Our existence depends on a network of highly unlikely circumstances. And when I say "our existence" I mean any form of life anywhere in the universe. For example...
A few days ago as I pen these words, a friend loaned me a rather interesting book called The Symbiotic Universe: Life and Mind in the Cosmos by George Greenstein (ISBN: 0-688-07604-1). This was published in 1988, at which time George was professor of astronomy at Amherst College (he may still be there for all I know). This little rascal (which you may take to encompass both the book and George) has certainly given me a lot to think about.
George starts off by explaining that our existence depends on a network of highly unlikely circumstances. And when I say "our existence" I mean any form of life anywhere in the universe. For example, let's consider the fact that we are a carbon-based form of life (at least, we are in my branch of the universal family). Until now I hadn't realized just how unlikely it is for carbon to be in the universe.
It is common knowledge that newly-formed suns are predominantly hydrogen; also that they primarily generate energy by taking two hydrogen atoms and converting them into a single helium atom using nuclear fusion. It's also reasonably common knowledge that suns like ours can use fusion to create elements all the way up to iron (heavier elements are created in supernova explosions, but we don't need to worry about that here).
To be honest I had sort of assumed that there was a simple progression here. For example, a helium atom has two protons, two neutrons, and two electrons, while a carbon atom has six protons, six neutrons, and six electrons. (Actually, I'm talking about Carbon-12 here, which accounts for about 98.89% of all carbon; the other stable isotope is Carbon-13 with seven neutrons which accounts for around 1.1%; and there are also trace amounts of radioactive Carbon-14 with eight neutrons.) Thus, if I'd given this any thought at all, I would have said that all that was required was for three helium atoms to be fused into a single carbon atom. It turns out that things aren't that simple. The nucleus of an atom is a tiny fraction of the size of the atom as a whole, so the chances of three helium nuclei being in the right place are infinitesimally small.
OK. In that case, what about fusing two helium atoms together to form a beryllium atom, and then taking this atom and fusing it with another helium atom to form a carbon atom. It sounds easy if you say it quickly, but in fact the Beryllium-8 isotope with four protons, four neutrons, and four electrons is extremely unstable (there are 12 isotopes of Beryllium, but only Beryllium-9 is stable), and remains in existence for only a tiny fraction of a second before radioactively decaying back into two helium nuclei.
The answer is a suite of resonances known as the Triple Alpha Process
that somehow amplify things such that suns can create sufficient carbon to form you and me. Explaining how this works in any more detail is beyond my humble abilities (not the least that I'm writing this from memory because I already returned the book to its owner). But the point is that it's a lot more complex than one might expect and if any number of "things" were even slightly different we simply wouldn't be here at all.
George then takes us on a journey that considers the relative strengths of the weak, strong, electromagnetic, and gravitational forces showing how incredibly finely balanced everything is. He also brings up points I'd never considered before (or, more truthfully, things that I'd simply taken for granted), such as the fact that the negative charge on an electron is EXACTLY the same (in terms of strength) as the positive change on a proton. Like I said, I've sort of taken this for granted, but why should it be so considering the fact that everything else about these little rascals (size, weight...) is so fundamentally different. The point is that if the two charges were even fractionally different in size … you guessed it, we wouldn't be here.
Something else that I really liked about this book was that it caused me to look at some very common substances in a completely new light. Take water for example, which turns out to be much more amazing than I'd ever appreciated. Consider, for example, the fact that frozen water is less dense than its liquid counterpart and therefore floats on top (the opposite to almost every other substance). Also the fact that the structure of the water molecule makes it incredibly good at dissolving things, which is why it's a major factor with regard to the blood's ability to carry substances around our bodies.
As George says: "No other commonly occurring liquid possesses anything remotely approaching the ability of water to dissolve things."
And later he notes: "The ancient alchemists labored without end in search of the universal solvent. Little did they know they were composed of it."
But I'm afraid that I'm wandering off into the weeds. The main thrust of this book is that it appears that the universe and life are symbiotically intertwined. That is, we (life in any of its guises) need the universe to be a certain way for us to exist, while the universe requires us (life) to define what it is and how it works.
"Pull the other one, it's got bells on,"
I can hear you muttering to yourself under your breath, but wait... let me regale you with one more topic from this book and then let's see just how sure you are.
