Science fiction films, often criticized for physical inaccuracies, may be right on one point - the gravity on most planets suitable for human visit will be very close to Earth
Spanish astronomers analyzed all the accumulated data on the planets with a hard surface known today, and found that the vast majority of them, although much more massive than Earth, will have a similar gravity. In theory, this allows a person to navigate exoplanets on foot in the same way as on their home Earth. The corresponding study is published in the journal Astrobiology, and its preprint is posted on the server of Cornell University.
The authors of the work decided to study gravity on the planets of other star systems in order to understand their prospects in terms of habitability, the possibility of the emergence and existence of terrestrial life there. Using data on planets discovered with the Kepler space telescope, astronomers have concluded that the gravity on the surface of most exoplanets will be much less than previously thought. In fact, almost everywhere it is pretty close to the earth.
The main reason for this lies in the fact that as the mass of the planet grows, its gravity becomes somewhat stronger. The speed required to leave such a planet becomes so great that the molecules of light substances cannot reach it. As a result, for bodies two or more times larger than the Earth in size, the average density begins to be determined not by rocky rocks, but by lighter elements: water and gases. Therefore, even super-Earths - much more massive than our planet, will have a surface gravity very close to that of Earth.
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Astronomers illustrate their thought on the well-known planets of the solar system. Venus. Uranus, Neptune and Saturn differ sharply in mass (0.82, 14, 17 and 95 from the level of the Earth). However, gravity on their surface - or in the lower dense layers of the atmosphere for Saturn - differs much less. On Venus, it is 0.91 of Earth, on Uranus - 0.9, on Neptune - 1.14, and for Saturn - 1.06 Earth. This is quite understandable, if we remember that the average density of the same Venus is three times higher than that of Uranus. Therefore, being on its surface, any object will be much closer to the center of gravity of the planet. Since gravity decreases in proportion to the square of the distance, proximity to the center of gravity plays a larger role than the total mass of the celestial body.
Scientists state that before the discovery of exoplanets it was often possible to come across the opinion that the example of the solar system is not indicative, since it is difficult to draw generalizing conclusions based on statistical material from several planets. However, now, having approximate data on a couple of thousand known exoplanets, we have to admit - despite the multiple difference in mass and size, most planets with a solid surface will have approximately the same gravity as the Earth. All this means that if they have their own forms of complex life, the external conditions in which their evolution will take place may largely coincide with the terrestrial ones.
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As the authors of the work note, an unexpected consequence of it is that numerous science fiction films, often criticized for inadequate understanding of the gravity of other worlds, were in fact close to the truth. Although Star Wars heroes move in the same way on a variety of inhabited worlds, this can hardly be attributed to the mistakes of their creators. Apparently, this would somehow be the case for real cosmonauts landing on another planet: the force of gravity with which they will collide will rarely exceed the earthly one.
