Newton's bucket and Galilean relativity

In summary, the conversation discusses Newton's thought experiment of the bucket and how he explained it through the concept of absolute space. It is also mentioned that Newton believed all motion to be absolute, which would have predicted the findings of the Michelson-Morley experiment. The conversation also touches on whether Newton believed there were mechanical experiments that could determine absolute motion. It is mentioned that the explanation of the curved surface of rotating water involves centrifugal force for all observers except for a stationary one. This leads to the concept of fictional forces and how they relate to gravity. However, it is noted that this is a weak point in Greene's book as it does not fully explain the significance of the bucket experiment and the concept of fictional forces.
  • #1
Hooleehootoo
6
0
I'm re-reading Greene's The Fabric of the Cosmos. He describes Newton as explaining his (Newton's, not Greene's!) thought experiment of the bucket by the existence of absolute space: something with respect to which rotating objects rotate, even in seemingly empty space.

Did Newton ever discuss why rotational motion was absolute, but constant velocity motion was relative? Or did he in fact think all motion was absolute? I guess that would mean he would have predicted that the Michelson-Morley would have found an ether wind.
 
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  • #2
He thought that time and space, and therefore all motion, was absolute.
 
  • #3
so he thought that when you were on a steadily moving ship and you dropped a coin from your hand, the reason it hit you on the foot was that both you and the ship were moving relative to absolute space?

Did Newton think there were mechanical experiments that could determine absolute motion?
 
  • #4
Hooleehootoo said:
so he thought that when you were on a steadily moving ship and you dropped a coin from your hand, the reason it hit you on the foot was that both you and the ship were moving relative to absolute space?

Did Newton think there were mechanical experiments that could determine absolute motion?

I'm not sure I understand your question. If you and the coin are on a steadily moving ship, the coin will drop straight down to the floor below where you held it when you dropped it.
 
  • #5
Geometer are you being funny?

Newton took into account velocities but the Lorenz transformation is the theorem that brings the observer into account and each level to predict an absolute K has not been established or verified.

As each article of matter has a relative affect on each other since the constant speed of light reveals a result; the realization of time, our fourth demension, has to be taken into account and to acknowledge the interwoven effect of everything to itself has beautified many explanations.

Has it been thought yet that a negative thereof could simplify dark matter?
 
  • #6
anyone help me?

i can't understand why Newton had to propose anything to explain the bucket? It seems that he could understand the individule water bits (whatever he wanted to call them) each wanted to proceed in a straight line and upon coliding with the bucket would pile up atop one another.

Why wouldn't he have concluded that? Surely I'm too uneducated to understand.

thanx
jerry
 
  • #7
Greene wasn't dropping the bucket he had it suspended from a rope which you wound up.

The bucket slowly starts spinning to unwind and now look at the reference frames .. look up "bucket argument" in wikipedia.

The problem is the water does not stay level it produces a concave shape.

All observers agree that the surface of rotating water is curved. However, the explanation of this curvature involves centrifugal force for all observers with the exception of a truly stationary observer, who finds the curvature is consistent with the rate of rotation of the water as they observe it, with no need for an additional centrifugal force. Thus, a stationary frame can be identified, and it is not necessary to ask "Stationary with respect to what?":

It leads into the problem of fictional forces (centrifugal force, Coriolis force, and Euler force) what are they pushing on if anything. Once you accept there can be fictional forces it leads directly into General relativity that is gravity is a fictional force quote below from GR in wiki.

In Einstein's theory of general relativity, gravitation is an attribute of curved spacetime instead of being due to a force propagated between bodies. In Einstein's theory, masses distort spacetime in their vicinity, and other particles move in trajectories determined by the geometry of spacetime. The gravitational force is a fictitious force. There is no gravitational acceleration, in that the proper acceleration and hence four-acceleration of objects in free fall are zero. Rather than undergoing an acceleration, objects in free fall travel along straight lines (geodesics) on the curved spacetime.

I think that is the only weak part of the book it never really explains why the bucket is important (in that it defies Newtonian analysis) and he never really brings in fictional forces.
 
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  • #8
Uglybb said:
Greene wasn't dropping the bucket he had it suspended from a rope which you wound up.

The bucket slowly starts spinning to unwind and now look at the reference frames .. look up "bucket argument" in wikipedia.

The problem is the water does not stay level it produces a concave shape.

It leads into the problem of fictional forces (centrifugal force, Coriolis force, and Euler force) what are they pushing on if anything. Once you accept there can be fictional forces it leads directly into General relativity that is gravity is a fictional force quote below from GR in wiki.

I think that is the only weak part of the book it never really explains why the bucket is important (in that it defies Newtonian analysis) and he never really brings in fictional forces.

This is an ancient thread :rolleyes:
Still it may be useful to give the explanation "straight from the horse's mouth", here:

http://gravitee.tripod.com/definitions.htm

Just press "cancel" and search for "water"; you'll find the discussion near the end of the Scholium.

Harald
 

1. What is Newton's bucket experiment?

Newton's bucket experiment was a thought experiment proposed by Sir Isaac Newton to challenge the concept of absolute space. In this experiment, a bucket filled with water is hung from a rope and set to rotate. Observers outside the bucket would see the water form a concave shape due to centrifugal force, while an observer inside the bucket would see the water remain stationary.

2. How does Newton's bucket experiment relate to Galilean relativity?

Newton's bucket experiment was used to support Galilean relativity, which states that the laws of physics are the same for all observers in uniform motion. In this experiment, the observer inside the rotating bucket would not be able to determine their state of motion based on the behavior of the water, as the water would remain stationary relative to them. This supports the idea that there is no absolute state of rest or motion.

3. What is the difference between absolute and relative motion?

Absolute motion refers to the idea that there is an absolute state of rest or motion in the universe, while relative motion refers to the idea that motion is only meaningful in relation to other objects or observers. Newton's bucket experiment and Galilean relativity support the concept of relative motion, as the behavior of the water in the bucket is dependent on the observer's frame of reference.

4. How did Newton's bucket experiment impact the understanding of space and motion?

Newton's bucket experiment challenged the traditional belief in absolute space and motion, leading to the development of the concept of relative motion. This experiment played a crucial role in the development of Galilean relativity, which has greatly influenced our understanding of space and motion in modern physics.

5. Can Newton's bucket experiment be replicated in real life?

No, Newton's bucket experiment is a thought experiment and cannot be replicated in real life. However, similar experiments have been conducted using rotating platforms and fluids, which have shown similar results to those predicted by Galilean relativity.

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