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Why is Everything in the Universe Just Right?

December 13, 2014

It shouldn’t be possible for us to exist. But we do. That’s the sort of puzzle I like exploring. So I will. Let’s start with the so-called ‘Cosmological Constant.’ This is an extra term added by Einstein in working out equations in general relativity that describe a non-expanding universe. The need for the cosmological constant is required to explain why a static universe doesn’t collapse in upon itself through the action of gravity. It’s true that the force of gravity is infinitesimally small compared to the electromagnetic force, but it has a lot more influence on the universe because all the positive and negative electrical charges in the universe somehow seem to balance out. Indeed, if there were just a 0.00001 per cent difference in the net positive and negative electrical charges within a body, it would be torn apart and cease to exist. This cosmological constant, therefore, is added to the laws of physics simply to balance the force of gravity contributed by all of the matter in the universe. What it represents is a sort of unobserved “energy” in the vacuum of space which possesses density and pressure, which prevents a static universe from collapsing in upon itself. But we now know from observation that galaxies are actually moving away from us and that the universe is expanding. In fact, the Hubble Space Telescope observations in 1998 of very distant supernovae showed that the Universe is expanding more quickly now than in the past. So the expansion of the Universe has not been slowing due to gravity, but has been accelerating. We also know how much unobserved energy there is because we know how it affects the Universe’s expansion. But how much should there be? We can calculate this using quantum mechanics. The easiest way to picture this is to visualize “empty space” as containing “virtual” particles that continually form and then disappear. This “empty space”, it turns out, “weighs” 1,093 grams per cubic centimetre. Yet the actual figure differs from that predicted by a factor of 10 to the power of 120. The “vacuum energy density” as predicted is simply 10120 times too big. That’s a 1 with 120 zeros after it. So there is something cancelling out all this “dark” energy, to make it 10 to the power of 120 smaller in practice than it should be in theory. Now this is very fortuitous. If the cancellation figure was one power of ten different, 10 to the power of 119, then galaxies could not form, as matter would not be able to condense, so no stars, no planets, no life. So we are faced with the mindboggling fact that the positive and negative contributions to the cosmological constant cancel to 120 digit accuracy, yet fail to cancel beginning at the 121st digit. In fact, the cosmological constant must be zero to within one part in roughly 10120 (and yet be nonzero), or else the universe either would have dispersed too fast for stars and galaxies to have formed, or else would have collapsed upon itself long ago. How likely is this by chance? Essentially, it is the equivalent of tossing a coin and needing to get heads 400 times in a row and achieving it. Go on. Do you feel lucky? Now, that’s just one constant that needs to be just right for galaxies and stars and planets and life to exist. There are quite a few, independent of this, which have to be equally just right. We can talk about those another time, but this I think sets the stage. I’ve heard this called the fine-tuning argument. I’m now rather interested in finding out who or what is composing this very fine tune.

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