Quantum Weirdness

Frankly, the way things behave at the smallest scales is simply not what we would expect. Why is this?

Physics is the science dealing with how the universe works at its most basic, fundamental level. There are many sub-categories of physics, each dealing with a particular aspect of the universe. The branch of physics dealing with how the universe operates at very small scales—interactions involving particles smaller than atoms—is called quantum mechanics. Quantum mechanics is weird. I suspect that most physicists would agree that of all the branches of physics, quantum mechanics is the strangest and least intuitive. Frankly, the way things behave at the smallest scales is simply not what we would expect. Why is this? Is there a better way to understand quantum mechanics, one that is more congenial to our expectations? And what does all this have to do with the Christian worldview?

Challenging Our Expectations

What are some examples of quantum weirdness? When you misplace your keys, you begin looking for them, expecting to find them at one particular location. But after you find them, you don’t continue looking because you know that your keys can only be in one place at one time. If they are in your pocket, then they cannot also be in between the couch cushions. This principle works very well at large scales, but not at quantum scales. Under certain circumstances, a subatomic particle can be in multiple places at the same time. Weird!

A satellite orbits because the earth’s gravity deflects the path of the satellite from a straight line into a curved (nearly circular) path. The distance a satellite orbits will depend on the total energy of its orbit. You can add a bit of energy, and the satellite will move into a higher orbit, or subtract a bit, and the satellite will move into a lower orbit. You can get the satellite to orbit at any distance you like by adding or removing the appropriate amount of energy.

The orbits of electrons are quantized, which is why this branch of physics is referred to as quantum.

You might think that electrons orbiting the nucleus of an atom would be the same way. But electrons can only orbit at certain distances from a nucleus. For example, they can orbit at level 1, or level 2, but you cannot get them to orbit anywhere in between. Consequently, you cannot add just a little bit of energy to an orbiting electron to make it orbit just a little bit further. It will not accept it. It will only accept exactly the amount of energy necessary to make it jump to the next allowed level. Weird! The orbits of electrons are quantized, which is why this branch of physics is referred to as quantum.

Rotation is also quantized on the subatomic scale. You can imagine spinning a wheel at 60 revolutions per minute, or slightly slower at 59 revolutions per minute. You could also spin it anywhere in between, such as 59.5 revolutions per minute, or 59.97632. Any value is allowed. But not so in the quantum world. At the atomic scale, particles can spin but only in certain quantized rates such as 1, 2, 3, 4, but not in between. So, 1.3 is not allowed. Moreover, the most basic particles, such as electrons, have a built-in spin whose quantity is unchangeable, and (in the case of many particles) is exactly half the rate allowed for larger, composite particles. Electrons have a spin of 1/2.

In our everyday experience, we know that for one thing to affect another, it has to be in contact with it. In baseball, if you want to hit a home run, you must strike the baseball with your bat. You can only move things that you actually touch. Your actions will have no effect on a baseball that you do not touch, such as one that is on the other side of the planet.1 You might think that the same would be true for subatomic particles. But you would be wrong. When two particles have been in contact with each other, even after they become separated, a change in one can instantly affect the other—even if they are now on opposite sides of the galaxy! This phenomenon is called quantum entanglement and has to be the weirdest aspect of quantum mechanics.

A Partial Explanation

Some of the weirdness of quantum mechanics began to make sense when scientists discovered that subatomic particles have a wave-nature. Imagine throwing a large rock into a pond. The initial splash creates a circular wave that travels away from the point of impact. This circle grows larger over time, with smaller ripples within that travel away from the center until they reach the circumference of the circle.

Physicists have studied the properties of waves for centuries. So we know quite a lot about how waves behave. Waves have peaks and troughs and travel through space. When two different waves come into contact, they can pass through each other, producing peaks and troughs that are the combination of the two waves. Imagine throwing two rocks simultaneously into two different locations in a lake. A wave will travel away from each impact, and eventually the ripples from one splash will contact the ripples in the other splash. When two peaks of the ripples are in the same location, they add up, and you will see a really large peak. However, when a peak in one wave is at the same location as a trough in the other wave, the two cancel out, and the water is temporarily level.

We have experimental proof that subatomic particles can behave in exactly this way. All particles have a wavelength that depends on their mass and speed. The less massive the particle, the longer the wavelength at a given speed. We do not notice the wavelength of large objects, like a car, because for such a massive object the wavelength is much smaller than an atom. But for tiny particles, their wave nature is very noticeable.

The weirdness of quantum mechanics exists not because of anything illogical about the universe, but rather because we have an incorrect picture of what is happening.

So, the weirdness of quantum mechanics exists not because of anything illogical about the universe, but rather because we have an incorrect picture of what is happening. We tend to think of particles like a point or a little sphere that exists at only one particular location in space. But in fact, subatomic particles are more like waves that are extended in space. So, of course, an electron can exist at more than one location because it expands over a volume of space like a wave.

