Tyler Johnson, MDiv
Tyler is a pastor and a former NASA engineer. He loves to explore truth through God’s word and God’s works. He lives in Iowa with his wife and four children and spends what little free-time he has pondering the mysteries of light
As we continue our look beyond the surface of our world. I have to admit, this week’s topic has got to be the most confounding mystery of our time. One that reminds me again how creative and mysterious our God is.
In 1906 Albert Einstein found that light could be described both as a wave or as a particle. This was remarkable because particles are pieces of matter, and waves are movements within matter. (A wave on the ocean isn’t water, it is a movement of water.) Light, it would seem, has a dual nature. Depending on the experiment, light acts like a particle or a wave. This is paradoxical since particles and waves are different things.
The mystery is just beginning.
The Double-Slit Experiment in full tri-chromatic, 2-D glory. But not to scale.
One of the famous experiments in quantum mechanics is the double-slit experiment in which light was shined on a barrier that had two small slits in it. These slits allowed light to pass through onto a wall on the other side. The light that shone through the slits formed a symmetrical pattern of light and dark lines on a detector. This pattern was formed by light waves from the two slits interfering with each other and this proved that light behaved as a wave. (If you want to dig into this experiment more, its Wikipedia page is pretty good. At least it has better graphics than the one I’ve created here.)
Fast forward a few years and a scientist named Louis DeBroglie found that light isn’t the only thing that has this dual nature, matter also can be described as particles or waves. Matter waves are a thing. Matter has a wavelength.
The mystery deepens.
After DeBroglie demonstrated that matter behaves like a wave too, it was just a matter of time before someone tried the double-slit experiment with electrons. What do you think he found?
If electrons are waves, then they would be able to interfere with one another like light does. When electrons are sent through the double-slit experiment one at a time, they form a pattern on a detector just like the pattern that light makes. The electrons hit the detector one at a time, but not all in the same place. As more and more electrons pass through the slits and hit the detector their locations reveal the same fringe pattern that light waves make. The electrons are acting like waves, interfering as they pass through the slits. But that is odd since the electrons are passing through one at a time. What would they be interfering with?
The mystery is getting interesting.
Counterintuitive answers cannot be dismissed simply because they are counterintuitive. The simplest answer is that the electron interferes with itself after passing through both slits. That’s right. And if you don’t trust me, perhaps you will trust the world renown physicist and theologian John Polkinghorne who writes, “The indivisible electron came through both slits!”* This makes no sense.
“Obviously,” we must think, “the electron cannot go through both slits at the same time.” The experimenters also thought this, so they decided to do the same experiment and carefully monitor the electrons as they passed through the slits, to see which one they went through. So with their special equipment the physicist observed the stream of electrons as they passed through the double-slits and found that indeed some went through Slit 1 and some through Slit 2. Phew, right? They weren’t crazy and electrons don’t pass through both slits at the same time. But wait. Watching the electrons as they passed through the slits changed the experiment. And changed the results. While they were watching the electrons pass through the slits, they noticed that the pattern on the wall had changed. Now the electrons hit the wall in a pattern that didn’t indicate waves, but indicated particles. Observing the route of the electrons changed the outcome of the experiment!
So when you break it down here is what happens when you pass electrons through a double-slit experiment. If you watch them pass through the slits, then they will act like particles and they will strike the detector in a ‘particle pattern’. If you don’t watch them when they pass through the slits, then they will act like waves passing through both slits at the same time and striking the detector in a ‘wave pattern’. Observing a different part of the experiment changed the experiment.
So what does this mean? Well, no one really knows. A few different interpretations have been offered. Some say that there is simply a problem with our physics that makes the quantum world look so weird. Some say that observing the world can have a causal effect on it. Some have suggested that there are many worlds out there and some of them are almost identical to our own and sometimes things in our world interfere with things in another world.
The point I want to make is that no one really knows what it means. No one. It is one of the profound mysteries that lies beneath the surface of our well-ordered world. It is one of the most counterintuitive and baffling realities that we can’t seem to get away from. For me it is another invitation to remember the infinite mystery that is God. The One who created all that we know, has imbued it will a small bit of mystery to continually humble us and draw us into awe and worship of Him.
At its best, that is what science does.
* For a great introduction to Quantum Physics see The Quantum World, by John Polkinghorne.