A Brief History of Gravity
What is Gravity? How
is gravity related to
time? Does gravity attract objects? Is the “force” a real pull,
or is it just space-time? No one has
ever isolated any gravity - directly measured it apart from assumptions
about matter and time. Newton
did not claim to know the cause of gravity. "Hitherto I have not
been able to
discover the causes of these phenomena, and I frame no hypothesis . . .
And to us it is enough that gravity
does really exist, and acts according to the laws which we have
explained, and abundantly
serves to account for all the motions of the celestial bodies, and our
sea." Saturn is a good illustration of the mystery of gravity. Why are
the rings so thin that we can see through them? Why do they rotate in a
plane? Why do the major moons of Saturn rotate synchronously, so the
same side always faces the planet? This is a view of Saturn as it
eclipsed the sun from the vantage point of the Cassini spacecraft.
Photo from NASA.
Archaic
thinkers could not imagine time or gravity as we do. Imagine
growing up in ancient Babylon. In school you learned about the
early kings who had lived for vast ages. The earliest kings reigned for
thens of thousands of years. (The longest, according to the record,
reigned for 43,200 years - 12 sars). Each generation of
kings
reigned a shorter time. In school, you studied how the planet gods gave
birth to
other gods. You learned about how the heavens
periodically become unstable when the planet-gods battled each other
for
supremacy. Every so often, a Great Year occurred, when planet-god
battles brought
chaos to earth. Cosmos, constants, or orderly laws of nature were not
what you learned in school. In the language of Babylon they did not
even have words for principle, concept or laws of nature. Babylonian
children learned about
catastrophic changes and continuous
changes. According to their traditions, time itself
changes, changing speed continually though the seasons. They even used
different quantities of water to time the "day watches: and the night
watches - that varied through the seasons. All ancient people believed
that their ancestors lived for eons. In fact the Greek word eon (aeon)
originally referred to the length of a human lifetime - according to
Aristotle.
The archaic people believed everything
physical continually changed. They believed that everything was better
in the olden days, the great golden age. They longed for the
past, when their ancestors
had lived immeasurably long lives. In that great long-ago time, people
did not age
like they do now. In that wonderful long-ago time, the earth had
produced abundantly. Then the times of chaos
came and wrecked the earth. Every ancient society had stories of the
battles in the heavens. Even the
Bible mentions such a battle in Job and Isaiah. In the Enuma
Elis, the younger planet
god Marduk (Jupiter) attacks the older planet goddess Tiamut. Marduk
sends in the
Evil Wind (perhaps a moon) to strike Tiamut and shatter her into
pieces. The other gods who marched at her sides fled in terror. But
Marduk captured them with his net. Then he assigned stations for the
gods, the year and the constellations for each of the 12 months.
Notice that it was a result of a great planet slitting war that the
orbits of the planets were
assigned by the young god Marduk - Jupiter. All archaic peoples had
similar myths describing the fearsome battles in the skies. During the
times of chaos, they believed some planets would approach Earth and
grow into
gigantic Titans. As the younger gods fought for supremacy, the older
planets who
formerly reigned, were pushed back into Tartarus - the cold darkness of
the nether gloom.
People who
believe that everything is changing cannot imagine unchanging time or
its cousin - the force of
gravity. Why not? No constants existed in their world view. Everything
changed - even the planet orbits. It was not until the Greek philosophers
invented assumptions to limit what can change that they were able to
invent logical, mathematical, and natural explanations for the cosmos. The
pagan philosophers spent hundreds of years in a long running debate
seeking
for a first principle on which to found a system of natural science.
Aristotle's
Gravity, Motion and Time
Aristotle used the word gravity in his Metaphysics. He said,
“exhibiting gravity compared with the fiery element, and levity by
comparison with the
opposites of fire.” 2 Gravity was the opposite of levity.
