The Earth - Does it spin? (probably not)

I present this not as an intrinsic proof or disproof of any particular theory, as I don't doubt the ability of globularists to come up with a legitimate seeming explanation in this particular instance - I present this as an honest question out of interest regarding what answer will come up.

Given, as you heliocentrists claim, the rapidly spinning motion of the Earth, why is it that when I jump in the air the Earth does not noticably move in the spin direction beneath my feet?

I anticipate that a potential answer is that the surrounding atmolayer is under the influence of Earth's gravity, and since it consequently also spins it pushes me with it. I pre-emptively assert that this cannot be the case given the relative density of my body to the surrounding atmolayer - why does the atmolayer not move around me with the motion of the Earth, still allowing the Earth to spin away beneath my temporarily suspended feet?

The absence of this phenomenon seems to suggest that the Earth lacks axial motion. As I said, I don't treat this as a watertight proof of anything in particular, I'm just interested to hear whatever explanations might arise from the globularist contingent of this website.

Fire away.

When you jump, you are only altering the radial component of your velocity, as you are pushing outward from the Earth.  Because your body resists a change in rotational inertia, even in the air you continue to spin with the same angular velocity as the Earth.  The atmosphere has nothing to do with it.

When you jump, you are only altering the radial component of your velocity, as you are pushing outward from the Earth.  Because your body resists a change in rotational inertia, even in the air you continue to spin with the same angular velocity as the Earth.  The atmosphere has nothing to do with it.

I see. This seems a little counterintuitive though - would the same apply to a rocket (assume Round Earth model)? What I mean is, (and I'm not trying to suggest for a moment that space travel actually happens here) why, according to globularists, don't rockets continue to spin in a similar way?

Quote from: cwolfe on December 23, 2007, 03:52:44 PM

When you jump, you are only altering the radial component of your velocity, as you are pushing outward from the Earth.  Because your body resists a change in rotational inertia, even in the air you continue to spin with the same angular velocity as the Earth.  The atmosphere has nothing to do with it.

I see. This seems a little counterintuitive though - would the same apply to a rocket (assume Round Earth model)? What I mean is, (and I'm not trying to suggest for a moment that space travel actually happens here) why, according to globularists, don't rockets continue to spin in a similar way?

They do.  In fact, rocket launches are typically done near the Equator, where the tangential velocity at the Earth's surface is greatest, and this motion is used as a boost.  This is why rocket launches are done toward the East, in the direction of Earth's rotation.

They do.  In fact, rocket launches are typically done near the Equator, where the tangential velocity at the Earth's surface is greatest, and this motion is used as a boost.  This is why rocket launches are done toward the East, in the direction of Earth's rotation.

So if a rocket were launched straight up (assuming for the sake of this argument that space travel is actually possible), its base would remain lined up with the part of the Earth it was launched from, even once it left the spherical atmolayer?

Quote from: cwolfe on December 23, 2007, 04:11:56 PM

They do.  In fact, rocket launches are typically done near the Equator, where the tangential velocity at the Earth's surface is greatest, and this motion is used as a boost.  This is why rocket launches are done toward the East, in the direction of Earth's rotation.

So if a rocket were launched straight up (assuming for the sake of this argument that space travel is actually possible), its base would remain lined up with the part of the Earth it was launched from, even once it left the spherical atmolayer?

Certainly, if it could only move in one direction (straight up).  They HAVE directional controls.

No.  As soon as it leaves the place it launched from, it needs to increase its horizontal (?) speed to maintain the placement above its area of launch as it is moving further away from the center of the spin.  Kind of the same idea as the Earth spinning faster at the Equator than in other areas.

-hopes that's understandable-

No.  As soon as it leaves the place it launched from, it needs to increase its horizontal (?) speed to maintain the placement above its area of launch as it is moving further away from the center of the spin.  Kind of the same idea as the Earth spinning faster at the Equator than in other areas.

-hopes that's understandable-

Sort of. But how come when I jump in the air I don't have to increase my horizontal speed to maintain the placement above the area of my launch?

