Astrophysicist Alexander Dolgov: Yesterday’s Sci-Fi Turns Today’s Discoveries

The head of the Laboratory of cosmology and elementary particles at Novosibirsk State University, Prof. Alexander Dolgov explains what awaits us after the discovery of gravitational waves, how scientists look to the future and why a Time Machine is far beyond anything we do today.

Researchers form LIGO-VIRGO collaboration have presented a remarkable result, a landmark discovery. We can shortly expect a new class of telescopes to appear. If they are sensitive enough to see gravitational waves, we can expect quite a few similar detections per year. It is a bit surprising that as soon as researchers turned on their sophisticated detectors, they saw what they expected but registered only one event. They might be working on other signals deciphering months of material collected and even hope to see the big bang.

The two sophisticated detectors used are still not enough to get a complete picture, so other detectors are developed in Italy (VIRGO) and Japan (KAGRA), as well as the first observatory in space to explore the Gravitational Universe, eLISA. Scientists work on unique instruments that will allow them to observe the collisions in the Universe that occurred across a distance of almost a billion light years of space.

We also expect new discoveries for dark matter and black holes. The gravitational waves detected were produced by two giant black holes, which weighed about 29 and 36 times the mass of the sun (M=(1.98855 ± 0.00025)×1030 kg). The two objects had begun by circling each other and finally merged releasing the energy of more than the total energy of all the stars in the Universe for that brief instant.

Gravitational waves come to Earth from everywhere. The Universe is not opaque to gravitational waves; it is completely transparent. The LIGO experiment proves it. The experiment is quite impressive, and the discovery is one of breakthrough moments in astronomy. We have opened a new window to the Universe through which we could eavesdrop on the catastrophes in space, see distant events and listen to a channel that will allow us to discover phenomena we have never seen before.

In fact, there were Soviet physicists Mikhail Gertsenshtein and Vladislav Pustovoit who suggested that it should be possible to detect gravitational waves using an interferometer working on optical beams. It was as early as in 1962 and seemed science fiction that was not exactly science then.

Back in 1930, Wolfgang Pauli, an Austrian-born Swiss and American theoretical physicist, said, “Today I did something a physicist should never do. I predicted something which will never be observed experimentally. He proposed the existence of a hitherto unobserved neutral particle with a small mass, no greater than 1% the mass of a proton, a neutrino

Eighty years later, we have neutrino telescopes that are used, for instance, in geological exploration, and they are a matter of fact.

The LIGO data perfectly agree with the theory. The finding completed the scientific arc of prediction, discovery and confirmation: first, the researchers calculated what they should be able to detect, then decided what the evidence should look like, and then devised the experiment that clinched the matter. The shape of the curve is exactly what they calculated. According to the delay in the signal, they obtained the angle the wave arrived at, the mass and the intensity.

Einstein’s theory of relativity is essentially a theory of gravitational interaction. He came up with a bright idea that energy, mass and matter in general cause the curvature of space (and of time). According to Galileo, gravitation accelerates all objects at the same rate regardless of weight. Einstein stated the equivalence principle, when he observed that the acceleration of bodies towards the center of the Earth at a rate of 1g is equivalent to the acceleration of an inertially moving body that would be observed on a rocket in free space being accelerated at a rate of 1g. Thus, the acceleration imparted to a body by a gravitational field is independent of the nature of the body. It is described through the curvature of space and movement along geodesic lines.

In Einstein's theory, space and time are aspects of a single measurable reality called space-time. Depending on the gravitational field, time also changes its pace. Here comes the issue of the Time Machine. According to one of the theories, some gravitational fields demonstrate loop time-like trajectories. You seem to depart from one point in space and return to the same point but back in time.

I believe that such a field can exist only when the substance is highly unstable. Before you depart anywhere, the field is likely to collapse and disappear, saying nothing about returning back, say, a few decades before, and meeting the grandad of yours. Time can move differently. For instance, if a body, say a rocket with space travelers, falls into a black hole, an outside observer sees it frozen on the boundary as the time seems to stop there. However, the travelers do not feel any difference with the time moving as usual, and they are not aware or worried about the hole. What awaits them in the black hole is a mystery. More exactly, we know what it might be, but it cannot be experimentally verified.