our galaxy, the Milky Way


What is Galactic time?

Why Galactic time ?

How Galactic time ?




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What is Galactic Time?


We measure time on our planet earth to organize our society. For agriculture and other seasonal interests we have the timing to the sun of our solar calendar: it describes what is called the Tropical Year. This timing is respected worldwide for the purpose of the civil calendar called the Gregorian Calendar. It was introduced in1582 as a reform to the Julian calendar of 45 B.C. that had run out of the seasons with 10 days. Next to that we also have timed our lives with sundials and waterclocks to the sun for thousands of years. This was abolished end of the eighteenth century when officially for pragmatical reasons mean (mechanical) time was introduced definitely estranging man from the ancient natural rhythm of cyclic time. But still the passage of the sun over the Greenwich meridian is the standard scientific reference of world-time (UTC) for modern timekeeping however twisted by modern time politics. (see articles)



In China, India and other eastern cultures one times one's month's and weeks to the moon in a lunisolar way: one respects the rhythm of the moon, but intercalates a month so now and then on that lunar calendar to keep track with the seasons: a leaped calendar. Because this can be done several ways the Romans for the West abolished this method with the Jullian reform seeing it leading to arbitrariness and corruption. The Islam for religious purposes manages a purely lunar calendar which is not leaped but is counting twelve lunar month's as a lunar (culturally conceived) year about 11 days shorter than the solar year. (see calendar-links)




Apart from our spinning moon which gives us lunar time and our spinning to the sun which gives us solar time, we also have timing to the stars.

Deep space by the Hubble Telescope

This timing is called sidereal time and is mainly used for purposes of astronomical observation and has little or no social relevance. This concept of time makes no real calendar, although it sets apart another sidereal zodiac from the seasonal one astrologers use. The siderical year describes days shorter with four minutes and a year one day longer because a sidereal day is defined as the time it takes to see the stars in the same position in the sky: 23 hr. and 56 minutes.




Galactic Time is the time that is described by our spin relative to the center of the galaxy.

The galaxy centre by the telescope from Cerro Tololo, Chile

Just like the moon spinning around the earth and the earth spinning around the sun, we all together, sun moon and earth and the other planets are spinning around the center of our galaxy, the Milky Way. stars in galaxy centre spinning animationThe animation to the left shows how in a time of six years the stars in the center of the Galaxy are spinning around the center. The center is situated in Sagittarius A, and is possibly a young black hole : a mass of two million times that of the Sun. A galactic day can thus be understood as one revolution around the sun of the earth relative to the center of the galaxy. It gives a slightly longer (about 1/71 day) 'galactic' year (in fact a galactic day thus) that runs through the seasons beginning when we are closest to the center of the galaxy (or at the greatest distance, there is no cultural precedent). This slightly longer year is due to the precession of the equinox causing the date of the galactic new Day to move upward through the calendar ( see also the Hutchinson Encyclopedia). A galactic year can be described as one revolution around the center of the galaxy which at a speed of about 250 km/sec. takes about 226 millions of years with a radius of about 26 thousand lightyears. The age of our solar system is about 20 of these revolutions. Thus we are 20 galactic years old departing from the supposition that our galaxy the Milky Way, is about 4.5 billion years old.



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