Why don't we feel the Sun's gravity pull?

Question

I am a student currently studying for a degree in aerospace engineering
I have asked several teachers and many other people the
following question but have not received any respectable answer:

The Earth is 93 million miles from the sun. Other planets,
and even much denser planets I might add, are much further
yet from the sun. The obviously strong gravitational attraction
of the sun holds all of these planets in orbits around the sun.
If gravity could be simply defined as a force that attracts matter,
and the sun's gravitational pull is sufficient to hold the Earth in orbit,
what keeps it from pulling me off the Earth? In fact, the gravitational
pull of the sun is so weak at this distance that It can't even produce
enough pull to raise a hair on my head. So how can it hold the Earth
and several even denser planets (even further out) in orbit?

So--if the gravitational force of the sun is powerful enough to hold
the Earth in orbit, then how could the Earth's gravitational force be
powerful enough to hold me down, counter-acting the gravitational
force of the sun? Please unconfuse me!

Answer 1

The Earth's gravitation force is powerful enough because the equation for gravity is squared. That squared factor is the difference.

Gravity = Mass times distance squared.

If you double the distance from the object, you lessen it's gravitation force upon you by a factor of 4. If you triple your distance from an object, you lessen it's gravitation force upon you by a factor of 9. If you increase the distance by a factor of 10, the gravitation force is lessened by a factor of 100.


Now think of this when you consider your distance from the Sun compared to your distance from Earth.

The Sun is not 93 million times larger than the earth, and you commonly not more than 93 million microns from Earth, never mind 93 million miles.

So, determine the number of microns in 93 million miles and then square that number. Then create a fraction with the digit 1 about that number in the numerator, while that number is in the denominator. For example (1/999,999,999,999,999,999,999,999).

This is not the actual answer, but it is the comparable force of the graviational pull of the Sun on you compared to the Earth.

That is not going to lift a hair off your head, or pull the free floating atmosphere away from planet Earth.

The Lagrange points ( the points in outer space when the gravitation pull of the Sun equals the graviational pull of the Earth are very close to Earth. Study the Lagrange points for more information. You do not have to travel very far from Earth to find the points in space where the graviational force of the Sun is equal to the graviational force of the Earth.

Then you say, why doesn't the Sun just pull the Earth into it.
The Sun does not pull the Earth into it, because the Earth is in motion around the Sun. If the Earth were to stop rotating around the Sun, the Earth would be pulled into the Sun. Just as if the Space shuttle stopped traveling 18,000 miles per hour around the Earth, it would be pulled back into the earth.

If you do not believe me, study the re-entry speed of SpaceShip One recently.

This is all basic Newtonian gravity. Any good science teacher would know this.

Answer 2

Gravity is based on two aspects. One is the mass of the two objects in question. Second is the distance between those two objects. The distance factor is actually squared, so even though the sun is many times more massive, its distance squared makes the gravitational effect on a person neglible.

However, the sun's gravitational effect does show itself in another phenomenon. It affect the tides that the earth's oceans undergo. If the sun and the moon are lined up with the earth (full or new moons), tides will be measurably higher or lower than when the moon is at an angle (1st and 3rd quarter moons)

Answer 3

Well without the ability to draw formulas here it is harder to explain...but go look at the formula for gravitational force. Here's one:

http://scienceworld.wolfram.com/physics/GravitationalForce.html

The key point is that you'll notice one term is of higher power than the others and it happens to be in the denominator. Put simply, it means this term can grow very rapidly and this term happens to be r, the distance between the two bodies under test.

So when you consider the distance between you and the earth as compared to the sun and the earth you should see why the force of the sun on you is too small for you to perceive.

So why does it have such a big effect on the earth then? Now look at the definitions of the terms in the numerator. Two of the terms are the masses of the bodies involved. Now since the mass of the sun is the same for both test cases, this leaves only your mass (and the earth's) to be considered. Just consider the MAGNITUDE of difference between your mass and the earth's and it becomes apparent why the force exerted on the earth is significant enough to cause it to orbit the sun.

Answer 4

look at the math

the gravity force equations show that the mass of both objects is involved in the attraction and the distance between the objects

very massive objects, very far away from each other, will have fairly powerful gravitic interaction

a large mass like the earth and a small mass like one of us, will have a strong interaction only if they are very close

notice how we don't have to get very far from the earth (space station orbit distance for instance) before the force of earth's gravity on us is negligible

we are much much farther from the sun (which is more massive than earth but still too far away to have a significant effect on a little mass like me)

it may help to review newton's law of universal gravitation:

F=G*(m1*m2)/D^2 (G is the universal Gravitational Constant)

the force is a function of the mass of both objects involved and the distance between them, note that the distance term is squared so that a little change in distance is a much greater reduction in the force

think about it
you can even use the formula above to calculate the force of the earth on your body and the force of the sun on your body and see how the one is your weight, and the other is too tiny to notice

here is a sight with some useful discussion on all this kind of stuff

http://www.krysstal.com/gravity.html

Answer 5

You won't feel the gravity because we are in orbit around the Sun with the Earth and the gravity is balanced by centripetal force. However what you could feel and measure is the Sun's tidal force which is really the difference in the Sun's gravity from the center of the Earth to the surface of the Earth. This force causes half of our tides. The other half is caused by the Moon. More equations would be necessary to explain all this.

Answer 6

the sun IS pulling on you, and moving you, along with the earth, in a nearly circular "fall" around it (at least that's one way of looking at it). The sun is certainly having a strong gravitational effect on you and me and the earth at the same time, anyway.

why don't you feel it? well, the force is pretty much constant, and the acceleration due to gravity is what keeps us going AROUND the sun rather than off in a straight line. so it just feels "normal"

as far as the gravitational force of earth vs sun goes, the earth is just so much nearer that it pulls us back down every time we try to jump off. but just get close enough to the sun (more than half the distance from sun to earth) and you will find the sun's gravity stronger, and be pulled inexorably towards it unless some rescue team interferes to bring you back

Answer 7

That does sound confusing and it is a very good question. I remember studying that in school, but darn if I remember. It has to do with our gravitational pull --here on Earth as you stated. Our planet is special. Think of the moon and others that have no gravity and you just drift off into space --supposedly. Plus the sun is soooooooo far away. Our planet was created with gravity and that is what keeps us from being enough to hold us down. Think of the other planets too--their weather and their unlivable conditions. Maybe that has something to do with why they aren't like Earth.

Answer 8

Sun Gravity

Answer 9

Remember that the Earth is in orbit around the sun. That means that the centrifugal force from the orbit matches the gravitational force from the sun. Technically, we are also in orbit around the sun, so that same balance happens for us. Given that, the next strongest force is that of the earth's gravity. We are *not* in orbit around the earth, so there isn't a balance there.

Answer 10

Do you remember how astronauts in a space craft orbiting around the Earth are weightless? This is because they are in a state of constant free fall. They have no weight because there is nothing of equal and opposite force to press them against a scale.
For the same reason why there is no weight from the Earth on the Astronaut as they orbit the Earth, there is no gravity of the sun affecting your weight here on earth.