It is hardly controversial that life on earth requires a shocking fine tuning of several fundamental constants of nature. Had this been just a little different, we would never have been here.
Take for example, the strength of gravity. It is trillionth of trillionth times weaker than the electromagnetic force, which holds together the particles that form atoms, molecules, and all of our everyday world. If gravity were only a few orders of magnitude stronger, stars are pressed together and die so fast that evolution would not have enough time to develop more complex forms. Gravity would crush everything that’s as big as we are. If that is weaker just a fraction no matter will composed in to a plants, stars and galaxies..
Similar to the gravitational constant, cosmological constant also in the sharp edge. However there are other physical constants and rules spread among the laws of physics that so interrelated and shows us some fine-tuning happened prior to emerge the life forms on earth.
The list of how clever nature is arranged can be much longer, and according to some researchers, this fine-tuning of the constants only be explained by the anthropic principle: they are exactly those that we are to live here. Our universe is set up for life.
Actually, the reasoning is not entirely convincing anyway. If we imagine that we had seen our universe when it was one second old and were familiar with all the laws of nature, we would probably have said that based on the current state it is completely no chance to achieve galaxies, stars, heavy elements, planets, for not to mention life.
– One says that the world must be established in a certain way based on the fundamental properties of natural laws. The second is that there may be other aspects of the world that not all can be explained in this way, and then decides instead to chance and the environment if we can exist.
The solution would then be in a multiverse, a giant collection of different universes that exist simultaneously. The physicists are talking about several different types of multiverse, parallel worlds, if you will, depending on what mechanisms you imagine leading to them.