The transit of Venus happens every 100 years. The last one was in June 2012, and the next one occurs in 2117. This happens as Venus directly passes between the Earth and the Sun. This once-in-a-lifetime astronomical alignment has been witnessed eight times since the telescope was invented. These eye-witness-accounts occurred in 1631, 1639, 1761, 1769, 1874, 1882 and 2004, and the last was in June 2012.Know More
The one-hundred-year pair-pattern for the transit of Venus is due to the orbital nodes of Earth and Venus. Since these orbital nodes are changing, transits which used to occur in May and November are now happening in June and December. Fred Espenak of NASA has released a Six Millennium Catalog of Venus Transits; and, it contains predictions based on geocentric calculations.
The transit of Venus has helped astronomers calculate Earth's distance from the Sun: It is calculated using the astronomical unit or AU. This transit was proposed by English astronomer Edward Halley in 1716. Scientists continue to study transits to this day, to discover extrasolar planets and exoplanets beyond the solar system. The Kepler Mission was launched by NASA in 2009 to find exoplanets; and, some are equal to the size of the Earth.Learn more about Time & Calendars
The formula for calculating whether a year is a leap year or not is as follows: if a year can be evenly divided by 4 (such as 2012), then it is a leap year unless it can also be evenly divided by 100 (such as 2100). There is one further exception: if a year can be evenly divided by 400 (such as 2000), then it is a leap year.Full Answer >
During spring, the axis of the Earth starts to tilt toward the sun, which causes the hours of daylight to increase in countries located in the Northern Hemisphere. Air, water and ground temperatures also increase, leading to growth of new plants. The animals that consume the newly regenerating plants begin to appear, followed by their predators.Full Answer >
Some holidays and events that happen in September include Labor Day, the start of school in many states, memorials for September 11 and more. September also signals the beginning of the fall season, with temperatures cooling in the northern portion of the United States.Full Answer >
Autumn is the season in which the Earth cools off from the hot summer and starts a slow but sure trek to the colder months of winter. Autumn is the start of the harvest season for many plants, and both humans and animals gather crops and pack them for the coming winter.Full Answer >