Counteracting the inertia of Earth's rotation

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The discussion centers on the concept of counteracting Earth's rotation using a drone at the equator. It explores whether a drone could hover in place after flying against the Earth's spin, with participants debating the effects of the atmosphere on the drone's motion. Key points include that the atmosphere rotates with the Earth, meaning the drone would need to maintain a specific speed to remain stationary relative to the stars or the Sun. Additionally, local wind conditions could affect the drone's ability to hover without being influenced by the Earth's rotation. Ultimately, the conversation highlights the complexities of motion relative to Earth's rotational dynamics.
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Hi guys , I'm a layman looking for an expert answer on the following hypothetical situation.
I am at the equator with a drone capable of 1000mph speeds and the ability to hover. If the sun (or another fixed point in space) was directly overhead and I waited for the earth to rotate 1000 miles then launched the drone and flew 1000mph against the earths spin till the sun was directly overhead again then hovered at that point, the earth should then be spinning under the drone right?
Much the same as if I were standing on a conveyor belt I would move with it , but if I ran against it at the same speed I would be running on the spot while the belt moves under me.
 
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Welcome to PF.

All things are relative. You must move with the surface of the Earth, or it will slap you with a mountain, or drown you.
What are you trying to solve?
What precisely is your question?
 
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Baluncore said:
Welcome to PF.

All things are relative. You must move with the surface of the Earth, or it will slap you with a mountain, or drown you.
What are you trying to solve?
What precisely is your question?
Will the earth spin under the hovering drone in the above scenario? Considering in the scenario the hovering point is a point n space and not on earth.
 
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Vic43 said:
Considering in the scenario the hovering point is a point n space and not on earth.
The drone is hovering in the atmosphere, and that is part of the surface of the Earth, in the same way that the oceans are part of the surface of the Earth. Do fish swim in space, or in the surface of the Earth?
 
Baluncore said:
The drone is hovering in the atmosphere, and that is part of the surface of the Earth, in the same way that the oceans are part of the surface of the Earth. Do fish swim in space, or in the surface of the Earth?
That isn't a good analogy. The atmosphere isn't part of the earths surface.
 
Vic43 said:
That isn't a good analogy. The atmosphere isn't part of the earths surface.
Think about a long conveyer belt , there is a mid point marker. Sit the drone on the conveyor belt at the marker , start the conveyor belt, let the drone move on the belt for a distance so it's moving at the same speed as the belt, then take off , fly it back to the marker and hover , the belt will move under the drone while it hovers at the marker. You've countered the inertia that was imparted onto the drone from the belt.
 
Vic43 said:
The atmosphere isn't part of the earths surface.
Many birds fly in the atmosphere, and nest in the same tree every night.
 
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Baluncore said:
Many birds fly in the atmosphere, and nest in the same tree every night.
Are you trolling ?
 
Baluncore said:
Many birds fly in the atmosphere, and nest in the same tree every night.
Think about a long conveyer belt , there is a mid point marker. Sit the drone on the conveyor belt at the marker , start the conveyor belt, let the drone move on the belt for a distance so it's moving at the same speed as the belt, then take off , fly it back to the marker and hover , the belt will move under the drone while it hovers at the marker. You've countered the inertia that was imparted onto the drone from the belt.
 
  • #10
Vic43 said:
If the sun (or another fixed point in space) was directly overhead and I waited for the earth to rotate 1000 miles then launched the drone and flew 1000mph against the earths spin till the sun was directly overhead again then hovered at that point, the earth should then be spinning under the drone right?
Yes, essentially. If you're wanting to cancel out Earth's rotation precisely you'd need to use the background stars as your reference target, or some ultra-precise gyroscope or something, as using the Sun will introduce a small error since we are moving around the Sun at the same time that we are rotating and have to rotate a bit more than 360 degrees to get the Sun back in the same spot in the sky a day later.
 
  • #11
Vic43 said:
Think about a long conveyer belt , there is a mid point marker. Sit the drone on the conveyor belt at the marker , start the conveyor belt, let the drone move on the belt for a distance so it's moving at the same speed as the belt, then take off , fly it back to the marker and hover , the belt will move under the drone while it hovers at the marker. You've countered the inertia that was imparted onto the drone from the belt.
If you want to avoid spinning with the Earth's surface and atmosphere, you'll have to fly with a ground speed of about ##1600 \ km/h## west (at the equator).
 
