Walk in lukewarm water, look into the distance and collect seashells. Who has been to the North Sea, he knows what it is - its shallow water. This place, which goes under water at high tide and drains at low tide, exists only because of the moon. Because it is she who makes it so that this strip of land several kilometers wide is either flooded or drained twice a day.
But the moon provides more than just beautiful scenery, ebb tides and shallow waters. There are many indirect effects - but be that as it may, the moon plays a crucial role in life on Earth. “The moon's most important influence on Earth is that it has stabilized the climate for more than four billion years,” explains geologist Ulrich Köhler of the Institute for Planetary Science at the German Aerospace Center in Berlin. Because without the moon, the earth's axis would vibrate much more. The equator is at an angle of 23.5 degrees to the orbit in which the earth moves around the sun. This is why there are different seasons of the year - as we know them. This tilt angle is very stable, and precisely because of the moon and its gravity.
Back in the 1990s, a group of scientists led by French astronomer Jacques Laskar calculated what would have happened if the moon had not existed: over the past billions of years, the Earth's tilt angle would have changed by 85 degrees. This would mean that the Earth's axis of rotation would be at the level of its orbit.
How it looks can be seen on the example of Uranus. With its angle of inclination of 97 degrees, it revolves around the Sun in such a way that during one half of the year its northern hemisphere is turned towards the Sun, and during the second half of the year - its southern. If the same thing happened on Earth, the climate would be different: “If there was no moon, the temperatures on Earth would probably reach extreme levels,” explains Koehler. In addition, in his opinion, much stronger winds would blow on our planet.
Another important effect of the Moon is that it slows down the Earth with its gravity. “It's a bit like rolling a raw and boiled egg. Raw stops faster,”says Köhler. This is due, according to him, to the fact that the liquid egg inside is also spinning and thereby inhibited. And without the Moon, the days on Earth would be much shorter.
And in general, it is possible that without the Moon there would be no life itself on Earth, with its much shorter days and a much harsher climate. “Weather conditions on Earth have been relatively stable for four billion years. And it is this that, perhaps, contributed to the emergence of life, - the scientist emphasized, - because nature loves stable conditions.
Astronomer Stephen Kane of the University of California has no doubt that the moon was one of the key conditions for the emergence of life on Earth. He is looking for habitable planets - and at the same time studying the influence of the moon on the Earth.
“The moon was instrumental in the origin of life on Earth,” stresses Kane. First of all, the point is in small puddles on the seashore, which at high tide are under water, and at low tide are cut off from the sea. “These puddles have a very high concentration of nutrients that potentially contribute to the development of life,” explained Kane. To discover habitable planets outside the solar system, he and his colleagues specialize precisely on planets that have satellites.
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So far, these searches have not been crowned with success. However, Kane connects this primarily with physical reasons: "We can now say with confidence that many planets cannot have satellites."
Scientists have studied planets from the Trappist-1 system, located about 40 light years from Earth. Seven planets revolve around this star. There probably is a "habitable zone" as astrobiologists call it (that is, an area where there may be water in a liquid state of aggregation) - but there are no moons. Reason: The star's gravitational force is too powerful for the satellites to have stable orbits around the planets. “This means that on many of these planets, climatic conditions would be chaotic - just like on Earth if there was no moon,” says Kane.
Friederike Meier
