Big Bang Theory

The Big Bang Theory posits that the universe began around 13.8 billion years ago from an extremely hot and dense state. According to General Relativity, space and time are interconnected and were created in this event. As the universe expanded, it cooled, allowing galaxies, stars, and planets to form. Extragalactic astrophysics studies phenomena beyond our galaxy, providing evidence for this theory through observations like cosmic background radiation and the redshift of distant galaxies, which show they are moving away from us. This expansion suggests that the universe is still growing today, leading to our current understanding of cosmology.