[WillT (OP)]

This week, Question of the Week comes in from listener Phil, who asks 'What makes up the space when subatomic particles move to a different place in space? Is it a void?'

[alancalverd]

Yes, at least from the point of view of the particle!

As far as we know, neutrinos don't "see" most solid matter at all: almost all of those that enter the earth's atmosphere exit on the other side of the planet.

The physics model uses "interaction cross sections" of different particles and media. The cross section "neutrino - anything" is so small that the neutrino's universe consists almost entirely of empty space.

On the other hand, practically all alpha radiation is absorbed in a sheet of paper. The cross  section of almost any interaction is very large and the world looks to an alpha particle like a brick wall looks to a human.

Neutron interaction cross section  depends strongly on the energy of the neutron  and the atomic weight of the material through which it passes, so hydrogen-rich materials like butane have a very large cross section but steel doesn't - it "looks like" relatively empty space -  and you can radiograph the contents of a liquid gas cylinder with a neutron beam.