Levitation is the overcoming of gravity, in which the subject or object is in space without support. The word "levitation" comes from the Latin Levitas, which means "lightness".
Levitation is wrong to equate with flight, because the latter is based on air resistance, which is why birds, insects and other animals fly, and do not levitate.
Levitation in physics
Levitation in physics refers to the stable position of a body in a gravitational field, while the body should not touch other objects. Levitation implies some necessary and difficult conditions:
- A force that can offset the gravitational pull and force of gravity.
- The force that can ensure the stability of the body in space.
From the Gauss law it follows that in a static magnetic field, static bodies or objects are not capable of levitation. However, if you change the conditions, you can achieve levitation.
Quantum Levitation
The general public first became aware of quantum levitation in March 1991, when an interesting photo was published in the scientific journal Nature. It showed the director of the Tokyo Superconductivity Research Laboratory, Don Tapscott, standing on a ceramic superconducting plate, and there was nothing between the floor and the plate. The photo turned out to be real, and the plate, which, together with the director standing on it, weighed about 120 kilograms, could levitate above the floor thanks to a superconductivity effect known as the Meissner-Ochsenfeld effect.
Diamagnetic levitation
This is the name of the type of being suspended in the magnetic field of a body containing water, which itself is a diamagnet, that is, a material whose atoms are capable of being magnetized against the direction of the main electromagnetic field.
In the process of diamagnetic levitation, the main role is played by the diamagnetic properties of conductors, whose atoms under the action of an external magnetic field slightly change the parameters of the movement of electrons in their molecules, which leads to the appearance of a weak magnetic field opposite in direction to the main one. The effect of this weak electromagnetic field is enough to overcome gravity.
To demonstrate diamagnetic levitation, scientists repeatedly conducted experiments on small animals.
This type of levitation was used in experiments on living objects. During experiments inan external magnetic field with an induction of about 17 Tesla, a suspended state (levitation) of frogs and mice was achieved.
According to Newton's third law, the properties of diamagnets can be used vice versa, that is, to levitate a magnet in the field of a diamagnet or to stabilize it in an electromagnetic field.
Diamagnetic levitation is identical in nature to quantum levitation. That is, as with the action of the Meissner effect, there is an absolute displacement of the magnetic field from the material of the conductor. The only slight difference is that to achieve diamagnetic levitation, a much stronger electromagnetic field is needed, however, it is not at all necessary to cool the conductors in order to achieve their superconductivity, as is the case with quantum levitation.
At home, you can even set up several experiments on diamagnetic levitation, for example, if you have two plates of bismuth (which is a diamagnet), you can set a magnet with a low induction, about 1 T, in a suspended state. In addition, in an electromagnetic field with an induction of 11 Tesla, you can stabilize a small magnet in a suspended state by adjusting its position with your fingers, while not touching the magnet at all.
Frequently occurring diamagnets are almost all inert gases, phosphorus, nitrogen, silicon, hydrogen, silver, gold, copper and zinc. Even the human body is diamagnetic in the right electromagnetic magnetic field.
Magnetic levitation
Magnetic levitation is an effectivea method of lifting an object using a magnetic field. In this case, magnetic pressure is used to compensate for gravity and free fall.
According to Earnshaw's theorem, it is impossible to hold an object in a gravitational field steadily. That is, levitation under such conditions is impossible, but if we take into account the mechanisms of action of diamagnets, eddy currents and superconductors, then effective levitation can be achieved.
If magnetic levitation provides lift with mechanical support, this phenomenon is called pseudo-levitation.
Meissner effect
The Meissner effect is the process of absolute displacement of the magnetic field from the entire volume of the conductor. This usually occurs during the transition of the conductor to the superconducting state. This is what superconductors differ from ideal ones - despite the fact that both have no resistance, the magnetic induction of ideal conductors remains unchanged.
For the first time this phenomenon was observed and described in 1933 by two German physicists - Meissner and Oksenfeld. That is why quantum levitation is sometimes called the Meissner-Ochsenfeld effect.
From the general laws of the electromagnetic field, it follows that in the absence of a magnetic field in the volume of a conductor, only a surface current is present in it, which occupies space near the surface of the superconductor. Under these conditions, a superconductor behaves in the same way as a diamagnet, while not being one.
The Meissner effect is divided into full and partial, independing on the quality of superconductors. The full Meissner effect is observed when the magnetic field is completely displaced.
High temperature superconductors
There are few pure superconductors in nature. Most of their superconducting materials are alloys, which most often exhibit only a partial Meissner effect.
In superconductors, it is the ability to completely displace the magnetic field from its volume that separates materials into superconductors of the first and second types. Superconductors of the first type are pure substances, such as mercury, lead and tin, capable of demonstrating the full Meissner effect even in high magnetic fields. Superconductors of the second type are most often alloys, as well as ceramics or some organic compounds, which, under conditions of a magnetic field with high induction, are only capable of partially displacing the magnetic field from their volume. Nevertheless, under conditions of very low magnetic field strength, almost all superconductors, including type II, are capable of the full Meissner effect.
Several hundred alloys, compounds and several pure materials are known to have the characteristics of quantum superconductivity.
Mohammed's Coffin Experience
"Mohammed's coffin" is a kind of trick with levitation. This was the name of the experiment that clearly demonstrated the effect.
According to Muslim legend, the coffin of the Prophet Mohammed was in the air in limbo, without any support and support. Exactlyhence the name of the experience.
Scientific explanation of experience
Superconductivity can only be achieved at very low temperatures, so the superconductor must be cooled in advance, for example, using high-temperature gases such as liquid helium or liquid nitrogen.
Then a magnet is placed on the surface of a flat cooled superconductor. Even in fields with a minimum magnetic induction not exceeding 0.001 Tesla, the magnet rises up above the surface of the superconductor by about 7-8 millimeters. If you gradually increase the magnetic field strength, the distance between the surface of the superconductor and the magnet will increase more and more.
The magnet will continue to levitate until the external conditions change and the superconductor loses its superconducting characteristics.