  • #12
Vic43 said:
That isn't a good analogy. The atmosphere isn't part of the earths surface.
If you ignore the atmosphere (e.g. it's an airless planet and the drone uses rockets for propulsion), then you can hover the drone in one spot w/r to the background stars (or the Sun) after decelerating from the initial velocity imparted by the rotational motion of the planet while the planet itself rotates under it.
The point Baluncore was making is that if you don't ignore the atmosphere, then the drone needs to keep moving to stay in one spot, as the atmosphere is dragged by the surface. I.e. the medium used for propulsion by the drone moves at ~1000mph w/r to the background stars and if the drone stops flying against it, it'll be dragged with it to match the surface rotation too.
 
  • #13
PeroK said:
If you want to avoid spinning with the Earth's surface and atmosphere, you'll have to fly with a ground speed of about ##1600 \ km/h## west (at

Bandersnatch said:
If you ignore the atmosphere (e.g. it's an airless planet and the drone uses rockets for propulsion), then you can hover the drone in one spot w/r to the background stars (or the Sun) after decelerating from the initial velocity imparted by the rotational motion of the planet while the planet itself rotates under it.
The point Baluncore was making is that if you don't ignore the atmosphere, then the drone needs to keep moving to stay in one spot, as the atmosphere is dragged by the surface. I.e. the medium used for propulsion by the drone moves at ~1000mph w/r to the background stars and if the drone stops flying against it, it'll be dragged with it to match the surface rotation too.
Thanks, I am sceptical about your last sentence though. There may be zero wind at the point you are hovering right? What will cause the drag on the drone if not the air itself in the form of wind? Actually the wind could be going the opposite direction.
 
  • #14
Vic43 said:
Thanks, I am sceptical about your last sentence though. There may be zero wind at the point you are hovering right?
No. The drone would need to fly at supersonic speed. Otherwise, you could fly in a helicopter from London to New York in 3 hours simply by hovering. You can only get from London to New York by flying at ##1000 \ km/h## through the atmosphere for about 5 hours. You can't do it by hovering in the atmosphere.
 
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  • #15
PeroK said:
No. The drone would need to fly at supersonic speed. Otherwise, you could fly in a helicopter from London to New York in 3 hours simply by hovering. You can only get from London to New York by flying at ##1000 \ km/h## through the atmosphere for about 5 hours. You can't do it by hovering in the atmosphere.
Sorry was replying to a different comment by bandersnatch
 
  • #16
I find this super interesting , I wonder if any experiments have been done?
 
  • #17
Vic43 said:
I find this super interesting , I wonder if any experiments have been done?
You mean like a worldwide commercial airline network?
 
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  • #18
Vic43 said:
Thanks, I am sceptical about your last sentence though. There may be zero wind at the point you are hovering right? What will cause the drag on the drone if not the air itself in the form of wind? Actually the wind could be going the opposite direction.
The air is rotating with the planet. Wind is motion of the air w/r to the observer (here, the drone). Since you've chosen the spot for hovering to be somewhere around the equator, as that's where the rotation velocity at the surface is approx. 1000mph, it would mean the still air is moving at that velocity w/r to the drone and the still air is perceived as 1000mph wind. Now, you could have some non-still air where the drone hovers, i.e. some local winds, that would change the perceived wind speed in either direction. But since there are no 1000mph winds even in the strongest hurricanes, you could never expect to nullify all that wind coming from the rotation of the atmosphere.
Of course you could have instead chosen a spot somewhere near the poles, where the rotation can be as leisurely as you want, including no rotation at all (at the poles). One can easily imagine some local wind patterns at least momentarily exactly matching the rotational velocity of the atmosphere so that your drone can hover in a spot.
 
  • #19
Vic43 said:
Thanks, I am sceptical about your last sentence though. There may be zero wind at the point you are hovering right? What will cause the drag on the drone if not the air itself in the form of wind? Actually the wind could be going the opposite direction.
Do the experiment with just a balloon; a hovering drone adds pointless complication. It's a windless day. The air and the ground and the balloon (only just managing to float) are all stationary relative to each other. You let the ball gently float upwards.
IS there any force on the balloon that would make it move east / west or will it just hang there?
You try the same experiment on the roof of a train. What happens to the balloon and why?
 
