On the Crookes Radiometer as a metaphor for our relationship with God

This is a typical example of a Crookes Radiometer. Inside a partially evacuated glass bulb is a needle, on which rests a set of vanes mounted on a very low friction hub. The vanes are white or shiny on one side, and black on the other. When you place this device so that it is illuminated by bright light, particularly the light of the sun, then the set of vanes spins merrily away, in the direction of the white or shiny sides. This Wikipedia page explains the origin of the device, and lists several different possible explanations of how it works. The short explanation is that each of the vanes acts as a tiny heat engine, converting incoming electromagnetic radiation (primarily infrared and visible light) into motion through subtle thermodynamic phenomena occurring right at the surface of the black side of each vane.

I have always been fascinated by these devices, and all the more so as I have gotten older. Besides the intriguing and unexpected physics of these devices, I have also found them very cheering to have around, especially on a sunny day in winter. It is strangely satisfying and uplifting to watch the vanes of a radiometer spinning furiously in bright sunlight. It can be, however, a bit subduing to watch the vanes spinning very slowly on a hazy day or very late in the day as the sun goes down, and even depressing to see them sit motionless on a gloomy day or in a room this is only moderately illuminated. 

About 6 years ago Mary and I decided to replace all of the windows in our house with top-of-the-line Anderson windows. The new windows greatly reduced our energy bill, both in winter and summer, which was what we were looking for. One of the primary ways the windows achieve these savings is through a slight tint, which allows very little infrared and ultraviolet to pass in either direction. However, one unintended and unwanted side effect of this blockage of light was that all of our plants began to get sickly. Although the diminution of light was so slight as to not be noticeable to the eye, it nonetheless had a big impact on our plants. It took Mary a while to find out how to position the plants so that they could still get enough light to thrive. Another side effect that perplexed and depressed me was that the new windows also blocked so much incoming solar energy that the radiometer spun very listlessly even on an apparently bright sunny day. You can visibly see the difference that the glass makes by simply sliding a window open so that direct sunlight passes into the room through the window screen alone. As soon as you do this on a bright day, the light instantly stokes up the radiometer vanes into a blur of motion. But the vanes go back to their half-hearted spin when you close the windows again.

One of my quirky predilections is an obsession with analogies and metaphors. (This is a very old interest, and it would take a while to explain how I got this way.) As a result of this obsessive tendency, I often notice analogical parallels between physical phenomena and more abstract ideas. It is surprising the turns this can take. All of the above is a long-winded prologue to an explanation about why a Crookes Radiometer makes me think about being a disciple of Jesus.

Recently, I have been thinking a great deal about being a disciple of Jesus, and about how one becomes a disciple, and especially how one helps others to become disciples. Jesus of course also used analogies a lot in His teaching, with the best known bits being His many parables. The use of these analogies is yet another dimension of why Jesus was such a powerful and effective teacher. By telling stories that tapped into people's everyday experience and understanding, He communicated His message about the Kingdom of God in a memorable and thought-provoking way. Everyone knew what a king or a shepherd or other character in one of His parables did, so it was easy to grasp at least some of what He was saying. The stories often had dramatic or exaggerated elements (the good Samaritan caring for the man set upon by robbers, or the king who compelled guests to come to his son's wedding feast) that made them easy to remember, but there were also puzzling elements which provoked the hearers to remember and ponder the parables later, and to ask questions.

Our highly secular and material age has lost a lot of this ability to grasp things on many levels at once. We look at the world, and we just see the world. We typically do not see the many layers of implied meaning that are available in what we are looking at. So I believe that there is a work to be done by believing Christians to find new parables and new metaphors that help communicate the timeless truth of the Gospel in the situations that we find ourselves today.

Let me draw out some of the many parallels between the ingenious and unappreciated Crookes radiometer and what it means to be a believing Christian living as an child of God.

• The radiometer is designed to work on light alone. In the same way, our souls are designed by God to work on the light of His grace.
• The radiometer works best when sitting in bright, unfiltered sunlight. In a similar way, our souls are healthiest, happiest, and most responsive when they are exposed to and filled with the fullness of the light of God available through a relationship with Jesus. 
• The radiometer works because the vanes are very thin and have little mass, so that it takes relatively little force to set them in motion.  The device would not work if the vanes had more mass. Similarly, if our souls are weighed down with self-concern, it is hard for them to respond to the gentle touches of God's grace.
• The hub that holds the vanes must be free to turn with little friction. Likewise,  if we are plagued with sinful tendencies that we cannot break free from, those also impede our soul's ability to respond to the light of God's grace.
• The radiometer's operation requires that the vanes be placed in a partial vacuum inside a glass bulb. If the air inside the bulb is denser, then the thermodynamic phenomenon that provides the thrust to the vanes will be swamped by all kinds of random motions in that air, and again the vanes will not turn. In the same way, if our minds are overactive, and densely packed with the sheer number of things we trying to pay attention to, then the grace that God wants to pour out on us is drowned out.
• The radiometer worked poorly even in apparently bright light if some of the most important wavelengths of that light had been filtered out. In a very similar way, if we are operating in an environment where God's graces have been excluded by custom or law ("Don't mention God at our Thanksgiving dinner. It will set off your Uncle Frank." "Explicit vocal prayer in schools in our district is not allowed.") or where we simply cannot spend explicitly Christian time with other believers on a regular basis, we will find ourselves slowly starved of the graces that God dispenses through each other.
• Even on a dark and gloomy day, a small flashlight held close can make a radiometer's vanes spin. Similarly, even if one is not feeling God's presence, experiencing grace through the love and friendship of another believer can be enough to awaken our soul's response to grace. That friend's light is not the same as the fullness of God's light, of course, but it is the provision that God has made for you to receive some of His light when you need it.

So, it seemed to me that a radiometer might be an interesting gift for a friend who is a Christian, particularly one who is in need of encouragement, and who is also appreciative of geeky science toys. But when you give it to your friend, explain the things that I mentioned above and tell them to look at the radiometer from time to time and to remember how much one's soul is like the radiometer. Practically speaking, that translates at least to these suggestions:

• Try to make time to expose yourself in every possible way to the brightness of God's love and grace.
• Ask the Lord to help you unburden yourself of self-concern by explicitly and repeatedly entrusting your life to God's care.
• Don't let sinful tendencies, even little ones, linger.
• Try to attend to only one thing at a time, and don't let your mental air get too "dense" by multi-tasking (which is really multi-worrying).
• Pay attention to the ways that your working and living environments invisibly filter out the graces that God would otherwise be showering into your life, and try to compensate for the missing elements.
• Ask a friend to share a little light with you, if you are going through a "dark" spell, and your spiritual radiometer is spinning very listlessly, or has even stopped.

However, also tell your friend "Think of your soul like a radiometer. And if it stops spinning, see what you need to do to get it spinning again."