## Sun’s Velocity

### How fast is the Sun (and our Solar System) moving around the Milky Way?

1 – What do we need to know?  We need to know the total length of the Sun’s path as it orbits the center of the Milky Way Galaxy.  We also need to know the time that it takes to make one complete orbit.  Speed is stated as a distance over time.  Like “miles per hour” or “feet per second”.

2 – To calculate the Circumference of the Sun’s orbit we will use the formula for the Circumference of a circle:  C = 2piR

We know that pi equals 3.14 and we know what 2 equals, so let’s find out what R (Radius) equals.

The Radius of the Sun’s orbit is 28,000 Light Years.  For now we’ll use Light Years as the distance unit.

A Light Year is the distance that light (the fastest thing in the universe) travels  in one year.  This is just under 6 trillion (6,000,000,000,000) miles per year ) = (670,616,629 miles per hour).  A trillion is 1 million millions.  That’s a VERY large number, so we’ll keep it simple until the end.

The orbit of the Sun = C = 2piR = 2 x 3.14 x 28,000 Light Years = 175,000 Light Years.

It takes the Sun 250 million years to orbit the center of the Milky Way.

Since we usually think of speed (or velocity) in terms of “miles per hour” or “kilometers per hour”, we will need to find out how many hours there are in 250 million years.  This is going to be a big number too.

365.25 days x 24 hours / day = 8,766 hours in 1 year.

250,000,000 years x 8,766 hours / year = 2,192,000,000,000 = 2.2 trillion hours

We know the distance = 175,000 light years x 6 trillion miles / light year = 1 quintillion miles  (that’s a 1 with 18 zeroes behind it = a billion billions)

We know that it takes 2.2 trillion hours

If we divide the distance in miles by the time in hours we come up with the “miles per hour”.

1 quintillion miles / 2.2 trillion hours = 450,000 miles per hour.

To summarize our calculations:  The Sun along with all of the planets and moons in the Solar System are orbiting the center of the Milky Way at 450,000 miles per hour.