On the afternoon of July 22, local time, India's latest lunar mission "Chandrayaan 2" lunar probe was successfully launched from the Satish Dhawan Space Center in Sriharikota, Andhra Pradesh, India, on the same day
According to foreign media reports, Chandrayaan-2 will fly for two months and then be positioned in a circular orbit 100 kilometers from the lunar surface
From there, the lander will separate from the main lander and make a soft landing on the surface near the moon's south pole, and if successful, India will become the fourth country in the world to soft land on the moon
Schematic diagram of chandrayaan-2 soft landing process on the moon
Also this year, on January 3, China's Chang'e-4 probe successfully landed on the far side of the moon and sent back the world's first close-up image of the back of the moon
Image from: Lunar Exploration Project Data Release and Information Service System
From the legend of Chang'e running to the moon to the flying of thousands of households, our ancestors continue to show their romantic imagination and passion for exploration of the universe, and the eyes of the whole world have not moved away from the moon, although the two are 380,000 kilometers apart, the moon is still the closest celestial body to the earth
So naturally, the Moon also affects the world we live in, constantly reflecting the Sun's light and the gravitational pull it exerts on the Earth to cause tides
But are you confused about how the moon can influence the evolution of living things? Let's start with a fish
<h1>Grunion and "Grunion Run"</h1>
The silver han fish in California, USA, is distributed in the United States of Oregon, California San Diego to the coast of Baja California, Mexico, the body is long shuttle,slightly flattened, the head is short, the fin length is slightly greater than the body height; the snout is pointed, the two palates are slightly equal length; the main upper palate is narrow, and its end does not reach the anterior edge; the protrusion above the anterior main palate is very short, shorter than the diameter of the eye; the teeth are small and pointed, and form a small narrow tooth band, and the inner teeth of the upper palate are larger
The dorsal fin is separated, the first dorsal fin is smaller, with 9 hard spines, its starting point is slightly behind the center of the dorsal body; the second dorsal fin has 1 spine and 12 soft strips, the fin has 1 spine and 23 soft strips, its base is larger than the second dorsal fin; the pectoral position of the pectoral fin, slightly equal to the length of the head, the end does not reach the base of the ventral fin; the ventral fin is in the middle ventral position; the caudal fin is deeply split; the body is thinly rounded, 13 longitudinal columns, and there are about 77 scales in a longitudinal column
The body is pale green , with a silver longitudinal band on the side of the body , the gill cover is yellow , and the body length can reach 45 cm
Of course, the silver han fish is best known for its unique spawning habits, in the spring and summer season (March to August), during the full moon and new moon, the silver han fish will be on the beach to spawn on the beach with the highest tide on four consecutive nights, and the whole process will last for several hours
They swim as hard as they can to the sand slopes away from the sea, and the female bends her body, uses her tail fin to dig out a small nest of semi-wet quicksand, and then twists and buries herself half into the sand grains, with her head pointedly erect, and then lays eggs into this small nest
The males inseminate around the female, and each nest will have up to eight males to provide insemination, and once the male is completed, he quickly returns to the sea and returns with the next wave, a process that usually takes only about 30 seconds
The spawning season generally occurs between March and August, occasionally in February and September, the peak spawning season is late March and early June, and adult fish generally spawn on a fifteen-day cycle for four days
Females can spawn six times per spawning season, laying about 1600 to 3600 eggs each time, and large females produce even more
The eggs are stored in sand during the highest tide of the month, after which they can be safely stored undisturbed during low tides, where they are in seawater-saturated sand grains and hatch before the next tide arrives
When the next tide returns, fierce waves flood the sand grains, causing the surface sand grains to loosen and jump, and the fry will return to the sea; this change occurs about 10 days after spawning
It's clear that without the moon's influence, a reproductive cycle like the silverfish would be unattainable, and there wouldn't be the "Grunion Run" that swept California, where adults over the age of 16 can catch it with a California sport fishing license
Then we turn our attention to the moon, which affects the breeding of silverfish
<h1>Silver man fish adapted to the "trend"</h1>
We know that high tide is a phenomenon caused by the gravitational (tidal force) of the sun and the moon on the surface of the ocean on the earth, and the change of tide is related to the relative position of the earth, the sun and the moon, and will be superimposed with the effect of the rotation of the earth
Earth- The distance from the Moon is shown, scaled relative to the size of the Earth and the Moon
The seawater or river water on the earth, affected by the gravitational pull of the sun and the moon and the rotation of the earth, will have a rise and fall of the water level every morning and evening, which is called the tide in the early and the tide in the evening
When the sea rises to its highest level, it is called high water;
When the sea surface drops to its lowest level, it is called low water.
The period from dry tide to full tide is called flood;
The period from full tide to dry tide is called falling "ebb";
The time from one full tide to the next, or from one dry tide to the next, is called the period of tide;
The difference in sea surface height between full tide and dry tide is called tidal range.
In most regions, the tide is mainly a half-day tide, and its period is 12 hours and 25.2 minutes, which is exactly half of the lunar tidal day, and it is also half the time it takes for the moon to reach the next middle day, and it is also the cycle of the same place on Earth that is once again facing the moon because of its rotation
From top to bottom, it is a half-day tide, a mixed tide, and a full-day tide
Because the moon rotates in the same direction as the earth, but the earth rotates faster than the moon rotation, the high tide is carried away by the earth's rotation
This makes the current lunar orbit about 38 mm away from the earth every year, and the earth's day is extended by about 23 microseconds, because the moon's gravitational pull on the earth treats the earth as a solid state, compared to the sea water on the side of the moon, it is closer to the moon, so the sea water on the side of the moon is "elevated", which causes the tide uplift at both ends and the twice-daily tide, that is, the full-day tide
The tidal difference of the half-day tide (the change in the highest and lowest positions of the waters in half a day) varies in two or 14-day cycles each, and during the new moon and full moon, when the sun, moon and earth are on one line, that is, synodic, the tidal forces of the sun and moon are superimposed, and the tidal difference of the tides will reach the maximum, called the spring tide.
When the Moon is in the position of the upper or lower chord, the Sun and the Moon as seen from the Earth are 90 degrees apart, so that the synergy effect of the two is minimal, and at this position of the lunar phase cycle, the tidal difference of the tide is the smallest, called the small tide (English neap tide)
This also explains why the phenomenon of high tide occurs in both the sea surface closest to the moon and the sea surface furthest from the moon, so that the spherical sea level becomes spindle-shaped
Changes in distance between the Moon and the Earth also affect the height of the tides, when the Moon is at perigee, the tidal spread of the tides will increase, and at the apogee the tidal difference of the tides will decrease, every 7.5 synodic months, the new moon or full moon will coincide with the perigee moon, causing the near point month tide to maximize the tidal difference of the tide
<h1>Moon with Silver Man fish summary</h1>
Every year in March to August, the evening of the 2nd to 4th day after the full moon, when the tide begins to rise, the female of the silver mantail begins the next generation of reproduction work, and then returns to the sea when the next wave returns, and the eggs begin to develop after about 10 days in the warm and humid sand
At this time, the low tide level does not flood the eggs, and when the next tide comes, the newly hatched small fish in the sand grains return to the sea with the tide, and only two known species of silver manta rays show reproductive behavior synchronized with the tide
The high tide is because the gravitational pull of the moon and the sun will cause ocean tides, but the moon has a greater impact, when the moon, earth and sun are in a straight line, the tide appears, and at other times, the sun and moon partially cancel out, so the tide amplitude is smaller