The curvature of the space-time

http://genrel2016.info/space-time-is-curved/

 

La matière dicte la courbure de l’espace. Et l’espace dicte le mouvement de la matière.  

 

Des scientifiques de la NASA ont annoncés que la mission Gravity Probe B a permit de confirmer deux prédictions de la théorie générale d’Albert Einstein.

Le satellite Gravity Probe B à été lancé en orbite à 644 km de la Terre en 2004, et a utilisé quatre gyroscopes ultra-précis, disposés dans un satellite pour mesurer les deux aspects de la théorie sur la gravité  d’Einstein (Relativité générale). Les gyroscopes sont des dispositifs utilisés pour mesurer l’orientation.

 

Les sphères parfaites sont les sphères à l’intérieur des gyroscopes Gravity Probe B sont considérées comme les sphères les plus parfaites du monde, mais de minuscules anormalités ont forcé les scientifiques à effectuer des calculs pour s’assurer que leurs observations étaient correctes.

 

Les gyroscopes ont alors mesuré deux effets :

• le premier est l’effet géodésique, qui est la déformation de l’espace et du temps, ou espace-temps, autour d’un corps, comme une planète. On peut visualiser l’effet géodésique en imaginant la Terre comme une boule de bowling et l’espace-temps comme un trampoline. La gravité de la Terre déforme l’espace-temps de la même façon que le ferait une boule de bowling au milieu d’un trampoline.  
• Le second effet, de la gravité, testé et mesuré par le Gravity Probe B est l’effet lense-Thirring, où aux alentours d’un immense corps en rotation, l’espace et le temps sont en quelque sorte « entraînés » avec le mouvement de rotation.

 

Le but de le la mission était de faire ce que Einstein croyait impossible à réaliser. Pour réaliser ces tests, Gravity Probe B a utilisé un appareil appelé suiveur stellaire qui suit une seule étoile, à savoir une étoile guide de référence qui est IM Pegasi. Elle sert, de référence pour mesurer la déviation des gyroscopes. Donc il faut savoir que si nous vivions dans un univers qui se comporterait comme prévu par Isaac Newton, et ce qui n’est pas le cas, dans lequel l’effet géodésique et l’effet lense-Thirring ne se produisent pas, alors les gyroscopes du satellite resteraient alignés avec l’étoile guide.

The spacetime

https://asd.gsfc.nasa.gov/blueshift/index.php/2015/11/25/100-years-of-general-relativity/

The simplest definition for spacetime is surely a space in four dimensions used in the theory of relativity to determine the position of one phenomenon.

According to Isaac Newton, space and time were two totally independent notions which could exist without the other one. It was for example natural to speak about a body without referring to the moment when this one was measured. But in the field of relativity these two notions go hand in hand, they are indivisible. For this reason this theory can only consider events : that is to say actions which happen in a precise space at a given moment. Speaking about space or time independently from one another doesn’t have sense. As a consequence the physicians unify these two concepts in a more general structure with four dimensions: three for space, length, width, depth and one for time. It’s called space-time.

The work which was at the origin of the general relativity is the mathematical expression of this spacetime with four dimensions done by Hermann Minkowski. His work is a part of a lot of other works made before like those of Henri Poincaré.

Experimentation

We tried to reproduce the curvature of spacetime by making an experience. So we weighed the different marbles and tried to associate them with the different planets of our solar system. After finding the representative marbles, we began the experience.

We stretched the cling-film on a bowl and put the marbles on it one at a time. We took a picture of each step. At the end we tried to show the curvature of the spacetime of a black hole by sticking the cling-film at the bottom of the bowl.

Our experiment shows the impact of the mass on spacetime, and the deformation when this is quite big. With our results we can imagine what would be the impact of  really heavy marble on this cling film.

Unfortunately the experience wasn’t a success and we weren’t able to show what we wanted. The reasons are that the cling-film wasn’t flexible enough.

