Facts about the moon

Space travel was not possible for us earthlings until the 20th century. The Soviet Union and United States were the first two countries able to launch satellites from 1957 to 1965. Later France, Japan, India, and China launched man made  satellites in orbit of the earth. In 1984 the 13-member European Space Agency (ESA) began its own launch program. None of the Islamic countries has yet been able to acquire the capability to undertake any such venture relating to space exploration.
Space probes have unearthed many secrets and provided scientific data on the nature and origin of the solar system and the universe. Artificial satellites orbiting earth and sent to other planets have expanded knowledge, improved global communications, weather forecasting, navigational aids, and examination of the earth's surface. 

The word "moon" appear 30 times in 28 verses in Yusuf Ali's translation of Holy Quran and 86 times in 68 hadiths in  translation of Sahih Bukhari.
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The diameter of the moon is about 3480 km (about 2160 mi), about one-fourth that of Earth. The mass of Earth is 81 times greater than the mass of the moon. New moon becomes visible in South Asia usually after a day or two of appearance in Mecca. In some parts of the earth moon may not be visible for many months. Therefore,  appearance of new moon at Holy K'aba must be good for the whole world. 

Our Ulemas keep on quarrelling whether or not the moon has been sighted and different months of Hijri lunar Calendar not only in different Islamic countries but also within the country; begin on different weekdays often with a gap of one to three days. 

The diameter of the moon is about 3480 km (about 2160 mi), about one-fourth that of Earth. The mass of Earth is 81 times greater than the mass of the moon. Temperatures on the moon range from a maximum of 127° C (261° F) at noon to a minimum of -173° C (-279° F) just before dawn. The moon moves around Earth at an average distance of 384,403 km (238,857 mi), and at an average speed of 3700 km per hr (about 2300 mph). It completes one revolution around Earth in 27 days, 7 hours, 43 minutes, and 11.5 seconds. The moon rotates on its axis in about the same time that it revolves, and so almost the same portion of the moon always faces Earth. 

What's it like to walk on the moon? 
Join the Apollo astronauts on the surface in this series of stunning 360-degree panoramas, one each from the six successful Apollo moon landings. Shot by the astronauts themselves
during their historic moonwalks, these images capture the magic and mystery of the moon like no standard photograph can. 
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As seen from the earth half the moon is always in sunlight but visibility of sunlit area varies as the moon keeps on rotating with a tilt of its orbit. The phases of the moon from a crescent to full moon were the basis of counting dates of a month in ancient times and valuable aid to navigators of ships. The moon is full when it is farther away from the sun than Earth is; it is new when it is closer. One month of lunar phases is 29 days, 12 hours, 44 minutes, and 2.8 seconds. 

Human Beings on the Moon
On July 20, 1969, astronaut Neil A. Armstrong stepped onto the surface of the moon. His first words were, “That's one small step for [a] man, one giant leap for mankind.” Astronaut Edwin E. Aldrin, Jr., joined him moments later. The U.S. spacecraft Apollo 11 returned to earth on July 24. Apollo 12 landed two astronauts on the moon in November. After successful landings in 1970 the moon landings program ended. 

Early Calendars
Most of the ancient calendars were based on lunar months. Because they failed to agree with the seasons, a month occasionally had to be intercalated (added) to reconcile lunar months with the solar year. A calendar that makes periodic adjustments of this kind is a lunisolar calendar. Such was the one used by the ancient Babylonians. The ancient Egyptians were the first to replace the lunar calendar with a calendar based on the solar year.

The visibility of the lunar crescent
At one time many Ulemas, especially in Saudi Arab held the view that for Islamic dates, the sighting must be made with the unaided eye. But their thinking has changed and they are now using telescope and reports of regional observatories as well as other means of communication on based on sighting in their own country. 

As discovered by the Muslim astronomers of 10th Century the date and time of each New Moon can be computed exactly. Their findings correspond to the research done by the modern observatories in Europe and USA. But the time that the crescent first becomes visible after the New Moon depends on many factors and cannot be predicted with certainty for any particular region. 

In the first two days after New Moon, the young crescent Moon appears very low in the western sky after sunset, and can only be viewed through bright twilight. It sets shortly after sunset. The sighting of the lunar crescent within one day of New Moon is usually difficult. The crescent at this time is quite thin, has a low surface brightness, and can easily be lost in the twilight or if the weather conditions are not clear. Pollution of atmosphere due to industrialization and space exploration may also hinder sighting on earth.. 

According to modern Astronomy, the time that the crescent actually becomes visible varies quite a bit from one month to another. The record for an early sighting of a lunar crescent, with a telescope, is 12.1 hours after New Moon; for naked-eye sightings, the record is 15.5 hours from New Moon. These are exceptional observations and crescent sightings this early in the lunar month should not be expected as the norm. Ulemas in Saudi Arabia hold the view that for Islamic festivals the month must be determined by the sighting made with the unaided eye. 

Obviously, the visibility of the young lunar crescent depends on sky conditions and the location, experience, and preparation of the observer. Generally, low latitude and high altitude observers who know exactly where and when to look will be favored. For observers at mid-northern latitudes, months near the spring equinox are also favored, because the ecliptic makes a relatively steep angle to the western horizon at sunset during these months (tending to make the Moon's altitude greater). 

If we ignore local conditions for the moment, and visualize the problem from outside the Earth's atmosphere, the size and brightness of the lunar crescent depend on only one astronomical quantity - the elongation of the Moon from the Sun, which is the apparent angular distance between their centers. For this reason the elongation has also been called the arc of light. If we know the value of the elongation at any instant, we can immediately compute the width of the crescent. There is detailed information about “ Phases of the Moon” at the web site of U.S. Naval Observatory
http://aa.usno.navy.mil/data/docs/MoonPhase.html

A Global Islamic Calendar based on astronomical calculations for appearance of crescent in Mecca is the best way to standardize Islamic dating procedures

Conversion of Dates from Hijri Calendar to Gregorian.

 Gregorian calendar used today in the Western world was introduced by Pope Gregory XIII in 1582 to replace the Julian calendar. To approximate better the length of the astronomical year (365.2422 days), years divisible by 100 are leap years only if they are also divisible by 400 (thus, 2000 will be a leap year, but 1900 was not).  

Under the Islamic Hijri calendar a year is around 10 days shorter than Gregorian year because Hijri calendar is based on lunar cycle and under it a month may comprise 29 or 30 days. According to the old traditions each month begins on the day immediately following the first observation of the new moon in the night sky. Owing to the earth's axial rotation, the time of this varies from place to place. New Year's Day, and the first days of all the months, are therefore also subject to variation and different months shifts slowly from one season to another in a cycle of around three decades. .