Tuesday, January 22, 2013

Galactic year

All humanity uses the light signals our good Lord has set up in the heavenly firmament also for time keeping.
And God said, “Let there be lights in the vault of the sky to separate the day from the night, and let them serve as signs to mark sacred times, and days and years, and let them be lights in the vault of the sky to give light on the earth.” And it was so.
Genesis 1:14-15 NIV
Today we know that these great time signals work on the principle of rotation:
  • Day is one rotation of Earth's axis
  • Month is one round of Moon on its orbit around Earth
  • Year is one round of Earth on its orbit around Sun
This works fine in all human cultures and days follow nights and vice versa. In modern times humanity has learned to calculate these rotations very accurately.

The problem with Solar system based time units is that they create enormous figures in Cosmology and Astronomy. Our earthly distance measurements are not all that practical in Astronomy and also our earthly time measurements are not so helpful in trying to figure out Cosmic time scale.

Astronomers have adopted a a variety of distance measurements from astronomic units to light years and parsecs as alternative to our daily kilometers and miles. However, no alternative unit exists to replace in the same manner our tiny days, months and years.

We can say that according to modern estimates the Universe known is about 13.77 billion years old. But what does that enormous amount of zeros really tell us - who can imagine billion years?

Galactic year
Well, what if we apply galactic time to express cosmic time spans?

Let us be consistent and use rotation of celestial bodies as the basis: astronomers estimate that it takes Sun about 225 million years to complete one round around the center of the Milky Way.

Let us call this a galactic year (gy)- 225 million human years.

The estimated age of the Universe is about 137.700.000.000 solar years
Galactic year is about 225.000.000 solar years
137.000/225 = 60.9

The age of the known Universe is thus 60.9 gy (galactic years).

The Sun and solar system was created about 4.500 million years ago
4.500/225 = 20

The age of the Sun is thus 20 gy (galactic years). 

Neat, eh!

(well, someone already noticed that before me... see wikipedia)

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