Will humans ever escape the earth?

Without the moon it would be pretty uncomfortable on earth

Without the sun as a source of energy, life would never have come into being on earth. But the moon, too, is more than a pretty appendage. If it didn't exist, the earth would be different today.

No question - without the moon, life on earth would be a lot duller. Who would want to miss the nights when the full moon is in the sky and the earth is bathed in a subtle light. And anyone who has ever experienced a total lunar or solar eclipse will have to admit that the moon is the celestial body for those special moments. The meaning of the moon is not limited to its aesthetic appeal. Much of what is ascribed to him arises from the realm of myths. But even if one ignores the lunar calendar, sleep disorders and the like, one can ask oneself: what would the earth be without the moon?

The other way around, the question is easy to answer: Without the earth, the moon would not exist. Because the moon is to a certain extent a descendant of the earth. As far as we know today, its formation is due to the fortunate fact that the earth was struck by a Martian-sized protoplanet about 4.5 billion years ago. As a result of the grazing shot, parts of the earth's crust and mantle were pulverized, and the impactor was also partially shattered. Its core connected with what was left of the earth. The cloud of debris, on the other hand, collected in orbit and over time there agglomerated to form the moon.

Tidal forces dent the earth

The relatively large mass of the moon (about one percent of the earth's mass) has direct consequences for the earth. These show up when you stand on the shores of an ocean where the water rises and falls twice in 24 hours and 49 minutes. The reason for this is the tidal forces that the moon (and to a lesser extent the sun) exert on the earth. These forces slightly deform the earth, so that two bumps form on the side facing the moon and the side facing away from the moon. Because of the earth's rotation, these tidal mountains move around the globe and periodically raise and lower the ground by a few centimeters. You don't notice anything on land. But the water masses of the oceans are free to move and are shifted by the tidal mountains. This is how ebb and flow arise.

Some sea creatures have adapted their habits to this interplay of the tides. So for them the moon is essential. But the moon also affects the earth as a whole. Because the sea water sloshing back and forth generates frictional heat, the moon robs the earth of energy. This causes the earth's rotation to slow down and the days to become longer by about 20 microseconds annually. At the same time, angular momentum is transmitted to the moon. As distance measurements with reflected laser light confirm, the moon moves away from the earth by 3.8 centimeters every year.

These are minimal changes that have no immediate impact on us. However, on long time scales these effects add up. Today it is assumed that shortly after its formation the moon circled the earth at a distance of 20,000 to 30,000 kilometers. That's not even a tenth of his current distance. As a result, the tidal forces must have been much stronger then than they are today. In retrospect, it is difficult to judge whether this favored the development of life in the seas.

The tidal friction that slows the earth's rotation depends on many factors. That is why it is no longer possible to reconstruct exactly how long a day lasted 4.5 billion years ago. Probably the length of the day was at most half as long as it is today, maybe it was only 5 hours. It is certain that 400 million years ago had 400 days. This can be seen from the coral fossils that lived back then. According to this, a day would have had almost 22 hours at that time.

Bulwark against chaos

Perhaps the most important effect of the moon, however, is that it stabilizes the inclination of the earth's axis. Currently the axis is inclined 23.5 degrees from the ecliptic. That is the reason why summer and winter alternate in the two hemispheres. But the inclination is changing. With a period of 41,000 years, it oscillates back and forth between 22.1 and 24.5 degrees. The following applies: The more the earth's axis is inclined towards the ecliptic, the greater the differences between the seasons. Indeed, this cycle seems to contribute to the occurrence of warm and cold periods in a complicated way.

Without the moon, the earth's axis would fluctuate much more. A few years ago it was thought possible that the surging influence of Jupiter and Saturn could tilt the earth's axis by up to 90 degrees within millions of years if the moon did not counteract it. The climatic consequences would be devastating. Instead of polar ice caps, there would be a bulge of ice around the equator. And in the temperate latitudes, extreme summers and extreme winters alternated. Microbes would probably be fine with it. It is doubtful that higher life would have developed on earth under these conditions.

In the meantime, however, it is believed that the conditions in our solar system are not quite as chaotic after all. Even without the moon, recent calculations show that the inclination of the earth's axis would only oscillate in a range of 10 to 50 degrees. And there would even be long periods of 500 million years in which the fluctuations would be limited to an interval of 17 to 32 degrees. The climatic conditions on earth would still be very uncomfortable in this case. But it seems that the existence of the moon is not essential for the development of higher life. Astronomers looking for extrasolar planets with life-friendly conditions should be happy to hear this.

And what's next with the earth and the moon? What is certain is that the moon will continue to move away from the earth in the future and that the earth's rotation will continue to slow down. In an estimated 50 billion years, the point would theoretically be reached where the earth and moon would have synchronized their movements. The earth would then rotate at the same speed as the moon orbiting the earth. An earth day would be 47 times as long as it is today. And the moon could only be seen from one side of the earth.

But it won't get that far. Because long before that, the sun will expand into a red giant and devour the planets Mercury and Venus. Whether the earth and moon can escape the flaming inferno depends on how much mass the sun loses in this phase. One thing is certain: the earth will then be a completely different planet than it is today - with or without a moon.