The stars and
fire contained levity - not gravity. Aristotle said, “gravity it is a
definite weight.” Gravity was
the internal property of an object that gave it weight. Different
objects had
different amounts of gravity. Aristotle believed that a stone fell
because it naturally
belonged with other stones. If someone threw a stone out over the
water, it would
fall through the air and water to finally come to rest with the other
stones on the bottom
of the stream where it belongs by nature. Water by nature seeks other
water
and so it runs to the sea. Aristotle also believed that heavier
objects, those
containing more gravity, fall faster than lighter objects.
According to Aristotle, a thrown
stone moved because it was being continually pushed along its
path. He believed that behind a moving stone there was a vacuum.
The universe abhorred a vacuum, so air
rushed in at the back of the flying stone and pushed it along its
curved path. Force was
something that was transmitted only by physical contact. There was no
such
thing as “action at a distance”: the idea that far away objects affect
things
without physical contact.
In Aristotle's cosmos, every place was not
the same. Each place contributes to motion. “The typical
locomotions of the elementary natural bodies -- namely fire, earth, and
the like -- show not only
that place is something, but that it exerts a certain influence. Each
is carried to its own place,
if it is not hindered, the one up, the other down . . . . It is not
every chance
direction which is ‘up’, but where fire and what is light are carried,
similarly, too, ‘down’ is not any chance direction but where what has
weight and
what is made of earth are carried - the implication being that these
places do
not differ merely in relative position, but also as possessing distinct
potencies.”
3
Aristotle
defined time differently from modern people. He wrote, “Not only do we
measure the movement by the time, but also the time by the movement,
because they define each other. The time marks the movement, since it
is its number, and the movement the time.” 4 “... regular circular
motion is above all else the measure, because the number of this is the
best
known. Now neither alteration nor increase nor coming into being can be
regular,
but locomotion can be. This also is why time is thought to be the
movement
of the sphere, viz. because the other movements are measured by this,
and time
by this movement.” 5 In Aristotle's system, time is a mere
accident, a numerical accident, as we count the cycles of the heavens
and use that count as a time marker. Although Aristotle
thought the universe always existed, he did not admit that this was an
infinity of time. The infinity is not actual. You cannot add up the
bits of past time to arrive at an infinite time - since the past does
not exist. Time is an accident, the numbering of the heavenly cycles,
not an actuality. Notice that in
Aristotle's system time did not have a private existence. It was
inseparable from the motion of the heavenly bodies.
Claudius
Ptolemy, the Geometrical Astronomer
Almost 500 years after Aristotle, Ptolemy
wrote an astronomy book, now called
the Almagest. Ptolemy was a Greek living in Roman Egypt. Ptolemy
mathematical procedures for calculating the position of the planets
based on circular orbits, offset by equants and
epicycles. He made no attempt to understand the causes of planetary
velocities,
retrograde motions and anomalies. He even used different planetary
models for
calculating a planet’s latitudes than for its longitude. Since the two
methods were
not physically compatible with each other, there was no attempt to
understand
physical reality. In fact, Ptolemy thought that physics was nonsense.
He wrote, "It is an attribute of all
existing things without exception, both mortal and immortal: for those
things which are perceptually changing in their inseparable form, it
(mathematics) changes with them, . . ." "physics (is guesswork) because
of the unstable and unclear nature of matter; hence there is no hope
that philosophers will ever be agreed about them." Mathematics, he
believed, is unshakable, because when matter itself changes,
mathematics changes with it. (Almagest Book One - G. J.Toomer
translation), People who think that matter is changing cannot imagine
laws of gravity. It was enough
that an astronomer could achieve a certain accuracy. Gravity had no
meaning as far as planets were concerned. Planet motions may
have involved the gods, since each planet was identified with a
celestial
divinity.
Galileo, The Experimenter
Fifteen hundred years later, Galileo watched
a chandelier swing like a pendulum
in the wind. He may have timed the swings by feeling his
pulse. He noticed
that
the
swings took the same number of pulses, no mater how far the pendulum
moved.
Galileo later rolled brass spheres down a grooved inclined plank. He
measured the distance they moved relative perhaps to a pendulum,
musical notes or his pulse (accurate clocks did not exist in his days).