  • #20
PeroK said:
You mean like a worldwide commercial airline network?
No because they can't hover , but yeah I guess they should be gaining speed relative to the ground (or the ground should be moving opposite to the plane) if they flew long enough in a straight line along the equator. Maybe they have to accelerate less after a certain distance to maintain the same speed relative to the ground.
 
  • #21
sophiecentaur said:
Do the experiment with just a balloon; a hovering drone adds pointless complication. It's a windless day. The air and the ground and the balloon (only just managing to float) are all stationary relative to each other. You let the ball gently float upwards.
IS there any force on the balloon that would make it move east / west or will it just hang there?
You try the same experiment on the roof of a train. What happens to the balloon and why?
I get what you are trying to say, but I disagree. The drone doesn't complicate it, and is a better tool as it has propulsion. The balloon will be moved by the wind in the Train example , if you let the balloon go when you are stationary the wind could be going any direction at the time and I don't think any force will be imposed on it if there is absolutely zero wind in the area. Similarly with the drone example , once it flew far enough against earths spin to counter the inertia the place where it hovered could have any wind direction at the time, just because it was flying against the direction of the spin doesn't mean it somehow affects the local wind at the destination of hover.
 
  • #22
Bandersnatch said:
The air is rotating with the planet. Wind is motion of the air w/r to the observer (here, the drone). Since you've chosen the spot for hovering to be somewhere around the equator, as that's where the rotation velocity at the surface is approx. 1000mph, it would mean the still air is moving at that velocity w/r to the drone and the still air is perceived as 1000mph wind. Now, you could have some non-still air where the drone hovers, i.e. some local winds, that would change the perceived wind speed in either direction. But since there are no 1000mph winds even in the strongest hurricanes, you could never expect to nullify all that wind coming from the rotation of the atmosphere.
Of course you could have instead chosen a spot somewhere near the poles, where the rotation can be as leisurely as you want, including no rotation at all (at the poles). One can easily imagine some local wind patterns at least momentarily exactly matching the rotational velocity of the atmosphere so that your drone can hover in a
Hmm I'm not sure I get the concept of the entire atmosphere moving at the same speed and direction with earths rotation. If a jet flew against the rotation, at the equator, at 1000mph , would it face 2000mph head winds? Similarly if it flew with the spin at 1000mph would it then face zero head wind?
 
  • #23
Vic43 said:
Hmm I'm not sure I get the concept of the entire atmosphere moving at the same speed and direction with earths rotation.
I think we all see that you don't get that concept. But, if the Earth is spinning and the atmosphere wasn't, then you'd have ##1600 \ km/h## winds on the surface.
Vic43 said:
If a jet flew against the rotation, at the equator, at 1000mph , would it face 2000mph head winds? Similarly if it flew with the spin at 1000mph would it then face zero head wind?
Hmm That's precisely what would happen if the atmosphere were not spinning. You've got the whole thing the wrong way round.
 
  • #26
You're getting confused by the changing reference frames. It's normal.
Planes fly w/r to the wind, not the ground, and certainly not w/r to the Sun (or stars). That is to say, their engines have to work with the medium they're pushing against.

A plane at the equator flying against the rotation of the Earth at 1000mph would hover w/r to the Sun (it would appear to chase the Sun). But its pitot tube's windspeed measurements, and its engines, and any unfortunate hand stuck out of a window, would all agree that it's going at 1000mph. If there were no local wind w/r to the ground, the groundspeed would similarly be 1000mph.
If it flew at 1000mph with the rotation, it'd measure the same windspeed (again, it's flying through the air), and the same groundspeed (again, in otherwise windless conditions). But from a point of view of the background stars, it'd return to the point of origin (again, w/r to the Sun, not the ground) in half the time than an otherwise stationary point on the surface would. The 'day' between two sunrises on the plane would last 12h instead of 24. But from the point of view of passengers waiting at the airport it'd travel just as fast either way.
 
