# 3.0 And Then There's Gravity 15

Last modified by MichaelBartmess on 2017/04/14 06:06
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What is gravity?  Why is it so easy for humans living on this massive body to ignore gravity?  After all the Earth is spinning and we don't feel it.  We don;t have to think about gravity to walk or run. Balance in this gravitational field is easy enough for young infants to absorb.

Gravity is a second only to Love as a music theme:  GRAVITY

Satellites circle overhead and it just seems natural, right?  It is more magic than science that explains how that satellite sending you music or television signals is kept in orbit.   Most of us don't even think about the [Could not locate page MichaelBartmess.Force of Earth's Gravity] it in our daily dealings with driving, with flying, with shooting a basketball.  But it's there all the time making sure the laws are obeyed.

NOTE: many vCalc equations are embedded throughout vCalc descriptive pages like this page.  Even though they may not stand out in the text, if you hover over the name of an equation it will likely be linked to an actual, pop-up executable equation. For example: [Could not locate page MichaelBartmess.Force of Earth's Gravity]

Contents

# Force of Gravity

Gravity is a most common phenomenon in our every day life.  As you sit or stand you are pressed or held against the Earth with the force that Newton defined to be the Force of Gravity Click on this link to see the fundamental definition of the universal law of gravitational force first enunciated by Sir Isaac Newton: Force of Gravity

Gravity is a naturally occurring phenomena that causes all matter, all things with mass to be attracted to all all other matter.  The force of gravity is defined by any two masses, the inverse square of the distance between the masses, and a constant -- the universal gravitational constant -- 6.67384E-11 N·m²/kg².

Gravity is the weakest of the forces we know as fundamental forces of the universe.  But masses the size of suns and galaxies and black holes cause the force to be readily observable and well understood.  In our close relationship with the Earth, we come to understand [Could not locate page MichaelBartmess.Force of Earth's Gravity] from the time we are infants.  Our first balancing steps overcome the encompassing effects of gravity.

Most grade school students understand that the standard acceleration due to gravity, estimated at sea level on the Earth, is 9.80665 m/s². This is the acceleration of a mass caused by Earth's gravity at the surface of the Earth.  It is this same acceleration due to gravity that gives a mass its weight on Earth. Weight is just the measure of the force exerted on a mass by the gravitational attraction of the Earth's mass.

# Attraction Between All Objects

Gravity, as stated in Section 1.0 above, is a force of attraction between ALL objects with mass.  This means ALL objects in the known universe are attracting each other, all at the same time. The vast number of massive objects in the universe, along with the extremely large distances between large massive bodies, causes the relative effect of distant stars and planets and galaxies to have very minute effects on things we see around us.  That includes the Earth itself, the Sun and the planets in our universe.

The force of gravity between the Sun and the Earth is the force that holds the Earth in its orbit around the Sun.  The force of gravity between the Earth and you or I is the force that holds us in place in our chair in front of the computer.

All masses attract each other.  So, the force of gravity holds all the larger bodies we know in the solar system in their orbits about the Sun.  Gravity holds Mercury in its orbit, Venus in its orbit, the Earth in its orbit, Mars in its orbit, Jupiter in its orbit, Saturn in its orbit, Neptune in its orbit, even the ice ball that is Pluto in its orbit.

Since all these massive bodies in our solar system have mutual gravitational attraction, in addition to the attraction of the Sun which predominates, the orbits are affected by "perturbations" caused by each planet.   In fact, if we were able to calculate the minute affects of the other closest suns, we would see they have minute effects on the orbits of the planets in our solar system -- but extremely small effects due to the distance between.

The closest stars to our solar system are three stars bound by gravity in the Alpha Centari system and these are 4.37 light years fron the Earth. Note our Earth is only 93 million miles from the sun (1.496E8 km).

Alpha Centari-A has about 1.1 solar masses, to see its equivalent mass, click here >> Mass of Alpha Cenari A.

So, the force of attraction between our sun and the Alpha Centari-A sun is estimated by the default inputs to the vCalc equation to be approximately:

Force of Gravity on Our Sun

# Gravity As a Curvature of Spacetime

Atomic Bonding Song

## Equations

• vLength
• Astro Travel Time