At the start of the film "Back to the Future", the hero, "Marty McFly", the teenage musician, seems to be living a miserable life.. His father is submissive and humiliated before his crazy boss "Biff Tannen", and his mother is fat, sick, desperate and addicted to alcohol.. But Marty meets a surprise that changes his life completely..
For on the twenty-sixth of October, 1985, he meets his friend, the brilliant scientist Dr. "Emmett Brown", who reveals to him a time machine he has built, in the shape of an old car.. And when he asked him about the fuel used.. it turned out to be radioactive plutonium.. The scientist tricked some terrorists.. and promised them he would make them a nuclear bomb.. then seized the plutonium to make the fuel needed for the time machine..
And the scientist and the young musician decided to test the machine by sending the first dog, which he named "Einstein", one minute into the future.. But suddenly the terrorists appear.. and they shoot the professor, who falls dead.. And in the midst of his panic.. Marty gets into the car and drives off in it.. And unintentionally he reaches the required speed.. 88 miles per hour.. as he tries to escape..
And Marty suddenly finds himself in the past..
Specifically on the farm of his grandfather, his mother's father.. And he finds it an opportunity to change the life of his entire family by fixing all the mistakes in it.. And he seeks to meet the professor, the maker of the time machine, in his youth.. and convince him of the matter.. so that he can help him return to his own time.. And it is the very same bit quoted in the film "Samir and Bahir and Zuhair".. And the events unfold over 4 wonderful parts..
And the last part is with relativity.. the one we have previously discussed, and it is in the first reference.. for whoever would like to review it..
Einstein exploded the term "spacetime" in his theory of relativity.. And travel through time and space was just an impossible dream and a wild, illogical fantasy...
But Einstein placed before us a new and extremely exciting piece of scientific information.. and he called it "time dilation"..
And in "Einstein's" theory we find that if an astronaut travelled in a vehicle that set off at the speed of light to a star one light year away from us and then returned to Earth, he would find that the two years he spent on that black journey of his.. had become half a century in Earth time..
And to put it more clearly, if this astronaut had a daughter who was 15 years old, and she stayed on Earth and bade her father farewell.. he would come back after the one year he travelled, to find her 65 years old...
And the explanation that (Einstein's) theory put forward for this.. is that the hands of the clock are tied to the time with which the spaceship sets off.. meaning they move at the same speed, while the clock fixed on Earth.. is in accord only with the speed of its rotation around itself and around the sun...
So the astronaut has had one year pass for him.. he could not have had more than a year.. and his daughter has aged 50 years...
But when the idea of "travel through time" was put forward with the spread of relativity and its books and its explanations.. many scientists were provoked and decided that the idea was a kind of "scientific idiocy"...
And as usual, another team of scientists got enthusiastic...
Those who rejected the idea of travel through time.. relied on the idea of "Causality".. And this idea depends on the fact that any small change in any equation leads to a change in all of its results, and consequently..
So imagine if someone travelled to the past and informed Hitler of the Allies' plan.. or handed him the idea of the atomic bomb before them..
Scientists sat in these fantasies and this argument, and Einstein watched them in silence.. because Einstein was never in his life interested in travel through time..
As we said, he was interested in travel through "spacetime"..
And before relativity, there was a scientist named "John Michell" who spoke about black holes.. and pointed out that these are stars.. whose matter has perished and burned.. and whose mass has been compressed thousands of times.. so their gravity became enormous.. and they appear to us in the form of a hole of intense blackness...
And because the density of the black hole is enormous and its gravity is terrifying.. even a ray of light, if it passes beside it, does not escape it.. and it bends, submissive, towards its terrifying gravity.. terrifying to the point that cosmic space itself bends and bulges around this black hole..
And then scientists came out to us with a new theory...
They told us: if you set off towards a black hole and it pulls you in.. then in reality you are passing through this hole to two other times and places in the universe...
Meaning you are moving through spacetime...
At last we have arrived at travel through time.. let us rest now.. Of course not.. because the gravity of this hole will not carry you and transport you.. if you reached it here in a spacesuit or aboard a spacecraft..
This enormous gravity will tear the metal of the spacecraft into tiny atoms.. before it tears the cells from your body, cell by cell.. and then it breaks down the cells themselves into atoms.. and pulls you into the heart.. of the hole.. like a sea whirlpool..
So there is no hope? We did not take long until we discovered "wormholes".. like the one drawn in imagination in "Image A"...
And these wormholes.. have a very special nature, for everything that passes through them acquires negative energy, such that it emerges from them at a time prior to the date of its entry..
Or to be more precise, it travels through time into the past...
And a new problem began.. these holes suddenly collapse.. meaning whoever enters them may never return.. Besides, their radioactive energy is lethal.. no one can withstand it..
Beyond that.. the mass of a body will increase with the increase of its speed, until it reaches the speed of light, at which point its mass becomes infinite, and that means it will also need infinite energy to propel it...
