Scientific Curiosity

[toat in a burtle]

One of my friends in lower sixth form said that the rotation of the Earth should be affecting our travel times. I was really confused, but now I'm actually curious. Does its rotation affect how long it takes us to get to or from somewhere, depending which way we're going?

[76561198117027862]

Opprinnelig skrevet av Mr. Shaggnificent:

Opprinnelig skrevet av Agni:

I can simplify it for you if you want. Just say what needs to be explained.

OK then, explain how centerfuges and G force work.

Centrifuges work due to the centrifugal force. But there is no gravity unlike earth's to keep everything from getting displaced.

G force is the phenomena objects experience when in a state of acceleration. If you are in a jet then it is your frame of reference. But you still experience the G force. So would a fly and if either doesn't keep up with the acceleration and stays at a constant speed then it will get displaced.

[Mr. Shaggnificent]

https://www.youtube.com/watch?v=ttZCKAMpcAo

[76561198117027862]

Opprinnelig skrevet av Mr. Shaggnificent:

https://www.youtube.com/watch?v=ttZCKAMpcAo

Opprinnelig skrevet av Mr. Shaggnificent:

https://www.youtube.com/watch?v=DXkmc2p_Zio

Rather than simply posting videos, if you are trying to make a point you would need to state it.

[Mr. Shaggnificent]

Rather than simply dismissing the videos, if you are trying to refute them you would need to watch them.

[76561198117027862]

Opprinnelig skrevet av Mr. Shaggnificent:

Rather than simply dismissing the videos, if you are trying to refute them you would need to watch them.

No one is going to refute the theory of relativity and I don't know what you want me to refute to begin with regarding the mythbusters.

[TheGamingWyvern]

Opprinnelig skrevet av Agni:

Opprinnelig skrevet av Sticky Honeybuns:

No, your understanding is flawed and what many people think. Our atmosphere is moving along with the rotation of the earth. Since the earth is our frame of reference is the earth it is considered as a stationary object. We can walk in any direction because of this and we do not have to overcome the rotational direction of the earth. In your example if we tried to walk against earths rotation we would have to overcome that force. Luckily we do not or we could only walk in one direction. Gravity does not exert a horizontal force only a vertical force. Go read up on frames of reference, it should explain what you are having trouble with understanding.

Actually that is wrong. Because if what you say is correct, centrifuges won't work. And g-forces would not be a thing.

The reason why we don't have to overcome it is simply because we are pulled along with it and in motion.

Hi, I'm just jumping in here to try and clear things up. Agni, you are correct, but for the wrong reasons. Gravity does not "pull along" objects. Gravity only pulls downward.

The first example I remember is that of the pen being dropped in the plane. The reason the pen does not shoot to the back of the plane is that it has momentum. When the pen is dropped, it still has the same velocity as the plane. Since the air inside the plane is *also* moving at roughly the same speed as the plane, there is little to no air friction causing the pen to slow down. Theoretically, if the pen floated there indefinitely then it would, eventually, hit the back of the plane because its going to slow down due to *some* force. Instead, gravity speeds it up *downwards*, the pen hits the floor, then friction between the pen and the floor takes over and continues keeping the pen at the same speed.

As far as a bird/fly inside a car/plane, the same rules apply. If it flies long enough eventually it would have to expend energy to keep up with the vehicle because something would be slowing it down, however that slowing force (which is usually air resistance) is almost nothing inside the vehicle since it is air-tight (or close enough to it), so it would take a *long* time to have that happen

[76561198117027862]

Opprinnelig skrevet av TheGamingWyvern:

Opprinnelig skrevet av Agni:

Actually that is wrong. Because if what you say is correct, centrifuges won't work. And g-forces would not be a thing.

The reason why we don't have to overcome it is simply because we are pulled along with it and in motion.

Hi, I'm just jumping in here to try and clear things up. Agni, you are correct, but for the wrong reasons. Gravity does not "pull along" objects. Gravity only pulls downward.

