your letter for so many years of gravitation in fact does not exist!(this is einstein said)

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our reporter xu bin

since newton's time, gravity appeared in scientific research of various occasions.more recently, it helps people"see"the extragalactic planet.american astronomer at the university of oklahoma, according to the recently published papers using nasa's chandra x-ray satellite data and micro gravitational lensing, at a distance we found in the galaxy of 38 light years a number of planets, this is the first time that the milky way.

gravity not cut constantly attract each other between material?why it can help scientists to"see"the planet?what is the nature of it?

let the apple doesn't fall, also let the planets orbiting the sun

about gravity, people always think of the story of the apple doesn't fall.story is sitting under the apple tree newton were brood to planetary motion problems when an apple fell in front of him, make him insight to make apple fell to the ground gravity, is that the moon around the earth.the earth attracts the apple not only, also attracted all objects on the earth's surface, including the distant stars.

today, disputed the truth of the story, and had little information.but what is clear is that gravity process is put forward, and not lingganshi epiphany.

as early as the 17th century, kepler according to the observation data of previous tycho brahe, summed up the planets in the solar system works, and puts forward the three laws of planetary motion.the three laws of involving the shape of the orbit of planets in the solar system, speed and cycle, to the orbital laws of planetary motion.

kepler's three laws of planetary motion makes truly become the center of the solar system planets orbit the sun, also let scientists began to think about, why would a planet around the sun?what is guided by their sport?

newton since the 1660 s began to think about this problem.he from kepler's third law calculates that the planet around the sun movement required force is proportional to the square of the distance with them from the sun.this is the prototype of the universal gravitation.

but gravity forward, until 1687.in the 20 years, newton to planetary elliptical orbit and is inversely proportional to the square of the distance of the relationship between the force were studied, and the universality of gravity was thinking.

in 1687, the publication of the scientific principle of natural philosophy.in this science book, newton put forward three laws of motion and the law of universal gravitation.he believes that the mutual attraction between two objects, that is gravity.the size of the force and two objects is directly proportional to the quality of the product, and is inversely proportional to the square of the distance between the objects.can be deduced from the law of universal gravitation, kepler's three laws.this shows that the planet is under the domination of gravity movement among the stars.

gravity, unveiled the moon and stars running of the inner mysteries.it became a cornerstone of human understanding and know the world.newton himself with the law of gravity for the interpretation of the tides, the phenomenon such as planetary precession, newton's friends harley use it to predict the return period of halley's comet, french astronomer levy and neptune's existence is calculated by the universal gravity.of aerospace enterprise play an important role in the first, second, the third cosmic velocity calculation, also have the law of universal gravitation.

it is worth mentioning that in newton's universal gravitation formula, there is a gravitational constant g.until more than one hundred years after the advent of gravity it by british scientists cavendish with a torsion balance design measure, make the law of universal gravitation more hasten is perfect.

nature doesn't exist, just the illusion of space and time

although once thought to be very accurate and perfect theory, newton's theory of gravity also has its limitations.for example, it can't explain what is the nature of gravity.there are some natural phenomenon, newton's universal gravitation can't explain.

astronomical observations have found that the perihelion of mercury's orbit around the sun at the speed of very slow moving, this is called the precession of perihelion of mercury.according to the law of universal gravitation can calculate the precession speed, however it with actual observations of accurate numerical differences between every 43 angle difference value is one hundred seconds.to compensate for this difference, the scientists made various attempts, such as the assumption of mercury and a nearby will affect its orbit"vulcan star", or the inverse square of the gravity field of the relationship, or adopt electromagnetic theory to explain.these attempts are confirmed, until einstein.

in 1905, einstein was based on the principle of the speed of light remains the same, completed the creation of a special theory of relativity, objects under the condition of high-speed movement, there will be no relativistic effects of newton's classical physics.ten years later, the landmark's theory of general relativity, targeting the source and nature of gravity.

unlike newton's theory, the theory of general relativity, time and space is no longer a relatively independent existence.the scene objects are considered, is no longer a three-dimensional space, but space and time related four-dimensional space-time and space.the movement of objects, in turn, will in time and space.

this two kinds of space are very different.newton's straight three-dimensional space is a euclidean space, newton's classical physics all theory based on this.einstein's theory of the four-dimensional spacetime could not straight-it may just is a delegate with spherical curvature space, may also is a delegate with saddle surface negative curvature space, only if the curvature is equal to zero it is simplified to a flat space.and the curvature of spacetime, decided by the material.

einstein's general theory of relativity to write field equations, illustrates this relationship:the substance of energy and momentum can make bending spacetime.and the equations of motion are explained in this space and time in the motion of matter.

