The moon may be responsible for the Earth’s climate…

If there were some kind of music in the spheres, as Kepler suggested centuries ago, it would accompany the majestic planets of the solar system that glide around the sun and occasionally nod subtly to each other.

It may all seem orderly, consistent, and predictable, and in the short term it is, but scientists analyzing the motions of the planets with powerful computers realize that there is a “cacophony” in the music of the spheres. In the New Scientific Dictionary the solar system is chaotic.

The results of chaos in the solar system are described in Scientific Review natureyears ago by a group of French scientists led by the French astronomer at the Paris Observatory and director of research at the French National Center for Scientific Research (CNRS), Jacques Lascard.

French academic Jacques Lascar

“Since 1880 thanks to the work of George Darwin, son of the famous Charles Darwin, it has been known that due to the tidal interaction between the Earth and the Moon, the Earth’s rotation slows down and the Moon moves away from the Earth. Since 1969, thanks to the laser reflectors placed on the Moon by the Apollo astronauts, The removal rate was calculated with great accuracy at 3.83 cm/year.After the lunar excursions, the age of the Moon was determined with great accuracy at 4.425 billion years.However, more than fifty years ago, it was realized that according to the current friction rate caused by tides, the model Darwin’s simple tides indicated that the Moon was formed and began to move away from the Earth about 1.5 billion years ago, which does not correspond to its age, ”describes d. Lascar, who works on the dynamics of planetary systems. In fact, in 1994 he was awarded the CNRS Silver Medal and in 1998 the asteroid “18605” was named in his honor.

The distinguished scientist now comes to Athens as a guest of the Hellenic Astronomical Society, which celebrates its 30th anniversary this year, to present the latest research results that answer the paradox he described above. doctor. Laskar comes to Greece for the first time to give a lecture open to the public on: The Earth and the Moon: In Search of a Consistent Scenario for Their Evolution in June 28 In the Eugenides Foundation.

Chaotic solar system

But let’s take things in order. Over long periods of time, despite the strong pull of the Moon from the Sun which essentially determines the motion of the Earth and other planets, the accumulation of small mutual gravitational perturbations from neighboring planets, together with their slightly oscillating rotations, can cause significant fluctuations in their orbits. planetary directions. These changes accumulate exponentially, and this compounding effect has dramatic consequences on time scales of millions of years. The scientists concluded that such behavior is completely unpredictable in the long run.

FORTH/The Astrophysical Institute

“It also means that not only their distances from the Sun but also the directions of the rotational axes of the planets, including Earth, have changed randomly at some point in their history. Mars is still going through extreme changes, which could explain its apparent history of climate extremes and the disappearance of water.” Surface The Earth could avoid a similar fate due to the stabilizing effect of the Moon, which, unlike the moons of other planets, is distinguished by being very large – only 80 times less than the mass of the Earth, “explains the professor. Astrophysics at the Department of Physics of the University of Crete and Director of the Institute of Astrophysics of the Technology and Research Institute (ITE) and the Skinaka Observatory, Mr. Vassilis Harmandaris, who will present, during the event at the Eugenides Foundation, Mr. And his works Laskar to the audience in Athens.

Dr. Laskar uses both historical and current data to predict the motion of planetary bodies within our solar system. The first accurate calculations of planetary motion became possible 350 years ago when Newton solved the so-called “two-body” problem. The greatest physicist in history was able to fully explain the movement of the Moon and also predict how the comet discovered by the then astronomer Royal Halley would move in the sky. Thanks to the amazing development of computer technology, but also to the innovative calculation methods developed by Laskar and his team, traditional celestial mechanics is more modern than ever and very revealing!

Movements in nature are absolutely inevitable

The relatively new science of chaos is exploring the connections between different types of anomalies. Movements in nature, such as flowing waters or zigzagging lightning and cloud formations which may seem random and erratic, on closer examination are often revealed to be entirely deterministic, as their movements are determined in principle entirely by preceding events. Events according to the laws of nature. Only recently have high-speed computers allowed scientists to perform the long and complex calculations that have revealed the chaotic motions of the planets.

Based on the numerical simulations, Dr. Laskar and his colleagues found that without the moon, Earth’s tilt, the angle between Earth’s daily axis of rotation and the plane of its annual orbit around the sun, could fluctuate dramatically by as much as 85 degrees. This probably happened in the early solar system before the moon formed and orbited the earth.

Being so large and so close to the Earth, the Moon exerts enough gravitational force on it that it not only creates the ocean tides familiar to us and “raises” the solid crust of the Earth almost half a meter, but provides a stable torque to tension the planet in tilt. “In this sense, the Moon can be considered as a potential climate regulator for the Earth,” the French researchers concluded.

While scientists don’t think a moonless Earth would necessarily be lifeless, it would certainly be a much bleaker place—and not just for beloved songwriters. “This unpleasant development is not very likely, and it could still happen. The Moon is moving away from Earth at a rate of about 4 centimeters per year, and thus, one theory predicts a tilt of the Earth at 60 degrees about two billion years in the future,” Professor Charmandaris estimates.

According to Dr. Lascar, although the motion of our planets hasn’t changed much in 3.5 billion years, the inner solar system is still chaotic by definition. This means that we cannot accurately predict the positions and motions of the planets in the past or the future after 60 million years.

This is because in celestial mechanics, the orbital motions of planets and even small bodies like asteroids as they move around the sun have a dynamic effect on the other planets in the solar system. “It is a chaotic system in the same way that weather is chaotic,” the French astrophysicist said on some occasion.

And just as meteorologists continue to work hard to make correct predictions about climate change and its consequences for humanity, so astronomers continue to stare at night at the bright celestial bodies that “wander” among the stars and planets between us and, using new technologies and fast computers, predict their positions as best they can. Even when these planets seem to be moving “backward” and worrying us…

NB: The French Embassy, ​​the French Institute in Greece and the Eugenides Foundation welcome Dr. Lascar, and organize a special event in which the distinguished French astronomer, with his distinctive personality and ingenuity, talks about all of the above.

The event will take place in Wednesday 28 June 2023 in 19:00 pm In the Listed for Eugenides Foundation in Valero (387 Syggrou Ave., Tel: 210-946-9600). the Entry to the public is free There will be simultaneous translation. The event will be presented by the Director of the Eugenides Foundation Digital Planetarium, Mr. Manos Kitsunas, who will also coordinate the discussion with the following audience.