The further the rocket is from the Earth, the less of a hold gravity has on the rocket (remember that gravity follows an inverse-square law).  In addition to this, gravity, in the grand scheme of the universe, is a pathetically weak force.  It pales in comparison to the other forces of nature (the electromagnetic force, and the strong/weak nuclear forces)

I would guess that, even without taking into consideration that you would in fact move with the earth while floating in the air, even if that wasn't the case.. you are already moving with the earth when on the ground. And as we know from newton's law, an object in motion tends to stay in motion. The only friction affecting your position while jumping is the air, and the air is not nearly enough friction to noticeably slow you down in the time of a jump. So that alone would keep the earth from passing under you. For example, if you're riding in a car, traveling at 55 mph, you can throw a baseball up and down from your hand into the air, and it is also moving at 55 mph in the air. Why doesn't the baseball slam against the glass in the back of the car? Because it's moving with the car when you throw it, so it continues to move with the car while in the air.

Like you said, an object in motion tends to stay in motion.  That includes rotational motion.  When you are standing on the Earth, you are actually rotating around an axis that runs through the north and south poles.  When you jump, you will continue to rotate because your body will resist a change in rotational inertia.

I must actually amend a statement I made earlier:

So if a rocket were launched straight up (assuming for the sake of this argument that space travel is actually possible), its base would remain lined up with the part of the Earth it was launched from, even once it left the spherical atmolayer?

The answer to this question is actually "no" because as the rocket moves away from the Earth, its moment of inertia increases with the square of its distance from the Earth's axis.  Now, rotational kinetic energy depends not only on the moment of inertia, but also on the angular velocity.  Since the rotational kinetic energy will tend to remain constant, the angular velocity will slow down in response to the moment of inertia increasing.  So as the rocket moves further and further from the Earth, it will move around the Earth's axis slower and slower.

once a rocket is in a nice stable orbit it shouldn't need to touch any thrusters to get it above the same place once it's velocity is a little bit quicker than the earths spin to make up for it being further away

To give you an idea of why the Earth does not seem to move under you, think about sitting in a train that is moving at a constant speed. Now imagine that you throw a ball vertically up in the air as you sit in your seat. Will you find that the train noticeably moves in its direction under the ball? No. The ball will fall vertically down into your hand again. The reason is that the ball already has a certain horizontal velocity due to the motion of the train, and since no force acts on it to change its horizontal velocity, it will keep the horizontal velocity it already has. Thus, the train will not move along under it or anything like that.

I present this not as an intrinsic proof or disproof of any particular theory, as I don't doubt the ability of globularists to come up with a legitimate seeming explanation in this particular instance - I present this as an honest question out of interest regarding what answer will come up.

Given, as you heliocentrists claim, the rapidly spinning motion of the Earth, why is it that when I jump in the air the Earth does not noticably move in the spin direction beneath my feet?

I anticipate that a potential answer is that the surrounding atmolayer is under the influence of Earth's gravity, and since it consequently also spins it pushes me with it. I pre-emptively assert that this cannot be the case given the relative density of my body to the surrounding atmolayer - why does the atmolayer not move around me with the motion of the Earth, still allowing the Earth to spin away beneath my temporarily suspended feet?

The absence of this phenomenon seems to suggest that the Earth lacks axial motion. As I said, I don't treat this as a watertight proof of anything in particular, I'm just interested to hear whatever explanations might arise from the globularist contingent of this website.

Fire away.

To give you an idea of why the Earth does not seem to move under you, think about sitting in a train that is moving at a constant speed. Now imagine that you throw a ball vertically up in the air as you sit in your seat. Will you find that the train noticeably moves in its direction under the ball? No. The ball will fall vertically down into your hand again. The reason is that the ball already has a certain horizontal velocity due to the motion of the train, and since no force acts on it to change its horizontal velocity, it will keep the horizontal velocity it already has. Thus, the train will not move along under it or anything like that.

Well, actually, the situation is kind of different as we're talking about an acceleration (I think) that varies with altitude, and the jump changes your altitude.  Luckily, not by very much or for very long. 

Quote from: Richard Kilgore on December 23, 2007, 05:08:09 PM

To give you an idea of why the Earth does not seem to move under you, think about sitting in a train that is moving at a constant speed. Now imagine that you throw a ball vertically up in the air as you sit in your seat. Will you find that the train noticeably moves in its direction under the ball? No. The ball will fall vertically down into your hand again. The reason is that the ball already has a certain horizontal velocity due to the motion of the train, and since no force acts on it to change its horizontal velocity, it will keep the horizontal velocity it already has. Thus, the train will not move along under it or anything like that.

Well, actually, the situation is kind of different as we're talking about an acceleration (I think) that varies with altitude, and the jump changes your altitude.  Luckily, not by very much or for very long. 

