Aether Mechanics provides a comprehensive aether theory to explain the cause of gravity.The cause of gravity can be fully explained and derived by Kinetic Theory of Gases.

**Aether Flow and Fourier’s Law**

Similar to gas particles, aether particles flow from higher pressure locations to lower pressure locations. For example, some aether particles are located between high pressure on the left-hand side and low pressure on the right-hand side. The left-hand side will have higher pressure than the right-hand side. The resulting pressure difference will force these particles in between to flow from left to right.

Aether pressure is related to energy density. And, energy density is directly proportional to mass density and the RMS speed square. Since the RMS speed is nearly constant, the difference of pressure is mainly due to the difference of the mass density. For the given example, the left-hand side with higher pressure has higher mass density than the right-hand side.

It is important not to be confused between flowing velocity and colliding velocity. The pressure is due to colliding velocity which is close to the speed of light. The pressure difference causes these particles to flow. These flowing particles have both microscopic colliding velocity and macroscopic flowing velocity. As mentioned before, the flowing velocity is observed from the global coordinate and colliding velocity is observed from the boat coordinate. The colliding velocity is much larger than the flowing velocity.

The aether flowing velocity is a steady state macroscopic velocity. The macroscopic flowing velocity can be calculated by taking the average of the microscopic total velocity observed from the global coordinate. The total velocity includes the microscopic motion of colliding and the macroscopic motions of oscillation and flowing. Note that what is discussed here is under the condition that aether macroscopic oscillation does not occur.

**Aether Flow between the Sun and the Earth**

Aether particles flow from high pressure locations to low pressure locations. The pressure is due to the impact force from the colliding of particles. Aether pressure is directly related to aether kinetic energy as shown. Based on Fourier’s law, aether flow can be related to the gradient of energy density as shown. Therefore, if we know aether energy density , we can know aether particle flow velocity .

The energy density field can be calculated from Laplace’s equation. Laplace’s equation of energy density can be derived from the conservation of energy and Fourier’s law.

In the Sun-Earth system as shown, the boundary conditions required for solving the Laplace’s equation are (1) a constant high energy density on the surface of the Sun, (2) a low background energy density at a distance far away from the Sun and the Earth, and (3) another constant energy density on the surface of the Earth.

The energy density outside the surface of the Sun has an energy density distribution similar to the curve on the left-hand side of the Sun. The energy density near the Earth due to only the Sun’s and background’s energy density is represented by a dotted curve line on the right-hand side of the Sun assuming that Earth does not exist in the space.

When the Earth is placed in the system, because the Earth has a lower energy density than the surrounding energy density represented by the dotted line, the Earth behaves like a sink and the aether flows into the Earth from its surrounding area. Aether flows faster on the left-hand side than on the right-hand side because the energy gradient on the left-hand side is higher.

**Gravitational Force and Bernoulli’s Equation**

Gravitational force will be shown to be the result of the difference of aether flow velocity around

an object. The detailed derivations of them are provided in chapters 2 to 7 of Aether Mechanics.

Gravitational force will be zero if there is no difference of aether flow velocity around an object. In the Sun-Earth example, the energy density is constant on the surface of the Earth. Therefore, the pressure on the surface of the Earth is also constant. The resulting force of the summation pressure on the surface of the Earth will be zero.

Gravitational force will not be zero if there is difference of aether flow velocity around the surface of the Earth. The aether flow velocity can be calculated from the gradient of the energy density following Fourier’s law. The energy density curve of the Sun-Earth system is shown to demonstrate how the flow velocity is related to the gradient of the energy density along a line passing through the Sun and the Earth.

On the surface of the Earth, the left-hand side of the Earth has a larger gradient of the energy density than the right-hand side does. According to Fourier’s law, the left-hand side of the Earth has a faster aether flow velocity than the right-hand side does. According to Bernoulli’s equation, the left-hand side of the Earth will have a smaller aether pressure, due to a larger pressure reduction from faster aether flow.

Gravitational force is shown to be the summation of the aether pressure on the surface of the earth. However, the derived gravitation is not exactly the same as Newton’s gravitation. The masses of objects in Newton’s gravitation are replaced by energy densities on the surfaces of the objects. This makes sense because mass cannot provide force in mechanics but energy does.