A mysterious cosmic recipe.
Today, we discuss the composition of the universe in the last article in the trilogy of the universe.
As the great German astronomer Johannes Kepler at the beginning of the 17th century, wrote: “when the storm and national wreck threats than anything we can do our peace studies of main shaft sinking land more worthy of the eternal.
So, again, let’s sink our anchor into paradise. Before that, we talked about what the expanding universe meant, and whether we could understand their most difficult problem – the origin of everything. Our question today? We know how much stuff fills the universe?
For the sake of clarity, I will break down the universe recipe into three main components: the things we make; Dark matter; And dark energy.
We make things.
In school, we know that everything in the world is composed of 92 natural existence of atoms – from hydrogen to uranium – and each atom is made up of three particles – only protons, neutrons and electrons – number is different. Hydrogen has one proton and one electron, and one of the uranium has 92.
In order to reduce the composition of materials around us (including the materials we make) to just three particles, this is a stunning achievement of 20th-century physics. This reduction is more than that, since protons and neutrons themselves are composed of more fundamental components, namely, upper (u) and lower (d) quarks. A proton is a uud composite, and a neutron is a udd composite. So, we can proudly say that the things that make up the world are made up of two different kinds of quarks and electrons. Three particles describe everything from water to bones, leaves, rocks, air, planets to stars.
Of course, the details are a bit complicated, because the particles need to interact – attract and repel – to make things. These are the forces between the particles – gravity and electromagnetism are two more familiar, and the strong and weak nuclear forces acting on the nucleus within very short distances. All four forces are described by the exchange of particles. A useful image is that two skaters glide along a lake, each carrying a bag full of tennis balls. When they throw balls at each other, they shrink back and imitate their repulsion. It’s like two equal charges. So, modern particle physics (aka high-energy physics) describes the material and the forces that are made up of basic components. If we count them all, we can get 12 things plus the higgs boson,
Surprisingly, this simple picture is well maintained and runs through the known universe and its history. The stars that are five billion light years from our sun are still made of hydrogen. All the atoms that make up 92 natural chemical elements come from stars. (when the universe is very young, it also produces light cores, such as helium and lithium, and some of their isotopes, as well as hydrogen isotopes deuterium and tritium.) In a sense, the star is the true alchemy furnace, capable of converting the lightest elements into all others, because they compete with their own gravity. As we say in astronomy, what happens to hydrogen when you wait long enough? The atoms in your body, the iron in your blood cells, the calcium in your bones, causes about 60 percent of the water’s oxygen and hydrogen to come from stars that died billions of years ago before the sun and earth formed. We are an animation of very old things.
There are other particles, such as the trillions of ghostly neutrinos (three of them) per second.
And the astonishing thing is that all of these by 92 atoms, neutrinos and photons – that is what we all around us and see everything in the sky – a total of only 5% of the poor. What’s the total? The rest fills the universe. This is where the mystery begins.
Astronomers in the 1930 s, the United States and Switzerland fritz wiki to notice, when galaxies ChengDaQun when they move much faster than he can use each other they should be applied to explain the speed of gravity. Zwicky speculates that galaxies carry far more mass than we can see.
He calls this invisible thing “dark matter” : it pulls the pull out, but it doesn’t shine. Now, humans and planets are invisible, but they are not dark matter. They can still reflect visible light, and can glow even though they are invisible in the infrared. (our eyes can only see a small window of the entire electromagnetic spectrum.) Dark matter is the real darkness, not the emission or reflection of light. The trouble is, no matter what dark matter is, it’s not made of quarks, electrons or photons – or neutrinos. (although neutrinos have been proposed for years as dark matter candidates, they are still remote.)
To make things more exciting, the current measurements suggest that about 26 percent of the universe’s materials are made of dark matter. This is five times as much as usual. We don’t know what it is or what it might be. Of course, there are some real candidates, because the mystery of dark matter has captured the imagination of thousands of physicists around the world. So far, though, there has been no luck, despite the ferocity of the search for the particles in ground and space-based detectors. Some even suggest that there is no dark matter, which is our understanding of gravity is limited. Either way, to solve the mystery of the dark matter will no doubt for the universe and its components of open a new window, the window seems to be very close, but so far have proved to be extremely deceit.
So, we still have 69 percent of the stuff in the universe. Here, we find the largest of all the problems in current cosmology – “dark energy”. In 1998, two teams of astronomers discovered that dark energy is often described as responsible for accelerating the expansion of the universe, apparently as a flexible force in space structure. (see our first article on how the expansion of the universe was caused by space stretching). It keeps distant galaxies away from each other as if they were steroids.
Current measurements account for 69 per cent of the missing. We don’t know what the dark energy is, although we make it into a very smooth liquid that fills the whole space, like the water in the bathtub. But a strange and unpleasant water is almost immeasurable, but it can drive everything. People are confused about this cosmic rejection and ask how we can’t feel it. The answer is that the effect of dark energy is true cosmology, that is, it can only be felt at large distances of millions of light years apart. Our solar system, our galaxy (only about 100, 000 light-years across) is glued together by the local gravity, much stronger than the dark energy repulsive.
Another strange fact about dark energy is that it seems to have been launched five billion years ago, not far from the sun and the solar system. This is often called the “problem of coincidence”. Then why?
Although we have made great progress in understanding the nature and composition of the universe, there is clearly much to learn. It should be. After all, a new problem for each of our answers is the nature of scientific inquiry. We move forward because we do not know the humble, because we face some of the most difficult questions we can ask. Life is not a bad way.