The first example I remember is that of the pen being dropped in the plane. The reason the pen does not shoot to the back of the plane is that it has momentum. When the pen is dropped, it still has the same velocity as the plane. Since the air inside the plane is *also* moving at roughly the same speed as the plane, there is little to no air friction causing the pen to slow down. Theoretically, if the pen floated there indefinitely then it would, eventually, hit the back of the plane because its going to slow down due to *some* force. Instead, gravity speeds it up *downwards*, the pen hits the floor, then friction between the pen and the floor takes over and continues keeping the pen at the same speed.

As far as a bird/fly inside a car/plane, the same rules apply. If it flies long enough eventually it would have to expend energy to keep up with the vehicle because something would be slowing it down, however that slowing force (which is usually air resistance) is almost nothing inside the vehicle since it is air-tight (or close enough to it), so it would take a *long* time to have that happen

False, it is due to inertia. Even in perfect vaccum and without friction, no object maintains constant velocity as some force will always act upon it

And gravity does pull along objects. It pulls perpendicularly, not downwards.

[TheGamingWyvern]

Opprinnelig skrevet av Agni:

Opprinnelig skrevet av TheGamingWyvern:

Hi, I'm just jumping in here to try and clear things up. Agni, you are correct, but for the wrong reasons. Gravity does not "pull along" objects. Gravity only pulls downward.

The first example I remember is that of the pen being dropped in the plane. The reason the pen does not shoot to the back of the plane is that it has momentum. When the pen is dropped, it still has the same velocity as the plane. Since the air inside the plane is *also* moving at roughly the same speed as the plane, there is little to no air friction causing the pen to slow down. Theoretically, if the pen floated there indefinitely then it would, eventually, hit the back of the plane because its going to slow down due to *some* force. Instead, gravity speeds it up *downwards*, the pen hits the floor, then friction between the pen and the floor takes over and continues keeping the pen at the same speed.

As far as a bird/fly inside a car/plane, the same rules apply. If it flies long enough eventually it would have to expend energy to keep up with the vehicle because something would be slowing it down, however that slowing force (which is usually air resistance) is almost nothing inside the vehicle since it is air-tight (or close enough to it), so it would take a *long* time to have that happen

False, it is due to inertia.

And gravity does pull along objects. It pulls perpendicularly, not downwards.

Eh, inertia is what I was describing. An object's momentum remains unchanged without a force acting on it, and inside the vehicle there is little to no force acting sideways.

As for gravity pulling perpendicularly, that's just untrue. Gravity is simply the force that pulls two objects together. In these kinds of physics problems, the two objects in question are the earth and something else (plane, pen, fly, bird, whatever). In order to bring these two together, earth's gravity pulls directly down, towards Earth's center.

Edit: Just saw your second half to the inertia bit

Opprinnelig skrevet av Agni:

Even in perfect vaccum and without friction, no object maintains constant velocity as some force will always act upon it

Actually, that's exactly what would happen. Any object in a perfect vacuum, with nothing touching it, will maintain a constant velocity. That's Newton's First Law
Edit 2: Actually, just realized my mistake. Gravity can affect objects in a perfect vacuum (and I guess the force of light but that's so miniscule its basically useless)

[TheGamingWyvern]

Oh, and to the OP, watch this video:
https://www.youtube.com/watch?v=3gNkgj9h2oM
very informative

[76561198117027862]

Opprinnelig skrevet av TheGamingWyvern:

Eh, inertia is what I was describing. An object's momentum remains unchanged without a force acting on it, and inside the vehicle there is little to no force acting sideways.

It need not be a force that acts sideways. Gravity is there and yes it has an effect. That is why you don't bullets travelling in a straight line. Hell, even light bends.

Opprinnelig skrevet av TheGamingWyvern:

As for gravity pulling perpendicularly, that's just untrue. Gravity is simply the force that pulls two objects together. In these kinds of physics problems, the two objects in question are the earth and something else (plane, pen, fly, bird, whatever). In order to bring these two together, earth's gravity pulls directly down, towards Earth's center.

Gravity only acts perpendicularly. there is no up or down. That is not untrue, that is a fact.

Shell theorem is one example of this.