How was the ball elevated in the first place?  It was accelerated.  The situation is no different.

To be honest, DogPlatter, and I'm not trying to be rude, your original post in this thread is evidence to me that you have never formally studied physics.

Quote from: Mr. Ireland on December 23, 2007, 05:15:42 PM

Quote from: Richard Kilgore on December 23, 2007, 05:08:09 PM

To give you an idea of why the Earth does not seem to move under you, think about sitting in a train that is moving at a constant speed. Now imagine that you throw a ball vertically up in the air as you sit in your seat. Will you find that the train noticeably moves in its direction under the ball? No. The ball will fall vertically down into your hand again. The reason is that the ball already has a certain horizontal velocity due to the motion of the train, and since no force acts on it to change its horizontal velocity, it will keep the horizontal velocity it already has. Thus, the train will not move along under it or anything like that.

Well, actually, the situation is kind of different as we're talking about an acceleration (I think) that varies with altitude, and the jump changes your altitude.  Luckily, not by very much or for very long. 

How was the ball elevated in the first place?  It was accelerated.  The situation is no different.

It is different.  The train isn't changing its horizontal velocity when you throw the ball up, so the ball simply stays (horizontally) in place (as it seems to you) when you throw it (as it already has the horizontal velocity of the train with it); whereas with the Earth, when you jump, you have the speed from the rotation of the Earth, but that speed isn't sufficient to keep you (horizontally) in place in relation to the place you jumped from (if you could jump high or long enough you could see it) as your altitude affects the amount of speed you need to maintain your horizontal location in relation to a place on Earth (whereas with the ball it doesn't).  This is assuming your train is simply an imaginary example that leaves out the effects of the Earth, of course.

I hate the way I used 'horizontally' in that.

Quote from: cwolfe on December 23, 2007, 05:17:06 PM

Quote from: Mr. Ireland on December 23, 2007, 05:15:42 PM

Quote from: Richard Kilgore on December 23, 2007, 05:08:09 PM

To give you an idea of why the Earth does not seem to move under you, think about sitting in a train that is moving at a constant speed. Now imagine that you throw a ball vertically up in the air as you sit in your seat. Will you find that the train noticeably moves in its direction under the ball? No. The ball will fall vertically down into your hand again. The reason is that the ball already has a certain horizontal velocity due to the motion of the train, and since no force acts on it to change its horizontal velocity, it will keep the horizontal velocity it already has. Thus, the train will not move along under it or anything like that.

Well, actually, the situation is kind of different as we're talking about an acceleration (I think) that varies with altitude, and the jump changes your altitude.  Luckily, not by very much or for very long. 

How was the ball elevated in the first place?  It was accelerated.  The situation is no different.

It is different.  The train isn't changing its horizontal velocity when you throw the ball up, so the ball simply stays (horizontally) in place (as it seems to you) when you throw it (as it already has the horizontal velocity of the train with it); whereas with the Earth, when you jump, you have the speed from the rotation of the Earth, but that speed isn't sufficient to keep you (horizontally) in place in relation to the place you jumped from (if you could jump high or long enough you could see it) as your altitude affects the amount of speed you need to maintain your horizontal location in relation to a place on Earth (whereas with the ball it doesn't).  This is assuming your train is simply an imaginary example that leaves out the effects of the Earth, of course.

I hate the way I used 'horizontally' in that.

Actually, the two situations are analogous.  In the case of the train, it is uniform linear motion.  In the case of the Earth, it is uniform rotation.

Actually, the two situations are analogous.  In the case of the train, it is uniform linear motion.  In the case of the Earth, it is uniform rotation.

But you, as the person jumping, don't keep that rotation aspect when you jump.

Quote from: cwolfe on December 23, 2007, 05:47:50 PM

Actually, the two situations are analogous.  In the case of the train, it is uniform linear motion.  In the case of the Earth, it is uniform rotation.

But you, as the person jumping, don't keep that rotation aspect when you jump.

Sure you do, you're only changing the radial component of your velocity by pushing outward.  In addition, unless you were able to attain escape velocity, you're still in a bound state with respect to the Earth.

To be honest, DogPlatter, and I'm not trying to be rude, your original post in this thread is evidence to me that you have never formally studied physics.

