Simplify the following text for a Grade 13 native English-speaking person.
Original: In cosmology , cosmic microwave background ( CMB ) radiation ( also CMBR , CBR , MBR , and relic radiation ) is thermal radiation filling the universe almost uniformly .
Simplified: Cosmic background microwave radiation ( CMB radiation ) is radiation in the microwave part of the electromagnetic spectrum , which comes from all directions in outer space .