- There are up to 25 'fundamental' parameters of the universe, like the strength of gravity or the strength of the charge of the electron, and if any one of them were even slightly different, the universe would be radically different and life as we know it would never have existed.
- Wikipedia, Fine-tuned Universe
- The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can occur only when certain universal dimensionless physical constants lie within a very narrow range, so that if any of several fundamental constants were only slightly different, the Universe would be unlikely to be conducive to the establishment and development of matter, astronomical structures, elemental diversity, or life as it is understood…
- A small change in several of the dimensionless physical constants would make the Universe radically different. As Stephen Hawking has noted, "The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron. ... The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life."
- If, for example, the strong nuclear force were 2% stronger than it is (for example, if the coupling constant representing its strength were 2% larger), while the other constants were left unchanged, diprotons would be stable; according to physicist Paul Davies, hydrogen would fuse into them instead of deuterium and helium.[9] This would drastically alter the physics of stars, and presumably preclude the existence of life similar to what we observe on Earth. The existence of the diproton would short-circuit the slow fusion of hydrogen into deuterium. Hydrogen would fuse so easily that it is likely that all of the Universe's hydrogen would be consumed in the first few minutes after the Big Bang.[9] This "diproton argument" is disputed by other physicists, who calculate that as long as the increase in strength is less than 50%, stellar fusion could occur despite the existence of stable diprotons.
- The precise formulation of the idea is made difficult by the fact that physicists do not yet know how many independent physical constants there are. The current standard model of particle physics has 25 freely adjustable parameters with an additional parameter, the cosmological constant, for gravitation.
- One explanation for the extraordinary position we find ourselves in, therefore, is that our universe may be just one of many within a 'multiverse', each having different properties and the vast majority being devoid of life. The precise 'fine-tuning' of the properties of our universe, therefore, may have been arrived at through a cosmic trial-and-error of mind-boggling scope.
- Imagine a universe where gravity was just a bit stronger, and you have an entire universe embroiled by plagues of ever-growing black holes that battle to consume each other. It would be forever in pitch darkness, having never been lit by stars or galaxies.