Understanding the Cause of Gravity

The question of what causes gravity has puzzled physicists for centuries. A common misconception is that space itself bends, but this is not the case according to our current understanding. Space and time, collectively known as spacetime, do not bend or warp in the conventional sense. Instead, the straight lines that objects follow (geodesics) can appear to curve in a curved spacetime.

Curvature and Space

Space does not bend or curve in the way we might imagine. Instead, the paths of objects traveling through spacetime can appear to curve because the straight line in a curved spacetime is actually a curved path. This is a fundamental concept in General Relativity, first proposed by Albert Einstein. In this framework, objects travel along geodesics, which are the shortest paths between two points in curved spacetime. This curvature is not the bending of space itself but the result of the interaction between mass and spacetime.

Einstein's Insight

Albert Einstein, one of the greatest physicists of the 20th century, provided a profound insight into the nature of gravity. In his General Theory of Relativity, he stated:

"As a result of the more careful study of the electromagnetic phenomena we have come to regard action at a distance as a process impossible without the intervention of an intermediary medium."

This quote emphasizes the need for an intermediary medium for action at a distance. In the context of gravity, this means that the curvature of spacetime is caused by the presence of mass, rather than space itself bending.

Mass and Curvature

So, what causes the curvature of spacetime? The hypothesis is that it is due to a spin 2 quantum field or a similar field that can explain the gravitational interaction. This is the best answer we currently have, but it remains a topic of ongoing research in theoretical physics.

No Interaction, No Curvature

Physically, we observe that space does not interfere with the motion of objects at rest or in uniform rectilinear motion. The principle of inertia, as described by Newton's first law of motion, states that an object will remain at rest or continue in uniform rectilinear motion unless acted upon by an external force. This is consistent with the idea that there is no interaction between space and mass in the absence of gravity.

Examples and Evidence

One piece of evidence for this is the behavior of hypothetical NASA boosters designed to maneuver in space. These boosters operate by expelling mass, not by interacting with space. This demonstrates that in the absence of interaction with space, there is no alteration of the boosters' motion. Similarly, the conservation of momentum during space travel and the observation of light in both Special Relativity and vacuum conditions show no interaction between space and mass.

Conclusion

In summary, the concept of spacetime curvature is not about space itself bending but the nonlinear divergence or convergence of geodesics due to the presence of mass. The absence of interaction between space and mass is evident in the behavior of objects in space and supports the idea that there is no curvature of space in the absence of mass. This understanding is crucial for our comprehension of the gravitational force and its profound implications for our universe.