 

Space-time

Mercury 3g

Venus 8g

Earth 16g

Mars 5g

Jupiter 66g

Saturn 45g

Uranus 39g

Neptune 28g

Because of the experiment with some moderately interpretable results, we are not able to explain our researches with what we did. So we are going to show you a short video of a few seconds to present the results that we tried to have.

Experimentation

Einstein and the General Relativity

http://www.humanite.fr/deconstructeur-de-la-physique-albert-einstein-redessine-le-monde-571569

He was born on the 14th March 1879, in Ulm (Baden Wüttemberg, Germany) and died on the 18th April 1955, in Princeton (New Jersey, USA). He was a  physician theorist. He published his theory of the special relativity in 1905 and his theory of gravitation, said general relativity, in 1916. In 1921 he received the Nobel prize. He is mainly known for the formula E=mc², the formula means that energy is equal to the mass time the velocity square. During World War II he was a refugee in the US and while he was there he discovered the interaction between the nucleus making a strong energy.

http://physics.stackexchange.com/questions/192318/can-anyone-explain-me-how-time-can-bend-according-to-einstein-in-simple-way

General Relativity or the general theory of relativity  is the geometric theory of gravitation published in 1916 and the current description of gravitation in modern physics. In it, Einstein determined that massive objects cause a distortion in space-time, which is felt as gravity.

We find 3 conceptions of gravitation. Firstly, gravitation is a force between bodies. Secondly gravitation is a distortion of space-time. Finally, gravitation is a fundamental interaction which is established by exchanges of virtual gravitations. With the general relativity to say that the Earth is turning around the Sun is incorrect. In fact, the Earth is going straight forward into the space-time, but it’s the space-time itself, which deformed by this important mass which is the Sun, is curved.

http://feelgrafix.com/935808-isaac-newton.html

Isaac Newton considered space and time as absolute, existing “without any reference to anything external”. They would be the same for everybody, whatever is the movement. And they would progress independently one from the other. In Einstein’s universe, this vision is swept. Each of us has its own clock and its own distance of measurement.  Time and space can dilate themselves, contract themselves, sprawl and contract with the speed.

So the speed acts like a fountain of Youth, a fountain that doesn’t rejuvenate but slows down unstoppably time.

For Einstein the passage of time isn’t real, time doesn’t pass anymore : it is simply here, motionless, like a straight line spreading at the infinity in both directions.

General definitions

http://www.pbs.org/wgbh/nova/next/physics/are-black-holes-real/

What is a black hole ?

The term “ black hole” was invented by the American physicist John Wheeler in 1967. A black hole is, first and foremost, characterised by the existence of an horizon : it is the spherical surface from which even the light won’t come out, which in that case is inexorably attracted towards a central singularity. The light is affected by the presence of gravity : the stronger the gravitational field is, the weaker the photons which slip from the light and the more displaced they are to a bigger wavelength. Nothing can escape from a black hole and it can be proved by a mathematical application. The equation of the escape velocity ‘v’ is  where G is the gravitational constant and G = 6,67 x10-11m3/kg.s², M is the mass of the object and R is the radius. The escape velocity of the Earth is around 11km/s, the escape velocity for a black hole would be superior to the light speed, and we know that nothing can go faster than the light speed.

Only very large stars, called supergiants can become a black hole. The star must be one and a half times the mass of the sun or larger to turn into a black hole. The limit is called the Chandrasekhar limit, so if the star is less heavy than the number it will turn into a smaller type of star but not into a black hole.

Example : 

If a friend dives in the black hole, the closer he’s going to be from this one, the slower he is going to fall. When he is going to reach the Schwarzschild radius (the blackhole’s horizon), this movement will take an undefined time. His picture will stay frozen to infinity. His picture will also turn red and then disappear.

