The Multiverse Hypothesis Explained by Brian Greene

what is the multiverse   can modern physics reveal the deep mysteries  of the nature of reality [Music] or realities if there are multiple universes does it really  mean there are infinite worlds where you   already know the answer to this question the word universe meant everything the totality  every star every galaxy of the whole shebang   so what sense could there possibly be in having  more than one everything and what we have found   in research that actually dates back a number of  decades but most vigorously relatively recently   is that our mathematical investigations are  suggesting that what we have thought to be   everything may actually be a tiny  part of a much grander cosmos   and that grander cosmos can contain other  realms that seem to rightly be called universe   just as our realm has been called universe  which means that you have many universes   multiple universes which we  call them multiverse [Music]   physicist sean carroll claimed that our universe  would have to be in an isolated island universe   in order for it to not interact with other  universes otherwise our universe would be   affected by the ripples from bubbles of another  universe that it bumps into as it passes by   multiverse models are problematic because they  cannot explain why the big bang happened at all   or why the laws of physics are as they are today  which seems to follow from mathematical constants   so how can you gain confidence in an idea that  speaks of realms that we can't see that we can't   touch we can't visit we can't observe directly  in some versions of the multiverse there can be   subtle connections between the universes that  might allow us to have some experimental window   onto them but hold that to the side for the  moment let's think about the ones where you   couldn't visit them well why do we think about  these things well we have a belief founded upon   really hundreds of years of experience that math  can provide a gateway to reality it can provide   a window onto a reality that at the moment  the math is being done we can't actually   see or observe that reality i mean einstein is the  greatest example right he wrote down his equations   of the general theory of relativity way back  1915 others looked at those equations and found   that they seemed to say the universe should be  expanding the math said the universe is expanding   einstein himself said no i don't actually believe  that but 12 years later observations show the   universe is expanding the math was confirmed by  observations other examples are black holes again   einstein's math gives rise to them einstein  didn't believe it observations now show that   there are black holes so we're following in that  tradition we are doing mathematical equations   following them and as we can discuss in some  specific cases they are leading us root by root   to the possibility that ours is only one universe  does that mean the math is right we don't know it   has to be confirmed ultimately through some  kind of observation or experiment but the   possibility that the math is revealing this new  picture of reality is sufficiently compelling   that many physicists including me are taking  it seriously and investigating it vigorously the concept of multiple universes depends on  the conception of reality as a four-dimensional   space-time continuum which everything that  could possibly happen does happen in some   universe it is often misinterpreted as implying  there exists many copies of you and indeed there   are different possible versions or replicas of  you in other universes similar to how different   possible ways for you to watch this video can be  imagined as occurring in parallel worlds however   this idea is more easily understood by  considering non-trivial quantum mechanics examples   such as schrodinger's cat schrodinger's cat  can simultaneously both be alive and dead   but such states are never observed because they  do not remain stable instead superpositions or   coherence between classical states break down into  one state or another collapse of the wave function   by interaction with their environment  following this example since the cat is   neither alive or dead it is reasonable to say  that it is in a quantum superposition of both   states however if we assume the many world  interpretation of quantum mechanics is correct   all quantum coherent superpositions including  those of schrodinger's cat exist as real physical   entities in distinct parallel universes  in which every possible outcome happens   and if we consider an electron that can have  two different spins at the same time then   this means there are actually two electrons  with two different spins simultaneously on   spin-up electron and one spin down electron  in distinct separate parallel universes   in some interpretations of quantum mechanics  this interpretation further implies that all   possibilities are realized subsequently every  possible outcome will happen in a parallel   universe thus there will be an infinite number  of universes that exist containing duplicates of   every physically possible circumstance by  mathematical investigation to imagine the   earth is not the center and then others using  similar kinds of reasoning noted that the sun   is actually not the center either and then similar  mathematical reasoning showed us that our galaxy   is not the center it's one of many many galaxies  we've gone through a sequence of if you will   cosmic demotions we may be on the threshold of the  next emotion by following exactly the same pattern   earth is not the center sun is not the  center galaxy is not the center our universe   may not be the center it may be one of many  universes following exactly the same pattern the multiverse hypothesis has been criticized  for a number of reasons some physicists claim   that the multiverse hypothesis is not falsifiable  and therefore not scientific in response defenders   claim that the multiverse is testable and some  suggest it may be more scientific than certain   other untestable theories some proponents of  the theory say there are an infinite number of   conceivable universes however cosmologists such as  max tegmark argue that only universes with matter   could be realized according to quantum mechanics  universes without any classical space and time   idealized to sets of quantum wave functions cannot  be directly observed as they do not interact with   anything in our universe and would have no  effect on future events in our universe the   american theoretical physicist and string theorist  brian greene discussed nine types of multiverses the quilted multiverse works  only in an infinite universe   with an infinite amount of space every possible  event will occur an infinite number of times   however the speed of light prevents us from  being aware of these other identical areas   the inflationary multiverse is composed of  various pockets in which inflation fields collapse   and form new universes the brain multiverse  version postulates that our entire universe   exists on a membrane or brain which floats in a  higher dimension or bulk in this bulk there are   other membranes with their own universes these  universes can interact with one another and when   they collide the violence and energy produced  is more than enough to give rise to a big bang   the brains float or drift near each other in  the bulk and every few trillion years attracted   by gravity or some of the force we do not yet  understand collide and bang into each other this   repeated contact gives rise to multiple or cyclic  big bangs the cyclic multiverse has multiple   brains that have collided causing big bangs the  universes bounce back and pass through time until   they are pulled back together and again collide  destroying the old contents and creating them anew the landscape multiverse relies  on string theory's manifold spaces   quantum fluctuations drop the  shapes to a lower energy field   creating a pocket with a set of laws  different from that of the surrounding space the quantum multiverse creates a new  universe when a diversion in events   occurs as in the many worlds  interpretation of quantum mechanics the holographic multiverse is derived from  the theory that the surface area of a space   can encode the contents of  the volume of the region the simulated multiverse exists on complex  computer systems that simulate entire universes the alternate multiverse contains every  mathematically possible universe under   different laws of physics in several theories  there is also a series of infinite self-sustaining   cycles for example an eternity of big bangs  big crunches and big freezers a multiverse of a   somewhat different kind has been envisaged within  string theory and its higher dimensional extension   m theory these theories require the presence  of 10 or 11 space-time dimensions respectively   the extra six or seven dimensions may either  be on a very small scale or our universe may   simply be located on a dynamical d3 brain  this opens up the possibility that there are   other brains which could support other universes  but we will discuss these theories extensively   in another video thanks for watching did you like  this video then show your support by subscribing   ringing the bell and enabling notifications  to never miss videos like [Music] this you

Channel: Science Time

Views: 417,788

Keywords: the multiverse, multiverse, the multiverse hypothesis, the multiverse hypothesis explained by brian greene, brian greene, string theory, m theory, universe, parallel universe, multiple dimensions, cosmos, multiverse theory, science, science time

Id: GzPqDVU9nCg

Length: 11min 4sec (664 seconds)

Published: Sat Jan 23 2021