Rotation of the Earth---settle this bet?

If you hover in a fixed spot of air and don't move, would the Earth move beneath or would you stay above the same spot of land?

Please avoid yes or no answers and listing sources and explanation will earn you 10 points.

Update:

Sorry I guess I wasn't very clear I can see how it would depend on what your are fixed relevant to.

Say you are inside the Earth's atmosphere and are in a helicopter and just hovering in place, not relative to the earth or not to the sun or anything just hovering in air. This may not even make sense to those of you who are a lot smarter than I am because I don't know a whole lot about physics but basically what we want to know is that if you're hovering inside the atmosphere would the earth mover beneath you or would you move with the rotation of the earth?

Relevance

in a fixed spot of 'air': then you'd stay over the same spot of land, except for any local wind moving you around like a fluff of cotton. In general, the air is entrained with Earth's rotation (otherwise, we'd have a thousand mile per hour wind at the equator).

If you stay on the same spot relative to Earth's centre and (let's say) a fixed star, then Earth would rotate under you at one turn per sidereal day (one turn in 23h56m).

Or -- different perception -- you'd have the impression of flying through the air at a speed of 1200 km/h (fast airplane) if you are at latitude of 45 degrees. (If you do this over the pole, you do not move relative to the Earth's surface).

If you do this at a fixed spot relative to Earth's surface and to the Sun, the rate is one turn per solar day (24 hours).

If you try to stay at a spot that is fixed relative to the Sun, around sunset, the Earth will rush away from you at 29.8 km/s (over 107,000 km/h or 67,000 mph). And yes, as the Earth gets smaller and smaller in the distance, you'd still see it rotate (one turn per day).

If you try to stay in a fixed spot relative to the thousands of neighboring stars, and if you pick the right time of year to do this, you see the solar system rush away from you at 19.4 km/s, plus the Earth orbiting the Sun at 29.8 km/s for a vectorial sum of close to 160,000 km/h or 100,000 mph (it is not a straight addition because the two movements are not in the same orientation).

If you pick the wrong time, the sun will come (almost) straight at you at 19.4 km/s (43,000 mph).

If you try to stay at a fixed position relative to the Galactic centre, then the Sun (and all the neighboring stars) would rush away from you at an average speed of 230 km/s (828,000 km/h = almost 520,000 mph).

If you tried to stay in a fixed position relative to the Cosmological Microwave Background radiation (which could be the only 'fixed' reference in the visible portion of our universe), the Galaxy would rush away from you at 400 km/s (1,440,000 km/h = 900,000 mph) -- of course, if you do it at the wrong time in the 200 million year orbit of the Sun, the galaxy would rush towards you instead).

Adding all these velocities together (and it would be a vectorial addition, since they are not lined up) would mean that if you pick just the right time to do this, you might see Earth moving at a combined speed of over 600 km/s (1.35 million miles per hour).

Be careful. Wear a helmet.

• Brant
Lv 7

The problem with this question as with many which involve such bets, is that it depends on an ill-defined term. In this case, "fixed spot." How you define that determines the answer to the question.

The rotation of the earth causes objects to keep their momentum in the same direction the earth is spinning. When a plane takes off headed west from say, Washington, DC, at 300 miles an hour, this is in relation to the ground and the air that moves with it. But it is really going *backwards* at about 400 miles an hour with relation to the earth as a whole. The earth is rotating eastward at 700 miles an hour.

Everything that goes up, has the rotational speed of the earth added to it, in an eastward direction. A balloon launched from the equator may appear to rise straight up, but it is really moving eastward around the planet at about 1000 miles an hour. So is the air. So is the ground.

The answer is that you would stay above the same spot of ground unless you accelerated westward. If you reached the speed that the earth is turning, you would stay at the same spot with respect to the sun, (or stars), not the earth. Your forward momentum, which we can't sense, is the key issue here.

Edit: Like I said with the balloon. Same goes for a helicopter. It was on a moving object when it took off: the surface of the earth. So it is propelled forward at several hundred miles an hour, along with the air and the surface of the earth. It would remain in that spot indefinitely unless it accelerated in one direction or another. It would never have to accelerate in order to keep up with the earth. That will be its natural path and speed.

• Anonymous

It depends of the nature of the magic spell used to hover.

The short answer is no. You're moving at a certain speed with the surface of Earth. When you jump, the Earth moves and your momentum is going to move you in the same direction. The atmosphere is moving too at the same speed (kinda...) so there's no much drag slowing you down. If you jump high enough, you're going to land away from your starting point. But the number of factors is high and you'll have to consider them all before making a judgement.

If you hover in the air, whatever it means, you're going to move with the air. The atmosphere is not fixed to the surface of Earth. It moves with it mostly, otherwise we'd be under a constant tornado, but it also moves in other speeds and directions. If you're fixed to a point "in the air" you're going to move with it.

If you can hover in a fixed spot, and I mean a fixed spot in the universe, the instant you get fixed, the Earth is going to move away from you at very very very high speed. Hopefully... it can also run you over. The hover thing, as you can see, it's relative.

No lets keep it simple and answer your question. Given you are hovering above the ground. You mention the earth moves beneath you so your statement implies you are stationary and not affected by gravity or air currents. Yes the earth rotates under you and you should come back to the same spot.

Well you would have to define a fixed spot relative to what celestial body.

If it was a fixed spot relative to the earth then the answer is no since you and the earth will have the same rotational period. If it was fixed to some other spot the yes the earth would have a different rotational period than you and would move beneath you.

When you say fixed spot of air, I interpret that you would be hovering right above the earth's surface. In that case your movement relative to the earth would not change because you are moving with the earth's rotation because of the gravitational pull of the earth.

• RickB
Lv 7

Well, define what you mean by "a fixed spot."

If you mean, "fixed relative to the earth's surface," then (by definition) you stay above the same spot of land.

If you mean, "fixed relative to the earth's center," then (by definition) the earth moves beneath you.

Either one of these conditions can be achieved in principle, depending on how you go about "fixing" your position.

Let's say you do it by means of magnetic levitation. In that case, before you turn on the levitator, you are certainly zipping along at 800 mph (or so) eastward as the earth's rotation carries you. When you turn on the levitator, you MAINTAIN that eastward momentum while the levitator lifts you. This is according to Newton's laws of motion. Because of your initial eastward momentum, you will stay over the same spot of land.

The same is true of any case in which you lift yourself up from the ground. You maintain your eastward momentum.

Source(s): I have a degree in physics.
• Anonymous
5 years ago

R MOORE is correct. Another consideration is that the sun doesn't rotate as a unit; the equator rotates much faster than do areas away from the equator. That's why the sun's surface is so stormy; magnetic field lines get wrapped and tangled and then break.

• Anonymous