There are several ways that Earth’s gravity influences us. Besides keeping
us anchored to the ground, it keeps the continents stable in place. More
importantly, it influences the path that most objects, such as solar
photons and space debris, take as they pass through the Earth’s
atmosphere.
While it’s easy to grasp what gravity does, the force of inertia, on the
other hand, is a little more complex. We often think about inertia when
someone tells us that they have a bad feeling about a forthcoming
adventure or risky undertaking. When the going gets tough, we sometimes
feel that our muscles have become so resistant to the pull of gravity that
we could defy it.
Inertia is the resistance that an object possesses to change in motion.
Inertial forces are always present, even when we are not conscious of
them. When someone pushes on a door, they impart inertia to the door
because they are forcing it to move. When a ball is dropped, it will
inertially roll until it reaches the ground. Once it hits the ground,
gravity takes over and the ball falls to the bottom.
Why Do We Care About Inertia?
Inertia is interesting because it is sometimes cited as the reason why
planets and moons move in their respective orbits. The force of inertia
simply attempts to keep an object in its current state of motion. When it
comes to our solar system, the planets and moons are generally believed
to have formed where they are due to gravity alone. This is because the
planets and moons are not big enough to counter the force of inertia
present in the system (i.e. the sun). As a result, objects in the solar
system travel in roughly the same direction that they are pushed,
regardless of their initial velocity.
The planets and moons in our solar system are held in their orbits by
means of gravitational forces. These forces are strongest between the
Earth and the sun, and somewhat weaker between the planets and moons
themselves. Inertia is the reason why Earth orbits the sun and why the
planets and moons do not collide with each other. If inertia was not a
factor, then the planets and moons would be flying everywhere and there
would be nothing but a cloud of dust surrounding the sun. As the
collision of dust clouds would result in darkness, we would no longer be
able to see the beautiful sunrises and sunsets described in nature
writings.
How Does Inertia Work?
Inertia is a result of a body’s mass. The more massive the body, the
greater the inertia. The most massive object in our solar system is the
sun, with mass almost equal to that of all the planets put together. The
earth also has considerable mass, which gives it a lot of inertia. This is
why objects with mass like cars, trucks, or industrial equipment travel
slowly and smoothly. They don’t change directions easily because they
inherit the inertia of the earth (or sun).
The reason why objects with mass like cars, trucks, or heavy machinery
accelerate so quickly when they are pushed is because they are not
inherently stable. They require more energy to maintain their speed than
they have available, and this energy comes from the force applied to them.
When someone tries to push an automobile, it will not move easily at first
but will keep on rolling until it reaches a speed at which it can remain
stable. This behavior results from the fact that automobiles are massive
and have considerable inertia. Most objects with mass are inherently
unstable.
What About Shooting Star Trails?
Sometimes when we look up at the sky, we see trails of light moving
across the night’s dark canvas. These are shooting star trails, the
result of a solar system’s worth of meteors burning up in the Earth’s
atmosphere. If you ever wondered where all the meteors come from, these
are the remnants of a solar system in formation as it passed through
space.
You don’t need to wait for a meteor shower to see the trails. What you
want to do is look up on a clear night and watch as the moonlight
illuminates the streaks of light as the planets, moons, and sun come
together in a spectacular show. In some instances, the planets and moon
can even be seen as overlapping circles. This is especially spectacular
when the moon is at its full phase and is reflected in the water
surrounding the earth. If you ever wondered where the phrase ‘look up at
the stars’ came from, this is where it originated. As the planets and
moons revolve around the sun, they sometimes pass in front of the sun
and this results in sunlight being blocked out as the planets and moons
pass in front of the star. When this occurs, we are sometimes presented
with the illusion that the star is moving faster than the rest of the
planets and moons. For some reason, this results in the star seeming
like it is ‘shooting’ towards the earth. This is the same phenomenon
that gives rise to the shooting star trails we mentioned previously. In
this case, the energy of the planets and moons is spent as they
accelerate, and the result is magnificent.
Types Of Inertia
There are four types of inertia, and it is important to know the
difference between them. The first one is gravitational. This is the
inertia that a body possesses due to the gravitational force acting upon
it. When someone pushes on a door, or when an automobile collides with a
building, gravitational inertia is at work. The second type of inertia is
frictional. Frictional inertia is that which results from two objects in
contact with each other. When your sneakers make contact with the carpet
in front of you, you feel the frictional effect as a stinging sensation.
Frictional inertia is also responsible for the stickiness of tar. The
third type of inertia is thermal. This is the result of a body’s heat when
combined with its mass. The heat from our bodies can make us move
initiastically, causing us to jump when suddenly startled or scared.
Finally, there is magnetic. When a magnet is placed in a magnetic field,
it becomes agitated and will move around until it finds a place where the
field is not as strong. When this happens, it becomes inertial and will
remain in this state until it finds another area of weak magnetic
fields.
Gravitational Inertia
Gravitational inertia is the result of an object’s mass and the
gravitational force acting upon it. This type of inertia will always be
present to some degree, as even empty space is filled with gravitational
pull. When we consider the pull of the moon on the Earth, we see how the
inertia of the Earth results from its mass and the gravitational force
acting upon it. The inertia of the Earth is responsible for giving the
Earth’s rotation on its axis. For all intents and purposes, the moon does
not change the speed at which the Earth rotates, it just makes the Earth
rotate faster. This is due to the fact that the moon is not massive
enough to generate its own gravitational field. Once the moon has
settled down into a circular orbit around the Earth, it does not impart a
great deal more motion to the Earth.
In our solar system, the sun has the strongest gravitational field, and
this is why it is held in place by the planets. When the planets orbit the
sun, they tend to move in the same direction as the sun’s rays. The
strength of the sun’s gravity is proportional to the mass of the planet it
attracts. The Earth has a very strong gravitational field, which is
responsible for making the surface of the Earth appear flat. This is
because massive objects, like planets, attract each other. When two
massive objects come together, they will experience an intense gravitational
force that tends to keep them together. This is due to the fact that the
gravitational force is directly proportional to the product of the two
masses.