The world revolves around a person

[silentwf]

This isn't the phrase egotistic or anything, but rather a random conversation i came up with my friends. We all know that people (and things) revolve around the world, but could one say that the world revolves around a person/thing? For example, if a car crashed into a wall, one could picture it as the car moving towards the wall, but from another perspective, one could view it as the wall moving toward a stationary car.

I know that in relativity, things must be in the same inertial frame, but the Earth is rotating, which isn't an intertial frame... so is it wrong to say the world revolves a person/thing?

(i'm not sure if this goes in general physics or relativity)

 

[tiny-tim]

hi silentwf!

I know that in relativity, things must be in the same inertial frame, but the Earth is rotating, which isn't an intertial frame... so is it wrong to say the world revolves a person/thing?

yes, you're correct … the Earth isn't an inertial frame

(we usually treat it as such, but that's not always accurate)

let's keep it simple by assuming that you are standing at the north pole …

if you can somehow position yourself on a platform which is not rotating with the earth, you would look down and see the Earth rotating about you

moreover, that would not be a merely permissible view, it would be the natural view to take, since you would have the inertial frame (i'm ignoring the motion round the sun, and round the galaxy etc), not the earth

at ordinary latitudes, it's not so straightforward, since your platform would have to roate around local vertical, but basically the reality is that the Earth is turning, and it doesn't make much difference which (parallel) axis we regard it as turning about

 

[silentwf]

So basically, you can only say things move in relative to another only when they're not accelerating? or is it only when they don't have any angular rotation about a common axis?

 

[tiny-tim]

an inertial observer (or an inertial frame) should have neither linear acceleration nor rotation

however, most laboratories are rotating with the earth, and going round the sun etc, and even if we adjust for that, the Earth's gravity would still make the laboratory non-inertial, requiring us to add a "fictitious" force of gravity (which we're so used to that we regard it as real! )

ultimately, you can have any non-inertial frame, so long as you introduce "fictitious" forces …

but often those forces are so small that they can be ignored! ​

 

[pmacias]

I would approach this question by first clarifying the terms being used. When we say "the world revolves around a person," we are using the word "revolve" to mean "to move in a circular or curving course around something." In this context, we are not referring to the literal rotation of the Earth around its axis or its orbit around the sun.

In terms of physics, it is important to understand that everything in our universe is in constant motion and is affected by the forces of gravity and inertia. The Earth's rotation and orbit are a result of these forces, and they do not revolve around any specific person or thing. Similarly, a car crashing into a wall is a result of the forces acting upon it, not the wall revolving around the car.

In the example given, it is important to consider the reference frame from which we are observing the situation. From the perspective of someone standing on the ground, the car is moving towards the wall. However, from the perspective of someone inside the car, the wall is moving towards them. This is due to the relative motion between the two objects and the different reference frames from which they are observed.

In terms of relativity, it is true that objects must be in the same inertial frame in order for the laws of physics to apply. However, the Earth's rotation does not necessarily mean that it is not an inertial frame. In fact, the Earth's rotation is constant and can be accounted for in our calculations. So, it is not incorrect to say that the world revolves around a person or thing, as long as we are using the term "revolve" in a non-literal sense.

In conclusion, while the phrase "the world revolves around a person" may hold some philosophical or metaphorical meaning, from a scientific perspective, it is not an accurate description of the physical world. The forces of gravity and inertia govern the motion of objects, and the Earth's rotation is simply a result of these forces, not a direct result of any one person or thing.