A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours. As a day passes at a given location it experiences morning, noon, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes.
A month is a unit of time, used with calendars, that is approximately as long as a natural orbital period of the Moon; the words month and Moon are cognates. The traditional concept of months arose with the cycle of Moon phases; such lunar months ("lunations") are synodic months and last approximately 29.53 days, making for roughly 12.37 such months in one Earth year. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months, based on the Moon's orbital period with respect to the Earth–Sun line, are still the basis of many calendars today and are used to divide the year.
A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days.
A year is the time taken for astronomical objects to complete one orbit. For example, a year on Earth is the time taken for Earth to revolve around the Sun. Generally, a year is taken to mean a calendar year, but the word is also used for periods loosely associated with the calendar or astronomical year, such as the seasonal year, the fiscal year, the academic year, etc. The term can also be used in reference to any long period or cycle, such as the Great Year.
Eclipses may occur repeatedly, separated by certain intervals of time: these intervals are called eclipse cycles. The series of eclipses separated by a repeat of one of these intervals is called an eclipse series.
A synodic day is the period for a celestial object to rotate once in relation to the star it is orbiting, and is the basis of solar time.
A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world, is the second, defined as about 9 billion oscillations of the caesium atom. The exact modern SI definition is "[The second] is defined by taking the fixed numerical value of the cesium frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s−1."
A lunar standstill or lunistice is when the Moon reaches its furthest north or furthest south point during the course of a month. The declination at lunar standstill varies in a cycle 18.6 years long between 18.134° and 28.725°, due to lunar precession. These extremes are called the minor and major lunar standstills.
The Moon orbits Earth in the prograde direction and completes one revolution relative to the Vernal Equinox and the stars in about 27.32 days and one revolution relative to the Sun in about 29.53 days. Earth and the Moon orbit about their barycentre, which lies about 4,670 km (2,900 mi) from Earth's centre, forming a satellite system called the Earth–Moon system. On average, the distance to the Moon is about 385,000 km (239,000 mi) from Earth's centre, which corresponds to about 60 Earth radii or 1.282 light-seconds.
A total lunar eclipse will take place between Monday and Tuesday, June 25-26, 2029. A central total eclipse lasting 1 hour and 41 minutes 53 seconds will plunge the full Moon into deep darkness, as it passes right through the centre of the Earth's umbral shadow. While the visual effect of a total eclipse is variable, the Moon may be stained a deep orange or red color at maximum eclipse. It will be able to be seen from most of the Americas, Western Europe and Africa. The partial eclipse will last for 3 hours and 39 minutes 32 seconds in total.
A total lunar eclipse took place at the Moon's descending node of the orbit on Tuesday, May 24, 1910 with an umbral eclipse magnitude of 1.09503. A total lunar eclipse takes place when the Earth comes between the Sun and the Moon and its shadow covers the Moon. Eclipse watchers can see the Moon turn red when the eclipse reaches totality. Total eclipses of the Moon happen at Full Moon when the Sun, Earth, and Moon are aligned to form a line. The astronomical term for this type of alignment is syzygy, which comes from the Greek word for being paired together. The Moon does not have its own light but shines because its surface reflects the Sun's rays. During a total lunar eclipse, the Earth comes between the Sun and the Moon and blocks any direct sunlight from reaching the Moon. The Sun casts the Earth's shadow on the Moon's surface. A shallow total eclipse saw the Moon in relative darkness for 49 minutes and 29.5 seconds. The Moon was 9.503% of its diameter into the Earth's umbral shadow, and should have been significantly darkened. The partial eclipse lasted for 3 hours, 35 minutes and 22.9 seconds in total.
An annular solar eclipse will occur at the Moon's descending node of orbit on Tuesday, January 5, 2038, with a magnitude of 0.9728. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide.
A total solar eclipse will occur at the Moon's ascending node of orbit between Monday, May 21 and Tuesday, May 22, 2096, with a magnitude of 1.0737. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. This will be the first eclipse of saros series 139 to exceed series 136 in length of totality. The length of totality for saros 139 is increasing, while that of Saros 136 is decreasing.
A total solar eclipse will occur at the Moon's ascending node of orbit on Saturday, December 5, 2048, with a magnitude of 1.044. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight and turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region spanning thousands of kilometres.
A total solar eclipse will take place at the Moon's ascending node of orbit on Friday, September 12, 2053, with a magnitude of 1.0328. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide.
An annular solar eclipse will occur at the Moon's ascending node of orbit on Sunday, December 16, 2085, with a magnitude of 0.9971. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. If a moon with same apparent diameter in this eclipse near the Aphelion, it will be Total Solar Eclipse, but in this time of the year, just 2 weeks and 4 days before perihelion, it is an Annular Solar Eclipse.
A total solar eclipse will occur at the Moon's ascending node of orbit on Monday, May 1, 2079, with a magnitude of 1.0512. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. The eclipse will be visible in Greenland, parts of eastern Canada and parts of the northeastern United States.
An annular solar eclipse will occur at the Moon's descending node of orbit on Friday, November 4, 2078, with a magnitude of 0.9255. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. The path of annularity will cross the Pacific Ocean, South America, and the Atlantic Ocean.
A total solar eclipse will occur at the Moon's ascending node of orbit on Tuesday, October 4, 2089, with a magnitude of 1.0333. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide.
In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.