{LENKE FJERNET}https://www.quora.com/Why-is-gravity-inside-a-spherical-shell-considered-to-be-zero

[TheGamingWyvern]

Opprinnelig skrevet av Agni:

Opprinnelig skrevet av TheGamingWyvern:

As for gravity pulling perpendicularly, that's just untrue. Gravity is simply the force that pulls two objects together. In these kinds of physics problems, the two objects in question are the earth and something else (plane, pen, fly, bird, whatever). In order to bring these two together, earth's gravity pulls directly down, towards Earth's center.

Gravity only acts perpendicularly. there is no up or down. That is not untrue, that is a fact.

Shell theorem is one example of this.

https://www.quora.com/Why-is-gravity-inside-a-spherical-shell-considered-to-be-zero

Just for clarification's sake, what do you say gravity is acting perpendicularly *to*?

As far as shell theorem, that's simply the application of integration over points of gravity. If you apply the same method to a large sphere (i.e. the Earth), you'll see that the force of gravity at any point *outside* a sphere points directly to the center the sphere. In the case of our examples, that is "down". This [themcclungs.net] is the full set of calculations to get that, if you are interested, but the bottom line is that for a perfect sphere gravity always pulls towards the center of the sphere (and earth is close enough to a perfect sphere that the differences don't matter on the scale of our examples)

[76561198117027862]

Opprinnelig skrevet av TheGamingWyvern:

Opprinnelig skrevet av Agni:

Gravity only acts perpendicularly. there is no up or down. That is not untrue, that is a fact.

Shell theorem is one example of this.

{LENKE FJERNET}https://www.quora.com/Why-is-gravity-inside-a-spherical-shell-considered-to-be-zero

Just for clarification's sake, what do you say gravity is acting perpendicularly *to*?

As far as shell theorem, that's simply the application of integration over points of gravity. If you apply the same method to a large sphere (i.e. the Earth), you'll see that the force of gravity at any point *outside* a sphere points directly to the center the sphere. In the case of our examples, that is "down". {LENKE FJERNET} This is the full set of calculations to get that, if you are interested, but the bottom line is that for a perfect sphere gravity always pulls towards the center of the sphere (and earth is close enough to a perfect sphere that the differences don't matter on the scale of our examples)

Perpendicular to the center of gravity, not necessarily to the centre of a given object. And our Earth is not a sphere. It is an Oblate Spheroid.

And down is subjective, hence the issue.

[Gus the Crocodile]

The centre of gravity/mass is a point; you can't be perpendicular to a point. Or to put it another way, all directions are perpendicular to a point.

[76561198117027862]

Opprinnelig skrevet av Gus the Crocodile:

The centre of gravity/mass is a point; you can't be perpendicular to a point. Or to put it another way, all directions are perpendicular to a point.

A point with no unit of dimensions is an idea. But such a thing does not exist in our universe. It has a dimension no matter how small, or in other words it occupies space.

[TheGamingWyvern]

Opprinnelig skrevet av Agni:

Opprinnelig skrevet av TheGamingWyvern:

Just for clarification's sake, what do you say gravity is acting perpendicularly *to*?

As far as shell theorem, that's simply the application of integration over points of gravity. If you apply the same method to a large sphere (i.e. the Earth), you'll see that the force of gravity at any point *outside* a sphere points directly to the center the sphere. In the case of our examples, that is "down". This [themcclungs.net] is the full set of calculations to get that, if you are interested, but the bottom line is that for a perfect sphere gravity always pulls towards the center of the sphere (and earth is close enough to a perfect sphere that the differences don't matter on the scale of our examples)

Perpendicular to the center of gravity, not necessarily to the centre of a given object. And our Earth is not a sphere. It is an Oblate Spheroid.

And down is subjective, hence the issue.

Perpendicular to a point? I'm not really sure what that means, perpendicularity is generally a property shared by two vectors/lines, and I've never heard of it between a vector and a point.

Yes, Earth is an Oblate Spheroid, but the minor shift in direction of gravity from "straight down" to "every so slightly angled from straight down" is going to be marginal, not nearly enough to explain pulling an object in the same direction a plane flies.

Also, while I do understand how down can be subjective (in space, for example), when referring to Newtonian Physics on the surface of a planet its generally considered to be "the direction towards the center of the planet".
At the very least, for the purposes of this discussion, can we just say that "down" means "the direction towards the center of mass of the Earth" and be done with it?