The theory of Albert Einstein is 100 years old. But beyond its most known conclusions, it continues to feed speculative research. What does it occur while following until the end its consequences?

A long time, relativity did not coincide with the priorities of the physicists, before the situation does not end up changing…Relativity, while shaking our designs, did not make close-cropped table of the preceding theories.

 

Despite everything, the things are not to be not so complicated, though not in the most intuitive direction. Because the restricted theory of relativity brings a rather clear answer to us on at least a point: time, implies it, does not pass.

Let us include/understand-well what we speak: we move in time, but does time itself pass for as much, or cross us of the successive states of one (space) immutable time?
This way of seeing the things is brilliantly reported on Brian Greene (the American author of the Elegant Universe) in his last work, the Magic of Cosmos .
 

Time and present
Relativity teaches us that space and time are intrinsically dependent: just like a displacement towards the North-East with a component towards north and a component towards the east, and the variation of one of the components will influence the other, the variation of a displacement in space influences displacement in time.

In the terminology of relativity, all the observers moving are equivalent: their clocks will function at the same speed and the light, in their reference frames (of inertia) will always move at the same speed in the vacuum.

According to speed, the “present” of an observer differs
But what they considering like their “present”, is the whole of the events which proceed at the same time (one moment which thus depends on the reference frame) in all the Universe, will vary with the observer according to its speed.

This variation is  immense that  the variations speed are important, for two close observers. But for those which - rightly - would be obstructed to consider an observer moving with, let us say, 80% the speed of the light, the effect is (qualitatively) the same one if one considered, instead of two “close” observers of which one goes very quickly, a motionless observer and another energy with, for example, only 5km/h, provided that this last is located very very far (several ten thousands of light-years for example) from the first.

To some extent, while moving at speed different, the observers cross various successions of states of the space time: they cut the space time differently. All is, as we will see it, question of angle.
 

Immutability of the space time
Let us visualize the space time like a large cake, each section (cut with right angle) representing one “present” for a stationary observer. An observer moving at high speed (compared to the observer of reference) will cut the cake with an angle all the more far away from the right angle that the variation speed is important.

And an observer moving at low speed (compared to the observer of reference) but located very far in space, will have one “present” which, in spite of an angle of very weak separation, will

deviate largely, with the distance, of that of the observer of reference: on the list of the events of the “present” of the remote observer in displacement will appear of the avengement located several centuries before or after the “present” of the observer of reference.
However, as no observer is privileged, that means that any cut/section/state of the space time are as legitimate as one (E) other. For such observer, its present will include events located in the future distance of the present of another observer, for a third, its present will be the past of a fourth, etc It should be concluded from it that the space time, such as it is modeled by general relativity, is immutable.

All the “present” are valid
Because let us insist on the fact that no observer not having to be privileged, all the “present” are at each “moment” as valid the ones as the others: it thus coexist, and, since they are characterized by a cut of the “cake space time” following all the possible angles, entirely include this one. In other words, reality is constituted of every present (and not only one which, consequently, would be arbitrate privileged), therefore of all the space time.

We reassure, nature is well made, because this immutability violates causality by no means. An observer having crossed one present containing the future event of another observer will not have (to be supposed that it actually observed the event) not time to warn the second before the present of this one did not reach the famous one avengement. The finitude the speed of the light is here in question.

That does not change anything with the observation made higher an immutable space time, which does not cross a state successive in itself. Only the observer crosses successive states of space in time, any space and times which are subjective for him, because basically different from those of its neighbor. According to the point of view that we must describe, reality includes at the same time all the points of the space time. There are not a reality at every moment, but a total, eternal, immutable reality.
 

Sections of space time
The totality of the space time visualized like a large cake.
For a motionless observer, a cut with right angle of the cake represents the “present”, that is to say the whole of space with three dimensions at a given time. The end furthest away from the cake thus represents the Big-bang.

For an observer moving, which it calls “present” is not a cut with right angle. Restricted relativity affirms indeed that its clock is slowed down compared to that of the motionless observer: two simultaneous events for the second are not it for the first. Contrary, the observer moving will considerers like simultaneous two events located on a plan of cut of the “cake slightly tilted space time” compared to the right angle. The effect is generally tiny if the observers are close, but important if their space separation (it is the case of the diagram above) is large. The observer moving will regard as pertaining to its present of the events located far in the past of the motionless observer (respectively far in the future) if it moves away from there (respectively approaches some).

As all the observers are equivalent, every present is it, therefore the totality of the cake space time, and not only one of its sections, constitutes what one owes appealers reality. Without relativity, reality would be only one cut with right angle, with, the past and the future becomes as real as the “present” without this not violating however causality.

More quickly than the light
 Do the tachyons exist?
A frequent error consists in believing that one of the postulates of restricted relativity (the constancy the speed of the light in the vacuum) introduced a limit higher at the speed of a particle.

Admittedly, the speed of the light is an insuperable limit (for that, it would be necessary to provide to the particle an infinite energy, according to equations' of Einstein, which is thus impossible) but it does not prohibit either the existence of particles which move always more quickly than the light.

