Light on the water at night from the moon. Moonlight - A brief overview of spectrum, intensity, photoperiod and its relationship to coral and fish reproduction

Many children, and some adults, are interested in the question, why does the moon shine? After all, this is not a star, it does not have a burning surface, it is a completely ordinary dense planet, and it does not have a high phosphorus content. What's the matter?

There used to be many different points of view. For example, the early Christians never asked the question “why does the moon glow.” Even on the first pages of the Bible it is said that God created the Sun to illuminate the day (daylight), and the Moon to disperse the darkness of the night (nightlight).

A little earlier, in the pre-Christian period, pagans considered the Earth’s satellite to be the patron goddess of the night. Even now in literature you can sometimes read about ghostly moonlight.

It is human nature to believe in miracles! What is its reason, since it is so different from the solar or artificial one we are all used to? Why does the moon glow?

In fact, the answer to the question “why does the moon glow” is very simple

The Moon is the natural and only satellite of the Earth, rotating both around it and around its own axis, and this happens over the same period of time, so the Moon is always turned to us with one side, which is where the expression “far side” comes from Moon."

The moon itself does not have the property of glowing, but why does the moon glow? It can only reflect sunlight or the light of the Sun reflected by the Earth onto the Moon. It often happens that the Earth blocks, completely or partially, the access of light to the Moon from the Sun; it is then that we see the waxing and waning Moon, that is, only part of it or not see it at all, as on a moonless night.

Very sharp temperature changes occur on the Moon, due to the lack of its own atmosphere, such as the Earth has and protects us from direct exposure to Sunlight and without which life would not be able to exist on Earth.

A day on the Moon lasts 14 days, which is why the Moon glows on these days, and during this time the Sun heats the surface of the Moon to more than 100 degrees Celsius, the next 14 days comes Moonlight, then the Sun does not hit the surface of the Moon and it cools down to - 200 degrees Celsius, heat cannot be retained on the surface of the Moon, since there are no atmospheric layers to stabilize temperature changes.

Both far and close
In the light of the night moon
I see the reflection of the stars,
Flying through my window.

Dream or reality?
Does it reflect the reflection of so many years to me?
From afar, a slightly perceptible ray,
How did you reach me?

In the light of the night moon,
In silence, I think:
The moon was shining just like that
Two thousand years ago
The temple, she illuminated...

Temple, so far and so close
Where are you, in my house?
In the glow of the candles are minors?
Where are you in Moscow, Barcelona, ​​Paris?
In Rome and Vienna and Uruguay,
Your lights are above Krasnoyarsk,
And in Budapest and in Washington,
In Brooklyn and Liverpool.
On Hanukkah, illuminating the world,
Where and who are you dreaming about?

Dawn rises over Jerusalem.
Prayers sounded there -
Prayers for peace
Aleynu - Praise be to you,

There is a Muslim temple, a Christian temple there...
And we only have a piece of the wall
How much grief and tears we have suffered,
The wall is completely washed with them,
Her war doesn’t subside,
For the right to live,
For the right to raise children in peace.
Both far and close
In the light of the night moon
I see the reflection of the stars,
Flying through my window.
Dream or reality?

I hear the Temple is being built!
I see it in the sun's rays,
The temple floats above the earth!

The holiday of candles, which are lit in honor of the miracle that occurred during the consecration of the Temple after the victory of the army of Yehuda Maccabee over the troops of King Antiochus in 164 BC. This holiday begins on the 25th of the Hebrew month of Kislev and lasts eight days.

In 332 BC. Judea came under the rule of Alexander the Great, who adhered to a policy of non-interference in the religious life of Jews. After Alexander's death in 323 BC. and the many wars that his heirs waged among themselves, the Egyptian Ptolemaic dynasty came to power and the next century passed in a state of relative stability.

