Contains gravity length and time

: Gravitation - the enigmatic force

Gravitation - the mysterious force - page 1

Is mass a property of the whole universe? A new physical theory

From Thomas v. Randow

If somewhere in space - even if it was at the end of the world - stars suddenly dissolved into nothing, then we would become heavier here on earth and the sun would shine brighter. This bizarre consequence arises from a new theory of gravity developed by the well-known English astrophysicist Fred Hoyle and his Indian colleague J.V. Narlikar published two weeks ago. In a sense, it is a comeback of the hypothesis about gravity that the Viennese physicist and philosopher made Seriously do set up in the previous century.

Based on the so-called "steady state" world model, which Hoyle vehemently advocated, and formulated in the language of modern mathematics, this theory again applies Mach's postulate, according to which the mass of an object is not its individual property, but depends on the whole of all masses in the universe.

Since the Hoyle-Narlikar hypothesis contains the relativistic theory of gravity developed by Einstein as a special case, just as it in turn allows Newton's theory to apply to special cases, it may well be a real extension of the current physical worldview.

Gravitation is one of the four forces that - as far as we know - rule world events. The strongest of these forces is the one that holds the building blocks of the atomic nucleus together, for example, and whose existence is revealed dramatically in the atomic bomb explosion: the strong interaction, that certain elementary particles exert on one another, provided that they are not more than a trillionth of a millimeter apart - this force does not reach any further.

In contrast, the range of the second strongest, the electromagnetic force, is unlimited. It holds the atomic shells and the molecules together and causes the chemical processes. We perceive it as heat, light, electricity or magnetism, and it activates our metabolism, our growth, our seeing, feeling and thinking.

Gravitation - the mysterious force - page 2

Gravity is the weakest

Number three on the strength scale is that weak interaction, which occurs in the disintegration or transformation of a series of subatomic particles. This force is billionenfadi weaker than the electromagnetic, but by far the weakest of the four natural forces is gravity, gravitation.

Two electrons that are five meters apart repel each other with a barely measurable electromagnetic force. However, this repulsion is stronger than the force of gravity with which the entire globe attracts an electron.

But we experience the effect of this weak gravity at every turn. It often makes life difficult for us, and to overcome it, for example in space travel, we have to spend billions.

It is astonishing that we know very few of this force, which compels us in its most elementary manner, especially since physics has just begun with the study of its properties. Galileo's experiments on the Leaning Tower of Pisa were dedicated to gravity, and whether or not the famous apple fell on Newton's head, the effect of gravity in any case stimulated the English scholar to consider the ideas that led to the formulation of the basic mechanical laws.

A technical paradise

The reason that the nature of gravity is still unknown is because of the fact that gravity is omnipresent; we can neither turn it off nor generate it artificially like electricity or magnetism. We can avoid the effect of electromagnetic force by shielding ourselves against it with a metal wall. Unfortunately, there is only a shield against gravity in utopian novels. In fact, the possibility of being able to switch off the influence of gravity would have unimaginable technical consequences: all transport problems, including those of space flight, would be solved in one fell swoop - provided, of course, that the switch-off device itself is not too cumbersome. But the hope that this could ever succeed is very small, because gravitation cannot be compensated by an opposing force like electricity or magnetism; no one has yet discovered negative gravity.

Gravitation - the mysterious force - page 3

However, some physicists think it is possible that there is matter that is repelled by gravity. These could, for example, be the antiparticles of the naturally occurring subatomic particles, i.e. those twin particles in which some properties are provided with the opposite sign anyway, such as the charge of the anti-electron, the positron. At first it looks like the anti-gravitational behavior of such particles should be easy to check, but in practice this should be extremely difficult, because at the high speed with which these particles fly through space, the effect of the weak force of gravity is not detectable.

