Is Time Travel Possible In Our Universe?

Formation:
Black holes are born from the remnants of massive stars that have exhausted their nuclear fuel and can no longer counteract the force of gravity. When these stars undergo supernova explosions, the outer layers are expelled into space, leaving behind a core that's too massive to be supported by other forces. If this remaining mass is above a certain threshold (the Chandrasekhar limit of about 1.4 times the mass of the Sun), the core will continue collapsing under its own gravity.

Event Horizon:
The collapsing core forms what's known as an event horizon, which is the boundary beyond which nothing can escape the black hole's gravitational pull. This boundary is defined by the Schwarzschild radius, a mathematical concept that depends on the mass of the black hole. Anything that crosses the event horizon is considered lost to the black hole forever, as the escape velocity exceeds the speed of light.

Singularity:
The core's collapse continues until it reaches a point of infinite density called a singularity. This is where all the mass of the original star is concentrated into an infinitely small and dense point. The singularity is hidden within the event horizon, and our current understanding of physics breaks down when trying to describe what happens at this point.

Types of Black Holes:
There are three main types of black holes, classified based on their mass:

Stellar Black Holes: These are formed from the remnants of massive stars and typically have masses between a few to several tens of times that of the Sun.
Intermediate Black Holes: These have masses between stellar black holes and supermassive black holes, ranging from hundreds to thousands of solar masses. Their formation is not fully understood.
Supermassive Black Holes: Found at the centers of most galaxies, these have masses ranging from hundreds of thousands to billions of solar masses. They are thought to have formed and grown over cosmic timescales through accretion of mass and mergers with other black holes.
Observation:
Directly observing black holes is challenging because they don't emit light. However, their presence can be inferred through their gravitational effects on nearby objects, such as stars and gas clouds. Astronomers also detect them indirectly by observing the X-rays emitted from the matter that's heated and accelerated as it falls into the black hole's gravitational field.

Black holes are still a subject of intense research and exploration, as they have profound implications for our understanding of the nature of space, time, and gravity.