In 198 BC. The Ptolemies were defeated by the Seleucids (Assyrian Greeks), into whose hands Judea also fell. At first, the general situation seemed unchanged and even somewhat improved. Jews received written guarantees confirming their right to live “according to the laws of their fathers,” and the tax burden was somewhat reduced. But then the Seleucids began to attempt to Hellenize the Jews. Greek philosophy and culture gradually began to penetrate the Jewish environment.

In 175 BC. Antiochus Epiphanes came to power, and under him the Hellenization of the non-Greek population acquired particularly harsh forms. The Torah became a forbidden book, observance of Jewish laws became a serious crime, and idols were installed everywhere. Antiochus gave his name to Jerusalem, the temple treasures were confiscated, and the Temple itself was plundered.

In response, a rebellion began in Judea led by the Maccabean family. Compared to Antiochus's army, the rebel army was small in number, poorly armed and trained. The leader of the army, Yehuda Maccabeus, realizing this, avoided open battles, not giving the enemy the opportunity to take advantage of the numerical advantage. Attacking individual detachments of the Greeks, the rebel army won one victory after another. In three years, she drove the conquerors out of the country and liberated Jerusalem, thereby proving that a high goal and fortitude are sometimes decisive.
Tradition says that, having climbed the Temple Mount, the Jews found in the Temple oil for lamps, sufficient to keep the fire burning for only one day. However, miraculously, the fire in the golden menorah burned for eight whole days, during which new supplies of oil were prepared. Thus the Temple was re-consecrated.

In memory of this event, candles are lit every evening on the holiday: one on the first day of the holiday, two on the second, three on the third, and so on, up to eight, using for this, as a rule, a special candlestick - Hanukkiah. Jewish wisdom says: “A little light is enough to dispel much darkness.”

On Hanukkah, children have holidays, and it is customary to give them toys and money. The game of Hanukkah spinning top is also reminiscent of ancient events, on each of the four sides of which is written the first letter of the words of the phrase “A great miracle was here” (if it happens in Israel) or “A great miracle was there” (in the Diaspora).

Moonlight is considered an important factor in the reproductive cycle of many species of corals and fish. In corals, the lunar cycle determines the date of reproduction, and the time of darkness more precisely adjusts the cycle and determines the hour and minute (then hormones are released into the water, which leads to mass reproduction). The periodicity of the lunar cycle influences the timing of reproduction in at least several fish species. It seems quite clear that changing lunar phases affect different taxa differently, if only temporarily.

Quite a lot of attention is paid to the issue of artificial lighting of the aquarium, while another natural type of lighting - moonlight - is usually deprived of attention. Although moonlight simulators have been on the market for many years, I would like to go into more detail on this issue. In this article we will look at the basic aspects of moonlight and discuss some common misconceptions. In addition, we will determine the spectral characteristics of moonlight, its intensity, the length of the natural photoperiod, and ways to simulate moonlight. We will also look at the effects (if any) of moonlight on coral spawning times (and comment, albeit briefly, on the effects of moonlight on fish spawning).

Photoperiod of the Moon in Hawaii

As we know, the lunar cycle is 29.5 days and is the basis of our calendar month. The phases of the Moon change predictably, depending on the position of the Moon, Earth and Sun. The phases do not depend on the fall of the Earth's shadow on the Moon (this effect is called a lunar eclipse). Figure 1 shows the phases of the moon and approximate days of the lunar month.

Figure 1. Lunar cycle and breeding activity of the stony corals Pocillopora meandrina (and P. eydouxi) in Hawaii.

The numbers above the moon phase images show the approximate length of the cycle in days.

The estimated time of coral reproduction is marked in red.

Figure 2 shows the expected moonlight times in Hawaii. Data is based on sunrise/sunset and moonrise/set times.

Figure 2. Moonlight times in Hawaii (latitude N 19 38").

The red dots indicate the breeding time of Pocillopora meandrina and

Pocillopora eydouxi on the western side of the Big Island (Hawaii Island) of the Hawaiian Islands.

