Infrequent flyer

A question sent in to New Scientist reads,
"My wife told me I should get out more. I replied that I am just about to celebrate my 66th free trip around the sun. Can anyone tell me how far I have traveled around the galaxy during that time?"
All of the information required to answer this question to a ballpark level of accuracy — along with a little elementary arithmetic — can be found in the Galaxy Song from Monty Python's comedy film The Meaning Of Life.
"We're thirty thousand light-years from galactic central point,
We go 'round every two hundred million years..."
So the circumference of the Earth's orbit is (roughly) pi times two times thirty thousand light years. That's approximately 188,495 light years. And we take 200 million years to complete an orbit, which means each year we cover 188,495/200,000,000 light years, which is 0.00094 light years.

So how far is a light-year?
"As fast as it can go, the speed of light, you know,
Twelve million miles a minute, and that's the fastest speed there is"
Twelve million is actually a bit high. C is precisely 299792458 meters per second¹, which is 186,282.4 miles per second, and that works out to 11,176,943 miles per minute. 186,282.4 miles times 86400 seconds per day times 365.24 days per year gives 5,878,464,425,192.5 miles to the light year. Each year we travel 0.00094 of those around the galaxy, which is 5,525,756,559.7 miles, or just over five and a half trillion miles. Multiply by 66 and you get 364,699,932,939 miles, give or take a few hundred yards.

So there's your galactic travel — call it 364.7 trillion miles over 66 years. I'm pretty certain that many frequent flyer miles upgrades you to a first-class seat.

#science #astronomy #MontyPython
¹ Yes, PRECISELY 299792458 meters per second. Because that's how we now define the meter: 1/299,792,458 of the distance traveled by light in a vacuum in free space in one second.
Flying in style, are we?
That's good wear for that mileage!
Isn't this ignoring the mileage accumulated as the earth revolves around the sun? Or maybe that's ignorable.
I may use this reasoning to not go for a run ;)
@Chris Johnson, the question wasn't what is the total distance we travelled (to which you also need to add 25,000 miles per day as the Earth rotates), but how far around the galaxy did we travel.
And if you add in how fast the galaxy cluster is moving, I assume you come agaist issues of a lack of reference frame. Especially since were receding away from some galaxies at more than the speed of light...(if I remember correctly)
Well ... sort of. Relativity gets funny that way.

You can pick a galaxy almost at our redshift horizon that's receding from us at a tiny fraction less than C. And you can pick another galaxy in the opposite direction that is also receding from us, in the opposite direction, at a tiny fraction less than C. But those two galaxies are still receding from each other at ... a tiny fraction less than C.

And to further complicate matters, the spacetime in between is expanding. And that is NOT limited to C, because C itself is relative to spacetime. Nothing in spacetime can move faster than C, or have a velocity greater than C relative to any other object, but spacetime itself can expand faster than C. So you could have two galaxies that have relativistic absolute velocities directly towards each other but will not only never reach each other, but will continue to get further and further apart, because the amount of spacetime between them is increasing faster than they can close the distance.

(Of course, they'd never be able to detect each other, so nobody would ever know.)
Exactly.. so we're actually moving further than we could possibly imagine...
And your frame of mind, @Phil Stracchino..
Well, that's crucial to everything. :)