  • #27
Bandersnatch said:
The air is rotating with the planet. Wind is motion of the air w/r to the observer (here, the drone). Since you've chosen the spot for hovering to be somewhere around the equator, as that's where the rotation velocity at the surface is approx. 1000mph, it would mean the still air is moving at that velocity w/r to the drone and the still air is perceived as 1000mph wind. Now, you could have some non-still air where the drone hovers, i.e. some local winds, that would change the perceived wind speed in either direction. But since there are no 1000mph winds even in the strongest hurricanes, you could never expect to nullify all that wind coming from the rotation of the atmosphere.
Of course you could have instead chosen a spot somewhere near the poles, where the rotation can be as leisurely as you want, including no rotation at all (at the poles). One can easily imagine some local wind patterns at least momentarily exactly matching the rotational velocity of the atmosphere so that your drone can hover in a

PeroK said:
I think we all see that you don't get that concept. But, if the Earth is spinning and the atmosphere wasn't, then you'd have ##1600 \ km/h## winds on the surface.

Hmm That's precisely what would happen if the atmosphere were not spinning. You've got the whole thing the wrong way round.
Yeah I guess you are right bout the fact if the atmosphere wasn't spinning at the same rate it'd be 1600kmph winds. Like I said I'm no physicist, just find it an interesting topic. It's a hard thing to grasp that the atmosphere is being pulled along with earth by friction as we can move so freely in it , and there are different local winds and weather patterns everywhere. I guess gravity is the thing that holds everything together and i was missing the fact that the atmosphere has weight/mass/particles that are affected by gravity . I think I find it easier to understand if I imagine the atmosphere as a solid lol. Anyway , I appreciate everyone's feedback.
 
  • #28
I'm still not sold on the explanations given about the counteracting of the inertia thing with the drone though (only using drone as an example as it can propel itself in a direction as well as hover) If a drone flew 2000mph against the spin at the equator it would have to fly for 1 hour to negate the inertia , if it then hovered relative to a star and the wind at that area was zero , the earth would have to spin under the drone at around 1000mph right? .....right? What am I (or you guys) 😉not getting?
 
  • #29
Vic43 said:
I'm still not sold on the explanations given about the counteracting of the inertia thing with the drone though (only using drone as an example as it can propel itself in a direction as well as hover) If a drone flew 2000mph against the spin at the equator it would have to fly for 1 hour to negate the inertia
This makes no sense. The drone would fly 2000 miles. If its engines stopped, it would soon by back at rest relative to the atmosphere and spinning with the Earth again. This is because the atmosphere exerts a force on the drone whenever its moving. You must be misunderstanding the concepts of force and inertia.

Vic43 said:
, if it then hovered relative to a star and the wind at that area was zero , the earth would have to spin under the drone at around 1000mph right? .....right? What am I (or you guys) 😉not getting?
The Earth is spinning, the atmosphere is spinning. The drone's motion must be relative to that. If the drone is not moving relative to the stars, then it must be moving relative to the surface and the atmosphere (except at or near the poles, of course).
 
  • #30
Vic43 said:
once it flew far enough against earths spin to counter the inertia
You'd need to translate that into English / Physics if you want a meaningful response.

You would be describing the very hard task of keeping a flying machine flying West fast enough to keep the Sun overhead? (on the Equator, of course). Or maybe using a powerful fan to achieve the same thing.

From your posts above, I get the impression that you have argued yourself into a corner in an attempt not to be wrong. PF is not the one who's out of step here.
 
  • #31
Inertia is the resistance to acceleration. What you have been conceptualising as countering here - the spin of the Earth - is velocity. In common parlance the distinction can be blurry.

When viewed from a non-rotating reference frame - here it means the point of view of the Sun and the background stars - a point at the surface of the Earth at the equator has some linear velocity. If you want the drone to hover above that point as seen from the non-rotating reference frame, it has to have equal but opposite velocity, in addition to its hovering action.
Once you impart that velocity through the use of some force (like the drone's engines), and in the absence of other forces (like drag from the atmosphere), it'll hover at that spot forever. This is Newton's first law of motion.
Inertia only comes into play here when the drone is accelerating to that velocity, as it determines how much force is required. This is Newton's second law. Inertia is the mass in F=ma.

So if what you need to hover w/r to the Sun at the equator is equal and opposite surface velocity, there's no point in ever going 2000mph. You just get to 1000mph and either cut the engines (if there's no drag) or keep firing them to maintain that velocity.
You'd only need more/less speed if you wanted to change where exactly you want to hover. Maybe you wanted the Sun to be directly overhead or something.

