Why is the black hole at the center of the Milky Way not a quasar?

In reality, the light comes from the accretion disk around a supermassive black hole. The disk is so bright that the galaxy around it cannot be seen. There is a black hole behind every quasar, but not every black hole is a quasar. It must be supermassive: millions or billions of times the mass of our Sun.

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Moreover, what's the gravity of a black hole?

The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now. The sun will never turn into a black hole. And another question, do wormholes exist? Einstein's theory of general relativity mathematically predicts the existence of wormholes, but none have been discovered to date. A negative mass wormhole might be spotted by the way its gravity affects light that passes by.

Is time Travelling possible?

In Summary: Yes, time travel is indeed a real thing. But it's not quite what you've probably seen in the movies. Under certain conditions, it is possible to experience time passing at a different rate than 1 second per second. What is the nearest black hole to Earth? The Unicorn 'The Unicorn' lies a mere 1,500 light-years from us and is just three times more massive than the sun. Astronomers have apparently found the closest known black hole to Earth, a weirdly tiny object dubbed "The Unicorn" that lurks just 1,500 light-years from us. The nickname has a double meaning.

What is inside a black hole?

At the center of a black hole, it is often postulated there is something called a gravitational singularity, or singularity. This is where gravity and density are infinite and space-time extends into infinity. Just what the physics is like at this point in the black hole no one can say for sure. People also ask how fast does a quasar spin? Using a new technique, researchers have determined the spin of five accretion discs - finding that one, in a quasar called the Einstein Cross, is zipping around at over 70 percent of the speed of light.