Breaking common sense!You can move in vacuum without "broken limbs"

Image source: UNSPLASH

How do I go to the right foot on my left foot? Maybe you step on one foot and let this foot fly down at a speed (preferably at the speed of light), and you can fly up a short distance (after all, the whole body is much heavier than one foot heavier than one foot. To. The good news is that scientists derive a possibility that it may provide motivation to stretch and shrink the body without having to use such a terrible way.

Written article | No week

Review of the school | Two Seven, Wang Yu

In movies about the universe exploration, sometimes a nightmare -like scene appears -astronauts float in space. Without items, no matter how can they wave their limbs, they cannot move towards the space station. This distance seemed close, but was out of reach. This is a reality determined by the law of physical law. Under the condition that there is no external force participation, in the initial state of static, no matter how you toss, you will only stay in place. At most, as the limbs are twisted, the torso rotates a little. Once you return to the initial posture, all struggles are futile.

Image source: UNSPLASH

Back to the peaceful earth, it is similar to the desperate struggle in space that we still need to change the shape of the body to move. After all, we pestled straight, and there was no power source of the power or vehicle under our feet. Of course, we could only stay in place. Obviously, no matter where it is, whether it is flying birds soaring, or fish swimming fish in the water, or winding crawling, as well as us human beings, through the deformation of the body, the creatures in the body can be converted into mechanical energy into mechanical energy into mechanical energy. , Can move up.

However, if the air beside the bird's wings, the water on the side of the fish, or the rough ground under our feet, then the body cannot use the environment to advance with the environment. The special thing about space lies in this -vacuum, we cannot exchange momentum with the environment, and we cannot change the position. This seems to be a fact that covered the coffin conclusion.

However, in 2003, Jack Wisder, a astronomer of the Massachusetts Institute of Technology (MIT), published an article on "Science" () stating that there is a loophole in this inference: if the astronaut is located Time and space is bent, so the transformation of object shape and position is likely to no longer follow the law of conservation of basic momentum. In other words, in the bending space, the astronauts waving his limbs in a specific way can "swim" in the vacuum.

Bend time and space and geometric phase

Time and space can be bent, which is equivalent to falling straight down when the object falls, but goes out of thin air and falls to the ground, and even does not fall at all. For us who are accustomed to the gravity of the earth, this is somewhat incredible.

So how does the curved space -time appear? According to Einstein's general theory of general relativity more than a century ago, we know that quality substances can cause time and space distortions, and distorted space -time will guide the movement of substances.

It is difficult for us to imagine how high -dimensional space that combines time dimensions can be described, but time and space can imagine space -time as a huge film with elasticity. Large -quality objects, such as stars, are usually placed on a spatial -time film like a shot, which can cause the depression of the film, which is the distortion of time and space. The quality of the planet is relatively small, and it will exercise the heart in a thin film depression like a marble.

Obviously, the obvious bending time and space usually appear near large -quality celestial bodies, such as stars and black holes. But in fact, the space -time curvature is everywhere, and the gravity we feel is caused by the mass space of the earth's quality. From the perspective of the cosmic scale, the space curvature of our lives is almost zero, which can be regarded as a straight space.

According to general relativity, spatial curvature will affect the movement of material. As a creature in a straight space, it is easy for us to imagine the movement on the two -dimensional plane. As shown in the figure above, we lift the right hand, start from a point, do not change the orientation of the body, complete a closed path on the plane, and return to the starting point. At the same time, let's write down the direction of our right -handed direction, and you will find that the direction of the record and the end of the record has not changed, which is in line with common sense.

But if the plane becomes a spherical surface, the direction of the right hand will change through the same closed path. The change (phase) of this angle is not caused by the active rotation of the body. It is completely determined by the geometric nature of the space where the movement path is located, so it is also called geometric phase.

Image source: Boyou

Therefore, even if we can't look at the curvature of space, through this method, we can also determine whether the curvature of the space is zero. The unique geometric characteristics of the bending space make some physical phenomena that are not allowed to occur in the straight space. For example, under the condition of no external force drive, the periodic geometric shape changes in the bending space to "swim".

"Bend" space in the laboratory

In theory, although it can derive the "space swimming" guide, how to verify this strange phenomenon in experiments has become a huge challenge. Obviously, human beings are currently unable to experiment near the black hole.

