Is our reality really real?

You’re on your way to work. As you’re running late, you gas on the approach to the highway to win some time. As you’re about to connect to the highway, you see a truck on your left side. The moment later you are dead. You cross break but it’s too late. You see the panic in the driver’s eyes as the time slows down, and your life is passing by. The headlights blind you as the sound from the cars ripping each other apart howls in your ears. The last thought ringing in your head “this must be a nightmare”. But sadly something tells you nothing has ever been more real.

But how could you be sure it wasn’t a dream? What would have happened if a window had been opened in the right corner of your eye the moment before? “Do you want to gas without looking for others?” followed by two buttons with the text “Continue” and “Cancel” on. Or if you felt your body and soul were travelling to another universe? If so, we would live in a The Matrix-alike simulation or in a parallel universe among many other universes. How can we tell what is real, and if the reality is real? The short answer is we can’t. The full answer doesn’t exist. Although this seems very confusing at first, I’m sure everyone has come in contact with the term reality at some point in their life. And in this context I’m pointing at how our brains perceive the world. Well now you probably think: is she out of her mind? Of course it’s real! What could be more real than a several tons heavy truck? [1]

OUR PLACE IN SPACE

In the human history there are two huge things we have misunderstood. How big our world is, and the power of the human mind to understand and visualise our cosmos. The first thing we can easily put up. The first humans didn’t have much to go on, even though nothing was written down we can say they had the seasons, stars, sun etc. that told them what the world looked like. Later on we had significant tools to help us understand the earth. Our famous Christopher Columbus believed the earth was round even though the conception of the world at that time was it was flat. Now we know Columbus was right all along. My point is that the human minds view of our world has changed a lot during history. So why should our cosmos be the only one existing when our sight of our world constantly expands?[2]

SIMULATION

Like I mentioned before there is a possibility that we are living in a computer simulation like Neo in The Matrix. This theory is not really connected with the multiverse hierarchy but I still believe it is something interesting and therefore I’m going to discuss it shortly. The theory that we are living in a computer simulation is something the most of us connect with science-fiction. It’s based on that it is our brains that put every individuals' reality. Therefore, we will never be able to tell what our real world actually looks like, which is directly connected to real science (see last paragraph in the introduction).

The strongest argument here I would say is we are extremely close to build an AGI (artificial general intelligence), a computer smarter than us. Here we are talking about just a few decades, if not less. Those who believe in this theory, argue that if we can build a genius computer, we could just as much live in one. [3]

OVERALL THINKING

Research around multiverses are something we cannot survey enough to get an answer because the science around it is just theoretical physics. It means we (for the moment) don’t have the ability to do physical experiment to prove our world is a multiverse (many worlds) and not a universe (one world). [4]

There are four different multiverse theories that we will have a closer look upon in this text (except for the computer simulation theory). 1: Since we cannot be sure what space-time really is, there is a possibility it is flat and infinite. This would mean there could be other universes out there(multiverse level I). 2: Based on eternal inflation, where some areas in space keep getting bigger while others stop inflating. This is where the bubble-multiverse-theory is from (multiverse level II). 3: The third theory is based on the quantum physics (how subatomic particles behave). Also, based on the law of probability which means for all possible outcomes there is a bunch of worlds (multiverse level III). 4: The professor of physics Max Tegmark's own theory where everything is mathematical structures. “A mathematical structure is something that you can describe in a way that's completely independent of human baggage”. This is a good argument since it would mean we humans aren't the only meaning in space (multiverse level IV). [5][6][7]

MULTIVERSE LEVEL I - TWINS

Multiverse level I is probably the easiest to understand. The theory here argues that if the Big Bang started with a period of inflationary growth, there would be a multitude of universes a lot like ours with the only difference that these have other arrangements of matter. These regions have another “beginning” (like our cosmos started with Big Bang) but the same laws and constants in physics. [8]

Like I mentioned earlier we cannot know for sure if any of these theories are true or not. But according to the cosmological inflation our universe had a short time(about 10−36 seconds after the Big Bang to between 10−33 and 10−32 seconds after) expanding extremely fast. The expansion has continued since then but with a considerable lower speed (this is what we hear about when people say the space is growing constantly). [9][10] This confirms half of the statement that if given infinitive space there would be an endless number of universes. This including an identical Hubble volume should exist around 10^(10^115) metres away from us, and an copy of yourself about 10^(10^29)metres away. The last part is the one we cannot prove to be wrong or right at all, since information cannot reproduce itself faster than the speed of light (Einsteins relative theories). [11]

MULTIVERSE LEVEL II - BUBBLES

Level II also argues there is an endless amount of worlds, but here each universe exists in a bubble separated the others. [12]

This theory is based on cosmological observations and shows how some places in space have stopped their inflation, while others are constantly growing bigger - which creates bubbles in space-time. This is called the chaotic inflation theory and could also be the evidence why other universes could have different laws in physics. This could in turn be used as explanation for why we cannot notice or reach these regions. The other big reason why we cannot reach these places, is because the space between us and the other universes is expanding faster than the speed of light (based on Einstein's relative theories and the chaotic inflation theory). [13][14]

MULTIVERSE LEVEL III - THE MANY WORLDS OF QUANTUM MECHANICS

Multiverse level 3 is a theory based on quantum mechanics, and thereby also known as a quantumverse. Since the multiverse level III is the same universe from the beginning spitted, there would be the same laws of physics unlike the level I and II multiverse. If we assume for a moment that we are living in a multiverse level III, our world should separate itself for each events consequences which would mean we have an unlimited amount of universities. This should also mean that all living things never were born and simultaneously are immortal. [15][16]

Back to the car crash. You didn’t die, not everywhere. Because like I said the level III multiverse is splitted for each events consequences, there is this world you died in, one you got injured and died on the hospital, one you survived with help from the doctors, one you looked for other cars and didn’t die etc. [17]

The theory is like I said based on quantum mechanics and is about a hundred years old today (of course it has developed but the evidence is the same). The thing about a level III multiverse is the position of the universe isn’t given in classical terms. Instead, its position is talked about as a wave function. This wave function is according to the Schrödinger equation answering to a rotation in Hilbert Space (an abstract vector space possessing the structure of an inner product that can measure length and angle). [18][19][20]

MULTIVERSE LEVEL IV - A MATHEMATICAL STRUCTURE

Max Tegmark, one of my favourite professors and scientists, believe everything is math. That our worlds are equations which together forms our living. This is multiverse level IV. In the level IV multiverse the laws of physics are different from ours. His biggest evidence for this is the mathematical democracy principle: “Any universe that is mathematically possible has equal possibility of actually existing”. However, Jürgen Schmidhuber - who is strongly against this theory - argues our own set of mathematical structures aren’t too well-defined to be true, which means it is more likely we are living in a computer simulation. [21][22]

If the level IV multiverse is our real reality, this should also give an answer on the Wheeler/Hawking question “Why these equations, not others?” since this theory would make other equations possible. I would say multiverse level IV has evidence from level III. Multiverse level III has a world for each events consequences based on the Schrödinger equation. [23][24] I mean that this theory combined with the probability theory could be put together like this: “Since there is a possibility for each event and its consequences, there would always be another world for the different outcomes”. This would imply we have a world for each possible mathematical set. And since level IV has an unlimited