Spectral characteristics of moonlight

Since moonlight is almost entirely reflected sunlight, you might think that the spectrum of moonlight would be the same as sunlight. However, it is not. The data presented in Figures 3 and 4 show that in moonlight, compared to sunlight, there is less blue and more red (measurements were taken during the “silver” Moon at its zenith. When the Moon sets, it often appears more orange to us).

Figure 3. Moonlight reaches its maximum in the red part of the spectrum (643 nm),

but appears "silver" when it is at its zenith on a clear night.

Figure 4. Spectral distribution of the lunar spectrum presented in Figure 3.

Moonlight intensity

The intensity of moonlight depends on the phase of the moon and the state of the sky. Figure 5 shows the moonlight intensity (in lux) under ideal conditions. Figures 6 and 7 show the full moon light intensity (PAR) over two nights (measured at a location a few tens of centimeters above sea level). Note that the intensity readings are lower compared to the data given by Jokiel (0.05 µmol·m²·sec, or about 1 lux). The low lunar light intensities reported here are due to several factors, including the presence of seawater vapor in the air, high, thin clouds, and the presence of a mixture of atmospheric humidity and volcanic haze from Pu-u O-o Crater and Halema Uma-u Caldera Kilauea volcano).

Figure 5. Moonlight intensity over a month under ideal conditions.

Figure 6. Photosynthetically active radiation during the December full moon in Kailua-Kona, Hawaii, recorded by the PAR recorder.

Tall, thin clouds caused a halo to appear around the Moon, resulting in less light intensity.

Figure 7. Photosynthetically active radiation for two days under a full moon before seasonal breeding.

stony corals Pocillopora meandrina and P. eydouxi in Kailua-Kona, Hawaii.

Factors influencing coral reproduction - in order of importance

Moonlight is one of the factors influencing the reproduction of corals. If other factors (nutrition, physical parameters, etc.) are normal, then the following factors will be significant:

Temperature: Temperature appears to be a significant factor affecting coral reproduction. If the temperature is too high, the condition of the corals deteriorates, and if the temperature is too low, the breeding season may be delayed until a suitable period in the next month (Hunter, 1988; Riddle - personal observations). Temperature has a dominant effect on the reproductive cycle of marine invertebrates (Olive, 1995). In the Hawaiian Islands the temperature threshold is around 24C (Paul Jokiel, personal communication).

Moonlight: Lunar cycles determine the breeding date of many coral species, and the lunar calendar can be used to accurately predict the process.

Daylight photoperiod: Solar photoperiod also influences the reproductive behavior of corals and determines the hour and minute of reproduction (Wiese et al. 2008). The timing of sunset is a factor in more accurately determining breeding times for many marine invertebrates, including at least some species of sponges and corals.

Corals don't have eyes: How do they perceive light? And what do they see?

Gorbunov et al. (2002) found that blue light around 480 nm (spectral width 110 nm at half maximum), at very low intensity, caused a response in coral polyps, although a description of the photoreceptors involved was not part of the experiment.

In 2003, Levy et al. subjected corals (not containing the zooxanthellae Cladopsammia gracilis) to bubble coral Plerogyra sinuosa, long-polypous ball brain Goniopora lobata, Favia favus, And Stylophora pistillata) exposure to light with different wavelengths (in the range of 400-700nm, with an interval of 20nm) and intensity (10µmol·m²·sec and 30 µmol·m²·sec; ~500 lux and 1,500 lux, respectively) and recorded the reduction of polyps. Coral Cladopsammia did not respond to exposure to light, whereas Plerogyra sinuosa and Favia favus polyps were reduced under the influence of light with wavelengths in the range of 400-520 nm (violet-blue-green). I wonder what Favia favus also responded to red light (660-700nm) at an intensity of 30 µmol·m²·sec or ~1,500 lux (see photosensitivity of rhadopsin-like compounds and cryptochromes below).

