Murphy's Law and the anthropic principle
Yes, I am firmly convinced that the anthropic principle is the causative force behind Murphy's Law. I posted a blurb about this on Facebook, but that medium is only really good for one-liners. Here, I offer a more detailed explanation, using a common manifestation of Murphy's Law:
Let's start with a very basic assumption about Life (as we know it): it needs liquid water. Oh, I know science fiction has postulated other bases for life, ammonia or methane or what-have-you... but the sober fact is that every known form of life needs liquid water to develop, much less survive, and no one has found an example (or even given a detailed postulation) involving other liquids.
So we shall concern ourselves only with water-bearing worlds. Right there, that puts constraints on the sorts of planets where Life can evolve. A Life-bearing planet has to orbit its star within a narrow range of distances: too close, the water boils away, too far, the water freezes. Simple, so far.
Likewise, even within that range of orbits, we have constraints on the planet's size. Too small a planet, like Mars, will have lost its liquid water well before Life evolved. So we can assume that Earthlike gravity, at a minimum, is a prerequisite for Life.
Each individual star will have its own range of water-permitting orbits. Around a cooler, red star, a planet will need to orbit closer, if it's to be warm enough to have liquid water. Such a planet would have very short "years", but that's not important. In terms of having water, the temperature of the star isn't as much of a factor.
But... now we get to the energy requirements needed for Life to evolve. You need a source, providing enough energy to get those complex chemical reactions a-going and keep them going. Considering the span of millions (billions) of years required for evolution, the only reliable energy source would be sunlight. Which means you need your star to produce lots of energetic photons, and you're just not going to get them from a star whose spectrum peaks in the red.
So right off the bat, merely by requiring liquid water, for the evolution of Life we need a star hotter than red -- say, yellow, like ours -- and a planet massive enough to hold onto its water -- say, Earth-sized at the very least -- orbiting at a distance where that water will be liquid -- say, around 1 Astronomical Unit.
The anthropic principle thus requires us to have evolved on an Earthlike planet, because had our world not been Earthlike, we wouldn't be here.
The keys factors here are, again, gravity and energy. All life forms require energy to survive. Ultimately, that energy is sunlight: plants collect it, convert it to chemical energy (stored in sugars and such). Other life forms eat the plants and process that energy; we ourselves either eat plants or we eat the other life forms, or both. Either way, in the end our energy comes from the sun via plants. That constrains how much energy our bodies have: even if we ate continuously all day, there's an upper limit in how much energy we'll have available to us, which constrains the sorts of things we can do.
From an evolutionary viewpoint, then, we're not likely to waste our body's energy by pumping blood twenty feet above the ground.
Sure, there's an example of an animal that does just that: the giraffe. But an animal that's to evolve intelligence must, of necessity, devote a greater fraction of its energy to the workings of its brain; it won't frivol it fighting gravity unnecessarily. Again, gravity and energy -- those two factors alone -- dictate that we be, very roughly, the size we are: twenty-foot intelligent humanoids, frequent though they may be in fantasy literature, aren't evolutionarily preferred, here on the only world where Life is proven to exist.
In particular, it means that -- given that we're upright bipedal figures -- the height at which we routinely handle objects will be, oh, three to five feet above the ground. An object, dropped from that height, takes about half a second to reach the ground. (A minor variance in timing doesn't affect our results.)
If an object is simply dropped all at once, of course, then it falls, plain and simple. Or if it's symmetrical, like a ball, it simply falls. But if the object has a certain moment of inertia -- say, if it's flat and broad, rather like a piece of toast -- and it's only released on one side while still supported on the opposite edge, then guess what? It develops a rotation as it falls.
And it can be shown that, for the range of flat objects small enough to be easily handled in one hand, that rotation is exactly enough to turn the toast through half a revolution as it falls -- independent of other factors! Sure, if we'd evolved on a world where the surface gravity were less, the toast wouldn't fall as fast... but humans could be taller for the same expenditure of bodily energy. So the fall would still take half a second, and the toast would still turn half a revolution.
All this, purely from gravity and energy considerations.
The toast lands on the buttered side because we would not have evolved under physical parameters that dictated otherwise.
Murphy's Law is a generalization, pure in its expression: Anything that can go wrong, will. But once you start examining a specific application of the Law -- and there are many, this is but one of them -- you'll see they're dictated by the fundamental nature of physical law, the ones so carefully tailored to allow our very existence. If the laws of physics were different that what they are, we would not exist -- and falling objects the size of a piece of toast would land with their "buttered" sides up.