He discovered that objects increased their velocity
(accelerated) an equal
amount during every interval. They also moved a
distance that
increases with the square of the elapsed time. He compared the speed of
large
and small objects as they fell, and found them equal. This contradicted
Aristotle's
opinion that objects with more gravity fall faster. Galileo explained
that large
rocks fall at the same speed as small rocks because a large rock is
just a bunch of
small rocks falling together.
Galileo also found that all smooth, even
motions are relative. He claimed that if
you dropped a stone from the mast of a smoothly sailing ship, it would
land at
the base of the mast. In his day, most professors believed the ship
would
sail on and
the stone would splash astern of the ship. Galileo's relativity meant
that the stone
had the same speed as the ship and would continue that same motion
during its
fall. A sailor who watched a flying seagull would only notice the
relative motion
between the
ship and the bird. Galileo noticed that how we see the world around us
depends
on our motion and the motion of the objects we see. Galileo's
relativity of motion
preceded Einstein's relativity by 300 years.
Galileo built a crude telescope that
magnified distant objects about 30 times.
On January 7, 1610 he turned his telescope to Jupiter, then at
opposition. He saw
three stars aligned through Jupiter. He recognized that it was unlikely
that these
were background stars. Subsequent observations revealed that the stars
followed
Jupiter in it's orbit, a miniature solar system of four moons moving
with Jupiter
and revolving around it. He also noticed the phases of Venus with his
telescope. This was not absolute proof that the earth and
the
planets orbited the sun, but it suggested that this was a possibility.
Galileo,
however, did not
imagine a force of gravity that affected the Jovian system or the
rest of the solar system.
Johannes
Kepler: Laws of Planetary motion
without Gravity
Kepler spent ten years trying to find a
mathematically precise solution for the
Martian orbit. He tested his calculations against Tycho Brahe's
observations. Kepler's solution showed that Mars moved in
an ellipse,
with the sun at one foci. A planet speeds up when it is
closest to
the sun according to his second law. His third law, ( T1 /T2)2 = ( R1 / R2)3 showed a
correlations between orbital period (T in years) and radius (R -
distance in
AU).
Kepler did not imagine that gravity attracted
the planets to the sun.
Instead he thought
there was an "anima motrix" - rays like light - coming from the sun
that pushed
the planets. Far planets intersected fewer rays and so moved slower. If
an
invisible string of rays held a planet to the sun, it would have to
move in a circle,
not an ellipse. Kepler proposed that magnetic fields
interacted with the
"anima motrix" to modify circular orbits into ellipses. According to
his idea, Mars would
have a
stronger magnetic field than earth because its orbit is more eccentric.
Today we know that Mars has no present global magnetic field.
Newton:
Inert time allows us to imagine
Gravity.
Newt
on explained that all objects are affected
by gravity. He unified astronomy and mechanics by showing that a
falling object
is reacting to the same force as the orbiting moon. Newton wrote
that,
“Gravity must be caused by an agent acting
constantly according to
certain
laws.” 6 He arrived at these laws of motion because
he took
"time" as the
independent variable. Newton wrote, “Absolute, true and mathematical
time, of
itself, and from its own nature, flows equably without relation to
anything
external.” 7 His absolute space and time successfully
predicted
planet motions and apples falling from trees. Newton's concept of
time,
allowed him to invent the force of gravity.
Newton studied in Western Europe, the
only
place on earth where clocks ticked
with equal sounding seconds. No other people in history
had ever
imagined
that time always moved at the same speed. Their histories mentioned how
the earliest people lived in the great time, the time of Kronos.
Everyone observed that
daylight
was shorter in winter and longer in summer. Ancient people varied the
amount of water in a water clock so that the durations of "time" slowed
down or sped up to fit the varying length of a day. Claudius Ptolemy
sometimes
measured astronomical events in “equal hours.” Equal hours were simply
angles
(time) measured along the equator instead of the ecliptic. He did not
imagine that
equal hours were really equal chunks of time. Why not? The sun and moon
move
at different speeds against the background stars at different times
of the
year. Three thousand years ago every village idiot knew that time ran
slower in the past and that it was
always
speeding up.