Five years later, a compound resembling rhadopsin was discovered in a stony coral. Acropora millepora(Anctil et al., 2007), which explains the way corals perceive light. Almost at the same time, Levy et al. (2007) described the blue light-sensitive cryptochrome protein in Acropora millepora. Other researchers have noted coral responses to light, suggesting the presence of rhadopsin-like compounds in at least some coral species.

This ability to perceive light explains the ability of corals to grow in the direction of light; and if corals are moved, they change the direction of growth (this process is called phototropism). This also explains how corals adjust their biological clocks through their ability to sense sunlight and moonlight.

*Rhodopsin is a photosensitive pigment found in the eyes of many animals (including humans) in receptors called “cones.” Cones and the rhodopsin they contain allow us to see in very low light conditions. Rhodopsin is sensitive to light with wavelengths ranging from 400 nm (violet) to red (~600 nm), but works best in the blue-green spectrum (Hunt, 1987).

**Cryptochromes (Greek: “hidden” light) are proteins sensitive to blue light; they are found in the photoreceptors of plants and animals.

Periodicity of biological rhythms and response to external factors

The process of reproduction involves the production of several compounds, this may be due to periodic cycles, or the result of external stimuli. In our case, periodic rhythms are those cycles that occur without the influence of additional external stimuli, such as sunlight or moonlight. Most likely they are controlled genetically. External factors (such as moonlight, etc.) can affect the production of compounds. Wiese et al. (2008) found that photoreceptors trigger the production of proteins that play an important role in the annual breeding cycle of stony corals Montastrea cavernosa.

Fish reproduction and moon phases

It is known that the spawning of many fish is synchronized with certain phases of the Moon, and this periodicity depends on the specific species. For example, Takemura et al., 2004 examined the influence of lunar phases on the spawning of Golden shigan Siganus guttatus. Under constant lighting conditions, these fish do not reproduce, and changes in spawning behavior were noted in specimens kept in complete darkness at night. Pressley (1980) described the relationship between lunar phases and reproductive behavior of the yellowtail damselfish, Microspathodon chrysurus.

It should be noted that circadian rhythms play an important role in the reproductive behavior of fish, and accurate imitation of the phases of the moon can be an important factor.

P Spectrum propagation in clean sea water

As mentioned above, several researchers have found that some corals respond to blue light. Perhaps the fact that light penetrates to its maximum depth at a wavelength of 480-500 nm is not just a coincidence. See Figure 8.

Figure 8. Light transmission (wavelength measured in 25 nm increments) through the clearest sea water (Type I Oceanic; according to Zherlov, 1976).

Note that ~500 nm blue-green light penetrates water best.

Moonlight and coral reproduction

It is believed that moonlight is one of the determining factors for the reproduction of corals. Jokiel (1985) examined a large number of specimens of Pocillopora damicornis and concluded that planula release occurs around the full moon. However, Hunter (1988) conducted experiments with two Hawaiian species of Montipora (M. verrucosa = capitata and M. dilatata) and found the following:

• Both corals bred at the same time as controls when both groups of corals were exposed to constant artificial moonlight (at a flux of 0.01 µmol m² sec, or about 0.5 lux).
• Without simulating the lunar cycle (constantly new moon), 43% of M. verrucosa reproduced simultaneously with control specimens, and in the next month - 1 week before the new moon. Montipora dilatata also reproduced simultaneously with the control specimens in the first month, and in the next month the difference from the normal schedule was 8 days.
• When the deviation was 14 days from the lunar phase, both corals reproduced at the same time as the control specimens, and a month later the difference was 2-12 days.

Artificial moonlight

As a rule, in practice it is difficult to organize natural moonlight in an aquarium, so its imitation is used. In my book The Captive Reef, published in 1995, I discussed ways to simulate moonlight using a blue incandescent lamp and a manual rheostat. Since then, technology has come a long way, and light-emitting diodes (LEDs) have become the most popular way to imitate moonlight. See Figure 9.

Figure 9. This blue LED acts as an artificial moon.

