The multiverse hypothesis: Is our universe the only one?

In the past decades, the idea that our universe is only one of many, has become popular among physicists. If there are several universes, their collection is called the “multiverse”, and physicists have a few theories for this that I explain in this video.

First, there is Eternal inflation
Second, the String Theory Landscape
Third, Many Worlds
Fourth, the Simulation Hypothesis
And fifth, the Mathematical Universe.

[vineethbhaskara]

This is the most info I have ever gained in 3 minutes!

[GururajBN]

Multiverse sounds like fiction, science fiction. Our universe itself is so vast that even at the velocity of light, there is never any hope of seeing it fully. Many such mathematical speculations mere clutter up clear approach to the subject.

[jianfengli]

My view on this is simple: if other universes does not have any connections with our universe, they DO NOT exist effectively. As to the simulated universe: even if our world is simulated by some upper-level people, something (like the substance of consciousness or conscious experience) must still be something REAL in the upper-level world.

[patricialauriello]

I don't know why I watch these videos. She is way above my head but I find them fascinating. She is erudite but clear, somewhat odd and a bit off putting, but I watch her again and again. I have no idea why.

[stimmons]

I could listen to your videos all day! Thank you

[Jollyprez]

"That's what my equation says, therefore reality must comply."

[SeJam]

So glad I was recommended this channel.

[antonius]

The "multiverse" seems me to be a good metapher for human understanding: Any human being lives in the center of its own perspective on the world. We are capable to understand each other, if we are told about another perspective, but we cannot really share it.

[susanne]

By definition: if a theory only explains properties or behaviour but cannot come up with falsifiable predictions about properties or behaviour it is not science.

The different theories of multiverse are a fascinating playground for the mind. But can they deliver predictions?

[jeffryphillipsburns]

I don’t know that I would lump the last two “theories” (scare quotes because I would call them, rather, speculative fancies) in with the multi-verse notion. It seems to me that neither requires other universes, although the possibility of other universes is inherent, I suppose in each. I first encountered an intimation of the video-game simulation fancy in the eighties in a book called “The Recursive Universe”. It’s now out of print, but your library may have a copy. I recommend it.

[CheapHomeTech]

Alright, in one day the subscriber count has gone from 3.8 to 3.9! This channel is so much fun I'm sure it will get into the millions!!!

[garygough]

Relativity would seem to have it's own multiverse, in as much as a moving object has it's own boundary that it can react with. But that would be largely shared with nearby objects. I do wonder if it would cause observable effects.

[BANKO]

There is an additional theory by Roger Penrose, which is fascinating. He thinks that the big bang recurs when the universe degenerates into energy without matter because at that point, there is no way that the universe knows its own size. (It's a bit more complicated than that).

[alphaomega]

1. Eternal Inflation should be called Internal Inflation -- where the bubble universes are allowed to expand in this void space as it cools (as mass separation occurs - where the emf of the object observed denotes the lowest speed available).


2. The String Theory Landscape should be called The Internal Clock of The Universe - where each universe is no more than a different channel (tuned to a different frequency) contained in one time-space volume (similar to your television set or radio box would allow you to do).


3. Many Worlds (QM version of ST) is very much similar to an Internal Clock. However: it does not make complete universes like String Theory. There is many disconnect promises and shifting alliances to form an agreement. Its predictive power is more realistic than most because it allows for a change of mind (individual systems becoming one to save on time to see what it wants - thus destroying other effects that could have occurred). String Theory is given less energy in our universe and thus we can't see its existence (E=MC^2 or at least 10% of it -- sadly, it seems to really be C^36 to actually accept every universe connected to our own).


4. & 5. Are really the same thing? The Simulation Hypothesis & The Mathematical Universe are self-contained. They can easily be created. That isn't science fiction. That is currently an observable fact with our current technology and formulas. We will improve despite any alien intervention and inhabit such many worlds. We will be known as gods to those there. That is our destiny. That is our fate. We imagined it. We will make it be so.

[Supernobody]

Anyone remember those pics of the Milkyway galaxy we saw in our textbooks? Who took those pictures? If they're paintings, how did anyone know what the galaxy looked like? The view depicted is from 10s of millions of miles outside the galaxy. There had been no claims of a space vehicle that could travel that far out. Those depictions of the galaxy haven't changed over the decades. All of the pics you see today in magazines and textbooks are artistic paintings and computer generated composites. The Hubel telescope doesn't take color photos either.

[mauro]

Hi Sabine! I really would like to know someone as you :)
I’ve been watching your videos all day, learn a lot, and been mesmerized by you. You are wonderful, have a wonderful life!

[tom-kzpb]

There are universal physical constants that not only seem arbitrary, but seem "fine-tuned" to support life. If you altered them a little, molecules would not coalesce, etc. In one book that I read, the main thesis was that the "fine tuning " was so improbable, that it had to be "planned" and that we humans were "meant" to be here. I.e, basically arguing for something akin to "God". While this was beguiling at first, I concluded that it was B.S. It would be contradictory for such an amazing intelligence and power to also produce such a troubled and capricious world. So what then accounts for the fine-tuning? The most convincing explanation seems to be multiverse and anthropic principle. Many laws of physics and physical constants generated. Only the ones that can support life will have sentient beings to contemplate their physical laws.

It would be nice to have a way to test this, experimentally. It is not a failing of the spirit of scientific method as long as we keep aspiring to do that someday. But it is not our fault if that proves to be impractical or impossible. This may be as far as we can ever go in our understanding. The only failing would be to become overly dogmatic and confident in something that is unprovable. By the same token, it would be a mistake to become overly dogmatic in rejecting multiverse as merely a "religion".

[sergeynovikov]

clever and clear explanations of the deep problems concerning modern science in a concentrated brief form. thanks, Sabine, for your nice videos)

[paulotex]

Love the babies in the background. Physics and babies/small children go well together ;-)

[wayneedward]

This has been my thoughts for many years now... totally explains the constant expansion theory.