The case with an atmosphere is no different than swimming against the current in a river. You want to stay at rest w/r to the river banks, you swim as fast as the current does, only in the opposite direction. Any other speed will move you w/r to the banks. And if you stop swimming = applying force against drag of the medium you're in, the current will quickly carry you away.
 
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  • #32
Vic43 said:
What am I (or you guys) 😉not getting?
Well, what I don't seem to be getting is relevant context when you use the words "hover" or "speed". Or, the relevance of anything to do with "inertia".

There's a difference between waiting for information and being confused.

Vic43 said:
Much the same as if I were standing on a conveyor belt I would move with it , but if I ran against it at the same speed I would be running on the spot while the belt moves under me.
Now, that's not confusing at all.
 
  • #33
hmmm27 said:
Now, that's not confusing at all.
Vic43 said:
Think about a long conveyer belt , there is a mid point marker.
That does not clearly specify, if the marker is on the moving belt material, or on the fixed frame, next to the moving belt. You must be more precise when there are multiple possible interpretations. You know what you mean, but we cannot read your mind.
 
  • #34
Baluncore said:
That does not clearly specify, if the marker is on the moving belt material, or on the fixed frame, next to the moving belt. You must be more precise when there are multiple possible interpretations. You know what you mean, but we cannot read your mind.
Apologies. Yep on a fixed frame next to the belt
 
  • #35
Bandersnatch said:
Inertia is the resistance to acceleration. What you have been conceptualising as countering here - the spin of the Earth - is velocity. In common parlance the distinction can be blurry.

When viewed from a non-rotating reference frame - here it means the point of view of the Sun and the background stars - a point at the surface of the Earth at the equator has some linear velocity. If you want the drone to hover above that point as seen from the non-rotating reference frame, it has to have equal but opposite velocity, in addition to its hovering action.
Once you impart that velocity through the use of some force (like the drone's engines), and in the absence of other forces (like drag from the atmosphere), it'll hover at that spot forever. This is Newton's first law of motion.
Inertia only comes into play here when the drone is accelerating to that velocity, as it determines how much force is required. This is Newton's second law. Inertia is the mass in F=ma.

So if what you need to hover w/r to the Sun at the equator is equal and opposite surface velocity, there's no point in ever going 2000mph. You just get to 1000mph and either cut the engines (if there's no drag) or keep firing them to maintain that velocity.
You'd only need more/less speed if you wanted to change where exactly you want to hover. Maybe you wanted the Sun to be directly overhead or something.

The case with an atmosphere is no different than swimming against the current in a river. You want to stay at rest w/r to the river banks, you swim as fast as the current does, only in the opposite direction. Any other speed will move you w/r to the banks. And if you stop swimming = applying force against drag of the medium you're in, the current will quickly carry you away.
I guess I have been using confusing language which made it hard for you guys to understand what I was talking about. I'm glad you got the concept anyway . Thanks for your detailed response
 
  • #36
It would greatly simplify your grasp of all these scenarios if you (correctly) consider that everything - from the Earth's core up to the top of its atmosphere - is on average moving along with the rotation of the Earth (including all the air).
 
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  • #37
sophiecentaur said:
You'd need to translate that into English / Physics if you want a meaningful response.

You would be describing the very hard task of keeping a flying machine flying West fast enough to keep the Sun overhead? (on the Equator, of course). Or maybe using a powerful fan to achieve the same thing.

From your posts above, I get the impression that you have argued yourself into a corner in an attempt not to be wrong. PF is not the one who's out of step here.
Seems I've been using wrong terms and confusing language. Sorry, I'm not trying not to be wrong. I guess it came across like that as my language wasn't precise and that made it hard for people to get what I meant. All good now , I think I've got my answers - I was right with the outcome of the concept , just didn't articulate the concept well enough.
 
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  • #38
Do any of you guys know of an experiment that has been done regarding this scenario?
 
  • #39
Vic43 said:
Do any of you guys know of an experiment that has been done regarding this scenario?
Yes, aircraft fly in the sky all the time. I imagine that at some time some airliner has been traveling west at just the right latitude and speed to cancel out Earth's rotation completely. In fact, at 56.5 degrees north or south the Earth's rotational velocity is about 575 mph, which is about the average cruising speed of a typical airliner. Anyone flying west into parts of Denmark, Sweden, or Latvia (or huge areas of Russia) is roughly canceling out Earth's rotational motion.
 