This revolves around the particle-wave duality of all fundamental particles including electrons, protons, neutrons, and even photons. (And before we go any further, irrespective of whether or not you accept the main premise of this book, let me just say that George gives the best lay-persons' description of particle-wave duality that I've come across thus far.)
Let's start with particles. Suppose we create an electron "gun" that "shoots" a stream of electrons toward a "wall". Assume that there are two tiny "slits" in the wall located very closely together, and also that there's enough uncertainty or jitter or randomness (or whether you want to call it) in the setup that some of the electrons will hit the wall between the two slits, some will hit the wall either side of the slits, and some will pass through one or other of the slits.
Now suppose that we put a row of particle detectors behind the wall. If we were to plot the resulting "detection profile", we would see that the particle detector "behind" the left-hand slit detects any electrons that pass through that slit; similarly for the particle detector on the right as illustrated in the following sketch I've just thrown together.
"Birds-eye" view of the experiment
Now, although I've indicated a whole bunch of electrons flying around, we could cause our electron gun to fire only one particle at a time, in which case – not surprisingly – one or other of our particle detectors would see the individual electrons as they passed through one or other of the slits (the "one or other" part of this sentence is important as we'll see).
From this experiment we might reasonably assume that electrons are particles (keep this thought in mind).
OK. Now let's think about waves. If we drop a pebble into a pond, we see a series of ripples radiating out from the impact point. If we drop two pebbles into the pond at the same time separated by some distance – say a meter – their associated ripples will interfere with each other and we'll see an interference pattern – in some places the peaks will reinforce each other to make higher peaks; in some places the troughs will combine to make deeper troughs; and in some places the peaks from one pebble will meet up with the troughs from the other and cancel each other out.
So, now assume that we remove the particle detectors from our experiment and replace them with a piece of photographic film that is sensitive to electrons. What do we expect to happen? If electrons truly are particles, we should see two vertical stripes of exposed film. What actually happens is that we see an interference pattern as illustrated below:
Hmmm; from this experiment we might reasonably assume that electrons are waves. So is an electron a particle or a wave? Well, it gets even stranger than this, because one of the ideas that people originally had was that the interference pattern was caused by multiple electrons bouncing off each other. But we still see the interference pattern even if we cause the electron gun to fire individual electrons, which means that each electron has to pass through both slits and then interfere with itself (eeek).
As an aside, there is a really, REALLY good video titled Dr. Quantum Explains the Double Slit Experiment
on YouTube that explains this much better than I ever could.
So the bottom line is that electrons appear to be either particles or waves depending on the technique we are using to observe them. Another way to look at this is that the act of observing them determines what they are (in a way).
This is where things start to get REALLY weird. The point to remember is that – using appropriate detectors – we can detect electrons as either particles or waves, but not as both at the same time. Now let's suppose we set up an experiment like those described above. Purely for the sake of discussion, let's assume that our electron gun assembly along with the wall with the slits is located in a satellite orbiting the earth (note that we haven’t powered the gun up yet). Also for the sake of discussion, let's assume that our detector is located one light year away in deep space. Last but not least, let's assume that we have some assistants in charge of the detector (they're living in a spaceship).
So our assistants set things up such that the detector can detect only particles. At some agreed time, we power up our electron gun. If everything remains as-is, then exactly one year later our assistants will start to see particles hitting their detectors. But our assistants are tricky. A few minutes before the first electrons start to arrive, they swap out the particle detector for one that will detect waves ... and lo and behold waves are what they detect.
One conclusion is that the universe goes back in time to change the way the electrons pass through the slits in the wall one year before they are ultimately detected! We might think of this as a small act of creation... in which life (us) affects the way the universe *is*.
The point is that such an experiment can actually be performed in a laboratory here on Earth (but with things measured in fractions of a light-second, of course). Experiments like this have been performed numerous times by numerous groups and the results are always the same – swapping out the detector before the electrons arrive causes them to arrive in a way that matches the detector, even if this requires changes to have been made in the past.
I'm sorry. I know that I'm not explaining this very well. But even with my muddy explanations I hope you can see that something very interesting is going on here. For a better explanation, all I can suggest is that you purchase a copy of The Symbiotic Universe
(you can get a new copy for $14.99 or a secondhand copy starting at $0.19 from Amazon).