According to the standard model, matter collides by a basic substantiality that light does not have, so:
“Two photons cannot ever collide. In fact light is quantized only when interacting with matter.” Wikipedia
In contrast, quantum realism predicts that extreme light in empty space will collide to form matter.
Lest this seem fanciful note that:
1. Photons confined have mass. A free photon is massless but if confined in a hypothetical 100% reflecting mirror box it has a rest mass because as the box accelerates unequal photon pressure on its reflecting walls creates inertia (van der Mark & t’Hooft, 2011). By the same logic, photons entangled in a node will have mass.
2. Einstein’s formula. That matter is energy works both ways so if nuclear bombs can turn mass into energy, photon energy can create mass. The Breit-Wheeler process describes how high energy photons can create matter.
3. Particle accelerator collisions routinely create new matter. Protons that collide and stay intact give new matter that didn’t exist before. If this matter comes from the collision energy, why can’t high energy photons do the same?
4. Pair production. High-frequency light near a nucleus gives electrons and positrons that annihilate back into space.
5. Light collides. When high-energy photons at the Stanford Linear Accelerator hit an electron beam to accelerate it at almost the speed of light, some electrons knocked a photon back with enough energy to hit the photon behind it, giving matter pairs that a magnetic field pulled apart to detect (Burke & et al, 1997).
That light alone can collide in a vacuum to give matter is a testable prediction but no experiment has yet unequivocally confirmed it. When beams of pure light collide in pure space to create matter, the boson-fermion distinction will fall and with it the standard model. Quantum realism predicts that matter evolved from light, so the future of physics lies in colliding light not matter.
The standard model expects the short-lived energy flashes of its accelerators to unlock the secrets of the universe but it isn’t happening, and quantum realism says that it never will. If matter evolved, billion-dollar accelerators are just discovering evolutionary dead-ends, as in evolution, what doesn’t survive doesn’t matter. Particle models assume that matter came first but in quantum realism, light was the first existence.