Disclaimer
I am not a physicist!
Remember: the outcomes this app selects are as random as random gets! Use with caution.
FAQ
How does it work?
It assumes the Everett (aka "Many Worlds") intepretation of Quantum Mechanics. Many physicists subscribe to this interpretation but it's not universally accepted.
Basically I just periodically retrieve a chunk of randomness from the quantum random number generator provided by Australian National University and then use that to select one of the outcomes in proportion to the number of universes you chose for that outcome.
My understanding is that the quantum randomness will effectively be different in different branches of the universe and so each branch will see a different outcome.
So technically the universe is already split as soon as the quantum randomness is sampled. The point of this app is to "amplify" the quantum randomness to the level of something meaninful so you can decide to do different things in different universes.
Which branch of the universe do you end up in?
You will end up in all of them! According to the Everett interpretation, you are a quantum system because you're made up of quantum systems and so you (your body, your brain, your consciousness) will split into many copies along with the rest of the universe.
Subjectively, it will seem like one of the outcomes happened at random but this is just because your memory and experience was split. This is related to "self-locating uncertainty".
Do I have to do whatever it says?
No! Think of it like a magic 8 ball. The universe is split regardless of whether you actually perform whatever action you input.
Is the Many Worlds / Evertt Interpretation correct?
I think it is and I think a majority of physicists who work in relevant fields now agree on this (citation needed).
For many years we suffered under the Copenhagen Interpretation. That's probably the one you've heard of about the "wave function collapse". Everett gets rid of the concept of wave function collapse (for which there is no evidence).
How is this different from a coin toss?
When you toss a coin the outcome is pretty easy to deterimine if you know the exact position and forces involved. So doing this does not cause the universe to branch: only one outcome ever happens.
Quantum randmess is truly random: unpredictable in principle. But this "randomness" is really just an instance of self-locating uncertainty from your perspective. There is nothing non-deterministic going on (unlike in the Copenhagen Interpretation).
How do I know that the other branches are real?
They are predicted by our best theory of how the world works at a fundamental level, the basis for most 20th century technology. You cannot accept a scientific theory without accepting all its consequences!
It is important to note that the Everett interpretation does not start off assuming the existence of the other branches. They "fall out" as a natural consequence of the math. Pretending that they don't really exist is just a kind of existential chauvinism, in my opinion.
Can I send a message to myself in the other universe?
No. The splitting process (called decoherence) is one-way. There is no way to interact with the other branches or for them to influence one another that we know of.
Why did you make this?
A few reasons really: I struggle with indecisiveness and I've been using the original paid Universe Splitter app for a while to help me make some decisions with less anxiety. I wanted a version that allows me to change the probabilities of each outcome. I also wanted to make something that anyone could use for free because the multiverse belongs to us all.
At a deeper level, it's difficult to put into words how profoundly the many worlds idea has affected my outlook on life. This is one example. I hope to write more about this in the future.
But what is really going on?
When we use words like "universe", "split" etc. these are all approximations to the underlying mathematic model.
It is "kind of like" there are multiple classical universes that split and from your perspective (pre-split) you can think of the probabilities as the chance of you ending up in each branch.
But, really
there are no separate universes
there is no "you"
there's just wave
function.
Media
My introduction to this idea was David Deutsch's the Fabric of Reality and I highly recommend this book.
Sean Carrol on Closer to Truth
This website is open source on GitHub
Do you store the outcomes of the split?
Nothing you enter into this site is sent to the server at all. So no, there is no way for me to even know what you entered let alone store it.
This app does not use cookies or local storage.
Is this a quantum computer?
No. Quantum random numbers are pretty easy to generate with the right hardware because the world around us is quantum at a fundamental level so you just need to be able to measure these miniscule fluctuations. Most computers do not have hardware to do this, so we rely on an randomness provided by ANU here: https://qrng.anu.edu.au/
Is there a native iPhone/Android app?
Not right now. On iPhones, you can install this to your home screen by clicking the "Share" button in Safari and selecting "Add to Home Screen", like this. There is probably something analogous in Android/Chrome but I don't know how to do it there.
I do have a native Apple Watch app that is in private beta. See contact details below if you would like to try it out.
How do I get in touch?
Feel free to file issues on GitHub for feature requests or bugs.