In fact, the wave nature of electrons explains why they can only orbit the nucleus of an atom at certain discrete levels, and not in between those levels. The levels at which electrons orbit are those levels at which the circumference of the orbit matches an integer multiple of the electron’s wavelength. If it were not, then the peaks and troughs of the wave would cancel, and the electron would cease to exist. Knowing this, we can mathematically calculate the levels at which electrons will orbit a hydrogen atom, and experiments have precisely confirmed this.

Nonetheless, some properties of the quantum world are still rather mysterious. For example, although subatomic particles behave like waves, they only do so sometimes. At other times, they behave like a particle—as if they exist at only one location in space. Apparently, all subatomic particles act like waves until any sort of measurement is made upon them. When we attempt to measure any property of a particle, it will—for that moment–cease its wave behavior. Physicists say its “wave function collapses.” The particle will no longer be extended over a volume of space like a wave but will assume a discrete position in space. Amazingly, the probability of finding the particle at a particular location is the square of its wave function. Basically, particles act like waves when you are not looking at them, and they act like particles when you are looking at them. And the particle is likely to be where the wave is a high peak or a deep trough. It’s weird but true.

Despite its counterintuitive nature, we have a very good reason to think that quantum mechanics is a reasonably good description of how the universe operates: it works amazingly well. Namely, the predictions of quantum mechanics have been repeatedly verified experimentally. They always make the correct prediction. So, we must be on to something. No one is claiming that quantum mechanics is the whole picture. Most physicists believe that even better approximations will be discovered in the future. But its success demonstrates that quantum mechanics must be a very good approximation of what is going on.

Nonetheless, there are interpretations of some aspects of quantum mechanics advocated by some scientists that are dubious and are not necessary to make correct predictions. For example, when making a measurement on a particle which collapses its wave function, we know that the particle will be found in locations where the square of the wave function is high. But we cannot predict which “peak” the particle will choose. Some physicists have proposed that the particle chooses every possible path—each in a separate universe. We just happen to live in the universe where we observed the given result. But in some other universe, the particle made a different choice. Obviously, this “multiverse” idea is nothing but conjecture. It makes no testable predictions, has no supporting evidence (nor could it even in principle), and therefore does not contribute to science.

Logic Versus Intuition

Sometimes laymen are doubtful about quantum mechanics because it is so strange—so contrary to our intuition. But should the universe be intuitive? Intuition is our everyday expectation about how things should work. We have neither the time nor intellect to explicitly compute from first principles what should happen in every situation in our lives. So we rely on experience and discover patterns that seem to work most of the time. Such experiences form our intuition about what to expect in future, unexperienced situations.

Often, our intuition is correct.

Often, our intuition is correct. Even a young child who knows nothing about Newton’s law of gravity will expect that a rock in his hand will fall to the ground if he lets go of it. Past experience tells him that, generally, things fall. But since intuition is based on experience, it works best in cases in which we have a great deal of experience. However, intuition fails most miserably in situations in which we have little or no experience. A child watching an astronaut on television may be surprised when the astronaut lets go of something, and it does not fall to the floor.2

Much of the weirdness of quantum mechanics may simply because most people have no experience with subatomic particles. We cannot directly see them since they are far too small. But notice that quantum mechanics violates no principles of logic. There is nothing irrational about the behavior of subatomic particles. There may be certain interpretations of experimental results that violate laws of logic—and those interpretations are therefore wrong. But the experimental results themselves are perfectly logical, even if they are contrary to our intuition.

In fact, if quantum mechanics were genuinely illogical, if it actually violated principles of logic, then we could never have discovered it. We use principles of logic to make scientific discoveries. We reason from experimental observations under the assumption that the universe is fundamentally logical—that it never violates correct principles of reasoning. But what justifies that expectation?

The universe is always logical because logic is a description of how God thinks.

The Christian worldview is what makes science possible. The universe is always logical because logic is a description of how God thinks. God is perfectly rational. And since God’s mind controls the universe, the universe will always be logical. Being made in God’s image, human beings have the capacity to think logically, although in our sin we sometimes fail to do so. The success of science is, therefore, evidence that the Christian worldview is correct. In a chance universe, why expect to find patterns in nature? Why expect those patterns to follow the laws of logic? The fact that secular scientists do expect to find patterns in nature, and expect such patterns to be logical, shows that in their heart of hearts they really do know God, although they suppress that truth in unrighteousness (Romans 1:18-20).

Although God is logical, he is also very creative. His ways and thoughts are far above ours (Isaiah 55:8—9). And therefore, some aspects of the way God has chosen to uphold his universe may seem very strange and surprising to us. Quantum mechanics is a great example of this. And yet, we trust that the universe will always be rational, if not always intuitive, because it is upheld by the mind of God. The success of science vindicates biblical thinking and challenges secularism. Furthermore, the study of the way the universe operates tells us something about the magnificence of the mind of God. As the creation scientist Johannes Kepler put it, to do science is to think “God’s thoughts after Him.”