A solar eclipse is a rare and awe-inspiring event: within the path of the Moon’s shadow day becomes night, and a black circle in the sky is ringed by a golden halo. Did you watch August’s eclipse and think, “Isn’t it amazing that the Moon is just the right size and distance from Earth to exactly block the sun?” The sun is roughly 400 times bigger than the Moon but also about 400 times farther away. Coincidence? Well, millions of years ago the Moon was closer to Earth and would have blocked out much more, and millions of years from now it’ll be too far away to block the sun completely, so we’re lucky to be around at just the right time to see this phenomenon. Or was it planned for us?
[Just as a side note: without the Moon (and such a large one) the Earth would rotate much faster (giving us 6 – 8-hour days), be much flatter at the poles, get hit by many more meteors, and have an axial tilt that might change radically from time to time, drastically altering our seasons (I can’t even wrap my head around the kind of seasons we might get if Earth rolled horizontally on its axis like a barrel in water!) It’s very possible that humans wouldn’t have survived without it. Thanks, Moon!]
If the precise sizes and distances that provide a solar eclipse were arranged by someone, it was nice of them to provide such an extravaganza for our viewing pleasure. But there are many more “cosmic coincidences” that have a greater impact on our well being. Without them, life as we know it wouldn’t exist at all. They’ve led scientists to say that we live in a “fine-tuned universe”. (Although it is slanted toward religious faith, this video provides a succinct overview.)
All matter in the universe is governed by four main forces: gravity, the electromagnetic force, and the so-called weak and strong nuclear forces that dictate the actions of sub-atomic particles. If the force of gravity had been just the tiniest bit weaker than it is, the kind of stars needed to support life couldn’t have formed. If the ratio of gravity to the electromagnetic force was any different, either planets wouldn’t form, or supernovae wouldn’t happen and there would be no carbon or heavier elements (so no carbon-based life like us).
If the nuclear forces were just the slightest bit different, the universe might be filled with only hydrogen—nothing heavier—or there might be almost no hydrogen at all, meaning no fuel for suns to burn.
If the mass of neutrons and protons were not precisely as they are, all protons would have decayed into neutrons soon after the Big Bang, and no complex atoms could have formed.
If the Big Bang had created equal amounts of matter and antimatter, all such particles would have cancelled each other out, leaving nothing behind.
If the universe had contained only a tiny fraction more matter than it does, it would have collapsed back into itself before life could form; any less matter and it would have expanded much too quickly for matter to condense into stars and planets (let alone people).
If any one of these, and many other characteristics of the cosmos, was not exactly as it currently is, the universe as we know it wouldn’t exist. We wouldn’t exist.
The odds that everything could turn out this way by pure chance are so astronomically small as to be unimaginable. There are simply too many factors involved and the precision required of each one of them is mind-boggling. So what gives?
There are a few possibilities. Some claim that the universe has to have an intelligent, conscious observer in order to exist, so it simply had to be exactly the way it is (this is known as the anthropic principle).
If you accept the concept of the multiverse (see my blog post about it here) then in an infinite number of possible universes there was bound to be one with the conditions just as we see them, and we happen to exist in that one.
There are also many people who believe that the cosmic coincidences are proof of intelligent design—that some being very carefully created the universe exactly the way it is, presumably to produce intelligent life like us. That being might be God (which always prompts sceptics to ask who fine-tuned God’s universe to produce Him?) Or it could be aliens from another dimension. Or maybe intelligent beings from an earlier version of the universe before the Big Bang. From a science fiction writer’s point of view, it’s a great workout for the brain to imagine universes where something is different, and the kind of life that might exist there (intelligent gas clouds, or living sunbeams?) It’s also a lot of fun to speculate about who did the designing, and how. Think of how many choices had to be made! Picture super-intelligent beings debating about whether to base life on carbon or silicon, or even metal. About whether intelligence should arise in flesh-and-blood animals or plant life or rocks?
Maybe the universe was designed by a committee.
No wonder it’s taken so long to get where we are!