What did the term matter include prior to the 20th century?
ordinary matter composed of atoms
And excluded?
other energy phenomena
What does science consider these particles to be?
massless particles
What is a type of massless particle?
photons
Is it matter?
no
What is one example of fundamental particles?
leptons
What's another?
quarks
What are they considered?
they are considered "point particles"
What is the term matter loosely used to refer to?
composite particles
What is the effective size of point particles?
no size or volume.