What causes Gravitational "attraction."

in #physics8 years ago

Hypothetically suppose that the earth is not moving through space.

Even if the earth is not moving through space, it would still be moving through time.

The path of that the earth takes through space and time is what we will call its "worldline line"

Consider clocks in space that are at rest relative to the earth. The mass of he Earth warp space-time .

This causes the clocks near the earth to run slower than clocks far away. The vertical axis represents time, and the X and Y axis represent two of the three spatial dimensions.

The third spatial dimension is not shown, as this image is limited to only a total of three dimensions.To be accurate, only a single two-dimensional cross section of the Earth should be shown, and this same two dimensional cross section at different points in time should form a solid vertical cylinder.

This image should not be changing as you watch the image, since time is already fully represented by the vertical axis.

These images therefore do not accurately represent the full picture, but they can nevertheless help us develop an intuition for concepts that would otherwise be difficult to visualize. Suppose we have an object that is initially at rest relative to the earth.

This object will move through time.

But, different parts of the object will want to move through time at different rates

As the object continues traveling through space-time in a straight line, the object starts moving towards the Earth.

Hence we have the appearance of a gravitational attraction.

The visualization does not accurately represent the full picture, since a point particle of zero volume would still follow the exact same path.

However, the full picture is also not accurately represented with the visualization that is typically given of the Earth causing an indentation on a rubber sheet.

Aside from the fact that this image falsely implies that the objects are more likely to be attracted to the South Pole, this visualization is incomplete in that it does not show time as one of the four dimensions

Without taking "time" into account, we would, for example, never be able to understand the apparent gravitational attractive force on an object starting at rest relative to the earth. Gravitational attraction is not the result of objects following straight lines through a curved 3-dimensional space, but the result of objects following straight lines through curved four-dimensional space-time.

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