Reading Griffiths (Introduction to elementary particles) I found this remark about virtual particles "If a photon is emitted on Alpha Centauri, and
absorbed in your eye, it is technically a virtual photon, I suppose. However, in
general, the farther a virtual particle is from its mass shell the shorter it lives, so
a photon from a distant star would have to be extremely close to its “correct”
mass; it would have to be very close to “real.” "
Does this imply every photon is virtual and off-shell? I thought there was a net distinction between real and virtual...