Is the Pen on My Desk a Geodesic and Is My Room an Inertial Frame?

In summary, the conversation discusses whether a pen on a desk and a room can be considered examples of a geodesic and an inertial frame, respectively. The conclusion is that a pen does not describe a geodesic unless it is in free fall, and a room is only a good approximation of an inertial frame if it is undergoing constant 1G acceleration through space.
  • #1
wpoely
6
0
Hi,

I was wondering: I'm sitting at my desk and on my desk lies a pen. Does the pen describe a geodesic? And is the room I'm sitting in an inertial frame?

I think the pen doesn't describe a geodesic because it's not in free fall and i think my room is a good approximation of an inertial frame for things that happen in my room.

Am i right? Thanks!
 
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  • #2
No. If the desk wasn't there, then for a few seconds the pen would describe a geodesic. Similarly, your room is no better inertial frame than an elevator.
 
  • #3
Your room would be a good approximation for the frame of a room undergoing constant 1G acceleration through space in special relativity.
 
  • #4
So, in practice, only when an object is in free fall, we know it describes a geodesic.

Thanks for the answers!
 

Related to Is the Pen on My Desk a Geodesic and Is My Room an Inertial Frame?

1. What is a geodesic frame and how is it different from an inertial frame?

A geodesic frame is a coordinate system that follows the curvature of a curved surface, such as a planet or a black hole. In contrast, an inertial frame is a coordinate system in which an object experiencing no external forces will move in a straight line at a constant speed. The main difference between the two is that a geodesic frame takes into account the curvature of space, while an inertial frame assumes a flat, non-curving space.

2. How are geodesic and inertial frames used in general relativity?

In general relativity, geodesic frames are used to describe the motion of objects in curved space, while inertial frames are used to describe motion in flat space. This is important because general relativity states that objects with mass cause a curvature in space, and the motion of objects is affected by this curvature. Both geodesic and inertial frames are necessary to accurately describe the behavior of objects in the presence of gravity.

3. Can geodesic and inertial frames be used interchangeably?

No, geodesic and inertial frames cannot be used interchangeably. While they both describe the motion of objects, they are based on different assumptions about the nature of space. Inertial frames assume a flat, non-curving space, while geodesic frames take into account the curvature of space. It is important to use the correct frame depending on the situation being studied.

4. Are geodesic frames only used in the study of gravity?

No, geodesic frames are not only used in the study of gravity. They can also be used in other fields, such as geology, in understanding the movement of objects on a curved Earth's surface. Additionally, geodesic frames are also used in navigation and GPS systems, which take into account the curvature of Earth's surface when calculating distances and directions.

5. How do geodesic and inertial frames relate to the concept of a reference frame?

Geodesic and inertial frames are both types of reference frames, which are used to describe the motion of objects in relation to a fixed point. However, geodesic frames are specific to curved space and take into account the curvature of space, while inertial frames are specific to flat space and do not take into account curvature. Both frames are important in understanding the motion of objects in different environments.

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