Almost 14 billion years ago there was an explosion at a point called singularity from where the universe started to form.
A real world explosion is expected to slow down over time until it stop, similarly it was expected that the Big Bang explosion would also be slowing down due to the effects of gravity and contracting the effects of Big Bang expansion. In the late 1990s two team of scientists set out to measure this slowdown rate using Hubble Space Telescope. They analyzed type 1a supernova explosion in the universe to determine the slowdown of the Big Bang explosion.
The result had shocked the scientists. It was not slowing down at all rather they found that the galaxy and the supernovas in it are zooming away from us faster than expected and it was accelerating. This kind of acceleration implies that there must be an enormous amount of mysterious energy that is driving this expansion and pushing these galaxies apart. According to Newton's first law of motion, an object in motion stays in motion with the same speed unless acted upon by external force. Scientists thus concluded that there has to be energy to push against the gravity, making these galaxies apart. They came to call that thing as dark energy, a mysterious energy that is making the universe to accelerate.
This energy of expansion is equivalent to more than 10 times of all the visible matters in the universe, in fact 70 % of the universe is comprised of dark energy. The leading theory is that dark energy is a property of empty space itself. The space itself, with no stuff in it at all, has dark energy.
It is a kind of anti-gravity, resulting in a runaway accelerating of the expanding of the universe. It does not mean much right now as we do not feel the direct effects of dark energy but after several trillion years, space will expand so rapidly that it will overwhelm all of the gravity of universe. At that time dark energy will be more prominent than the gravity. All matters including stars, planets, sun in the universe will be torn apart due to the expansion. This is the one way that predicts the end of our universe. There will pure energy which will dissipate into the cold darkness of an unimaginably vast universe.
In 1920 Hubble discovered that our universe is expanding.Hubble was the first tool to measure really precise distance to supernovas out near the edge of the observable universe, and it showed us that out there, ancient galaxies and the supernovas in them are zooming away from us faster than anywhere else. In fact, astronomers realized that they were flying away even faster than expected. At that time, we thought the universe was dominated by gravity, which pulls things together, so seeing everything accelerate apart was weird. Because of this ,scientists concluded that there had to be something else going on, something pushing these galaxies apart. They came to call that thing as dark energy. It is still really mysterious and there is a lot we do not understand about it. One explanation is that it is a property of empty space. This means that space itself, with no stuff in it at all, has dark energy. This energy pushes space apart, creating new space which in turn has dark energy. As this is a property of space, that also means we can not dilute it. Its density will always be the same, no matter how much space expands. If we average the whole universe which is mostly empty space, there is more dark energy than anything else. So it dominates and the universe as a whole expands. That's why the most ancient galaxies are also moving away the fastest. It is taken a long time for their light to reach us, so the universe has had more time to stretch.Now, this might all make dark energy seem super strong after all It makes up more than two thirds of all the stuff in the universe and it is pushing apart entire galaxies.But it is only powerful because there is a lot of it. Within small spaces, specially those full of planets, dark energy is actually pretty weak. Like, the gravity between the Sun and the Earth and the Moon, is more than enough to overpower the repulsive dark energy between them. In fact most of the universe's mass is concentrated in galaxy clusters,and these pockets of matter are completely immune to dark energy. They are simply not expanding.Dark energy is truly not stretching our galaxy at all. This is because it is not a force like gravity, so it works a little differently.Gravity is too strong so our galaxy will never expand because if it can not stretch even a little, then it can not create more space and that means the amount of dark energy inside will never grow. Eventually, in the really distant future, fewer galaxies will be visible from Earth and in 100 billion years or so, deep space will be almost empty. Even as the universe stretches, the glow of our galaxy will still be overhead, and we will have stars,constellations and even a handful of galaxies bound by gravity to ours.
A real world explosion is expected to slow down over time until it stop, similarly it was expected that the Big Bang explosion would also be slowing down due to the effects of gravity and contracting the effects of Big Bang expansion. In the late 1990s two team of scientists set out to measure this slowdown rate using Hubble Space Telescope. They analyzed type 1a supernova explosion in the universe to determine the slowdown of the Big Bang explosion.
This energy of expansion is equivalent to more than 10 times of all the visible matters in the universe, in fact 70 % of the universe is comprised of dark energy. The leading theory is that dark energy is a property of empty space itself. The space itself, with no stuff in it at all, has dark energy.
It is a kind of anti-gravity, resulting in a runaway accelerating of the expanding of the universe. It does not mean much right now as we do not feel the direct effects of dark energy but after several trillion years, space will expand so rapidly that it will overwhelm all of the gravity of universe. At that time dark energy will be more prominent than the gravity. All matters including stars, planets, sun in the universe will be torn apart due to the expansion. This is the one way that predicts the end of our universe. There will pure energy which will dissipate into the cold darkness of an unimaginably vast universe.
In 1920 Hubble discovered that our universe is expanding.Hubble was the first tool to measure really precise distance to supernovas out near the edge of the observable universe, and it showed us that out there, ancient galaxies and the supernovas in them are zooming away from us faster than anywhere else. In fact, astronomers realized that they were flying away even faster than expected. At that time, we thought the universe was dominated by gravity, which pulls things together, so seeing everything accelerate apart was weird. Because of this ,scientists concluded that there had to be something else going on, something pushing these galaxies apart. They came to call that thing as dark energy. It is still really mysterious and there is a lot we do not understand about it. One explanation is that it is a property of empty space. This means that space itself, with no stuff in it at all, has dark energy. This energy pushes space apart, creating new space which in turn has dark energy. As this is a property of space, that also means we can not dilute it. Its density will always be the same, no matter how much space expands. If we average the whole universe which is mostly empty space, there is more dark energy than anything else. So it dominates and the universe as a whole expands. That's why the most ancient galaxies are also moving away the fastest. It is taken a long time for their light to reach us, so the universe has had more time to stretch.Now, this might all make dark energy seem super strong after all It makes up more than two thirds of all the stuff in the universe and it is pushing apart entire galaxies.But it is only powerful because there is a lot of it. Within small spaces, specially those full of planets, dark energy is actually pretty weak. Like, the gravity between the Sun and the Earth and the Moon, is more than enough to overpower the repulsive dark energy between them. In fact most of the universe's mass is concentrated in galaxy clusters,and these pockets of matter are completely immune to dark energy. They are simply not expanding.Dark energy is truly not stretching our galaxy at all. This is because it is not a force like gravity, so it works a little differently.Gravity is too strong so our galaxy will never expand because if it can not stretch even a little, then it can not create more space and that means the amount of dark energy inside will never grow. Eventually, in the really distant future, fewer galaxies will be visible from Earth and in 100 billion years or so, deep space will be almost empty. Even as the universe stretches, the glow of our galaxy will still be overhead, and we will have stars,constellations and even a handful of galaxies bound by gravity to ours.
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