Gravity is weak force of nature
4 minutes
astronomylaws
Intermediate
Gravity is not a force according to General Relativity published in 1915 by Albert Einstein.
Gravity is inherent natural curvature of 4-dimensional spacetime.
Amazingly, Issac Newton, in 1687, published simple formula for calculating gravitational force (equivalent to spacetime curvature) F between two objects.
Measurements show that formula is correct when distance between objects is at least 200 μm.
Newton's Formula, which is very accuate for large distances in space, is as follows.
Fm1m2dG=G⋅d2m1×m2=mass of one object=mass of another object=Distance between two objects=Gravitaional Constant=6.67×10−11m3/(kg⋅s2)
Observations
- G is very small quantity in multiplication. This will reduce F.
- d is squared. d2 is in denominator. That means, if distance increases, then F decreases quite a lot. If you increase d by 100, F will decrease by 10000.
- If you consider two objects of 1 kg mass, 1 m apart, gravitational force will be G Newton, which is extremely small number - very negligible.
- If you consider two humans of 70 kg mass, 1 m apart, gravitational force will be 3.2683×10−7 Newton, which is extremely small - very negligible.
- Even a child with quite weak muscles can jump away from Earth. Looking at size of earth, gravity of earth can be considered weak as even child can jump away from it, albeit momentarily. If earth was a magnet, same child would not be able to pick small iron piece from surface of earth.
- We can easily a pick a book and hold the book away from earth against gravity of earth whose mass is 5.972×1024 kg, and book is near to earth !
- Repulsion (due to electromagnetism) between stable atomic structure in your shoes and floor's stable atomic structure keeps you from falling through floor, even though there's a gravitational attraction between you and Earth.
- Gravity is weakest among four of fundamental forces. Smaller the scale, gravity become even more weak. At a small scale, other forces control environment. For example, electromagnetic force between two electrons is approximately 1036 times stronger than the gravitational force between them.
- If you combine gravitational forces of Sun, Moon and Sagittarius A*, even then that combined force is negligible compared to earth's. See calculations below. Human is essentialy affected by earth's gravity and rest is negligible.
Gravitational force calculations
Here is table showing gravitational force, as calculated with Newton's formula, on human by individual celestial bodies.
Body | Gravitational Force on Human of 70 kg mass | Relative to Earth's gravitational force |
---|
Earth | 690 Newton | 1 |
Moon | 2.6991×10−3 Newton | 0.0000039118 |
Sun | 4.1495×10−1 Newton | 0.00060139 |
Sagittarius A* | 6.2639×10−13 Newton | 0.0000000000000009078 |
It is clear from above table that relative to Earth's gravitational force, other forces are negligible.
Data
mhumanmmoonmearthmsunmSagittarius A*=70kg on average=7.347×1022 kg=5.972×1024 kg=1.989×1030 kg=8.54×1036 kg dhuman-humandhuman-moondhuman-earthdhuman-sundhuman-Sagittarius A*=1m on average=3.565×108 m (nearest)=6.357×106 m (nearest)=1.496×1011m average distance=2.523×1020 m (typical)