Figure 10 shows a typical LED spectrum with a maximum in the blue part of the spectrum ~450 nm.

Figure 10. This blue LED produces nearly monochromatic light, peaking at about 450nm.

Controllers

There are currently controllers on the market that manufacturers claim are capable of simulating the timing and varying intensity of natural moonlight. In this article we will not consider all the options on the market. Instead, I will describe the system I use myself - the Tunze Multicontroller 7095. The main function of this device is to control Tunze pumps, but also includes an LED to simulate moonlight. The only thing the aquarist needs to do is turn on the LED during a natural full moon, and the controller will automatically do the rest. When the main lighting of the aquarium is turned off, the photosensor will turn on the LED simulating moonlight; The intensity of moonlight in all phases is controlled on a 29-day cycle. Figure 11 is an enlarged image of the photosensor/LED, and Figure 12 shows the spectral characteristics of the applied LED.

Moonlight is considered an important factor in the reproductive cycle of many species of corals and fish. In corals, the lunar cycle determines the date of reproduction, and the time of darkness fine-tunes the cycle and determines the hour and minute (after which hormones are released into the water, leading to mass reproduction). Changing lunar phases may, at least temporarily, disrupt the established reproductive process in at least several species of corals. The periodicity of the lunar cycle affects the time when reproduction occurs in some fish species. Interestingly, short-term exposure of some fish species to artificial moonlight at a constant intensity could interfere with reproduction, while some corals had no effect. It seems quite clear that changing lunar phases affect different taxa differently.

Even though moonlight appears white or silvery, the facts above show that using blue LEDs to simulate moonlight is correct, at least for some coral species. Using white LEDs is likely also an option. However, the light intensity of even one blue LED will likely be higher than natural moonlight measured here in Hawaii. Light penetration in an aquarium, given the shallow depth and hopefully clear water, should not be a problem, so using LEDs that peak in the 450nm - 460nm range may actually be an advantage due to their low intensity at 480nm.

Since the minimum measurable value for most PAR meters is 1, they are virtually useless in determining the correct location of the light source to simulate natural lunar light. On the other hand, a lux meter is capable of measuring moonlight at maximum intensity, although the measured value will be around 1. Therefore, we will most likely be forced to visually select the correct location for the moonlight source. At present, the effects of excessive aquarium lighting at night are not yet known, but it is possible that this factor may affect the reproductive behavior of fish or invertebrates.

There are a large number of controllers on the market that can simulate moonlight. In the absence of a special device, aquarists can make a controller-simulator of moonlight with manual control, using a rheostat and a low-power incandescent lamp.

Test equipment

The spectral characteristics of natural moonlight and LEDs were measured using an Ocean Optics USB2000 spectrometer and SpectraSuite software. The data was entered into an Excel spreadsheet for further processing. Moonlight intensity was measured using a Li-Cor 1400 meter/recorder and a response-corrected quantum sensor.

Gratitude
Thanks to my brother David for providing the photo of the Moon.

Since ancient times, there has been a kind of “confrontation” between the sun and the moon. This is one of the strongest, most ancient and most “dangerous” legends, since according to legend, those people who wanted to test it faced simply terrifying consequences, sometimes even death. But we are not afraid, we will simply analyze this legend one by one, say what has survived to this day and what scientists think about it. The first (the sun) gave a person strength and energy, and the second took it away.

If you don't believe it, you can do the experiment yourself. You can take anything (a piece of apple, a blade, or any other object) and place it under the window so that the moonlight looks at it. The effect only intensifies during the full moon.

After a couple of days, you can pick up an object from the windowsill and see how much it has rotted, dulled, and so on. The effect was especially strong with food and flowers. That is why it is believed that in the bright light of the moon you cannot sow or plant any crops, because they will wither and die very quickly.

In the old days, the Slavs knew this very well and therefore tried not only to protect themselves from moonlight (and most of the harm from this comes to small children and pregnant women), but also received benefits from it. Thus, the juiciest and most delicious meat is obtained from a slaughtered animal during the full moon.

