QuantumTunneling
As Wheeler pointed out, matter is percentage wise, only marginally more dense than the vacuum. Like the vacuum, matter consists of energy or propagating differences. Most signals propagate through matter as easily as through the vacuum. It is only the signals frequencies that an object is "tuned" to receive that are stopped. The only thing that can stop the signal in quantum mechanics is the attempt to occupy and occupied state. State may exist at each Plank length which accommodates differences changing at each unique energy (momentum) in plank units. Excluding occupation of occupied states forces the manifestation of independent state. That is the same mechanism that prevents objects from passing through each other. The total frequency of interaction of a mass is determined by its mass, f=m*c2/h. In the quantum, this is how often it manifests state. If the mass is moving a sufficient speed such that it is unlikely to interact in the time it takes to pass though an object, then it makes no attempt to occupy any occupied state while in the barrier since there is no interaction except at wavelength (alternation cycle distance) multiples. This is the meaning of the DeBroogie wavelength. An alternate view is that the high speed object is simply at too high of a frequency to occupy an occupied state because no momentums in the barrier are that high. The barrier is not listening to it's frequency since its energy states are not occupied, and receives no signals.
The vacuum is composed of only low energy signals (only low momentum occupied states) such that the momentums of higher energy signals are never occupied and the higher energy signals are never impeded. Mass seems solid because higher energy states are occupied forcing reflection of other masses and some signals. Xrays, for example, are high enough energy to pass through many objects without reflection due to the inability to proceed without occupying occupied energy levels.