Looking at the quite night sky, one might think of the Universe is a peaceful place. However, our modern theoretical models of Astrophysics, as well as the whole army of modern space technology, and powerful telescopes, have all revealed to us a Universe full of the most mysterious and violent objects imaginable.
Let us start our journey 13.8 billion years ago with most violent and mysterious event: The Big Bang. The whole Universe exploded. A theory of quantum gravity is essential for us to understand more, as well as more experiments are needed. Travelling fast into the future of the Universe, we can observe galaxies with huge black holes in their nuclei, such as galaxy M87. Perhaps the next most violent event would be the collision of two huge galactic black holes. This can happen as galaxies merge quite often, and their supermassive black holes collide with each other after dancing a cosmic tango. Below you can see a picture of the massive core of M87, which is a recent landmark discovery:
Supernovae explosions are by far less violent events, but they are still one of the most violent events inside a galaxy. When they occur they become more bright than all the other stars of the galaxy combined together. Black holes and and neutron stars (pulsars) are formed after the death of a star with a supernova explosion. Today, we don't understand enough about matter to know of a mechanism that would prevent it from infinitely collapsing, under strong enough gravity (this is a black hole). Hence, a black hole is exactly an other mysterious object of infinite density, and violent behaviour. The tidal forces near a black hole tend to disintegrate matter into particles. The accretion disk of materials near many black holes emits x-rays, which would kill instantly any human.
Neutrons stars and white dwarfs are also extremely violent and mysterious states of matter. Our sun will become a white dwarf in a few billion years, and life on Earth will become extinct.
We must certainly agree that this is a violent event for the human standards. Observers from nearby stars, will know nothing about the hell of human extinction, they will only see a beautiful planetary nebula :
Even at the scale of our solar system, there are many violent events. The beautiful comets with their tales and the spectacular meteor showers, are only relatives of the mysterious object that collided with Earth before 150 million years and caused extinction of life on Earth. The dinosaurs were killed together with the 2/3 of the forms of life on the planet.
The object must have been an asteroid with a diameter of 16 km. The exact mechanism of extinction remains unclear. However it is certain that the object caused a disturbance of the natural balance of mechanisms on Earth. Temperature was too high for life to survive, and a cloud of materials probably covered the Earth, making it impossible for solar rays to vitalise the most life. Asteroids and comets are obviously objects of common origin, but they display different behaviour and intrinsic composition. When considering violent events we must also mention that the Moon was formed after a collision of the Earth with a massive planet. Materials were exploded into space and soon combined to form the Moon. In the early solar system collisions between planets was possible, but in our age they are impossible. However, we must still develop our technology to defend against a future and inevitable asteroid impact. Our bodies are made of chemical elements that were formed not during the Big Bang, but during supernovae events. Let us, embrace cosmic violence as a creative force for us. After all, we wouldn't be in existence today had the dinosaurs not become extinct !
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