And at the peak of the scientists' feverish research to solve these problems.. new discoveries appeared.. of bodies moving "faster than light"...
So there is hope.. and there is a solution..
So what is this thing that moves faster than light? The universe is expanding at an astonishing speed.. and this forces galaxies and celestial bodies at the edges of the vast universe.. to move faster than the speed of light.. and their speed cannot decrease.. because with the rapid expansion of the universe.. they would instantly perish and vanish..
The optical equivalent of the sonic boom is faster than light.. And the sonic boom is the boom that happens when you break the sound barrier.. Consequently, when certain particles breach the speed of light.. they emit what we can call a "light boom".. and this is faster than light.. and it happens a lot daily in nuclear reactors.. this light boom emerges.. and they call it "Cherenkov radiation", which is in "Image B"...
There is a small star, a "red dwarf", named "Proxima Centauri", and this star travels faster than light..
So the matter is possible..
And by pure coincidence.. and in an experiment they called the "OPERA experiment".. scientists noticed that a particle moved faster than light.. so much so that it reached its target.. "before" it moved from its source...
And let us repeat this sentence once again.. so that you do not imagine it is a typo or that it slips past you in the talk: "The particle reached its target.. before it moved from its source"..
Meaning this particle had in fact travelled through time into the past...
And in the laboratory.. the Russian scientist "Chernoprove" built a time machine.. He put inside it five atomic clocks.. set exactly in accord with atomic clocks outside it.. and he launched it when it was supposedly 7 seconds in the past..
And when the machine stopped and Chernoprove opened it.. the atomic clocks inside it were indeed seven seconds behind..
Meaning the clocks had travelled into the past for a period of seven seconds...
And for some reason.. possibly military.. the scientists suddenly announced after a while that the OPERA experiment had been the result of a calculation error.. even though they had repeated it 3 times..
And Chernoprove joined the Russian armed forces.. which provided him with a laboratory and kept him and his team under wraps, and his research became secret and banned from publication..
But this placed before us a new possibility...
Travel through spacetime is possible.. according to Einstein's equations..
And this raises other possibilities for us...
Could someone tamper with history? Could someone go back and give Hitler the secret of the atomic bomb, for example..
Science says this is impossible.. because if you travelled through time you would not find material events...
You would find yourself in the middle of a big cinema film.. you walk and watch and record, and you are unable to take part in the events.. just an illusory image.. you cannot intervene in it..
Why.. because it has already elapsed...
The matter is like you watching through a telescope a distant planet.. distant by a hundred million light years.. meaning this planet, its ray of light took 100 million light years to reach us from it and for us to see it..
During these hundred million years.. events happened to it and followed one another.. and perhaps it moved or exploded in space and no trace of it remains..
Meaning in reality you are not seeing the planet.. you are watching an image of something that has no existence...
You are seeing its ancient, deeply rooted past..
As if you were in a three-dimensional theatre.. watching Umm Kulthum presented by a holographic projector.. if you tried to shake her hand you would not find her materially real.. just a three-dimensional holographic image...
The same thing about travel through time...
The surprises of relativity and its oddities do not end.. and Einstein refuses nothing but to astonish us constantly even after his death.. And talk about relativity needs references and volumes.. And what we have done here together, of a modest, over-simplified sort.. is not enough..
It is enough only that it gives us an idea about the subject.. and that we have come to understand what this mysterious theory is talking about.. and that we have removed some of the obscurity surrounding it...
"Relatively"...
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References
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1 - Previous blog posts:
A - ( https://goo.gl/QZB12B) and;
B - (https://goo.gl/pS67Hb) and;
C - (https://goo.gl/hKIeE0) and;.
D - (https://goo.gl/ySNFF2) and;
E - https://goo.gl/X74hi1.
2 - Everett, Allen; Roman, Thomas (2012). Time Travel and Warp Drives. University of Chicago Press. p. 167.
3 - Elias Gravanis; Steven Willison (2007). "`Mass without mass' from thin shells in Gauss-Bonnet gravity". Phys. Rev. D 75 (.
4 - Davies, P. C. W. (1978). "Thermodynamics of Black Holes"
5 - Arkani–Hamed, N.; Dimopoulos, S.; Dvali, G. (1998). "The hierarchy problem and new dimensions at a millimeter". Physics Letters B 429 (3–4): 263..
6 - Polchinski, Joseph (1991). "Weinberg’s Nonlinear quantum Mechanics and the Einstein-Podolsky-Rosen Paradox". Physical Review Letters 66 (4): 397.
7 - Gott, J. Richard (2002). "Time Travel in Einstein's Universe": 82–83.
8 - Visser, M.; Bassett, B.; Liberati, S. (2000). "Superluminal censorship". Nuclear Physics B: Proceedings Supplement 88: 267–270.
9 - Raine, Derek; Thomas, Edwin (2009). Black Holes: An Introduction (2nd ed.). Imperial College Press. p. 143.
10 - النظرية النسبية الخاصة . د على مصطفى مشرفة...