Why Does This Cosmologist Refer To Galaxies As "Particles"

[Gizmo j]

5 minutes and 45 seconds in, this guy says that he's going to refer to galaxies as particles....

He then says particles for the rest of the lecture instead of galaxies.

Why?

 

[nakedfrog]

Found particle man, triangle man hates him.

 

[Stiff Clamp]

Universe man, universe man, size of the entire universe, man