In a recent study published in the "Academy of Sciences", research teams made by Georgia Institute of Technology and other universities have built a curved time and space model in the laboratory. You may be curious, how can humans "bend" in the laboratory?

In fact, the peculiar movement in the bending space will not only occur in the space that was distorted by the material, but also can be equivalent to the movement of objects on the curved surface. As a result, the research team cleverly built a robot that can change its own shape- "swimmer", which can move freely on the curved surface. Swim "swimmers" and column "swimmers": consisting of adjustable bases, air bearing, power arm, curved orbit, and four servo motors. (Image source: Original Thesis)

As shown in the figure above, the skeleton of the "swimmer" robot is two vertical cross -curved orbit. Four motors that can accurately control speed and position can be moved freely on the track. The entire robot is connected to a fixed base through an air bearings. Due to the extremely low friction coefficient of the air bearing, theoretically the "swimmer" can actively turn around the air bearing around the air bearing in the horizontal plane during the transformation of the motor. Adjusting the curvature of the cross -track and the radius of the rotation of the rotation of the robot winding is equivalent to regulating the spatial curvature of the "swimmer". In the figure above, the researchers set up two warriors -spherical "swimmers" and column surface "swimmers" (in the dotted frame box above) by regulating the track curvature of the vertical direction.

"Swimmer" needs to be changed according to the period A of the A period of A. Figure B shows the definition of robot shape transformation: the angle combination of the motor and the center of the ball; and the definition of the movement displacement of the robot: the angle of the initial position is deviated from the initial position. (Image source: Original Thesis)

Violation of intuition "swimmers"

According to theoretical derivation, the four motors of the spherical "swimmers" need to cycle positions in the order of the above figure. Because rotation is limited to the horizontal plane, the impact of friction and gravity on the process can be reduced to the greatest extent. In fact, the position of the heavy object is actually equivalent to changing the shape for the entire robot. Observing the changes from Figure A1 to Figure A5. Obviously, the spherical "swimmers" have successfully promoted a small step around the horizontal plane through a shape transformation cycle.

The experiments also gave basic results. "The phenomenon of theoretical predictions happened, and it violated intuition: As the robot changes its own shape, it will actively exercise on the sphere in a way that interacts with the environment." The person in charge of this research, Georgia Institute of Technology Physicist Zeb Rocklin said.

In the absence of external force participation, the "swimmer" rely on its own deformation, turning the angle of the naked eye around the axis in 4 minutes. (Image source: Original Thesis)

At first glance, this is indeed puzzling. But this is like adjusting the location of the vehicle in the parking space. We repeat the cycle of driving, turning, and backwards several times to achieve tiny side translation. During the parking process, we will drive out a distance and eventually return; we will change the direction and eventually recover; the side position we change cannot be returned to the initial change. The deformation movement of the bending space is the same. It seems that all parameters in cyclical transformations remain unchanged in the cycle, but there is a variable in it -geometric phase, which will accumulate in the cyclical movement, showing the displacement of space.

Interestingly, researchers have found that although there is no external force driver in the horizontal direction, rotation displacement caused by deformation will cause small friction on the bearing to accumulate and accumulate reverse dynamics for the robot. After stopping the periodic deformation, the robot will return to the initial position under the action of reverse momentum.

However, the astronauts in space do not have to worry about this problem (without friction). After they find that they are in a bending space, the first thing they need is to find the periodic "deformation" scheme suitable for their bodies. Unfortunately, because the distribution of human body quality is relatively uniform, it is not like the "swimmer" model. It has a heavy block on the end of the limbs, which means that we will have low efficiency through stretching and contraction of limbs to regulate rotation inertia.

Obviously, human beings are destined to be "swimming health generals" in space. But the good news is that more curvature bending space can help us improve efficiency, provided that humans in it can withstand stronger twisted stretching. That's right, in the bending space, we need to overcome no longer gravity, but to "bend" our body, to move our body, to move our heads and feet along different directions.

The thesis link:

https://www.pnas.org/doi/10.1073/pnas.2200924119

Reference link:

https://www.sciencealert.com/robot-shows-possible-swim-the

'Swimming in Spacetime: Motion in Space by Cyclic CHANGES in Body Shape' ''

https://mp.weixin.qq.com/s/srq8d6jik7zzdf0yRPa

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Does not represent the position of the Institute of Physics of the Chinese Academy of Sciences

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Source: Global Science

Edit: Just_iu

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