Everything about sleep is quite ambiguous. On the one hand, in the old days (around the end of the 14th century) such a glow on a sleeping person was definitely bad. But after the beginning of an active study of astronomy, scientists found out that such a bright light of the moon, which was previously attributed to evil spirits closely watching a person and waiting to capture his soul, is just a stream of reflected light from the sun and its brightness varies in different phases moon. And the brighter it is, the stronger the effect on a person.

So, for example, there are very frequent cases when, when illuminated by moonlight, a person will not get enough sleep, he will feel tired, irritated, and small “oversleeps” of 1-2 hours will not bring a feeling of rest. In addition, melatonin production ceases, which not only “blurs the boundaries” between the period of rest and the period of wakefulness, but also causes depression. It is impossible to go crazy if you look at the moon for a long time, even if it is full. However, you can become hypnotized, and there are often cases from practice when people looked at her all night without looking away and without even blinking.

This often occurs in people with a good imagination who suffer from depression and in teenagers suffering from puberty, enjoying the romantic light, especially with a significant other. But be careful - very impressionable people and people with a weak psyche can become overexcited and their “blueness” can only intensify, they may lose sleep, and there will be frequent mood swings. But you don’t have to believe anything about the “experts” who shout at every step that you can go crazy from this.

Indeed, this is possible, but this is, firstly, a 1 in 1000 chance, and secondly, if the person previously had serious mental disorders. However, even if you are a fanatic who repeats “it is impossible for moonlight to fall on a sleeping person” in a whisper and closes all the curtains, there is not much left before madness.

But what is useful to know is the negative effects proven by doctors that can affect a person, such as:

• slowdown of metabolism, “braking” of the whole body, which is associated with insufficient blood flow to the brain
• Fluid overflows in the organs, especially those located around the heart. This effect is enhanced many times over for people who suffer from heart disease.
• people who often take medications should be aware that the effect of the medications is reduced at this time.

In conclusion, I would like to say that in the modern world, as we know, there is a division into “larks” and “night owls”. For example, for owls, the full moon is considered the best moment, since the energy of the body is recharged by two luminaries at the same time and the body works at double speed, without experiencing any serious stress.

ANCIENT EGYPTIAN MYTH

The god of time and the god of the Moon was Thoth, the viceroy of the god Ra. When Ra descended on his boat along the Heavenly Nile to the Western Mountains and began sailing along the Underground Nile, Thoth, taking the form of the Moon, set off along his path across the Sky. Slowly and thoughtfully he made his circle along the heavenly path.
The Moon God Thoth was also the god of wisdom and the patron of scientists.

ANCIENT GREEK MYTH

Selene, the daughter of the titan Hyperion and Theia, was the sister of Helios. When the goddess Nobody (Night) throws her black blanket over the Earth, everything is shrouded in impenetrable darkness. Only the stars, as if frightened by the dark night, tremble and emit a pale light. There are many of them, they dot the entire Sky, but they are powerless to drive away the darkness of the night that has swallowed the entire Earth. And then a faint, gentle glow appears in the east. It gradually intensifies, as if the heavenly distance is engulfed in flames... After some time, the majestic goddess of the Moon, Selene, begins to rise on the horizon in the east. She stands calmly in her golden-red chariot, which is slowly drawn across the sky by victorious bulls. From her yellow-golden clothes and from the crescent moon above her brow, a gentle silvery light pours onto the sleeping Earth, which drives away the darkness of the night.
Having completed her heavenly path, Selene descends on a chariot into a deep cave located in the Latum Mountains near Caria. There lies the son of Zeus, Endymion, plunged into eternal sleep. Selena is in love with Endymion. She quietly bends over him, strokes his head, caresses his face and whispers the most tender love words. But Endymion does not feel her caresses. Therefore, Selena is always sad and illuminates the Earth at night with the same sad light.