Physicists have discovered the mechanism that prevents us from seeing the Kingdom of God by electromagnetic waves:

The string theory has been developed for several decades, with a goal to become "the theory of everything", that is, to unify all four fundamental forces - gravity, electromagnetism, strong and weak nuclear forces. A revolutionary discovery of the theory is that the whole universe should have nine or ten dimensions of space, instead of three dimensions (length, width and height). Then, why do we see only three dimensions? In the earlier version of the string theory, it was assumed that those extra dimensions were too small to be observed. Thus, the whole universe is essentially the same as the 3D world. If this were true, there would be no place for God. Fortunately, a few years before 2000, researchers began to realize that those extra dimensions could be as large as the ordinary three dimensions. The reason why we cannot see extra dimensions is because all matter and electromagnetic waves (photons) are confined in a three dimensional sub-universe called "braneworld".

At present, the major agent we use to see or detect things is the electromagnetic waves which include radio waves, microwaves, infrared, visible light, ultraviolet, and x-ray. Since the electromagnetic waves are confined in our braneworld, this immediately explains why we cannot detect God if He lives outside our braneworld. The relationship between our braneworld (three dimensional) and the whole universe (ten dimensional) is like a flat (two dimensional) TV screen in our house (three dimensional). Suppose there is a creature confined on the TV screen, he cannot see us even if we are only a centimeter away from him. Similarly, if God lives in the ten dimensional space but outside our braneworld, we cannot see Him even if He is only a centimeter away from us.