I did get a physics GCSE, but you're right, beyond that my knowledge of physics is autodidactic. To be honest though, assuming the Conspiracy exists, study of "physics" in the sense you mean it can have little value (though study through empiricism is a different kettle of fish entirely).

Sure you do, you're only changing the radial component of your velocity by pushing outward.  In addition, unless you were able to attain escape velocity, you're still in a bound state with respect to the Earth.

Velocity?  Your direction is always changing when you go round and round with the Earth.

Quote from: cwolfe on December 23, 2007, 05:32:26 PM

To be honest, DogPlatter, and I'm not trying to be rude, your original post in this thread is evidence to me that you have never formally studied physics.

I did get a physics GCSE, but you're right, beyond that my knowledge of physics is autodidactic. To be honest though, assuming the Conspiracy exists, study of "physics" in the sense you mean it can have little value (though study through empiricism is a different kettle of fish entirely).

But all credible sub-fields of modern physics (String Theory and other unifying theories aside) are based on empirical evidence.  A science based on speculation alone is not a science at all.

Quote from: cwolfe on December 23, 2007, 06:04:53 PM

Sure you do, you're only changing the radial component of your velocity by pushing outward.  In addition, unless you were able to attain escape velocity, you're still in a bound state with respect to the Earth.

Velocity?  Your direction is always changing when you go round and round with the Earth.

The direction is changing, but the magnitude is not.  Thus your kinetic energy remains the same.

edit:  And I'm not sure why you're arguing me... we have the same answer to DP's question about rockets.  If you look back you'll notice that I've amended my answer to his question.

The direction is changing, but the magnitude is not.  Thus your kinetic energy remains the same.

So we agree it's not velocity.  What's even the point in arguing, anyway?  Do we both agree the ground does move (albeit by a very, very small amount) when you jump?  Or is this how it started?

Well, no, I argue that it doesn't move at all under you, for the same reason that a ball thrown upward isn't deflected above you:  The Earth is moving you with it, and when you jump, you're only changing the outward radial component of your velocity.  Because the acceleration due to gravity is radially inward, it only affects the radial component of your velocity, and thus the horizontal component is unaffected.


Though, I suppose if you were to jump really really really really high, your moment of inertia would change enough that the Earth might movie underneath you a very small amount, now that I think about it.


So I suppose we're both sort of right.  It's funny, I spend all day at school studying complicated atomic/molecular physics, and I have to actually think about it to answer questions about simple kinematics.  It's amazing how quickly you forget that stuff.

Well, no, I argue that it doesn't move at all under you, for the same reason that a ball thrown upward isn't deflected above you:  The Earth is moving you with it, and when you jump, you're only changing the outward radial component of your velocity.  Because the acceleration due to gravity is radially inward, it only affects the radial component of your velocity, and thus the horizontal component is unaffected.

But when you jump, you're taking a longer route around the Earth than the surface of the Earth where you jumped from is.  So, although you're moving at the same speed, it would take you longer to get around the earth if you were in one constant jump than the place you jumped from, and therefore when you land you'll be in a different place.

Quote from: cwolfe on December 23, 2007, 06:29:39 PM

Well, no, I argue that it doesn't move at all under you, for the same reason that a ball thrown upward isn't deflected above you:  The Earth is moving you with it, and when you jump, you're only changing the outward radial component of your velocity.  Because the acceleration due to gravity is radially inward, it only affects the radial component of your velocity, and thus the horizontal component is unaffected.

But when you jump, you're taking a longer route around the Earth than the surface of the Earth where you jumped from is.  So, although you're moving at the same speed, it would take you longer to get around the earth if you were in one constant jump than the place you jumped from, and therefore when you land you'll be in a different place.

If I jump 6ft in the air that is really nothing compared to the size of the earth. that is why I do not notice any displacement. Also the time it takes to rise and fall is very short so the air resistance will be very small when you take newtons equations into account

Well, no, I argue that it doesn't move at all under you, for the same reason that a ball thrown upward isn't deflected above you:  The Earth is moving you with it, and when you jump, you're only changing the outward radial component of your velocity.  Because the acceleration due to gravity is radially inward, it only affects the radial component of your velocity, and thus the horizontal component is unaffected.

Did you forget that rotating bodies exhibit centripetal acceleration?

If I jump 6ft in the air that is really nothing compared to the size of the earth. that is why I do not notice any displacement. Also the time it takes to rise and fall is very short so the air resistance will be very small when you take newtons equations into account

I'm aware.  Scroll up.