At the moment, I am reading the book Relativity, written by Albert Einstein regarding his special and general theory of relativity. In his introduction to general relativity, he poses a thought experiment:
Suppose we have a large chest in space far away from any appreciable mass (stars, planets, etc.). Inside of this chest, we have an man (it's a large chest) standing on the floor of the chest with strings holding him to the chest floor. Furthermore, he is holding a rock in his hand.
Now let's suppose there is a hook on the outside of the lid of the chest that allows some immaterial being to pull the chest "upward" relative to its current plane with a constant force F.
The book describes how if he let go of the rock, it would fall to the floor. Why would it not fall upward? Here is the direct quote from the book:
Can someone please explain this bolded excerpt? Why is this true?
Suppose we have a large chest in space far away from any appreciable mass (stars, planets, etc.). Inside of this chest, we have an man (it's a large chest) standing on the floor of the chest with strings holding him to the chest floor. Furthermore, he is holding a rock in his hand.
Now let's suppose there is a hook on the outside of the lid of the chest that allows some immaterial being to pull the chest "upward" relative to its current plane with a constant force F.
The book describes how if he let go of the rock, it would fall to the floor. Why would it not fall upward? Here is the direct quote from the book:
Quote:
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We imagine a large portion of empty space, so far removed from stars and other appreciable masses, that we have before us approximately the conditions required by the fundamental law of Galilei. It is then possible to choose a Galileian reference-body for this part of space, relative to which points at rest remain at rest and points in motion continue permanently in uniform rectilinear motion. As a reference-body let us imagine a spacious chest resembling a room with an observer inside equipped with apparatus. Gravitation naturally does not exist for this observer. He must fasten himself with strings to the floor, otherwise the slighest impact against the floor will cause him to rise slowly towards the ceiling of the room. To the middle of the lid of the chest is fixed externally a hook with a roped attached, and now a "being" begins pulling at this with a constant force. The chest together with the observer then begins to move "upwards" with a uniformly accelerated motion. In course of time their velocity will reach unheard of valuesprovided that we are all this from another reference-body which is not being pulled by a rope. The acceleration of the chest will be transmitted to him by the reaction of the floor of the chest. He must therefore take up this pressure by means of his legs ... [this all makes sense to me thus far]. He is then standing in the chest in exactly the same way as anyone stands in a room of a house on our earth. If he releases a body which he previously had in his hand, the acceleration of the chest will no longer be transmitting to this body, and for this reason the body will approach the floor of the chest with an accelerated relative motion. |