole, and even though our universe has been rapidly expanding, we could still be hidden behind a black hole's event horizon.