in curved spacetime, a lot of rules have changed.for example, the shortest line between two points is no longer a straight line, but a called geodesic curve.to this, the most intuitive example is the shortest route from beijing to los angeles distance, is not directly through the east pacific ocean, but rather to the first flight and then northeast to the southeast direction back into a curve of the continental united states.the reason is that the plane is flying along the three-dimensional sphere, both through is the shortest route between two places and the center of the earth to make a large circular arc, tortuous route is it on the 2 d map projection.

the movement of material in the curved spacetime is different from our intuitive understanding.from einstein's equations of motion, can solve the freedom is not affected by external forces of particle in the curved trajectory of the space, it is a spiral curve of the four dimensional space-time.if the projection to the three-dimensional space, it happens to be a planet in the solar gravity elliptical orbit.that is to say, planetary motion around the sun, but it is in the movement of inertia in the four dimensional space-time, don't need any gravity.

einstein created one of the motivations of general relativity, gravity is not included in the special theory of relativity theory framework.in his new theory, the end-result of gravity was does not exist!

people often use the sheets to analogy the situation.if you don't consider the effect of material of time and space, so our space and time is like a stretched flat sheets.in the middle of the bed sheet placed a shot put, the sheets will sag, is like because the material of the general theory of relativity and curved spacetime.if a ball on the hollow sheet, it will roll towards the direction of the shot put in the past, seem to have the attraction of the shot put.in fact, the movement of the ball just because of the space geometry effect.newton thought gravity almost everywhere, is essentially nonexistent.

to build the most sophisticated telescopes, search for distant planets

with the general theory of relativity, the precession of perihelion of mercury problem solved.einstein calculated mercury perihelion precession speed and perfect fit.when published the general theory of relativity, einstein predicted that, due to the bending spacetime, flying out of the sun's surface of photons frequency redshift, distant star's light bending happens near by the sun.these predictions were observed after one by one to confirm, confirm the general theory of relativity in the description of the world in terms of accuracy.especially the gravitational deflection of light.although the newtonian theory of gravity can also calculate the bending angle of the light, but the questions and the precession of perihelion of mercury, the results deviation is too big.

gravitational lensing is gravitational deflection of light.galaxies such as massive celestial objects(lens) will make it near the bending spacetime, when the rear light background objects from the curved spacetime through bend light will happen just like light through a lens.according to the background objects, object lens, the different position of the relations between the observer and eventually formed in the eyes of the observer more like or ring like.in 1987, the american astronomer jacqueline hewitt first observed gravitational lensing form annular ring like--einstein.today, human beings have seen many similar gravitational lens image.

gravitational lens bending angle to the light, depending on the quality of the lens body.if the lens is not big enough, the quality of the celestial bodies such as just a star, what happens?this is to help astronomers find micro gravitational lensing of the planet.

calculations show that the star quality of the lens body of einstein ring is very small, even the most advanced telescopes cannot distinguish it.people see, but because the gravitational lensing effect more brighter background objects.and the formation of micro gravitational lensing as though there is at most a few years time, compared with the gravity through the mirror at the existence of millions of years of time, is fleeting.

although difficult, astronomers found that micro gravitational lensing can lead in search for exoplanets.when the star quality level from background objects before through the micro gravitational lens can let background objects in a short time look brighter, reflect on the photometric curve is a projection of peaks.but if the photometric curve of the observed to appear on more than one peak, then the stars near the quality and other small objects, such as the planet.using this feature, to judge the existence of extraterrestrial planets, analysis its quality parameters such as distance and the stars, even if the telescope never appeared in this planet.

if compare micro gravitational lensing to a telescope, its advantage is very obvious, such as allowing people to explore the world more distant planets.in 2003, two teams of researchers for the first time in this way to find exoplanets, 16000 light-years from earth.in the latest findings, astronomers innovative use of the method of micro gravitational lens, the scope of the human search for planets extends to the outside of the milky way.

simple speaking, in the latest study, astronomers comprehensive utilization of the gravitational lens and micro gravitational lensing to find planets--the galaxy's gravitational lensing make rear background objects formed multiple virtual image, a galaxy of stars and planets of micro gravitational lensing effect, make the virtual image of luminosity and line frequency changing.observation and simulation results show that the rx j1131 in 38 light-years from earth-1231 galaxy's center, home to a group of planets, quality between the moon and jupiter's quality.with micro gravitational lens caused by the"telescope", the precision of the highest accuracy over the earth and the sky observation instruments, let the first find evidence of the existence of planets in other galaxies.

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