Such particles (hypothetical) cannot indeed go down in lower part from the speed of the light, for the same reasons as those which prevent an “ordinary” particle to exceed it. But that does not mean that they cannot exist.

They are same the equations of restricted relativity which were at the origin of their description per Gerald Feinberg in 1967. Baptized tachyons by the physicists who is expertised of particle rediation & engineering, these particles, if they really exist, have calculable characteristics completely surprising.

Imaginary mass, infinite acceleration…
Initially, their mass is an imaginary number, then, these particles lose energy while accelerating, which implies that a tachyon of null energy is “infinitely fast”! In addition, an electrically charged tachyon would thus lose energy (by producing a radiation known as of Cherenkov, radiation characteristic speeds superiors to that of the light in the vacuum) would accelerate without end…
All this is obviously disconcerting, but, once again, is not prohibited by the equations. Problem, the tachyons are not invisible in theory (it there not of logical reason which would prevent their observation in all the cases): the physicists imagined experiments which would make it possible to detect them. And until now, no tachyon was however observed.

But if it proved that they exist indeed, another question comes immediately to mind: could one be useful himself of a tachyon to transmit a signal more quickly than the light? (What, for the blow, would violate restricted relativity). The answer, say the theorists who, in their demonstration, fon to intervene a quantum sales leaflet, is not. On the other hand, the existence of tachyons would pose some problems with the concept of causality…

The physicists, as a majority, thus doubt the existence of these particles. For some of them, they are same the sign of a drift of the theory of the fields. Contrary, the science fiction seized the concept with more or less of happiness.

Party for the future
 Holes of worm
Relativity and quantum physics drew up a landscape of the entirely new space time: this one is deformable, perhaps fluctuating under the effect of quantum phenomena, and, as the advance the theory of the cords, could perhaps comprise much more than three dimensions of space to which we are accustomed.

Consequently, why not consider a particular type of deformation of the space time, in which two points very distant while following one or the other from our three familiar dimensions, are in fact very close in a fourth? So close that one can, to some extent, to dig a such worm a “hole” making the junction between these two points via additional dimensions.

In 1935, Einstein and Rosen discover that the singularities of the space time form gravitational wells of density and curve of infinite space times. They formulate then hypothecate it that of such singularity can play the part of junctions (baptized bridges of Einstein-Rosen) in the space time (they do not evoke of an additional size, but the idea is the same one). It is that which we need: holes of worm! Short cuts of the space time.
 

On a journey
Yes, but…
Unfortunately, to suppose that they existent, the holes of worm pose, it is the least which one can say, of the practical problems. The study of these very particular connections started in 1956 with John Wheeler, who gave them their name.

For factory a hole of worm usable, it is necessary to accumulate mass (- energy) negative! It is at least what it arises from the equations of the theory of Einstein (which, for the specialists, give the tensor of energy-impulse of the matter to obtain a definite geometry).

All kinds of difficulties emerge
And this mass must be subjected to an extreme density. And the scale must be that of Planck (10 power minus 33 cm). A little tight like passage. And a little hostile. Without counting that intervene of the quantum fluctuations good avenues.

To crown the whole, structurally, the hole of worm is composed of a black hole associated with a “white hole” (opposite of the black hole to some extent). This last, alas, violate the second principle of thermodynamics because it creates matter “from nothing”.

In short, from many difficulties emerge. And still, we leave side of it! To only use a hole of worm, it would finally be necessary to be able to increase the passage on our scales without it auto detrains, and in addition to make it stable (bus differently, he being closed again on him even into 10 power minus 43 S: work your reflexes). It is not tomorrow the day before which one will be able to travel in the hyperspace.

Space turns with me: I am a black hole
General relativity indicates to us that the presence of mass (- energy) curve the space time. That means that texture even (whatever it is) space time is modified. Space is deformed, but also time.

What does it occur near a mass, either motionless, but in rotation? The equations of general relativity (in the vicinity of a mass in rotation) gives us the answer once again. It is Roy Kerr, a New Zealand mathematician, who it first, in 1963, in obtained the resolution.

It discovered a phenomenon enough surprising: in the vicinity of the mass in rotation, the space time is involved with it. When I turn on myself, I involve space (and time) with me. Of course the effect is completely negligible on our scales, but if I am a black hole, there…

Space turns with me

Extreme drive of the space time
Because the black hole is equipped with such a mass that its gravitational field retains until the electromagnetic radiation (thus the light: from where the term “black hole”). And the black holes turn on themselves: they are thus the ideal candidates for the phenomenon of drive of the space time.

An observer O approaching at constant speed of the black hole and, while admitting (what is absurd) that it is not dislocated in elementary particles, would see the black hole advancing towards him in straight line at constant speed. But an observer P which would look at the scene by far (there still, it acts of an experiment of thought) would see O turning more and more quickly, and approaching black hole more and more slowly (P would even never see O entering the black hole, the time of O, at this time, being infinitely slowed down compared to that of P).
It is well the space time itself, and not O, which distort and turns in the vicinity of the black hole.
 

