People typically wash their hands seven times a day in the United States, but they do it at a far higher temperature than is necessary to kill germs, a new study says. The energy waste is equivalent to the fuel use of a small country.

Amanda R. Carrico, a research assistant professor at the Vanderbilt Institute for Energy and Environment in Tennessee, told National Geographic that hand washing is often “a case where people act in ways that they think are in their best interest, but they in fact have inaccurate beliefs or outdated perceptions.”

Carrico said, “It’s certainly true that heat kills bacteria, but if you were going to use hot water to kill them it would have to be a way too hot for you to tolerate.”

Carrico said that after a review of the scientific literature, her team found “no evidence that using hot water that a person could stand would have any benefit in killing bacteria.” Even water as cold as 40°F (4.4°C) appeared to reduce bacteria as well as hotter water, if hands were scrubbed, rinsed(冲洗)and dried properly.

Using hot water to wash hands is therefore unnecessary, as well as wasteful, Carrico said, particularly when it comes to the environment. According to her research, people use warm or hot water 64 percent of the time when they wash their hands. Using that number, Carrico’s team calculated a significant impact on the planet.

“Although the choice of water temperature during a single hand wash may appear unimportant, when multiplied by the nearly 800 billion hand washes performed by Americans each year, this practice results in more than 6 million metric tons of CO2 equivalent emissions annually,” she said.

The researchers published their results in the July 2013 issue of International Journal of Consumer Studies. They recommended washing with water that is at a “comfortable” temperature, which they noted may be warmer in cold months and cooler in hot ones.

Forget drinking countless glasses of water or getting your beauty sleep．The secret of looking young is simply to stay out of the sun．

A study of hundreds of women has revealed that those who avoided the sun’s rays looked up to 20 years younger than they actually are. However, other supposed rules for a youthful complexion, from drinking lots of water to sleeping well and exercising regularly, failed to hold back the hands of time.

Only keeping out of the sun, and wearing sunscreen when this wasn’t possible, made a difference, the American Academy of Dermatology’s annual conference will hear today.

The finding comes from a study of 231 women of all ages who were quizzed about their lives, including whether they were sun-loves. When researchers from Massachusetts General Hospital in the US guessed how old the women were, they found those who took care in the sun tended to have aged more slowly.

Four lucky women had so few wrinkles and age spots and such a glowing complexion，that they appeared to be twenty years younger than they really were．

Researcher Dr．Alexa Kimball said the popular belief that we drink lots of water to stay healthy is false and the body is “pretty good” at judging how much we need．Previous research by the British Nutrition Foundation reached a similar conclusion．

It isn’t clear why the women who slept well didn’t have younger-looking skin．But it may be that the question they were asked was too narrow and didn’t consider their long-term sleep patterns．

Check your change and empty your money box! You may be the owner of coins that contain mistakes or imperfections that could make them worth thousands of dollars. Collectors go crazy for tiny minting errors (铸造错误) that appear when they are made at the Royal Australian Mint in Canberra. The errors are mostly so fine that they go unnoticed to the untrained eye.

A 5 cent piece from 2007 that incorrectly had the Queen’s head on both sides of the coin was sold for thousands of dollars. Town Hall Coins and Collectables expert Matthew Thompson said that mistake was named a “double-obverse”. Obverse is what coin experts call the side with the Queen’s head on it.

“The last one I sold was for $3,500,” he said. “That one was in top-end condition and so was worth thousands. One in really poor condition, you’d still be looking at a few hundred for.”

Mr. Thompson said a simple check through coins could earn eagle-eyed people a lot of money. “People don’t expect institutions like the mint to make mistakes,” he said. “But from time to time things can go wrong. If you see a mistake on a coin, if you have something interesting or out of place, then other people are likely to find it interesting, too.”

Mr. Thompson said a $1 piece in 2000 was accidentally stamped with the head from a 10 cent piece. “The head side is a little smaller, so it gives a double-ring effect,” he said. “If you see two rings on your dollar coin, it could be worth a few hundred or up to $4,000 in really good condition.”

A more common mistake is a kangaroo on the $1 piece appearing to have rabbit ears. These coins can be worth about $30. Another coin that has a slightly curly “2” on the 20 cent piece from 1966 can be sold for up to $2,000.