Gravity seemed to fit Newton's linear
time. However, Newtons gravity uses circular
reasoning. Gravity supposedly emanates from all mass. Mass was assumed to be an unchanging value,
since matter was not supposed to change its properties as it ages. To
measure an unchanging force, one must assume an unchanging time. To
measure an unchanging time, one must assume that the properties of
matter are not emergent. We cannot in the long term measure the
velocity or the acceleration
without assuming linear time and unchanging mass. As Einstein
pointed out, "The weakness of
the principle of inertia lies
in this, that it involves an argument in a circle: a mass moves
without acceleration if it is sufficiently far from other bodies; we
know that it is sufficiently far from other bodies only by the fact
that it moves without acceleration." Gravity is the force that comes
from mass. It
is also the force that moves it. Wait a minute, you say. We measured
the mass repeatedly and
it always accelerated the same way. How can you say this is circular
reasoning? The assumption that time is unchanging is essential to
reasoning about
gravity and even measuring it.
Yet no clock ever isolated any time or precisely compared a past
second
to a modern one.
Newton's gravity revolutionized science and
philosophy. One man's ideas
introduced a rigorous mechanical view of the universe.
Einstein: Relative Time and
Gravity Fields
At the beginning of the 20th
Century, everyone accepted Newton's gravity.
However, Einstein questioned the assumptions about
absolute
space and time. In Einstein's universe, each observer has his own clock
and his
own ruler, but all observers measure the speed of light equally in
every reference
frame. Einstein extended Galileo's relativity to include relativity of
space
and time.
In 1915, Einstein produced his General
Theory
of Relativity. In Einstein's thinking, gravity is not a force pulling
us
towards some
distant mass but rather the evidence of space-time curvature. All
straight
lines are
bent by the presence of massive objects because space and
time are
intertwined. Time is slowed down by mass because mass warps
space-time, in his theory.
Einstein could
explain the acceleration of
gravity without the use of an attractive
force. Clocks in the vicinity of massive objects slow down. The greater
the mass
the more all clocks slow down. Apples fall
from trees
because clocks run a tiny bit faster on the branch than on the ground.
Space-time is
much harder
to visualize than Newton's gravity. The mathematics of gravity is also
much
simpler than the mathematics of space-time. No one uses complex fields
and
partial derivatives to compute an orbit when the assumption of gravity
is so
much simpler.
Experiments, however, showed that clocks
really
do slow down in the vicinity of massive objects.
Einstein, like Newton, used an operational definition of time. He said,
“Time is
what clocks
measure.” An operational definition is not concerned with the actuality
of time. Einstein just assumed that time is real because he defined it
with clocks.
Einstein's system also depends on assumptions.
No one ever directly
detected any space-time or even isolated any time. If we deny the
existence of time, nothing in the universe would change, therefore we
have a right to claim that time is a synthetic idea. Like Newton's
gravity, space-time involves
perpetual motion without the expenditure of "energy." No one ever
detected bends in the vacuum of space as space-time forces the huge
earth to continually accelerate as it follows the bends in the vacuum.
What is gravity?
Gravity, like
time, is illusive. You think you understand it until you try to explain
it. In
Einstein's thinking, gravity cannot be divorced from time. Every
attempt to isolate any space-time, gravity waves or gravitons has ended
in failure. Can we prove Einstein
is right?
We can prove his theory is more accurate, if we accept the assumptions
and
operational definitions upon which his gravity theory depends.
Newton and Einstein's concepts of gravity result in different
predictions. Einstein's mathematics correlates more accurately with
angular changes in
Mercury's orbit better than Newton's gravity. The bending
of starlight in the vicinity of the Sun is more accurately predicted by
space-time
than by gravity. Clocks carried in aircraft or rockets compared to
identical clocks
that remained “stationary” show the blue shift and red
shift of clocks as Einstein predicted.
