Space-time
Note: The following article is Stephen hawing. As admin, I merely report to clear the youtube text, which you can hear at the bottom.
We have the confidence to consider gravity as a force that attracts objects to Earth. But Einstein had the first idea to consider gravity as an effect of the curvature of space and time in the presence of very large bodies.
Einstein realized that nothing can exist at a certain point in space without existing simultaneously in a given tempo.Lo Space and time appear to be twisted together to form the flexible structure of the four-dimensional 'universe, the so-called space-time.
Space-time is almost impossible to imagine, because our sensory universe is limited to the three dimensions of our everyday experience. For us, the easiest way to get into Einstein's world is to imagine that space and time are like a rubber band plan.
If the time-space was empty, the elastic plan would be absolutely devoid of relief, but much larger bodies such as the Earth and the sun folding curl it slightly elastic surface. This curvature is the concept Einsteinian gravity: the greater the mass of a star or a planet, the more pronounced the curvature of space-time around it, and therefore the greater its gravity. Launched on the elastic plan something extremely heavy as a star collapses on itself, and you end up with a universe full of holes.
When a massive star cools, as it implodes bends more and more space around them. At the end, when it reaches a certain critical mass, literally create a black hole in space-Tempo.Gli objects can fall into a black hole, but they can not get out.
The most terrifying concept in astrophysics lurks at the bottom of a black hole. This is the Singularity. Anything that falls into a black hole, it is annihilated by Singularity, reduced to an infinitely dense and infinitely small point. Even the space and time lose their meaning. All that remains is outwardly a perfect sphere of total darkness, the specter of a dead star gravitation. This sphere is called Event Horizon, and marks the 'brink of' abyss.
L 'Event Horizon is not made of matter. In a sense, it is not even the Space-time distortion. It 's just a coordinate. And 'the only place where gravity is so strong that nothing can escape from within. While the 'event horizon can also have a diameter of only a few kilometers, the' immense gravity of the Singularity creates inside a depression so deep as to be calculable.
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