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  • #40
Vic43 said:
Do any of you guys know of an experiment that has been done regarding this scenario?
What scenario?
We live in the real world and understand the physics of the Earth. What experiment could disprove our understanding.
 
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  • #41
Drakkith said:
Yes, aircraft fly in the sky all the time. I imagine that at some time some airliner has been traveling west at just the right latitude and speed to cancel out Earth's rotation completely. In fact, at 56.5 degrees north or south the Earth's rotational velocity is about 575 mph, which is about the average cruising speed of a typical airliner. Anyone flying west into parts of Denmark, Sweden, or Latvia (or huge areas of Russia) is roughly canceling out Earth's rotational motion.
What would be observed looking down at the ground from the aircraft? And I suppose it would have occurred flying east aswell, wht would be observed in this case?
 
  • #42
Vic43 said:
What would be observed looking down at the ground from the aircraft? And I suppose it would have occurred flying east aswell, wht would be observed in this case?
It seems that you have lived your whole life, secluded in an apartment, without experience of transport in the real world. Do you ever go outside, to catch a train for example?
 
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  • #43
Vic43 said:
Do any of you guys know of an experiment that has been done regarding this scenario?
You mean like getting rid of the Earth's atmosphere and using a rocket-powered drone?
No.
And I would not be in favor of it.
 
  • #44
Baluncore said:
It seems that you have lived your whole life, secluded in an apartment, without experience of transport in the real world. Do you ever go outside, to catch a train for example?
Why are you being disrespectful chap? Ofcourse I've experienced transport. I just never seen the earth spin under a stationary craft (relative to a position outside our atmosphere like a star or whatever). If there was a wide train with a clear bottom that had a marker on the track underneath, that was travelling, and you had a drone travelling on the train , you let the drone travel a distance with the train so it was going at the same velocity , then you hovered the drone , it would be still going the same speed as the train , but if you then flew the drone in the opposite direction of travel until you got to the marker on the track and came to a hover over that point, I would assume that the train would then move under the drone?
 
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  • #45
Thread is paused for a bit for Moderation...
 
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  • #46
Vic43 said:
What would be observed looking down at the ground from the aircraft? And I suppose it would have occurred flying east aswell, wht would be observed in this case?
Nothing special. It would look like you're flying normally no matter what direction you're flying in.

Edit: Sorry Berk, didn't see the thread was locked.
 
  • #47
No worries Drak. :smile:

@Vic43 -- I don't think folks are being disrespectful, some are just getting a bit frustrated that you are only understanding some parts of the explanations.

In summary, the speed of the aircraft (it needs to be a plane, not a drone) with respect to a stationary reference frame is the aircraft's speed relative to the ground, plus the speed of the ground (and air) with respect to a stationary reference frame. So if you want the aircraft's speed to be zero in a stationary reference frame (call it the star background reference frame), the aircraft has to fly west at 1000mph at the equator with respect to the Earth's surface and the associated atmosphere. As Drak points out, you can fly slower at latitudes away from the equator and still remain stationary in the stationary reference frame.

Thread is reopened in case that is not clear enough.

Edit/Add -- and if you stand at the North or South Pole, all you have to do is spin slowly (in the correct direction) to remain stationary against the star background... :smile:
 
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  • #48
Vic43 said:
just never seen the earth spin under a stationary craft
Why do you need it to, to understand the math? The math is very simple. An airplane flying flying east to west at the equator at 1,000 mph would see the sun remain stationary in the sky. A plane flying at 500 mph would see the sun move a (1000-500)/1000 = 50% of normal speed. What's the problem?

The world has supersonic aircraft. They've flown east and they've flown west. Has one ever flown west at exactly 1,000 mph at the equator? Why does it matter, to understand what they would see?

Note, you can approximate this at higher latitudes and slower speeds. I recently "saw" the sun travel backwards on a plane ride from the US to Asia. (in quotes because I had the shades closed, but I'm sure the pilots literally saw it.)
 
  • #49
I recently flew from the east coast of the US to the west. My plane took off at 6PM (eastern time) and arrived at 8PM (pacific time, three time zones west of my departure). I watched the sun get low in the sky and then set for nearly 5 hours.
 
  • #50
Thanks for the extra answers everyone, appreciated. I just want to make something clear, I am not trying to prove anything or anyone wrong , I just find the topic interesting.
 
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