How do we know that
gravity does not change throughout history? How do we know that
the
gravitational constant is really a constant?
Does
gravity change? Robert
Dicke.
The 
physicist,
Robert H. Dicke, tried to determine if gravity
changes over time. Gravity is the weakest interaction known.
Dicke used the effect of
the sun on test masses suspended on a quartz fiber in a vacuum chamber.
His experiment was designed to test his Scalar-Tensor theory of
gravitation. In this
theory subatomic mass ratios, electrical charges, and the gravitational
constant
may all vary in time. Dicke ran his apparatus for nine months and
concluded that
there is very little room for the change of electron charge with time.
Dicke's apparatus used a small test mass and a short experiment. It
also relied on the basic assumption of science - the scientific first
principle.
To test the long term stability of gravity - one
should use planet sized objects over long durations. One should not use
clocks in such a test, since clocks and gravity seem to be related. Why
can't we use radar or laser ranging? If relational change exists, it
would affect both clocks and gravity. A test for the stability of
gravity should use optical parallax of large bodies over lengthy
durations, not radar.
What is
gravity?
Is it a real
force, or is it the effect of space-time? The force of gravity is not
proved because mathematical formulas are able to accurately describe
orbits measured circularly by the units invented with the basic
assumption.
The reader may
think, we measure the force of
gravity with instruments, therefore it must
exist in reality. Not necessarily! Pseudo
forces
exist. Scientists measure Coriolis with precision accelerometers. If you
fire a rocket north in the northern hemisphere, Coriolis
appears to veer the rocker to the right. The same rocket fired in the
same
direction in
the southern hemisphere appears to veer to the left. Why? We measure a
Coriolis force because we are turning, moving as the earth spins.
What
about plants that wind around a pole in the opposite direction in
the
northern hemisphere than the southern? Aren't they reacting to the
Coriolis force?
No! The plant is growing on a moving earth. We invent a
Coriolis
force to correct for a “rotating earth based co-ordinate system.” We
are justified
in saying Coriolis is a pseudo force because we can imagine a
co-ordinate system in which the Coriolis force
disappears.
Centrifugal force is also a pseudo force. If
you speed
around a corner in your car, you will feel a force pushing you
towards the outside of the turning circle. Your body is trying to go
straight while the
car is veering
off. The force is not a real force, even though
instruments can
measure it. The pseudo force comes from the acceleration of the
reference
frame that
contains the instruments. A reference frame can be imagined where the
force
vanishes, so it is unlikely to be a fundamental physical force.
Sir James
Jeans: “The theory of relativity shows that
if motions are attributed to forces, these forces will be differently
estimated, as
regards both quantity and quality, by observers who happen to be moving
at
different speeds, and furthermore that all their estimates have an
equal claim to be
considered right. Thus the supposed
forces cannot have a real objective
existence;
they are seen to be mere mental constructs which we make for ourselves
in our
effort to understand the workings of nature.” 8 “When
Newton had found laws of motions of a mechanical system which were true
(apart from the minor refinements of the theory of relativity), he put
science on a
wrong track for two centuries by interpreting them in terms of forces
and absolute
space and time. It was much the same with the supposed force of
gravitation.” 9
Forces
and inertia are not necessary to make sense
out of the
universe. Harvard professor Owen Gingrich derived Kepler's laws
without the
concept of force for his History of Science class. He uses conservation
of
momentum and energy as axioms in his formulas. This demonstrates that
the
concept of force and inertia are not essential to an understanding of
the universe.
They are simply Newton's way of explaining motion.
Assumptions:
the weakest link in the mighty chain
of Knowledge
Our
fundamental assumption affects our ideas about space, time and gravity.
A fundamental assumption is also known as a first principle. The
historical first principle of science is the idea that the properties
of matter
are not emergent. What would our universe look like if all substance is
continually changing itself?
