The expanding universe emerged from a cataclysmic event called the Big Bang

The universe began as an infinitely dense cosmic singularity which began its expansion in the event called the Big Bang, which can be described as the beginning of time
During the first 10–43 second after the Big Bang, the universe was too dense to be described by the known laws of physics

The universe began as an infinitely dense cosmic singularity which began its expansion in the event called the Big Bang, which can be described as the beginning of time