Returning from an evening in the city the other night we were tooling east along the New York State Thruway when my co-pilot asked if I realized how fast I was going. I guess it was the scolding tone that got to me. Since she was sitting right beside me I stated that I was traveling the same speed as she was. Didn't win any points for that one. A lengthy period of silence ensued. After all I was only driving a tad over 65. Well, maybe more like a hair under 70, but I think my speedometer is off by a few miles per hour.
During the following quiet period I conducted a thought experiment about how fast we were actually traveling. Let's see, driving east at 68 mph we get a boost from the Earth's rotational speed. At our latitude of 42 deg. (Albany) the longitudinal degrees are just over 51 miles apart. With the Earth rotating at 15 degrees per hour I'm getting a 766 mph tail wind. No wonder NASA always launches orbiters to the East. Now my actual speed is 834 mph. Whee! Wait there's more.
The Earth is orbiting the Sun at once per year. That seems slow, but consider the distance it covers. With a mean radius of 93 million miles times 2 times pi we get a path of around 584,337,600 miles. This all comes out to 66625 mph. Since it's approaching midnight we can add that to our forward velocity. Now we're doing 67,459 mph. That'll blow your hair back. But wait...
We're approaching the Winter solstice when I believe the Earth lies on the opposite side of the Sun as the galactic center. This means we're traveling in roughly the same direction as the Sun's orbit around the Milky Way's core. Ok, so now we add another 491,040 mph. (1) Now my husky six banger SUV is tooling along at 558,499 mph. I know the critics will say that the plane of the solar system is tilted with respect to the galactic disk so I should be calculating vectors instead. Come on, we're having some fun here. NASCAR eat my dust.
Oh oh, I almost forgot. The whole Milky Way is also moving through space. Some say it's being sucked toward "The Great Attractor" at a respectable 1,339,200 mph. I have no idea what that direction is from our perspective. Just for grins let's pretend for a minute it's just over the eastern horizon giving a final kick in the pants. Now we're red-lining at around 1,830,240 mph.
"Sorry officer I didn't realize I was over the speed limit." (chalk it up to a rounding error)
(1) Another source - Astronomy Magazine Sept. 2011 page 31 puts the orbital speed at 537,000 mph. Stay tuned for further updates.
Monday, October 12, 2009
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