First of all, the lunar tides would stop in the water and air envelopes, as well as in the solid body of the Earth. However, this would not entail any unpleasant consequences.
1. There would be no eclipses on Earth - neither lunar nor solar.
If there was no moon, it would be impossible to dream of any eclipses. Obviously, if it were not for the Moon, we would not be able to watch how it passes in the shadow of the Earth on successful full moons and turns into a dark red disk.
Without the Moon, there would be no solar eclipses - there would be no object capable of at least partially covering the solar disk. We are very lucky that the Moon is located at such a distance from the Earth that its angular size is almost the same as that of the Sun. If there were no moon, the largest object capable of flying between the earth and the sun would be Venus; very cool when something like this happens, but it's far from a solar eclipse.
The absence of the Loupe would have dealt a very sensitive blow to astronomy. Then the solar eclipses would have stopped, and it is precisely at the moments of total eclipses of the Sun, when the Moon covers the dazzling solar disk, that scientists get the best opportunity to observe and study the upper layers of the solar atmosphere, the so-called corona.
2. It would not have been possible to use the Moon as a space repeater of radio waves. The absence of a natural satellite of the Earth, apparently, would have a certain influence on the development of science. It is highly likely that it could delay the discovery of the law of gravitation. After all, it is well known that this law was discovered by Newton on the basis of studying the motion of the moon around the earth.
3. The tides would be weaker
Without the Moon, the Sun would have a major influence on the ebb and flow of the earth. Although the Sun is 400 times the diameter of the Moon, it is, on average, 400 times farther from Earth and only 27 million times heavier than the Moon. Why only? Because tidal forces do not depend on the magnitude of the gravitational field, but on the degree of its inhomogeneity, and with increasing distance from the source of the field, the inhomogeneity decreases faster than the magnitude of the field itself, and the Sun must be 4003 times more massive than the Moon (64 million times) in order to exert the same effect on ebb and flow.
It turns out that the tidal force of the Sun is about two times weaker than the tidal force of the Moon, and if the Moon suddenly disappeared, we would definitely notice the difference.
Perhaps the navigators of sea navigation would have greeted the news of the disappearance of our natural satellite even with some joy: after all, then they might not have taken into account the constant changes in the level of the world ocean caused by lunar tides. But, on the other hand, many seaports would be closed to shipping.
An obviously undesirable consequence of the cessation of lunar tides would be the impossibility of building tidal power plants using the potential energy of the raised tidal wave of seawater.
4. If you happened to be outside the city on an absolutely moonless night, you most likely noticed that: 1. the sky on such nights looks amazing - thousands of stars are visible, the bright Milky Way, and even some nebulae can be detected with the naked eye; 2. Except for the sky, you don't see a damn thing anymore.
People have good night vision, especially when the moon is shining in the sky. But as soon as it disappears, our night vision ceases to be so effective. Anyone who has spent the night in a tent somewhere far from the city lights can attest to this. Most likely, if it weren't for the moon, our night vision would have developed a little differently, and we would have seen better in the dark than we do now.
5. Cessation of the Earth's breathing would probably entail a certain weakening of tectonic activity.After all, elastic vibrations of the earth's crust, occurring under the influence of lunar attraction, can serve as a kind of impulses leading to the development of earthquakes and other changes in the earth's crust.
Although it is possible that the cessation of periodic elastic oscillations caused by the attraction of the Moon could entail some unexpected consequences. But atmospheric processes in the absence of Lupa would probably have become much more stable.
6. A day on Earth would be much shorter, only 6-8 hours (we would have 1100-1400 days a year)
It seems that the length of the day does not change at all over time. In fact, this is not the case: due to the effect of tidal friction, the rotation of the Earth around its axis is constantly slowing down, but the changes are so small that you have to wait centuries to notice something. And in millions of years, the effect will already be quite noticeable.
The average increase in the length of a day is approximately +1.7 milliseconds over a hundred years. It turns out that after a very long time the rotation of the Earth will slow down so much that it will always be facing the Moon with one side (as has already happened with the Moon). The moon will constantly "hang" over one point on the earth's surface and will not be visible from one of the hemispheres.
It turns out that in order for the Earth to rotate at a speed of one revolution in 24 hours at the present time, in the past, the Earth had to rotate much faster. The duration of a day on Earth at the beginning of its existence could be about 8 hours, and if there was no Moon, the Earth's rotation would not slow down, its poles would be more compressed now, and we would have more than 1000 days a year.
7. The tilt of the earth's axis would change dramatically over time
You are most likely aware that the Earth's axis of rotation is tilted by ≈ 23.5 °, but have you ever wondered why the tilt angle does not change over time? Just like the axis of a rotating top, the axes of the planets perform uneven oscillations, nutations, as a result of which the angle of inclination of the axis is constantly changing. The magnitude of fluctuations for each planet is different, so the angle of inclination of the axis of Mars varies from 15 ° to 35 °.
However, the Earth stands out a little against the background of other planets. It has an external nutation stabilizer - the Moon. Thanks to the Moon, the tilt of the earth's axis changes slightly - from 23 to 26 degrees, and if it were not there, these fluctuations would be very noticeable.
The moon plays a critical 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. Because without the moon, the earth's axis would oscillate much more strongly. 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.
What would happen if there was no Moon: The tilt of the Earth would change 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 hemisphere. If the same thing happened on Earth, then the climate would be different:
If there were no moon, the temperatures on Earth would probably reach extreme levels. In addition, much stronger winds would blow on our planet.
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.