Letter: A virtual answer to the dark matter mystery?

From Bryn Glover, Kirkby Malzeard, North Yorkshire, UK

Your story “Muons point to new physics” brought to mind an issue that has nagged me for a while (17 April, p 14).

If pairs of particles/antiparticles “pop into existence” and then vanish “moments” later, they would, nonetheless, be part of our physical universe for very short periods of time. They also have mass, which is (presumably) the same for both partners in the pair.

I am curious as to whether proposals for dark matter to account for the missing mass that astronomers say is needed to explain the universe take into account the aggregate masses of all the possible virtual particles.