I should add that the "requantization scaling factor" mentioned by Langan is the formal description of why "time frame dilation" happens, and why "dark matter" and "dark energy" appear. As depicted in the Conspansion diagram, the states of objects are determined reflexively via the overlapping or entangled waveforms serving as "universal computers", in conjunction with the overall state of the universe.

As for dark matter, the outer edge of the galaxy rotates faster than expected because the inner portion of the galaxy is scaled to slower factor.

The same logic applies to "dark energy", ie the "accelerated expansion" of the universe. The CTUM formally predicts dark energy...

"...because the rate of shrinkage is a constant function of a changing size ratio, the universe appears from an internal vantage to be accelerating in its “expansion”, leading to the conspansive dual of a positive cosmological constant..." CTMU

Photons don't act differently when observed, rather they seem to act differently when there's NO PHYSICAL MEANS TO OBSERVE THEM, versus when there is a physical means to observe them (observe their trajectory).

In the double-slit experiment, a waveform is observed when the photon can't be observed, meaning it's physically impossible to tell which slit is traversed. The photon can't be observed specifically because there's ONLY ONE PHOTON present, this being the precise terms of the experiment. To observe one photon, at least one more photon is required (plus electrons to "register" the data), but where no other photons exist, a "trajectory" can't be established whatsoever, and instead a waveform appears.

The instant the photon can be observed, it reverts to a "particle pattern". The technical details of this are described by the Principle of Conspansive Duality, per the CTMU. Here's a diagram of the Conspansion process wth a technical description... https://ist6-3.filesor.com/pimpandhost.com/1/_/_/_/1/a/t/O/s/atOs6/di-G3XQOQ.png

Conspansion is the inversion of an "expanding" universe (with static-scaled content). From General Relativity, we already know that objects and time-scales have no precise value, so the "expanding" universe model is just a heuristic tool, and not a very good one for describing the deep nature of reality. Via conspansion, the objects and time-scales of the universe "contract" internally to a static domain (primordial black hole, unbound infinity).

Coherence means "sums to zero value", and so analytically, a static model of the universe is the only coherent model even possible.

Back to the photons, the Conspansion process is a 2-stage, "out and back" process whereby the "overall state" of the universe serves the dual-role of the "syntax" (rules of transformation) by which the universe evolves. Quoting Langan...

"Hology is a logico-cybernetic form of self-similarity in which the global structure of a self-contained, self-interactive system doubles as its distributed selftransductive syntax; it is justified by the obvious fact that in a self-contained system, no other structure is available for that purpose." C.M. Langan, Introduction to the CTMU

"Conspansion consists of two complementary processes, requantization and inner expansion. Requantization downsizes the content of Planck’s constant by applying a quantized scaling factor to successive layers of space corresponding to levels of distributed parallel computation. This inverse scaling factor 1/R is just the reciprocal of the cosmological scaling factor R, the ratio of the current apparent size dn(U) of the expanding universe to its original (Higgs condensation) size d0(U)=1. Meanwhile, inner expansion outwardly distributes the images of past events at the speed of light within progressively-requantized layers. As layers are rescaled, the rate of inner expansion, and the speed and wavelength of light, change with respect to d0(U) so that relationships among basic physical processes do not change…i.e., so as to effect nomological covariance." C.M.Langan, Physics & Metaphysics

The point I'm trying to make is that the local arrangement of photons and the arrangement of the two slits are likewise part of the global arrangement. Where no possibility of observation exists, the "system" returns the waveform values at the local level, these being the statistical average of trajectories given the two slits. As already stated, when the local arrangement of photons allows the photons to be observed, a "particle pattern" forms reflexively (discontinuously).

The inclusion of the "overall system" in the formation of local states is required per Bell's theorem. Because particles can be entangled and instantaneously resolved over any possible distance, the entire system is implicated.

"Originally called the Computation-Theoretic Model of the Universe, the CTMU was initially defined on a hierarchical nesting of universal computers, the Nested Simulation Tableau or NeST, which tentatively described spacetime as stratified virtual reality in order to resolve a decision-theoretic paradox put forth by Los Alamos physicist William Newcomb" ibid

By modeling particles as "collapsing", effects are contained inside the cause. Where each quantum state amounts to a "universal computer", the "parallel processing" of nested, universal computers is the formal description of the reflexive "out and back" functioning of the Conspansion process.

"* Because physical objects unambiguously maintain their identities and physical properties as spacetime evolves, spacetime must directly obey the rules of 2VL (2-valued logic distinguishing what is true from what is false). Spacetime evolution can thus be straightforwardly depicted by Venn diagrams in which the truth attribute, a high-order metapredicate of any physical predicate, corresponds to topological inclusion in a spatial domain corresponding to specific physical attributes. I.e., to be true, an effect must be not only logically but topologically contained by the cause; to inherit properties determined by an antecedent event, objects involved in consequent events must appear within its logical and spatiotemporal image. In short, logic equals spacetime topology.*" ibid

So when there's no possible way to observe a photon's trajectory, it's final outcome is determined by whatever information is available, namely the two slits being present, and hence the waveform appears. I hope you can wrap your head around my answer, but it took me many weeks and months of study to comprehend.