However for the person who is coming closer to  the black hole, the time is not going to change. but when he looks at your watch, an hour will be accomplished in a second, a millisecond, a microsecond… He will be able to observe the entire future history of the Universe and maybe its end. In a black hole the gravity is stronger and stronger while we go down into it. So the gravity isn’t the same in one black hole. If a friend went in the black hole his feet first, the lower he would get, the more different the gravity would be between his feet and his head, so his body would be quartered (that’s why the name given is “spaghetti effect”). We commonly speak about tidal forces to describe the differences of the gravitational forces with the different distances. The formula of this gravitational attraction is :   and when the distance to center is different, then the force is different and the “spaghetti effect” happens.

Only very large stars, called supergiants can become a black hole. The star must be one and a half times the mass of the sun or larger to turn into a black hole. The limit is called the Chandrasekhar limit, so if the star is less heavy than the number it will turn into a smaller type of star but not into a black hole.

Stephen William Hawking :

http://www.linformaticien.com/actualites/id/33048/stephen-hawking-l-intelligence-artificielle-est-elle-un-loup-pour-l-homme.aspx

 

He was born on the 8th January in 1942, in Oxford (England). He is a physician theorist, a math teacher at the University of Oxford and a cosmologist. He now works principally to find singularity theorems on the general relativity and to predict theoretically that black holes should produce radiations. His principal domains of research are cosmology and quantum gravity. He wrote “A brief history of time”.

One of the main thing that realized Hawking is that the event horizon of a black hole is not stable, it gets bigger whenever something falls into the black hole. So the event horizon can not get smaller.

“A Brief History of Time: From the Big Bang to Black Holes” was first published in 1988. It was written by Stephen Hawking for ‘normal’ people who are not specialist of scientific theories. Hawking explained the Universe and its development, structure, origin, etc… with non-technical terms. Anyone can read the book and understand Space a lot better because of the easy terms and the simple explanation of the author. The author talks about basic concepts like time and space, basic theories that could be hard for an average person to understand. They are 12 chapters about spacetime, black holes, the Universe… It became a bestseller by selling more that 10 million copies in less than 20 years. It was translated into 35 languages in 2001. A Brief History of Time explains a range of subjects in cosmology to the nonspecialist readers. In total there is only a single equation : E=mc², but the book still employs complex models and diagrams to illustrate the concepts.

Sagittarius A*

https://www.nasa.gov/mission_pages/chandra/multimedia/black-hole-SagittariusA.html

Sagittarius A* is a galactic black hole in the middle of the Milky Way found by Robert Brown and Bruce Balick in February 1974. It is situated in the constellation of Sagittarius and make 4.31 million times the weight of the Sun in a radius of 44 million kilometers so (4.31± 0.38) x 106 M☉ (solar mass). It attracts the gas produced by the massive stars next to it, it doesn’t absorb them but rejects 99% of them. Sagittarius A* is thought to have swallowed at least 2 celest objects during the past few centuries. Chandra is one of the satellites in orbit around the Earth. The satellite probes the quasars while observing Sagittarius A*, precisely its X-rays. With it the NASA has detected a flash 400 times brighter than usual. The black hole is  3 times shinier than the one observed in 2012, which was the previous record of luminosity. The cosmologists have isolated the hypothesis that it could be the emissions associated to the presence of the famous cloud of G2 gaz. In fact the eruption observed by Chandra’s instruments was a lot closer to Sagittarius A* than the cloud. The astro-physicians think that the black hole was sleeping and it just woke up.

Quasar : it is a galactic core with a supermassive black hole (1000 billions times brighter than the Sun) producing in the ultraviolet light, infrared light, the visible light, X-rays, gamma rays and the radio waves.

Cygnus X-1 is the first black hole to be discovered in 1972. It is also the astronomic object to be accepted by the scientific community as a ‘Black Hole’. So it has a lot of importance in the history of cosmology. It is situated in the Swan constellation. It was used for a lot of experimentations. Cygnus X-1 is around 9 solar mass.

The actual record of mass is hold by the black hole in center of elliptic galaxy NGC 4889 which reigns on more than a thousand of galaxies, tied together with gravitation. Its mass is 21 billion of solar mass, and it is not that far away from the Milky Way, only 300 million of light-year.