I just want to do a quick post here so I won’t go into too much detail or include all arguments.
There seems to be some sort of wired-in expectation that things should be more or less symmetrical. Let’s not get too into supersymmetry here – though I should point out that the supersymmetry theory (SUSY) took a hit recently from results at the LHC. BSmeson decay was set to one in every 300 million Bsmesons, close to what the standard model predicts. Those of you that are more science savvy will probably understand why this is a hit to SUSY but basically it’s like god of gaps argument. It is an ever-receding range of likelihood; if BSmeson decay ends up being the rate predicted by the standard model, there’s no space for SUSY any more. As I said above, one in 300 million is getting pretty close, so the possibility of SUSY being successful just got smaller.
Anyway, back on topic. We seem to think things should be basically symmetrical. You can see this on a spiritual scale, with the concept of karma. There’s even that sort of mentality where if you’ve done something wrong, you can assuage your guilt through good deeds (altruism). On a more scientific note, people have an expectation that the universe is perfectly balanced. Everything was “perfect” because if it wasn’t, the universe wouldn’t have formed the way it did. Everything was “perfect” for the conditions of life. We can get a little more technical and even claim the universe is perfectly “even”, as shown by the cosmological principle which suggests homogeneity.
Let’s take a look at this assumption of “perfect balance”. Well, first of all, people often quote homogeneity wrong. The universe is not completely even, nor symmetrical. That much would be obvious if you actually put some thought into it yourself instead of quoting homogeneity. The average density (as well as other factors) of the universe is the same no matter where you look, but it’s not completely uniform.
Next up, the matter-antimatter imbalance. People are often asking “if antimatter exists, where is it all?” or “how come we live on planets made of matter instead of antimatter?”. Well, let me put to rest any doubts you have about the existence of antimatter. It is real, and created on a daily basis at facilities such as the LHC. As for the imbalance? The leading theory is CP violation. Again, I don’t want to get too deep into another theory but basically CP symmetry postulates that all negative equivalents of particles should have the exact same properties (but reversed) as their positive counterparts. CP violation (or CP symmetry violation) is basically the violation of that rule. There’s quite a lot of evidence for CP violation and it can be reproduced in experiments to show that antiparticles do not, in fact, replicate their positive counterparts. Specific to the matter-antimatter imbalance is the fact that antimatter has a much shorter decay rate. Basically, it disappears faster than matter does, which is why we’re left with a predominantly matter filled universe (though I do have some evidence that could suggest antimatter clusters; I’ll save that for another post).
Finally, let’s go to the very beginning. After the Big Bang spread a cloud of cosmic gas, gravity acted to cause these to cluster and form stellar bodies. But think about it for a second. If this matter were spread perfectly evenly throughout the universe, then gravity would act on each individual particle with the exact same force in every direction. There could be no formation of anything unless there was an imbalance, an imperfection in this uniformity.
The reality? Our universe was born imperfect, and that’s why we exist today.