Consider the
strange measurements of the ancient astronomers. They are the
only
measurements that have a long enough base line
to test our ideas of space, time, and gravity. The ancient astronomers
did not have our assumptions. They
made
two types of time
measurements. Interval
measurements are often accurate. The average synodic periods of
the
planets (in days and fractions of days) were known by the Babylonians.
Yet, eclipses, their dates and locations, are
almost always in error when compared to our calculations. The
ancient space measurements,
the angles and distances, radically conflict with our computer models.
Eclipses are extremely precise events. Three solar system
objects precisely align when an
eclipse occurs. Why do their eclipse records disagree with our
computers?
Why did they consistently measure a smaller solar system and larger
planets diameters, as Ptolemy did? How could Ptolemy's errors
cancel so that
his system worked? Why did eminent astronomers like Cassini and
Flamsteed, using independent parallax methods, arrive at
a solar system 7% smaller than we do? What the ancients measure
suggests a continually expanding solar system.
The
simplest test of gravity is a visual
test. Primordial galaxies look like tiny seeds, often seen
in
equally spaced chains. Closer galaxies begin to eject little
globs packed with stars. At closer ranges we see how these stars
continually accelerate outward as they take up more space. In
spiral galaxies we see that the properties of matter change as the
stars and gas continually accelerate outward. We see with
sight that the atomic frequencies, the inertial properties and the
space matter takes up keeps on changing relationally. We see how
billions of spiral
galaxies grew, spread out,
changed into huge growth spirals. What is visible
violates every law of science because it violates the scientific creed
that the properties of matter are fixed - not emerging. This
is
a tiny primordial galay in the Hubble Ultra Deep Field just beginning
to eject a string of equally spaced blue star clumps. NOtice that the
stars are moving in teh opposite direction of all the laws of gravity.
What could cause such a universe? The Bible clearly states that the
creation is in bondage to phthora - internal change. It even states,
in Greek, that gold is presently corrupting itself. Do the properties
of matter change as matter ages? We can see the past with our eyes. We
can see that the properties of matter always changes. Every clock,
atomic and orbital, in the universe
visibly accelerates. The earliest primordial galaxies shine with atoms
that clocked 10% of the frequencies of modern atoms. Why then do we
measure clock-like orbits here in
the solar system? When matter changes its properties relationally, the
atomic clocks, the orbits of the Sun and Moon, the rotations and most
of
the scientific
units of measuring are affected in
parallel.
The most
important assumption you can think about is the modern first
principle. It was invented by Aristotle about 2350 years ago. This idea
was adjusted by the Catholic scholastic to the essence of all substance
is
unchanging. If matter changes AS A
RELATIONSHIP, we
could not measure it locally since it would affect everything, our
units of
measurement and our instruments.
Yet we
can see the evidence with our eyes.
Look at the universe with
sight.
Observe the history of how galaxies
formed and you will get more knowledge about gravity than you will ever
find in a physics book. Look! The visible history of the
universe violates every idea about gravity. This is because it violates
the basic scientific assumption that the properties of matter are not
emerging continually.
1. Mathematical Principles of Natural
Philosophy by Isaac Newton, Great Books of the Western
World Vol 34, page 372.
2. Metaphysics by Aristotle, Library of the Future 3rd
Edition,
1994 World Library Inc.
3. The Copernican Revolution by Thomas S. Kuhn, MJF Books 1957, page 98
4. Physics by Aristotle. Book 4, Chapter 13, Library of the
Future, 1994 World Library Inc.
5. Physics by Aristotle, Book 4, Chapter 14, Library of the Future,
1994 World Library Inc.
6. Mathematical Principles of Natural Philosophy, Isaac Newton, Great
Books of the Western
World 1952 Vol 34, page 8.
7. Mathematical Principles of Natural Philosophy, Isaac Newton, Great
Books of the Western
World, 1952 Vol 34 page 372.
8. Physics and Philosophy by Sir James Jeans, Dover Publications 1981,
page 14.
9. Physics and Philosophy by Sir James Jeans, Dover Publications 1981,
page 190.
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