Earth probably shouldn’t exist.
This is because the orbits of the inner solar system planets – Mercury, Venus, Earth and Mars – are chaotic, and models suggest that these inner planets must have collided with each other by now. Is not …
New study published in the journal May 3 Physical Review X (opens in new tab) It may eventually explain why.
by going deep into Model of planetary motion , researchers found that the motion of the inner planets is constrained by certain parameters that act as tethers that inhibit the system’s chaos. The new research insights may not only provide a mathematical explanation for the solar system’s apparent harmony, but also help scientists understand the orbit of the solar system. exoplanet Surrounding other stars.
unpredictable planet
Planets are constantly exerting a gravitational pull on each other, and these little tugs are constantly fine-tuning their orbits. The much larger outer planets are more resistant to small tags and thus maintain relatively stable orbits.
However, the problem of inner planetary orbits is still too complex to be solved precisely. In the late 19th century, mathematician Henri Poincaré said,three body problem As a result, uncertainties in the details of planetary starting positions and velocities swell over time. In other words, we can have two scenarios where the distances between Mercury, Venus, Mars and Earth are slightly different, and one time the planets collide with each other and another time they move apart.
Illustration of two rocky planets colliding (Image credit: NASA/JPL-Caltech)
The time it takes for two trajectories with nearly identical starting conditions to diverge by a certain amount is known as the Lyapunov time of the chaotic system. 1989, Jack Lasker (opens in new tab) an astronomer and research director at the National Center for Scientific Research and the Paris Observatory, and was calculated to be a co-author of the new study Characteristic Lyapunov time (opens in new tab) Because the orbits of the planets in the inner solar system were only 5 million years old.
“Basically, it means we lose an order of magnitude every 10 million years,” Laskar told Live Science. So, for example, if the initial uncertainty of the planet’s position is he is 15 meters, then after 10 million years this uncertainty will be 150 meters. After 100 million years, he loses another 9 orders of magnitude, giving him an uncertainty of 150 million kilometers, equivalent to the distance between the Earth and the Sun. “Basically, we don’t know where the planets are,” Lasker said.
100 million years may seem like a long time, but the solar system itself is over 4.5 billion years old and there have been no dramatic events such as planetary collisions or planets being ejected from this chaotic motion. has long puzzled scientists.
Lasker then looked at the problem differently. Next he simulated the orbits of the inner planets over five billion years, by stepping from one moment to the next. He found the chance of a planetary collision to be only 1%. Using the same approach, we calculated that it would take, on average, about 30 billion years for any planet to collide.
control chaos
Lasker and his colleagues delved into the mathematics to identify for the first time “symmetries” or “conserved quantities” of gravitational interactions, creating “a practical barrier in the chaotic wanderings of planets,” Lasker said. rice field.
The amount of these emergents remains fairly constant, inhibiting certain chaotic movements but not completely preventing them. Raising the rim of your dinner plate can help keep food from falling off your plate, but it won’t completely prevent it. Our solar system is apparently stable thanks to these quantities.
Renu Malhotra (opens in new tab) A professor of planetary sciences at the University of Arizona, who was not involved in the study, emphasized how subtle the mechanisms identified in the study are. Malhotra told his Live Science that it is interesting that “the orbits of the planets in our solar system show very weak chaos.”
In other studies, Lasker and colleagues are looking for clues as to whether the solar system’s number of planets was different from what we see today. Stability is obvious today, but whether it was always so billions of years before life evolved is an open question.
