The orbital motions of planets and comets, as depicted here, are governed by the laws of mechanics.
Click on image for full size
Windows to the Universe original artwork by Randy Russell.
Mechanics is the term used to refer to one of the main branches of the science
of physics. Mechanics deals with the motion of and the forces that act upon
We need precise terminology to describe the way objects move. Kinematics is
the sub-field within mechanics that supplies this lingo in the form of concepts
like position, velocity, acceleration, and rotation rates. Forces and the motions
they produce, as specified by Newton's Laws of Motion, are within the realm
of the closely related discipline of kinetics.
The abstract concept of energy also plays an important role in the study of
mechanics. We speak of potential energy in situations such as a ball at rest
at the top of a hill, and kinetic energy when that ball is rapidly rolling
along after descending the hill. Conversion of energy from one form to another
is constrained by the Law of Energy Conservation.
The mechanics of individual, solid objects are the simplest to understand,
but mechanics also deals with the more complex motions of loosely linked collections
of particles. Fluid mechanics describes the motions and forces associated with
traditional liquids, such as water. It also delves into the behaviors of other
including gases such as air and the plasma that makes up the atmosphere of
Complex behaviors also arise when objects start spinning or moving along curved
paths instead of along straight lines. Earth orbits the Sun along a nearly
circular path while spinning upon its axis once each day. Rapidly rotating
stabilize satellites, while electrons and protons spiral downward along Earth's
magnetic field lines to create auroras.
Shop Windows to the Universe Science Store!
Our online store
on science education, classroom activities in The Earth Scientist
specimens, and educational games
You might also be interested in:
How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable....more
Isaac Newton was an English scientist and mathematician who lived between 1642-1727. He had one of the most brilliant minds the world has ever known. Legend has it that seeing an apple fall gave Newton...more
The short answer is that a fluid is a gas, a liquid or a plasma. More technically, a fluid is something which can't support a shear stress. This sounds more complicated than it is. A shear stress is when...more
Liquid is one of the four common states of matter. The three others are gas, solid, and plasma. There are also some other exotic states of matter that have been discovered in recent years. A liquid does...more
Gas is one of the four common states of matter. The three others are liquid, solid, and plasma. There are also some other exotic states of matter that have been discovered in recent years. The air in Earth's...more
Earth has a magnetic field. If you pretended that Earth had a gigantic bar magnet inside of it (it doesn't really, of course), you would have a pretty good idea about the approximate shape of Earth's magnetic...more
The polar aurora is formed when Field-Aligned currents (FAC's) short-circuit through the atmosphere. Particles from the Sun traveling along magnetic field lines collide with particles in the atmosphere....more
When you inflate a balloon or a tire, you are increasing the pressure on the inside of the object in order to "blow it up". Pressure is a scientific concept that applies to gases and liquids. Pressure...more