Reveal dark energy:Wukong, why do you want to search
for dark matter?
On December 17, 8 12 points, when the dark matter particles detection "the wukong" in jiuquan satellite launch success.For more understanding about the mysteries of dark matter, we around the "monkey" to this event with the national astrophysical observatory scientists, the book the translator team on interstellar through gou lijun, wang LAN, try a gain, Wang Qiao four teachers are discussed, the following is a conversation.
What is dark matter?
We usually feel when using ropes rotate an object, the faster the rotational speed rope stretch tight tight, this is because the object rotation need to provide greater centripetal force.Objects in the universe rotates, offer rotating centrifugal force is gravity.
But in 1933, the California institute of technology in astrophysicist fritz, wei base found around the orbit each other between the galaxies have huge exception.He through astronomical observations, estimate the relative speed between the galaxies, the quality of the galaxy, and get it in other galaxies.These galaxies movement speed quickly, so that the gravity can't put them in the same cluster.In theory, the cluster must be scattered, was soon destroyed.If with a rope rotating case, is the rope can't afford this speed and be left off.
(we study the base of the coma cluster of galaxies)
So, we make the one according to the power base: coma are sure to be filled with some kind of "dark matter", their gravity is strong enough, can put the clusters bound together.
This is like weighed, originally we according to the girl's body to estimate her weight is 50 kg, results the scale showed 200 kg.In check the bathroom scale, gravity is no problem, we can only guess at the girl who has something we can't see occupy a large part of the body weight.
The invisible substance, defined as invisible on science, namely the electromagnetism is very weak and even have no substance.But also they can produce enough gravity, even if we can't see, there are also other ways they were observed.By the 1970 s, we already know very well that the so-called dark matter pervades almost all even a single galaxy clusters.To the early 21st century, we already know that dark matter will have gravitational lensing effect on the light of distant galaxies.Now, these lens effect was used to detect the distribution of dark matter in the universe.
Dark matter in galaxy cluster Abell 2218 gravitational lensing effect, which produces to the more distant galaxies diagram by gravitational lensing effect galaxies into arc (purple circle of galaxies)
Understand dark matter, dark energy?
We know that the universe originated from an explosion, 13.7 billion years ago, scientists call the "Big Bang" (Big Bang).While it's still don't know the cause of the big bang, but we know from that moment on, the universe becomes full of high temperature gas of the vast ocean, and the rapid expansion in all directions.As time goes on, the universe cooled, formed a variety of fundamental particles of which matter make up our universe.
The evolution of the universe of (our)
If there is no any bondage, the expansion of the universe will continue indefinitely.But all matter in the universe, stars, galaxies, galaxy clusters and dark matter, etc.) between through gravitational attraction.The existence of gravity should make the expansion slow down its speed.
But in 1998, two research teams have independently discovered a shocking phenomenon: the expansion of the universe is accelerating.If our universe is seen as a blow up the balloon, we predict the expansion of the universe, before one end should be a balloon in the inlet, the other end in the gas, the balloon expansion rate should be more slowly, or even likely to close a balloon.But the observations show that the balloon is almost no vent, intake is more and more, expand faster!
Why the universe acceleration?
There are two possible: on the one hand, Einstein's relativity theory of gravity is wrong;On the other hand, in addition to ordinary matter and the dark matter in the universe, there is another material existence, this kind of material of gravitational repulsion.
Many physicists strongly supported the laws of physics, Einstein's relativity completely don't want to give it up, so they tend to repulsion.This kind of imaginary things with repulsion is named "dark energy" (dark energy).
This problem has not yet been determined, but if the exception is caused by the dark energy, then through gravity observation we know that for roughly the current total mass in the universe than, dark energy accounted for 68.3%, 26.8% dark matter, and you and I, planets, stars and galaxies of ordinary matter (or called baryons material) is only 4.9%.
Why this satellite is named "the wukong"?
It is said that the reason that the scientists named the scientific experiment satellite "monkey", is looking forward to it like the famous monkeys have turned into the danger of courage, like a Monkey King drawn in the vast space, identification of dark matter, go to "grasp space", the development finally overcome the Buddha as the authentic texts of dark matter.
(so, but scientists have not calculated tiangong 1 psychological shadow area?)
"What is the wukong"?
The wukong space for more accurately, a high-energy particle detector, mainly detect electronic cosmic rays, high-energy gamma rays, and nuclide cosmic rays, etc.If read detective novels will know there is a law of roca - "every contact, will leave traces.Dark matter particles could be because the annihilation or decay collision, and cosmic rays, we can through the traces of these cosmic rays, namely the specific spectrum to detect dark matter.
(dark matter particles probe DAMPE "monkey")
Dark matter particles probe "Monkey King" is China's first scientific experiment satellite launch, observation can segment the widest range in the world, the optimal detection of dark matter particles energy resolution satellite, its complexity and engineering implementation difficulty than ever before.It can measure the charge number, incident direction of incident particles and the incident energy, and to distinguish the types of incident particles.According to detecting data, there is the possibility of the introduction of evidence of the existence of dark matter.
What is the meaning of detecting dark matter?
In fact, we have now found some dark matter, such as neutrinos is one of them, but according to the calculated found neutrino mass proportion is very small, so the universe there must be more dark matter has not yet been found.Sending a probe to space is one of the means, the United States has a similar mission, but from the point of feedback data, confidence level is not high, is not enough evidence of dark matter as the universe.
We know that in the first half of 2013 the European organization for nuclear research, announced that confirm that found the higgs boson, the predictions of the standard model of a fundamental particles were finally found, fill in the standard model dig the pit.The 2013 Nobel Prize in physics is no suspense to awarded in the study of the higgs boson make a significant contribution to the francois engler and Peter higgs.
(when detecting the higgs boson - proton collision trajectory diagram)
Scientific research is often assume that a theory first, dig a hole, and then by everyone together to fill in the pit.If dark matter particles probe "monkey" to find evidence of the
existence of a large amount of dark matter in the universe, is the equivalent of digging a bigger hole, let us further understanding of our universe.This discovery is certainly Nobel Prize level, but also gave rise to more Nobel Prize level research.
At this stage it can be difficult to find the practical significance of the application examples of detecting dark matter directly.Like Albert Einstein proposed that the theory of relativity, quantum mechanics Copenhagen school development, then people will not think of these theories has such a big influence on we now live.Our daily application of GPS satellite positioning requires application of theory of relativity, and the quantum mechanics for emerging now computer can also become the development direction of the future computer.
If you want to use a popular, for example, to illustrate the scientists explore the purpose of dark matter in the universe, may be like the girl weighed, found himself under a lot of weight with the expected deviation, total want to find out the reasons to explain.Or, we can also according to the new scientific discovery, produce like star trek through "good science fiction movies and books.