Simplify the following text for a Grade 11 native English-speaking person.
Original: A related definition of the term universe is everything that exists at a single moment of cosmological time , such as the present , as in the sentence `` The universe is now bathed uniformly in microwave radiation '' .
Simplified: A similar definition of the term Universe is everything that exists at a single moment of time , such as the present or the beginning of time , as in the sentence `` The Universe was of size 0 '' .