My views on Cosmology and Physics
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Book by David Michalets
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Section BG of 35
This section has background for several terms used by Einstein.
Galileo defined a basic understanding of simple motion on Earth.
He observed free fall acceleration.
When an object was released from a height above Earth's surface, it would accelerate at the same rate, regardless of its mass.
He is assigned credit for the Galilean transformation, which is simply that vectors of velocities are additive.
A simple story explains it.
If a cannon on a ship can fire a cannon ball at a constant velocity, then the velocity of a ball is affected by the motion of the ship carrying the cannon firing the ball.
If the cannon is pointed in the direction of motion, like over the bow, then the ball gets an increase in its velocity, from the ship.
If the cannon is pointed opposite, like over the stern, then the ball gets a decrease in its velocity.
Galileo just explained something which is rather intuitive.
It is important to note that this observation is with objects in motion having a particular velocity.
If the ship had a very long fuse to light the cannon and it burned at the constant rate of 1 foot or 1 meter per hour, its rate of burning in any direction is unaffected by the motion of the ship. Its rate remains constant.
Isaac Newton described other things which were rather intuitive.
He described absolute time and absolute space. The 2 excerpts are from Wikipedia
According to Newton, absolute time exists independently of any perceiver and progresses at a consistent pace throughout the universe. Unlike relative time, Newton believed absolute time was imperceptible and could only be understood mathematically. According to Newton, humans are only capable of perceiving relative time, which is a measurement of perceivable objects in motion (like the Moon or Sun). From these movements, we infer the passage of time.
Since Newton's lifetime. we have agreed on the definition of 1 second, for a "consistent pace" and developed atomic clocks to maintain an absolute time independent of all humans.
Wikipedia has a topic about Coordinated Universal Time. This technology can be used as Newton's absolute time.
When this transmission cannot be received in the future, an observer could synchronize their devices, and maintain a copy of that UTC, like before launching a probe.
With current technology, an observer will not use "hands on a clock" as done in 1905, when making precise space and time measurements.
Absolute space, in its own nature, without regard to anything external, remains always similar and immovable. Relative space is some movable dimension or measure of the absolute spaces; which our senses determine by its position to bodies: and which is vulgarly taken for immovable space ... Absolute motion is the translation of a body from one absolute place into another: and relative motion, the translation from one relative place into another ...
— Isaac Newton
In my view, absolute space is the universe having no observable limits and always similar and immovable, because no change in a feature could reveal motion.
So, absolute space it is just empty space.
However, this apparently infinite space has many objects unevenly distributed in this space. Those objects are what we see from Earth and have fascinated astronomers for countless generations.
Newton also described inertia, or matter at rest tends to stay at rest, and matter in motion tends to stay in motion.
One must apply a force to start a stationary object moving, and one must apply a force to change or stop its motion. Friction is a force.
Newton defined a force is required to affect this inertia, with a simple equation, F = ma, where Force = Mass times acceleration.
Maintaining a force for a time results in a known velocity, where velocity = acceleration multiplied by the time of the sustained force.
Newton defined the fundamental force of gravity, which acts simultaneously, and instantaneously on the 2 masses.
Newton's force of gravity has a simple format ( where x is multiplied by):
F = G x (m1 x m2) / r^2
where m1 and m2 are the two masses, r is the distance between them, and G is the gravitational constant, which accommodates any effect from the medium between the masses, and defines the transition of the ratio of m^2/r^2 to a force.
The masses are multiplied because the force is mutual when acting on both simultaneously.
The distance is squared because each mass deploys a field for its mass. This field diminishes linearly by distance.
Because each mass has its field diminishing by distance, then the mutual, simultaneous force between both masses over this distance is divided by the distance squared because the force dminishes by both distances, which is the mutual distance.
There is no time variable in the equation.
The force of gravity is instantaneous.
Galileo's free fall acceleration is the result of gravity as defined by Newton, many years later.
The behavior is somewhat an illusion, when hiding the true nature of gravity.
