A fly in your car is going 5 mph. That is his speed from his perspective as the observer.
But your car is speeding down the road at 65 mph. So for the guy watching you from the roadside table, that fly is going 70 mph.
But the road you have taken is on the equator and the circumference of the earth at the equator is 24,901.55 miles and the earth rotates once every 24 hours. So that fly is now going 1,100 mph + 70 mph = 1,170 mph.
Moreover, the orbital length of earth traveling around the sun is 149,600,000 miles, traveled in 365.25 days. That is 67,000 miles per hour. So add that in, and the fly is going 68,170 mph.
The sun orbits the Milky Way galaxy at a speed of 486,000 miles per hour. Add that in, and the fly is now going 554,170 miles per hour.
All of this and we haven’t gotten to the accelerating expansion of the universe, i.e. space/time itself. Space/time doesn’t pre-exist – it is created as the universe expands.
A galaxy 1 million light years away would seem to be moving away from us at a rate of 60,000 miles per hour. For every 3.26 million light years further out that we look, the galaxies seem to be moving away from us at an additional 162,000 miles per hour. In sum, the universe is currently at least 156 billion light years wide.
And that is looking at motion from the fly’s perspective. If we go in the other direction as "observer" – the quantum – the cumulative velocities are even more mind-boggling
And if I squish it, ‘cause it’s messing with my driving, my arm is going 554,171+ mph
I hate flies in my car while I’m driving.
:>)