Surfing on the space time
The exceptional gravity of a black hole stretches the light and involves the structure even of space in its rotation. Here a hot iron gas “surfant” on a vagueness of the space time near a black hole is represented.
 

Gravity which pushes back

Cosmological inflation
The model of the Big-bang is a theoretical success of first order. When in 1963, Penzias and Wilson discovers radiation cosmological - this trace of the Universe when this one was old only 300.000 years -, the model is essential and remains, today, the framework of reference.
For as much remain many mysteries: measurements confirm it, our Universe is extraordinarily flat (i.e. that its curve is quasi null): how to explain it? Because one would have needed that certain physical parameters “are fixed”, for the very first moments of the Universe, in a manner absurdly specifies. It would be more satisfactory scientifically to have a theory or the flat character of the Universe emerges from a phenomenon which does not require what English indicates by the term fine tuning: an exegetic adjustment quasi-mystic.
 

Fields of Higgs and general relativity would explain inflation
Another mystery: size of the irregularities of the cosmological radiation. That there are irregularities is logical: a perfectly uniform Universe could not have led to the formation of galaxies (matter aggregates) and would have remained eternally uniform… But what poses problem, it is that if these irregularities, as it it is thought, are due to quantum fluctuations of the paramount universe (then of tiny size), it should have remained too small to correspond to the evolution observed of our Universe.

The cosmological theory of inflation (initiated by American Alan Guth there is a quarter century) brings an elegant response to these two enigmas: if a short period ago (but then really very very very short: 10 power minus 35 seconds!) during which the Universe had grown bigger of a gigantic factor, then the irregularities would have been sufficiently increased, and the initial curve of L '' Universe would have been leveled… This period is cosmological inflation.

However inflation possible if a particular field is considered, is called field of Higgs - today still purely theoretical - who has the strange property not to have not zero value in his state of lower energy. Then the equations of general relativity intervene…
 

Negative pressure and repulsive gravity!
If a field of Higgs exists, it would have been responsible, with the whole beginning of the Universe, of a negative pressure, pressure which, according to the equations of general relativity, causes a repulsive gravity explaining inflation.

According to Einstein, gravity is related to the presence of matter-energy. It thus depends on the one hand on the density of potential energy (always positive) and on the other hand of the pressure exerted by the matter on its environment, the pressure being finally a form of energy.
This pressure can be positive or negative (an example of negative pressure is the pressure of the vacuum, one can also consider it like the analogue of the tension of a spring). In the majority of the cases, the negative pressure is negligible in front of the potential energy, but in the case of a field of Higgs, the conditions at the very first moments of the Universe would have led to a negative pressure largely higher than the potential energy, thus rocking the sign of “gravity”.

The field of Higgs, who is a field says scalar (it is not directed), produced (in the theory inflationary of Alan Guth that we simplify here to the extreme), as energy dropped after the Big-bang, of the “false vacuums”, states of great “tension” and kinds of bubbles faggots of negative pressure. These bubbles are thus characterized by a repulsive gravity: space (- time) itself dilates of a gigantic factor. It is cosmological inflation.

History of the Universe
The Big-bang determines the origin of time. At that time the Universe was incredibly dense, incredibly hot and thus energetic. While cooling, it could pass by a transition from phase which appeared by bubbles of “false vacuum” due to a field of generating Higgs and equipped with an enormous negative pressure, according to the equations of general relativity, a “repulsive” gravity: the space time would have thus enlarged exponential event gigantic factor during a time unimaginable short.

The Universe then started its phase of current expansion. 300.000 years after the Big-bang, the photons could circulate freely without being continuously absorbed by the particles: cooling uncouples photons and matter. The resulting radiation is that, discovered by Penzias and Wilson and now cooled with -270 Celcius degrees, that probes COBE and WMAP WMAP could detail.

1) The restricted theory of relativity establishes that all the observers moving at constant speed observe the same physical phenomena, and in particular the displacement of the light in the vacuum at a finished speed and fixes C which constitutes an insuperable limit for any physical element (matter or radiation).

2) The consequence of the finitude the speed of the light and the principle of relativity leads Einstein to postulate that the time of an observer moving with a certain fraction the speed of the light passes more slowly than that of a “motionless” observer (on Earth for example), and than the distances measured by the first are shorter compared to measurement than would carry out the second.

3)The variation of the component “spaces” of a displacement in time influences the component “time”: both are dependent in a relativistic space time. These considerations for summer have checked with precision.

4) Einstein will then seek to include the gravitation in his theory (this one is neglected in restricted relativity), which will lead it to regard gravity as equivalent, of the point of the observer, with an acceleration. This acceleration can itself interpreter like a curve of the space time caused by the presence of mass.

5) Einstein will propose moreover, in 1905 also (in a posterior article with that dealing with restricted relativity) his famous equation establishing equivalence mass-energy, the second being equal to the first multiplied by the speed of the light squared. He connected this equation to relativity.