|There are many constants and physical values in the universe which are just right for life to exist, but which are improbable if they came about by chance.
For example, if the protons in atoms were a mere 0.2 percent more massive than they are, their instability would cause them to decay into simpler particles, and hence atoms would not exist.[ask 5]
Or if the Earth was much further from or closer to the sun, water would freeze or boil. We are just the right distance from the sun.[ask 6]
To some extent, these "just right" values can be explained by the anthropic principle (the values are just right where we are, because if they weren't we wouldn't be here).
That is, there may be a range of environments with different sets of physical values, and it is to be expected that we would exist in the environment that is suited to our existence.
However, the anthropic principle is inadequate to dismiss the argument from fine tuning.
Some of the constants and values apply across the universe, i.e. there is not a range of values from which to choose, but just one value.
Yet the anthropic principle assumes a range of values.
Some people try and get around this problem by proposing that there are multiple universes, each with its own set of constants and physical values.
However, this proposes something for which there is no evidence, and for which there can never be any evidence, and it is therefore unscientific, yet this argument is mainly used by people who reject God as an explanation because He is not able to be tested scientifically.
The argument from fine tuning is so strong that a number of philosophers have argued that the only answer to it is the multiverse theory.[ask 7]
"There are many ... examples of the universe’s life-friendly properties—so many, in fact, that physicists can’t dismiss them all as mere accidents." —Tim Folger[ask 8]
||What does "Yet the anthropic principle assumes a range of values. " mean? It is utterly incomprehensible.
Assuming this relates to the distance of the Earth from the Sun, Earth's orbit is elliptical and the distance of the Earth from the Sun varies from approximately 86 million to 94 million miles on any given year. Every star has a "habitable zone" that is affected by the size of the star and its intensity. The Sun's habitable zone is approximately 0.95 astronomical units (AU) to 1.37 AU. An AU is the Earth's average distance from the Sun, or approximately 93,000,000 miles. Therefore the Earth's orbit could decrease by 4,500,000 miles, or increase by 34,000,000 miles and still be within the habitable zone. With an inhabitable range of roughly 38,500,000 miles it can hardly be said that there is but "a single value from which to choose" but an extremely wide range of values which provide for life as we know it.
Furthermore, specific points about the position of the Earth, etc., ignore the fact that there are some 100 billion galaxies in the universe, each containing millions to trillions of stars, and it is entirely reasonable to posit that among all those, at least one star-system would have a planet capable of supporting life as we know it.
The argument assumes that all possible universes had an equal probability of arising and that life as we know it is the only possible form of life, both of which require additional support that is not provided. Imagining a large number of hypothetical, alternative universes does not indicate anything about the universe we are in. (An analogy would be to ask what is the probability of your car being red if there are a lot of other blue cars!) Notably, the range of the constants (0.2%) is largely irrelevant to the argument.
Furthermore, the argument for fine tuning only works if you simplistically assume that you can only change one constant at a time. If you experiment with changing various constants simultaneously then various universes become possible.[rw 2]
Finally, arguing that an event could not have occurred because it was highly improbable that it could occur is very fallacious; one could use the same logic to argue that no one ever wins the lottery. And in the particular case of the universe's constants, even arguing that it is "highly improbable" that the constants should be exactly right is a stretch; we know little to nothing about the possible range of values into which these constants could fall (only having observed them in one configuration) and it could very well be a dead certainty that the constants were to take the values they did. Even if the universe is improbable, it is not clear why God creating it is the best option.