Fall Astronomy Day 2024 is on Friday, October 4, 2024: When is Fall or Autumn coming?

Friday, October 4, 2024 is Fall Astronomy Day 2024. FallADayLogo-Astronomy-Day-October.jpg FallADayLogo-Astronomy-Day-October.jpg

It feels like fall right now, and most people think of the month of September as being fall weather-wise. The first day of Autumn though is September brings the last day of summer and the first day of fall. Here is a list of the precise moments and dates when fall arrives for the northern hemisphere:

September 23, 2007 at 5:51 am EDT

September 22, 2008 at 11:44 am EDT

September 22, 2009 at 5:18 pm EDT <<<<<<<<<

September 22, 2010 at 11:09 pm EDT

September 23, 2011 at 5:04 am EDT

September 22, 2012 at 10:49 am EDT

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can somebody help me study for astronomy?

1. The sun is directly over the equator on both the first day of spring and the first day of fall. Since Sept 22 is the first day of fall it will be at the zenith at noon - 12 PM.

2, Again this is related to the seasons. June 21-First day of summer in Northern Hemisphere and First day of winter in Southern Hemisphere is the day when the sun reaches its furthest point north. It's also the first day of winter in the southern hemisphere. If you are in Australia looking at the sun it is low in the sky and will cast a long shadow. But if you are in the USA the sun is at its highest point and will cast a short shadow.

Hope that helps.

Edit: To further clarify ( I hope). The earth is tilted on it's axis about 23 degrees. as a result one hemisphere is always pointed towards the sun and the other hemisphere is tilted away from the sun. This is why when it's winter in North America it is summer in Australia, Around December 21 or 22 the southern hemisphere it pointed most directly at the sun and the northern hemisphere is pointed away from the sun. About March 22 and Sept 21-22 the sun is over the equator. The sun reaches its furthest point north around June 21, and begins to get lower in the sky. On Sept 21-22 the sun crosses the equator again and keeps moving southwards in the sky until Dec 21-22 when it starts moving northwards again.

How is time and day Calculated in Hindu Calender?

The earliest sources of the Hindu calendar system are texts dating from about 1000 BC.

This divided a solar year of 360 days into 12 lunar months of 27 (according to the Taittiriya Samhita) or 28 (according to the Atharvaved, the fourth Veda).

The Jyotish Vedanga of 500 BC provided rules for calculating positions of the new and full moons amongst the 27 nakshatras and of the 'ayanas` which fall in cycles of five years, each of 366 days. In five solar years, there were 67 lunar months.

A year of 12 months would be retained, if the 31st and 62nd months were omitted from each cycle. This system was widely used in ancient India.

Examples are also found in the Jaina literature dating from this period. The Taittiriya Samhita constitutes the statements of nakshatras. These nakshatras each measure an area of 13 degrees 20`` of the ecliptic circle. The position of the sun at midnight was calculated from the nakshatra that culminated on the meridian at that time. The year was divided into three_thirds of four months, each heralded by a special religious rite _ the 'chaturmasa`. Each of these periods was further divided into two parts (seasons).

Another interesting feature of the old system was the division of the two_year moieties: the 'uttarayana`, (northern course) when the sun rises further North every morning and the 'dakshinayana` (southern course) when it rises progressively further south.

After the influence of Greek and Mesopotamian astronomy, the nakshatras and a quarter of one made up one zodiac period or sign (30 degrees).

The names of the nakshatras are derived from the constellations on the horizon since those times have remained unchanged (Chaitra, Vaisakha, etc).

Eight types of planetary movements (describing their speeds of rotation) are also detailed in these works. It is amazing that in the absence of sophisticated instruments, our thinkers developed such advanced theoretical formulations.

Unlike contemporary science where 'simulation` of situations is available to validate a hypothesis, these ancient astronomers had only the crudest of implements (the water clock, circle and quadrant were extant in those times). This context of their epistemology is what makes their achievement so remarkable.

Later the revolution of the planet Jupiter was also used in Hindu astronomy. Jupiter`s synodic period brings it into conjunction with the sun every 398 days and 88 minutes. A year can be dated as a month of a 12_year cycle of Jupiter. This is extended to a unit of five cycles, or the 60_year cycle of Jupiter (Brihaspati chakra), and a 'century` of 60 years results.

From the 6th century AD, this new s ystem becomes evident.

These calculations reveal a ph enomenal development in ancient India cosmogony. These developments were significantly governed by certain principles (which, of course, varied over the ages). The 'Pitamaha` principle computed a year as 365 days and 21 1/2 ghatikas.

The 'Surya` principle analysed the movement of planets through constellations to draw up 'nadikas` (symbolic periods in days of the planet). On this principle, 584 4/11 days of Mercury (for instance) equalled 89 days and 2 hours. In the 'Romak` principle a year meant 365 days, 14 ghatikas and 18 palas. The ancient Indian calculation of time is easily superior to even present nuclear time_keeping devices. The Hindu 'truth` is obtained when one divides a second (in the western system) with 33,750 equal parts!

The Hindu 'panchanga` system (analogously derived in its etymology from the 'fine limbs`) is any day more complicated than western calendars. In the Hindu panchanga, there are five basic elements in time division:

The vara (weekday) is the natural solar day (savana divasa) beginning at sunrise. This vara has numerous sub_divisions:

A sura (prativa pala) = 0.006 secs

60 prativa palas = 1 vipala = 0.4 secs

60 vipalas = 1 pala = 24 secs

60 palas = 1 ghatika = 24 min

60 ghatikas = 1 divasa

A further refinement was the division:

10 vipalas = 1 prana (4 secs)

6 pranas = 1 pala (24 secs)