Wave-Particle Duality and Hidden Reality
The double-slit experiment — and the things which are not seen
If light were only a wave, you would predict that firing light through two slits onto a screen would produce two bright bands — one behind each slit. But the experiment, first done by Thomas Young in 1801, produces an interference pattern: many bands, alternating bright and dark. That is the classic fingerprint of waves — like ripples in a pond — overlapping and cancelling and reinforcing one another. So light must be a wave.
But Einstein in 1905 (the same year as his special relativity paper) showed that light can also behave as discrete particles called photons — tiny packets of energy. The Nobel committee gave him the prize for this, not for relativity. So light must be a particle.
Which is it? Both. Quantum physics calls this wave-particle duality. Light is both, and what it shows up as at any given moment depends on the situation. The bigger surprise came when physicists ran the same double-slit experiment with single electrons — ordinary particles of matter, fired one at a time. They produced an interference pattern too. The single electron, somehow, was going through both slits at once and interfering with itself.
And then the truly disturbing finding: when a detector is placed to see which slit the electron actually goes through, the interference pattern disappears. The electron stops behaving like a wave and starts behaving like a particle. The act of observation changes the reality being observed. The double-slit experiment is, in the words of Feynman, the experiment that contains all of quantum mechanics. It tells us that the world beneath our senses is not what our senses report.
1Ἔστι δὲ πίστις ἐλπιζομένων ὑπόστασις, πραγμάτων ἔλεγχος οὐ βλεπομένων… 3πίστει νοοῦμεν κατηρτίσθαι τοὺς αἰῶνας ῥήματι Θεοῦ, εἰς τὸ μὴ ἐκ φαινομένων τὸ βλεπόμενον γεγονέναι.1Now faith is the assurance of things hoped for, the conviction of things not seen… 3By faith we understand that the universe was created by the word of God, so that what is seen was not made out of things that are visible.
μὴ σκοπούντων ἡμῶν τὰ βλεπόμενα, ἀλλὰ τὰ μὴ βλεπόμενα· τὰ γὰρ βλεπόμενα πρόσκαιρα, τὰ δὲ μὴ βλεπόμενα αἰώνια.As we look not to the things that are seen but to the things that are unseen. For the things that are seen are transient, but the things that are unseen are eternal.
ὅτι ἐν αὐτῷ ἐκτίσθη τὰ πάντα, τὰ ἐν τοῖς οὐρανοῖς καὶ τὰ ἐπὶ τῆς γῆς, τὰ ὁρατὰ καὶ τὰ ἀόρατα…For by him all things were created, in heaven and on earth, visible and invisible…
1Ἐν ἀρχῇ ἐποίησεν ὁ Θεὸς τὸν οὐρανὸν καὶ τὴν γῆν. 2ἡ δὲ γῆ ἦν ἀόρατος καὶ ἀκατασκεύαστος, καὶ σκότος ἐπάνω τῆς ἀβύσσου, καὶ πνεῦμα Θεοῦ ἐπεφέρετο ἐπάνω τοῦ ὕδατος.1In the beginning, God created the heavens and the earth. 2The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters.
Zetting’s ‘Christmas Lights’ Analogy
Dennis Zetting offers a memorable picture for what the double-slit experiment may mean theologically. Imagine a house with a million Christmas lights hung over every square inch — the trees, the lawn, the swimming pool, the fence. The owner spent eleven months stringing them. On Christmas Eve he gathers his neighbors, but instead of flipping all the switches at once he turns them on one at a time — the house, then the lawn, then the trees, then the pond. Were the lights real before they were switched on? Of course. But from the neighbors’ perspective they were not perceptible until the switch was thrown. Zetting’s argument: Genesis 1 may describe exactly this. Genesis 1:1–2 says the earth was without form and void (Hebrew tohu wa-bohu; LXX aoratos kai akataskeuastos, literally invisible and unconstructed) — an undetectable wave-state. Then in verse 3, God speaks: «Let there be light,» and creation is observed into existence — the switch is thrown. Genesis is, on this reading, the most detailed ancient description of what quantum physicists call the wave-to-particle transition.
What the Bible Already Said About ‘What Is Seen’
Hebrews 11:3 is one of the most quietly radical sentences in scripture. It says what is seen was not made out of things that are visible. In Greek: eis to mê ek phainomenôn to blepomenon gegonenai. The visible world has its origin in things invisible. For two thousand years that statement puzzled theologians. Now physicists are saying the same thing: the macroscopic visible world rests on a microscopic substrate that is not visible at all and does not even behave according to visible-world rules.
The Observer and the Observed
One of the deepest implications of the double-slit experiment is that the universe at the quantum level is not the kind of thing that simply is independent of who is watching. Reality at the bottom is relational — it answers to observation. Some interpretations of quantum mechanics (the Copenhagen interpretation, most famously) take this to mean that consciousness itself is a fundamental ingredient of physical reality. Others disagree. But all serious physicists agree the data are baffling. From a theological angle, this is unsurprising: scripture says there is a Conscious Observer who has been watching every quantum event since before the foundation of the world. The eyes of the LORD are in every place, keeping watch on the evil and the good (Prov 15:3).
‘Things Not Seen’ Is Not Anti-Reason
Hebrews 11:1 defines faith as the conviction of things not seen. Modern readers sometimes recoil from that, hearing it as a license for credulity. But modern physics has demonstrated, with mathematical rigor and laboratory verification, that some of the deepest and most certain truths about the physical world are about things not seen. The atom is not seen. The electromagnetic field is not seen. The Higgs boson was predicted by mathematics 50 years before it was verified at CERN. Faith and sight are not opposites; they are a sliding scale, and the further into reality you press, the more you live by reasoned conviction about things not seen.
Pleasant Springs Church — Discipleship School