Let's start with a very basic assumption about Life (as we know it): it needs liquid water. Oh, I know science fiction has postulated other bases for life, ammonia or methane or what-have-you... but the sober fact is that every known form of life needs liquid water to develop, much less survive, and no one has found an example (or even given a detailed postulation) involving other liquids.
So we shall concern ourselves only with water-bearing worlds. Right there, that puts constraints on the sorts of planets where Life can evolve. A Life-bearing planet has to orbit its star within a narrow range of distances: too close, the water boils away, too far, the water freezes. Simple, so far.
Likewise, even within that range of orbits, we have constraints on the planet's size. Too small a planet, like Mars, will have lost its liquid water well before Life evolved. So we can assume that Earthlike gravity, at a minimum, is a prerequisite for Life.
Each individual star will have its own range of water-permitting orbits. Around a cooler, red star, a planet will need to orbit closer, if it's to be warm enough to have liquid water. Such a planet would have very short "years", but that's not important. In terms of having water, the temperature of the star isn't as much of a factor.
But... now we get to the energy requirements needed for Life to evolve. You need a source, providing enough energy to get those complex chemical reactions a-going and keep them going. Considering the span of millions (billions) of years required for evolution, the only reliable energy source would be sunlight. Which means you need your star to produce lots of energetic photons, and you're just not going to get them from a star whose spectrum peaks in the red.
So right off the bat, merely by requiring liquid water, for the evolution of Life we need a star hotter than red -- say, yellow, like ours -- and a planet massive enough to hold onto its water -- say, Earth-sized at the very least -- orbiting at a distance where that water will be liquid -- say, around 1 Astronomical Unit.
The anthropic principle thus requires us to have evolved on an Earthlike planet, because had our world not been Earthlike, we wouldn't be here.
The keys factors here are, again, gravity and energy. All life forms require energy to survive. Ultimately, that energy is sunlight: plants collect it, convert it to chemical energy (stored in sugars and such). Other life forms eat the plants and process that energy; we ourselves either eat plants or we eat the other life forms, or both. Either way, in the end our energy comes from the sun via plants. That constrains how much energy our bodies have: even if we ate continuously all day, there's an upper limit in how much energy we'll have available to us, which constrains the sorts of things we can do.
From an evolutionary viewpoint, then, we're not likely to waste our body's energy by pumping blood twenty feet above the ground.
Sure, there's an example of an animal that does just that: the giraffe. But an animal that's to evolve intelligence must, of necessity, devote a greater fraction of its energy to the workings of its brain; it won't frivol it fighting gravity unnecessarily. Again, gravity and energy -- those two factors alone -- dictate that we be, very roughly, the size we are: twenty-foot intelligent humanoids, frequent though they may be in fantasy literature, aren't evolutionarily preferred, here on the only world where Life is proven to exist.
In particular, it means that -- given that we're upright bipedal figures -- the height at which we routinely handle objects will be, oh, three to five feet above the ground. An object, dropped from that height, takes about half a second to reach the ground. (A minor variance in timing doesn't affect our results.)
If an object is simply dropped all at once, of course, then it falls, plain and simple. Or if it's symmetrical, like a ball, it simply falls. But if the object has a certain moment of inertia -- say, if it's flat and broad, rather like a piece of toast -- and it's only released on one side while still supported on the opposite edge, then guess what? It develops a rotation as it falls.
And it can be shown that, for the range of flat objects small enough to be easily handled in one hand, that rotation is exactly enough to turn the toast through half a revolution as it falls -- independent of other factors! Sure, if we'd evolved on a world where the surface gravity were less, the toast wouldn't fall as fast... but humans could be taller for the same expenditure of bodily energy. So the fall would still take half a second, and the toast would still turn half a revolution.
All this, purely from gravity and energy considerations.
The toast lands on the buttered side because we would not have evolved under physical parameters that dictated otherwise.
Murphy's Law is a generalization, pure in its expression: Anything that can go wrong, will. But once you start examining a specific application of the Law -- and there are many, this is but one of them -- you'll see they're dictated by the fundamental nature of physical law, the ones so carefully tailored to allow our very existence. If the laws of physics were different that what they are, we would not exist -- and falling objects the size of a piece of toast would land with their "buttered" sides up.