particle horizon
Astronomy
noun
A notional surface surrounding an observer, from beyond which no particle or information could have reached the observer during the lifetime of the universe.
Origin
1950s.
- plain-looking
- plainly
- plain man
- plain muscle
- plainness
- plain-paper
- Plain People
- plain sail
- plain sailing
- plain-saw
- plain sawing
- plains bison
- plains buffalo
- plain scale
- Plains Cree
- Plains culture
- plain service
- plain sewing
- Plains hunter
- plain sight
- Plains Indian
- plainsman
- Plains of Abraham
- plainsong
- plain-speaking