The tiny masses, like a feather with a heavy ball, being used are trivial compared to that of Earth.
In reality, the tiny mass exerts a tiny force on the massive Earth, but it is impossible to measure.
This experiment was repeated by Apollo astronauts on the Moon.
Free fall acceleration is a behavior in a very narrow context. It has no application in the context of cosmology, where nothing is in a free fall.
This behavior is present in what we call a gravitational field. Once you are is on Earth's surface, after moving to a distance above the surface, and then bering released, then you will free fall toward Earth.
For a tiny body to leave this context of a gravitational field, the body must accelerate to an escape velocity which is calculated from the large mass, like Earth. After attaining escape velocity than the tiny body has escaped the gravitational field of the massive body.
When NASA calculates a slingshot trajectory of a probe passing any number of planets, moons, or the Sun, only Newton's force equation is used. A probe never transitions to free fall acceleration, because it was never actually on that body's surface and then accelerated away.
A gravitational field has no application in cosmology, where Newton's force equation applies, which is a mutual force between masses, though diminishing by inverse-sqaure of the mutual distance.
James Clerk Maxwell is important in our understanding of electromagnetism.
He explained how electric and magnetic fields work,
Coulomb's Law defines the electric force between two charges.
The electric force has a simple format:
F = K (q1 x q2) / r^2
where q1 and q2 are the two charges, r is the distance between them, and K is Coulomb's constant, which accommodates any effect from the medium between the charges, and defines the transition of the ratio of q^2/r^2 to a force.
The charges are multiplied because the force is mutual when acting on both simultaneously.
The distance is squared because each charge deploys a field for its charge. This field diminishes linearly by distance.
Because each charge has its field diminishing by distance, then the mutual force between both charges over this distance is divided by distance squared.
There is no time variable in the equation.
The electric force is instantaneous.
Maxwell also explained how light is the propagation of synchronized, perpendicular, electric and magnetic fields.
Light has no particle and cannot exhibit acceleration or deceleration. Its rate of propagation is defined by the medium at that instant.
A straight straw through the surface of water will appear broken by the change in propagation at the change in medium at the surface.
Light has no mass and cannot be affected by gravity.
Light has a constant rate of propagation which cannot be affected by the motion of the light source.
Light is considered a transverse wave.
Sound is a longitudinal wave whose rate of propagation is defined by the medium.
The motion of source of the sound cannot affect the velocity of the sound.
However, the motion of the source can cause a Doppler effect where the wavelength or frequency of the sound is affected by the velocity and direction of the source.
Though light is a transverse wave, the motion of the light source participates in the emission.
The distribution of energy around the sphere of wavelengths in a continuum around the source is affected by the motion of the source.
I have written several books on this subject.
For someone interested, here is the reference:
Distant Spectral Shifts
This background into the fundamental forces is very important because in 1905, Einstein proposed many changes to this foundation of physics.
Einstein also refers to the Lorentz transformation.
This is the math required to determine the final motion of one motion in the context of another motion, where a frame of reference is the context for each object. Each frame of reference is an individual Euclidean geometry, with its x,y,z, and t.
Lorentz math with its 4-dimensions is a more complicated context than the simple Galilean transformation.
The math in the Lorentz algorithm includes the simpler scenario in the Galilean.
Einstein apparently requires the Lorentz transformation to obtain the special observer's motion.
The 4 inputs to the tensor equations are changes in space location, as dx, dy, dz, with the corresponding change in time, for each increment of motion..
Rather than checking for the presence of objects involved with the forces of gravity and electromagnetism, Einstein looks for only masses exerting a gravitational field, a concept not applicable beyond the context of Earth, to manipulate these 4 values to curve the path of the special observer. This path cannot match the result of the mutual, instantaneous forces acting at inverse-square of the mutual distance.
Using the word Einstein.
In this book being reviewed.
The word we is used consistently.
In this review I will use the word Einstein when referring to the author. Einstein is the author of this book. No other contributors are named.
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last change 05/07/2022