Whether mass can be negative by analogy with an electric charge - scientists have been trying to find out for more than a hundred years. Recently we managed to obtain a strange substance that behaves as if its mass were minus. This opens up a new area of research.
How to stabilize a wormhole
A wormhole does not live long in space-time. Its neck collapses due to gravity, without even having time to pass a ray of light. To make it passable, a substance with a negative mass is required, which creates an antigravity effect - the so-called exotic matter. Through a similar wormhole, you can get to another universe. This idea was used in the science fiction film "Interstellar" - at the suggestion of the American theoretical physicist, Nobel laureate Kip Thorne.
“Kip Thorne is a fundamental physicist, so he forgets about technology. How much energy is required for this? How to ensure the utilization of excess heat for such a power plant? In theoretical physics, a lot is allowed, but any real technology is subject to restrictions in the form of the principles of thermodynamics, the law of conservation of energy, the special theory of relativity. It reminds me of the fantasies of a century ago, when it was believed that you can turn any substance into pure energy and fly to the stars on this. In theory, yes, anyone. And practically - only uranium, plutonium and lithium deuteride, but there are big problems with them too,”- comments to RIA Novosti Anton Pervushin, science fiction writer, specialist in the history of cosmonautics.
Hunting at the speed of light
If ordinary bodies attract everything, then bodies with negative mass repulse. Could matter with such a strange property exist in nature? In 1954, physicist Herman Bondi of Cambridge showed theoretically that there are no laws prohibiting substances with negative mass. A particle of ordinary matter, writes physicist Richard Hammond of the University of North Carolina, must run away from a particle with negative mass, and that particle chases it. Such a pair will begin to accelerate, gradually approaching the speed of light. Can this be used to create an engine for an interplanetary ship? “The idea, alas, is crazy. With acceleration, mass grows - according to the special theory of relativity. Moreover, as it approaches the speed of light, the mass tends to infinity. Due to which the negative mass of the "repulsive" particle will increase,and ad infinitum? In reality, these particles will repel each other and scatter until they find themselves outside the limits of their gravitational fields, and there they either continue their free flight or interact with other particles,”says Pervushin.
A particle with negative gravitational mass is chasing an ordinary particle. Illustration by RIA Novosti. Depositphotos / vectorcreator.
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Against all intuition
In 2017, an article by American physicists from Washington State University who received a strange substance in the laboratory, which did not accelerate in the direction where it was pushed, as prescribed by Newton's second law, made a lot of noise. This is possible only if its inertial mass is negative. With the help of a laser, physicists created a superfluid of rubidium atoms, cooled them to a temperature of almost absolute zero, and a special state of matter arose - the so-called Bose-Einstein condensate, in which the atoms move very slowly. With the same laser, a cloud of Bose-Einstein condensate was, as it were, locked in a separate area of space and forced to change the spin - there is such a quantum characteristic of particles. The more pushed this cloud, the more it accelerated in the direction opposite to the applied force. As if a tennis player was hitting the ball and it flew towards him,and not to the opponent.
In order to hit the ball from the substance with negative mass towards the opponent, the tennis player must push it even harder towards himself. Illustration by RIA Novosti. Alina Polyanina, Depositphotos / blueringmedia.
These results were explained by theorists from Australia, Great Britain and Russia. However, in this case we are talking about the effective mass - a mathematical solution when describing the Bose-Einstein condensate, and not about the fundamental property of matter. An electron in a crystal acquires a negative effective mass due to the spin-orbit interaction, says Sergei Baranov, Doctor of Physics and Mathematics, Leading Researcher at the Laboratory of Radiation-Matter Interaction at FIAN, RIA Novosti. “Consider a satellite in orbit. If we try to slow it down (apply a force against the speed), the satellite will move to a lower orbit and its speed will not decrease, but increase. And the kinetic energy, in spite of the negative work done on it, too. And if we accelerate the satellite, pushing it from behind, the speed will decrease - well, what is not negative mass. In fact, the paradoxical gain (or loss) of kinetic energy is compensated by the loss (or gain) of potential energy - since the satellite is in the gravity field. The negative effective mass is the result of interaction with the environment (and it is impossible without the external environment), be it a crystal or a gravity field, or some other external field. But in modern physics there is a stronger statement: any mass is always the result of interaction with the environment,”explains Sergei Baranov. But in modern physics there is a stronger statement: any mass is always the result of interaction with the environment,”explains Sergei Baranov. But in modern physics there is a stronger statement: any mass is always the result of interaction with the environment,”explains Sergei Baranov.
Tatiana Pichugina