Does Leaving Fluorescent Lights On Save Energy?

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Fluorescent lamps, including compact fluorescent lights (CFLs), use about 75 percent less energy than incandescent bulbs and last six to 15 times as long, according to the U.S. Department of Energy (DOE).

But it's widely believed that these popular bulbs use a lot of energy to start up. So, is it more energy-efficient, then, to leave them on when a room is unoccupied?

The "in-rush" of electrical current that occurs when you flick on a fluorescent light lasts 1/120th of a second, and uses about the same amount of electricity as a few seconds of normal light operation. "Turning off fluorescent lights for more than five seconds will save more energy than will be consumed in turning them back on again," the DOE explains.


However, the lifetime of your bulb is affected by the number of times you turn it on and off. The real issue, then, is whether the electricity saved by turning off the lights can offset the cost of changing your fluorescent bulbs, which are more expensive than incandescent bulbs.

In light of these considerations, the DOE proposes a simple rule of thumb: Leave your fluorescent light bulb on if you will be out of the room for 15 minutes or less. Otherwise, turn the light off.

                                                              Source - Livescience

Can Lightning Strikes Us When We're Indoors?

An estimated 24,000 people are killed by lightning strikes around the world each year and about 240,000 are injured as a result of the strike. Lightning strikes can produce severe injuries, and have a mortality rate of between 10% and 30%, with up to 80% of survivors sustaining long-term injuries. These severe injuries are not usually caused by thermal burns, since the current is too brief to greatly heat up tissues instead, nerves and muscles may be directly damaged by the high voltage producing holes in theircell membranes, a process called electroporation.

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In a direct strike, the electrical currents in the flash channel passes directly through the victim. The alternating stroke currents behave more like AC electricity, where the energy travels on the surface of the conductor and at the frequency typical of lightning, "everything becomes a conductor", therefore the energy may pass relatively benignly "around" the body, minimizing injury. Lightning is a very dangerous force that, yes, can even reach you indoors if you're in contact with the telephone or plumbing.

If lightning strikes the phone line outside your house, the strike will travel to every phone on the line -- and potentially to you if you are holding the phone. So, if you are indoors during a lightning storm, stay off the phone. If you must call someone, use a cordless or cell phone -- that way, you're not in contact with any wires that run outdoors.

Stay away from plumbing pipes like your bath tub or shower, as well. Lightning has the ability to strike a house or near a house and impart an electrical charge to the metal pipes used for plumbing. If you're touching those pipes or anything connected to those pipes, that electrical charge has a path to you. This threat is not as great as it used to be, because PVC (polyvinyl chloride) is often used for indoor plumbing these days. If you are not sure what your pipes are made of, wait it out.

And while you're at it, switch off your appliances and electronics before the storm hits. Such devices as your computer, television and air conditioner all provide potential pathways between the lightning and you.

                                                      Source - Howstuffworks, Wikipedia

Beautiful Death Of A Star - Eskimo Nebula

Image courtesy N. Ruiz et al, IAA-CSIC/CXC/STScI/NASA

Discovered in 1787 by astronomer William Herschel, The Eskimo Nebula, also known as the Clownface Nebula, is a double-shell planetary nebula. The nebula is located more than 2,870 light-years in the constellation of Gemini. 

The Eskimo Nebula resembles a person's head surrounded by a parka hood. It is surrounded by gas that composed the outer layers of a Sun-like star. The colorful "parka" or outer shell of gas and dust is expanding at speeds of 31,000 miles (50,000 kilometres  an hour, and is lit up by the radiation blasting out from the remains of a dying red giant at the center of the nebula.

The part of the gas cloud glowing at a million degrees near the center appears pink to Chandra's x-ray eye, while Hubble's vision highlights intricate streamers of gas in the outer shell in red, green, and blue.

Source National Geographic, Nasa.gov, Wikipedia