DISCLAIMER: This is a very simplified version of M-theory, because if anyone truly understands it, their minds will implode. Cheers!
For a very long time, humans have tried decoding the secrets of the universe. It started with the Big Bang and proceeded to get very complicated thereafter. There are currently 4 forces that govern the laws of physics: these are gravity, the strong nuclear force, the weak nuclear force and electromagnetic force. However, there was a time when all of these were one extremely powerful force, and that time was the instant (give or take one millionth of a millionth of a second) of the Big Bang.
Now, these forces are considered irreconcilable, as the mathematics behind them is as different as iOS and Android. Attempts to reconcile them have resulted in one prevalent theory: string theory. String theory introduces the contribution of external dimensions that humans cannot process and equates them to strings. These strings interact with each other to influence space and time without us being able to notice. Bringing in these extra dimensions allows us to decode the nonsensical math that we get when trying to mix general relativity and quantum mechanics. However, the thing with extra dimensions is that they don’t have a testable hypothesis. How can you experiment with something that doesn’t interact with…anything?
Et voila, enter M-theory. This theory uses the concept of string theory but takes it to an even more complicated level and talks about the use of objects known as “branes” and “D-branes” to describe it. M-theory described at low energies consists of 11 dimensions lying in supergravity. It focuses on “compactifying” its 11 dimensions (that we can’t even think about processing) to our known 4 dimensions (x, y, z and time). By doing this, it opens up avenues of experimentation which will lead us one step closer to understanding the true nature of the cosmological behemoth that is our universe.