What does CMBR stand for in astrophysics?

CMBR stands for Cosmic Microwave Background Radiation. This term refers to the thermal radiation filling the universe, a remnant of the Big Bang that occurred approximately 13.8 billion years ago. Following the Big Bang, the universe was in a hot, dense state and as it expanded, it cooled. The photons emitted from this early state continue to travel through space today, revealing crucial information about the origins and evolution of the universe.

The Cosmic Microwave Background Radiation is uniform in all directions, indicating that the universe was once hot and dense before it expanded and cooled. Its discovery has provided significant evidence for the Big Bang theory and helps scientists understand the large-scale structure of the universe.

The other options presented do not accurately reflect the established terminology in astrophysics. They either misinterpret the components involved (like "micro black radiation" or "molecular background radiation") or refer to concepts that aren't recognized in scientific discussions about the universe’s early state and subsequent evolution. By understanding CMBR, one gains insight into fundamental questions regarding the beginnings of the cosmos.