SfC Home > Physical Science > Physics >
Explanation of Gravitation - Succeed in Understanding Physics. Also refer to Law of Universal Gravitation, fundamental forces, Isaac Newton, matter, attraction, force, mass, gravity, Einstein, relativity, dark matter, physical science, Ron Kurtus, School for Champions. Copyright © Restrictions
Gravitation
by Ron Kurtus (revised 26 September 2009)
Gravitation is the force that attracts objects toward each other. It is one of several fundamental forces of matter. Its strength is weak compared to the other forces, but its range is far-reaching.
The concept of that matter attracts other objects was formulated in 1687 by Isaac Newton as the Law of Universal Gravitation. This force of attraction is defined in the theory’s Universal Gravitation Equation, which states that the gravitational force is proportional to the masses of the two objects and inversely proportional to the square of distance between them. Gravity is considered a special case of gravitation for objects near the Earth.
This theory has been superseded by newer theories of gravitation, such as Einstein’s General Theory of Relativity and theories concerning Quantum Mechanics and dark matter.
Questions you may have include:
- What role does gravitation play in the fundamental forces?
- What is the Law of Universal Gravitation?
- What are some newer theories?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
Useful tools: Metric-English Conversion | Scientific Calculator.
Gravitation is a fundamental force
Gravitation is one of four fundamental forces that affect the way that objects or particles of matter interact with each other at a distance. The fundamental forces are, in order of strength: strong nuclear, electromagnetic, weak nuclear and gravitational.
Comparing the forces gives a good perspective on the role of gravitation.
Strong nuclear force
The strong nuclear force is the attraction that holds the nucleus of an atom together, overcoming the repulsive electrical force of the protons within the nucleus.
The relative strength of the strong nuclear force is designated as 1. The range of this force is small, approximately the diameter of a medium-sized nucleus (10−15 m), after which it becomes too small to have an effect.
Electromagnetic force
Electromagnetic force consists of a combination of electric and magnetic forces.
Electric force
Electrical charges can be positive (+) or negative (−), where like charges repel and unlike charges attract each other.
Magnetic force
Moving and spinning electrical charges create a magnetic field, depending on their direction or motion. Magnetic poles can be north (or north-seeking) and south (or south-seeking). Like poles repel and unlike poles attract.
Strength and range
The relative strength of the electromagnetic force is 1/137 of the strong nuclear force. The range of the electromagnetic force is unlimited, but its strength drops off as the square of the distance between the charged particles.
Weak nuclear force
The weak force in a nucleus allows deuterium fusion to take place, which is necessary for our Sun and the stars to burn. The strength of the weak force is 10−6 that of the strong force, and its range is only 10−18 m, which is about 0.1% of the diameter of a proton.
Gravitation
Gravitation is the force of attraction between particles or objects of matter. It is the weakest of the fundamental forces, with a gravitational strength of only 6*10−39 of the strength of the strong nuclear force at a sub-nuclear distance.
Note: 10−39 equals 1/1039, where 1039 is 1 followed by 39 zeros. It is a very small number.
However, at distances beyond the sub-nuclear range, the strength of gravitation is much larger than the nuclear forces, which are essentially zero at those distances.
Since gravitation primarily concerns very large quantities of matter, such as planets and stars, its effect overshadows that of the stronger electromagnetic force, which operates on a much smaller level and at shorter distances.
Law of Universal Gravitation
The Law of Universal Gravitation (also called the Theory of Universal Gravitation) states that all objects are attracted toward other objects, due to a force called gravitation. This includes everything from subatomic particles to massive stars and planets.
Universal Gravitation Equation
Newton formulated the Universal Gravitation Equation, which allows the calculation of the force between two objects. The equation is:
F = GMm/R2
(See Universal Gravitation Equation for more information on the subject.)
Confusion concerning gravity
There is sometimes confusion between the expressions gravity and gravitation.
Gravity is defined as gravitation on or near the surface of the Earth. It is a special application of gravitation. The expression is also used for other objects in space, such as gravity of the Moon, gravity of the Sun or of the other planets, provided the planet is named.
(See Force of Gravity for more information on the subject.)
Gravitation is universal, while gravity is specific to the object. It is the force near the surface.
Further development
Although the Universal Gravitation Equation can explain many phenomena, some astronomical anomalies required a better solution.
General Theory of Relativity
It wasn't until the early 1900s that Albert Einstein gave another interpretation of the gravitation in his General Theory of Relativity. He stated that gravitation was the result of the curvature of space around matter and not due to some force.
This theory says that a "straight line" in space curves or bends toward matter. An object traveling along this line—even a ray of light—will then seem to be attracted toward the matter. The Universal Gravity Equation is just an approximation of a more complex relativistic equation.
One proof of this idea was first seen when position of stars seemed to shift as their light passed near the Sun.
Quantum Mechanics
Recently there have been new theories that the force of gravity is caused by graviton particles or by gravity waves. These theories satisfy rules of Quantum Mechanics that Einstein's concepts didn't.
Dark matter
There is also a theory that there exists some sort of "dark matter" that repels instead of attracts, resulting in anti-gravitation.
Summary
Gravitation is one of the fundamental forces of matter, being much weaker than the strong nuclear force but affecting objects at much greater distances.
Isaac Newton formulated the Law of Universal Gravitation, stating that all matter attracts other matter to it. This force of attraction is defined in the theory’s Universal Gravitation Equation. Gravity is a special case of gravitation for objects near the Earth.
Einstein’s General Theory of Relativity and new theories concerning Quantum Mechanics and dark matter bring other
explanations for gravitation.
See the Side Menu for more Gravitation and Gravity topics
Enthusiasm is infectious
Resources
The following resources provide information on this subject:
Websites
Acceleration due to Gravity Calculations - from Western Washington University
Gravitation and Gravity Resources
Books
Top-rated
books on Simple Gravity Science
Top-rated
books on Advanced Gravity Physics
Mini-quiz to check your understanding
If you got all three correct, you are on your way to becoming a Champion in Physics. If you had problems, you had better look over the material again.
What do you think?
Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. We will try to get back to you as soon as possible.
Share link
Feel free to establish a link from your website to pages in this site.
Or use our form to send this link to yourself or a friend.
Students and researchers
The Web address of this page is:
www.school-for-champions.com/science/gravitation.htm
Please include it as a reference in your report, document, or thesis.
Where are you now?
Gravitation