I am sitting in my living room seemingly stationary. But I know I’m really moving, very very fast and in some direction or other. What direction and how fast?
Considering that the Earth rotates at a known speed. It revolves around the sun at a known speed. The solar system is circling around the Milky Way galaxy at a known speed. And the universe is expanding at a known speed. Each of the directions for all these are also known.
So is it possible to determine how fast I am really traveling and in what direction? Or does figuring out all the variables just too complicated?
So first of all, according to a Wikipedia summary of Einstein’s work,
That said, our galaxy is moving towards the Great Attractor at about 630km/s, if you average out the relative speeds of other local objects so that “Hubble Flow” (expansion of the universe) dominates. If you choose the cosmic microwave background – presumably the place that the Big Bang was? – then the Milky Way velocity is 552 ± 6 km/s.
Our sun and solar system are all revolving around the center of the Milky Way at about 254km/s. If you’ve seen the Milky Way on a starry night you have seen its tilt in the sky – the angle is about 60 degrees, and so the most that our solar system’s velocity can change the larger velocity is by 86% of the solar system’s velocity (.866 = sin 60 degrees). That’s about 220 km/s.
Earth’s orbital speed is about 30km/s and is small potatoes comparatively. The earth’s rotation adds not quite 0.5 km/s on top of that. You can increase the velocity slightly by going to either a higher altitude or equatorial latitude, which is why rockets launched into orbit are often launched from low latitudes or high altitudes – they get a boost from the earth’s rotation.
If everything lines up perfectly – you stand at the equator on top of the highest equatorial mountain, on the day when the earth’s velocity lines up with the sun’s velocity, and both are at the point where the solar system’s velocity makes its maximum contribution, then your speed relative to cosmic background radiation will be roughly 800 km/s.
Lord Ronald said nothing; he flung himself from the room, flung himself upon his horse and rode madly off in all directions.[indent]Stephen Leacock, “Gertrude the Governess”, Nonsense Novels (1911)[/indent]
No, in an absolute sense it is not possible, and that is not because it is complicated, it is because motion can only be meaningfully specified relative to some reference frame.
If you say “How fast am I going, and in what direction?” the only helpful reply I can make is “Relative to what?”
Relative to the Earth, for instance, you are not moving.
In one second, you travel:
1500 feet to the east (Earth’s rotation)
18 miles around the Sun (Earth’s orbit)
125 miles around the center of the galaxy (our solar system’s orbit)
That’s as far as I can go with it, don’t remember where I read it.
