eHow launches Android app: Get the best of eHow on the go.
A switch is a mechanical device that completes or breaks the flow of electricity through a wire or circuit. A limit switch is a special type of electromechanical switch used in applications where an electrical circuit must be "opened" (stopping the flow of electricity) or "closed" (allowing electricity to flow) when a mechanical... more »
Laser pointers have long been used for demonstration purposes and by anyone wanting to highlight something by casting a small bright light upon its surface. Lasers are available in red, orange, green, and blue. The first red laser pointers went on the market in the early 1980s. In 2000, green lasers were introduced to the market.... more »
So it’s come to this. You’re looking in the mirror at your deranged, unkempt appearance, at the mountains of trash and armies of cats that dominate your apartment, and thinking “This is it. I’ve lost my mind.” But wait. Doesn’t this nervous breakdown deserve some appropriate and complementary music? Of course it does. more »
When you consider what subjects you want to photograph, think about the photographic medium and its uses. The camera can be used as a scientific instrument, for objective exploration or to record and document the world. Recording the multitude of subjects in the natural world and their potential and possibilities can bring new... more »
You can use your camera for a number of different purposes. It can be used as an artistic tool as you interpret and comment on what you see through the viewfinder. A camera can be an instrument for recording the human world and the nature that surrounds us. As a scientific tool, the camera looks at the world and records it. In truth,... more »
Observing the stars is a hobby that requires good equipment if you plan on getting the most out of it. Astronomy can be done from home or while... more »
A telescope is a link to the heavens, and depending on how much of an enthusiast you are, you're going to want to have it with you when you... more »
Saturn is best known for the series of rings surrounding it. This ringed planet has so much to offer to students not only of science, but also of... more »
A laser pointer is a small device that emits a beam of light used to pinpoint objects of interest. Laser pointers come in different colors... more »
Jupiter, the largest planet, is also the most interesting to observe in the sky. This huge planet has so much to offer to students not only of... more »
Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earths atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe.
Astronomy is one of the oldest sciences. Astronomers of early civilizations performed methodical observations of the night sky, and astronomical artifacts have been found from much earlier periods. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, and even astrology, but professional astronomy is nowadays often considered to be synonymous with astrophysics.
Since the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring and analyzing data, mainly using basic principles of physics. Theoretical astronomy is oriented towards the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the observational results, and observations being used to confirm theoretical results.
Amateur astronomers have contributed to many important astronomical discoveries, and astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena.
Old or even ancient astronomy is not to be confused with astrology, the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin and a part of their methods (namely, the use of e read more at » http://en.wikipedia.org/wiki/Astronomy
Connect with people who share your interest by joining one of our Groups:
How to Get Fired Gracefully
How to Stop a Shopaholic
How to Drive Defensively During the Holidays
Wonders of the World
Copyright © 1999-2009 eHow, Inc. Use of this web site constitutes acceptance of the eHow Terms of Use and Privacy Policy. en-US Portions of this page are modifications based on work created and shared by Google and used according to terms described in the Creative Commons 3.0 Attribution License.
