# What is the difference and/or similarity between multiple universes in inflation and in quantumphysics? [duplicate]

Some theories propose that there are more universes.

In one of them it is said that there are parallel universes, due to inflations after the big bang that created them.

But in the two-slit experiment is also known the multiverses theorie. The probability wave is not collapsing but each possibility is creating a universe on his own.

So they both speak about other universes. But is there a link between them? Or are that just completely different things/theories?

## marked as duplicate by ACuriousMind♦, CuriousOne, unsym, user36790, Qmechanic♦ quantum-mechanics StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); May 5 '16 at 7:50

• The link is that neither of those theories has anything to do with actual physics or the real world. – AccidentalFourierTransform May 4 '16 at 15:02
• I believe that Max Tegmark considers them being qualitatively different (and perhaps both 'real'), but part of a single theory. space.mit.edu/home/tegmark/home.html and internationalskeptics.com/forums/showthread.php?p=9864224#2462 – Keep these mind May 4 '16 at 15:09
• If I recall correctly the inflationary ones are just too far apart for them to be observable from the others... And perhaps that there are so many of them, that some/any of them must have practical twins?! (Maybe I'm just making this up.) – Keep these mind May 4 '16 at 15:29
• Define "parallel universe" without philosophical waffling, please. – ACuriousMind May 4 '16 at 16:39
• At this point you can throw every book and text that mentions "parallel universe" into the recycling bin. It was a waste of paper to print it. – CuriousOne May 4 '16 at 22:50

The inflationary theory you mention is probably eternal inflation. In this theory there is just one universe but different parts of it are causally disconnected i.e. the different parts cannot affect each other in any way. Whether these constitute a multiverse comes down to terminology. In principle there is a continuous spacelike straight line that links any two points in the multiverse, so I would not describe this as separate universes.

The theory you mention in connection to the two slits experiment is the many worlds interpretation of quantum mechanics. However the physical reality of the many worlds is a contentious issue. So once again whether this really counts as multiple universes is a matter of opinion.