In the meantime, Einstein assumed that there is no such thing as anti-gravity. He interpreted the force with which masses attract each other as the result of a structure of the space-time continuum bent by the mass, i.e. not as a force, but as a geometric event. According to this "general theory of relativity", the elliptical orbits of the planets around the sun are straight lines in the space curved by the masses of the sun and planets and four-dimensional due to the addition of time. More precisely, the planetary orbits are geodesic lines in that non-Euclidean space, which, like the straight lines in Euclidean space, are the shortest connections between two points.

According to Einstein, mass has the property of changing the geometry of the space surrounding it and changing time. The mathematical formulas that express these indistinguishable relationships yield, if one inserts the size of the masses and their mutual distances, the observed strength of the force of gravity. Newton's simple formula of attraction of mass gives the same results for orders of magnitude up to that of our solar system, but is insufficient for larger spaces and larger masses.

Einstein's general theory of relativity considers gravity similar to Maxwell's theory of electricity and magnetism, namely as a field. Mass and electrical charge have in common that they change their environment, and the extent of this change decreases in the same way with distance in both of them. It therefore makes sense to look for further common properties. Unfortunately, most of the experiments that led to the discovery of the electromagnetic properties cannot be carried out analogously for gravity because it is much too weak.

It may well be that a fast moving mass emits gravitational waves like a moving electron emits radio waves. But in order to be able to generate measurable gravitational rays, one would have to throw gigantic masses around. Einstein calculated that an iron rod about three feet long, rotating at such a high speed that it is barely torn by centrifugal force, emits less than a trillionth of a trillionth of the energy that a flashlight uses.

Are there gravitational waves?

Perhaps we are constantly surrounded by gravitational waves that come from somewhere in the universe, such as the light of the stars or the cosmic rays. Recently, astronomers have discovered processes in the depths of the cosmos in which unimaginably large masses are moved at high speeds. So there should be enough sources for gravitational rays, but how can you receive them?

Gravitation - the mysterious force - page 4

At the University of Maryland, physicists have just constructed a gravitational wave antenna; it consists of a solid aluminum cylinder half a meter in diameter and around three meters long. This one and a half ton rod is suspended in a vacuum chamber and connected to an ultra-sensitive vibration meter. Should there be gravitational waves and their frequency should have a component - a kind of overtone - of 1675 Hertz, then the aluminum cylinder, whose natural frequency is exactly 1675 Hertz, would have to get into resonance oscillations. When asked why this particular frequency was chosen, Professor answers Joe Weber, the leader of the experiment: "We couldn't afford a larger device with the resources available."

In fact, the fundamental frequency of gravitational waves should be much lower. Perhaps the earth has the right natural frequency: one oscillation in 54 minutes. But so far measurements of the earth's pulses have not given any indication that they originated from gravity waves. Of course, that doesn't mean very much, because the globe is a bad antenna that doesn't even have a sixth of the sensitivity of a radio set.

If there are gravitational waves, there could also be gravitational quanta, "gravitons", which play a role similar to that of the photons in the electromagnetic field and the pions in the strong interactions.

All of these questions are still completely open, and they remain so in the new theory of gravitation proposed by Hoyle and Narlikar. In it the idea of ​​the curvature of the surrounding space-time continuum caused by mass is retained, but not the idea of ​​a gravitational field. Instead, the two researchers postulate a long-distance effect of the masses on one another that propagates at the speed of light. However, this does not lead to contradictions with other physical facts only if one always takes into account the interaction of all masses of the universe, namely a "steady state" universe that expands, but maintains its mass density because new matter is constantly being created.

The new theory finds its mathematical expression in a very complicated system of equations, which, however, is reduced to the simpler Einstein equations, as long as it is assumed that the entire mass of the universe is unchangeable.

In general relativity, gravity is a local property of the space-time continuum, whereas Hoyle and Narlikar define gravity as a property of the universe. An almost revolutionary consequence of this would be that cosmic events would have to make themselves noticeable as a change in gravity at any point in space, including on earth. Incidentally, from the formulas of the two researchers it also follows, which does not necessarily follow either from Newton's or from Einstein's theory, that gravitation can only be an attractive force. So there is no anti-gravity and thus the possibility to cancel gravity afterwards.