What is Space, Stephen Tiley
The Reality of Space
Two questions immediately arise:
1) what is space? [metaphysical question]
2) how can we know space? [epistemological question].
Needless to say, both questions are intricately connected: in order to ask what space is we must ask how, if at all, we can know acquire knowledge of it.
The two main historical positions concerning the nature of space are absolutism [or substantivalism] and relationalism.
Absolutism, most prominently expressed by Newton , argues that space has an existence over and above the objects contained within it.
Relationalism, most prominently expressed by Leibniz, argues that space has no existence over and above the relations between objects contained within it.
Both offered intricate arguments to support their respective positions.
According to Newton , as space is ontologically prior to the objects contained within it, viz., space can exist even when there are no objects contained within it, his view entails that objects in space can have absolute positions and velocities.
For Leibniz, on the other hand, space exists only as a relation between objects, and therefore has no existence apart from the existence of those objects; motion exists only as a relation between those objects.
Leibniz believes that such notions as absolute position and velocity, as espoused by Newton ’s absolutism, are meaningless and lead to contradictions.
The two arguments he offers us rely on his principle of sufficient reason and the identity of indiscernibles.
Leibniz thought-experiment:
He asks us to imagine two universes situated in absolute space. The only difference between them is that the second is placed five feet to the left of the first, a possibility available if such a thing as absolute space exists. Such a situation, however, is not possible according to Leibniz, for if it were:
a) where a universe was positioned in absolute space would have no sufficient reason, as it might very well have been anywhere else, hence contradicting the principle of sufficient reason, and
b) there could exist two distinct universes that were in all ways indiscernible, hence contradicting the Identity of Indiscernibles.
In defence against Leibniz, Newton offered us his famous ‘Bucket’ thought-experiment.
Newton’s Bucket:
The rotating bucket argument attempts to show that true rotational motion cannot be defined as the relative rotation of the body with respect to the immediately surrounding bodies. It is one of five arguments from the "properties, causes, and effects" of true motion and rest that support his contention that, in general, true motion and rest cannot be defined as special instances of motion or rest relative to other bodies, but instead can be defined only by reference to absolute space.
Water in a bucket, hung from a rope and set to spin, will start with a flat surface. As the water begins to spin in the bucket, the surface of the water will become concave. If the bucket is stopped, the water will continue to spin, and while the spin continues the surface will remain concave. The concave surface is apparently not the result of the interaction of the bucket and the water, since the water is flat when the bucket first starts to spin, becomes concave as the water starts to spin, and remains concave as the bucket stops.
This argument attempted to demonstrate the necessity of the existence of absolute space to account for phenomena like rotation and acceleration that cannot be accounted for on a purely relationalist account. Clarke argues that since the curvature of the water occurs in the rotating bucket as well as in the stationary bucket containing spinning water, it can only be explained by stating that the water is rotating in relation to some third thing, namely absolute space.
http://www.bun.kyoto-u.ac.jp/phisci/Newsletters/bucket.jpg
According to Newton , absolute space has the following properties:
1) Space has an ontologically prior existence to the objects contained within it.
2) Space can affect the objects/matter contained within it, but these objects cannot affect/influence space itself.
On a first reading absolute space seems to be endowed with a rather bizarre ontological status: it can exert an influence on objects contained in it but cannot itself be affected. It is immutable, eternal and unchanging.
Furthermore, if we cannot exert and influence of space itself, how can we possibly acquire knowledge of its existence?
As all we can really interact with are the objects contained within space, surely it follows that only these objects can be said to exist….?
Two questions immediately arise:
1) what is space? [metaphysical question]
2) how can we know space? [epistemological question].
Needless to say, both questions are intricately connected: in order to ask what space is we must ask how, if at all, we can know acquire knowledge of it.
The two main historical positions concerning the nature of space are absolutism [or substantivalism] and relationalism.
Absolutism, most prominently expressed by Newton , argues that space has an existence over and above the objects contained within it.
Relationalism, most prominently expressed by Leibniz, argues that space has no existence over and above the relations between objects contained within it.
Both offered intricate arguments to support their respective positions.
According to Newton , as space is ontologically prior to the objects contained within it, viz., space can exist even when there are no objects contained within it, his view entails that objects in space can have absolute positions and velocities.
For Leibniz, on the other hand, space exists only as a relation between objects, and therefore has no existence apart from the existence of those objects; motion exists only as a relation between those objects.
Leibniz believes that such notions as absolute position and velocity, as espoused by Newton ’s absolutism, are meaningless and lead to contradictions.
The two arguments he offers us rely on his principle of sufficient reason and the identity of indiscernibles.
Leibniz thought-experiment:
He asks us to imagine two universes situated in absolute space. The only difference between them is that the second is placed five feet to the left of the first, a possibility available if such a thing as absolute space exists. Such a situation, however, is not possible according to Leibniz, for if it were:
a) where a universe was positioned in absolute space would have no sufficient reason, as it might very well have been anywhere else, hence contradicting the principle of sufficient reason, and
b) there could exist two distinct universes that were in all ways indiscernible, hence contradicting the Identity of Indiscernibles.
In defence against Leibniz, Newton offered us his famous ‘Bucket’ thought-experiment.
Newton’s Bucket:
The rotating bucket argument attempts to show that true rotational motion cannot be defined as the relative rotation of the body with respect to the immediately surrounding bodies. It is one of five arguments from the "properties, causes, and effects" of true motion and rest that support his contention that, in general, true motion and rest cannot be defined as special instances of motion or rest relative to other bodies, but instead can be defined only by reference to absolute space.
Water in a bucket, hung from a rope and set to spin, will start with a flat surface. As the water begins to spin in the bucket, the surface of the water will become concave. If the bucket is stopped, the water will continue to spin, and while the spin continues the surface will remain concave. The concave surface is apparently not the result of the interaction of the bucket and the water, since the water is flat when the bucket first starts to spin, becomes concave as the water starts to spin, and remains concave as the bucket stops.
This argument attempted to demonstrate the necessity of the existence of absolute space to account for phenomena like rotation and acceleration that cannot be accounted for on a purely relationalist account. Clarke argues that since the curvature of the water occurs in the rotating bucket as well as in the stationary bucket containing spinning water, it can only be explained by stating that the water is rotating in relation to some third thing, namely absolute space.
http://www.bun.kyoto-u.ac.jp/phisci/Newsletters/bucket.jpg
According to Newton , absolute space has the following properties:
1) Space has an ontologically prior existence to the objects contained within it.
2) Space can affect the objects/matter contained within it, but these objects cannot affect/influence space itself.
On a first reading absolute space seems to be endowed with a rather bizarre ontological status: it can exert an influence on objects contained in it but cannot itself be affected. It is immutable, eternal and unchanging.
Furthermore, if we cannot exert and influence of space itself, how can we possibly acquire knowledge of its existence?
As all we can really interact with are the objects contained within space, surely it follows that only these objects can be said to exist….?
Labels: epistemology, metaphysics, physics rotation space Newton Leibniz, science
posted by bloggin the Question at 2:58 PM
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