Griffith Observatory (天文台) is a national leader in public astronomy，and one of the most popular attractions in Los Angeles. It is located on the southern slope (山坡) of Mount Hollywood in Griffith Park at 1,134 feet above sea level.

    Visitors may drive to the observatory and park in its parking lot or on nearby roads. No reservation (预订) is required to visit. Parking is limited，and the busiest time is weekends. Buses，taxis，and car pools are welcome. LADOT provides weekend public bus service from the Sunset/Vermont Metro Red Line Station.

    Griffith Observatory is open six days a week. Admission and parking are free.

    Hours of Operation

    Tuesday—Friday    12 noon—10 p．m.

    Saturday—Sunday      10 a．m.—10 p．m.

    Monday  Closed

    Thanksgiving Day and Christmas Day Closed

    Samuel Oschin Planetarium

    The Samuel Oschin Planetarium theater offers 8 to 10 live，half-hour presentations each day. There are usually four different shows from which to choose.

    Shows are presented every 60 to 90 minutes. Check the website，information desks，or the box office for each day's show time. Being seated late is not permitted.

    Samuel Oschin Planetarium tickets must be purchased at the observatory and are only available on the day of the show. The ticket prices for shows are：

    Adults (13—59 years old)      $7.00

    Children (5—12 years old)         $3.00

    Seniors (60 years and older)        $5.00

    Students                        $5.00

    Children under 5 years old will be admitted only to the first show each day.

    Hearing assist devices are available on request.

    Public Telescopes

    Free public telescopes are available each evening the observatory is open and skies are clear.The Zeiss telescope on the roof is generally open by 7 p．m.All observing must be completed by 9：45 p．m.

    In an unmanned supermarket, a customer waits to pay. With the use of advanced digital payment technology, including biological recognition and in-depth learning, the man leaves in a minute. There's no cashier in the store. At a large university, students use a hand-scanning machine that authorizes their entry into the gym. Those people are using "smart machines" which identify people by their physical characteristics. These new devices use fingers, hands, faces, eyes and voices. Some machines may even use smells. This new technology, called biometrics, gets information from parts of the body.

    In the past, biometric machines were used mainly in government agencies or in prisons. But now that the cost of the technology is lower, these machines are starting to be used everywhere, from border services to schools.

    Some people, however, are concerned that these machines will mean the destruction of personal privacy. They worry that the machines will get personal information about them, know it seems like these machines are invading our privacy, but actually, biometric machines help to protect it," says Jay Tarkett, who works at a company that develops the machines, "They can be used instead of passwords on a computer, for example. They can also identify criminals at airports. So, really, they help to promote public safety, and all the information stored is kept confidential by the machine itself."

    Some people don't like the idea of using fingerprints because they associate them with criminals, and feel like they are being accused of something, In addition, they don't work for some people, such as bricklayers, who wear down their fingerprints. Yet, face recognition does work well because the subject doesn't really have to do anything, To cash a check at a bank, for example, the customer has to do nothing more than look at a machine similar to an automatic teller. If the face matches the picture kept on file, the customer gets the money with no problems, The need to carry identification with you from place to place, then, would all but cease. It has been found that the hand scan works well ill the college gym. Before this machine was used, students at the college entered the gym using cards similar to credit cards. The problem was that students often lost or forgot their cards. With the hand-scanning machine, however, the problem was solved right away.

    But the machines are still new, and there can be problems. For example, voice recognition works on the phone, but it is not precise, and can be tricked. Another constraint(限制)we notice；, with machines that use face recognition in particular, is that they can be fooled if people color their hair or gain a lot of weight. However, this particular problem may be solved by a new type of technology that scans a person's iris, the colored part of the eye. It can even identify the person from a few feet away, recognizing a customer as he or she approaches the ATM.

    While staring out of the window during a flight, not everyone will think carefully about the question why airplanes have rounded windows rather than square ones.

    Over the years, aerospace engineering has made huge steps in airplane technology, meaning planes can carry more passengers and go faster. The planes have also changed shape to increase safety—including the windows. As commercial air travel took off in the mid－20th century, airline companies began to fly at higher altitudes to lower their cost—the air density(密度) is lower up there, creating less drag(阻力)for airplanes. However, higher altitudes came with problems, like the fact human beings can't really survive at 30，000 feet. To make that possible, the cabin was changed to a cylindrical(圆柱体) shape to support the pressure inside. But at first, plane builders left in the standard square windows and this expansion meant disaster. The de Havilland Comet came into fashion in the 1950s. With a closed cabin, it was able to go higher and faster than other aircraft.

    However, where there's a corner, there's a weak spot. Windows, having four corners, have four potential weak spots, making them likely to crash under stress—such as air pressure. By curving the window, the stress that would eventually break the window corner is distributed and the chance of it breaking is reduced. Rounded shapes are also stronger and resist deformation(变形), and can thus survive the extreme differences in pressure between the inside and outside of the aircraft.

    Fortunately, designers figured out the lack of design pretty quick. Now we have nice, rounded airplane windows that can resist the pressure of traveling altitude. It gives being able to gaze out of your window to the world from 35，000 feet a whole new outlook, doesn't it?

    Many of us have reached in our pockets, feeling a vibration (振动), wrongly believing our mobile phones have just rung. The phenomenon even has a name: phantom (幻觉的) vibration syndrome—and found it is surprisingly common.

    Now scientists believe that we are so alert (警觉) for phone calls and messages we are misinterpreting slight muscle spasms (痉挛)as proof of a call. Robert Rosenberger, an assistant professor at the Georgia Tech Institute of Technology has studied the delusional calls. He said sufferers describe a vague tingling feeling which they think is their mobile phone indicating it has received a text message or call while on 'silent'. But when the device is retrieved, there was no one on the other end.

    Dr. Rosenberger said he found so many people say, "This happens to me, but I thought I was the only one. I thought I was odd." It seems that the syndrome particularly affects people at the beck and call of mobile phones or pagers. A 2010 study by Michael Rothberg and colleagues found that nearly 70 per cent of doctors at a hospital in Massachusetts suffered phantom vibrations. A more recent study of US college students found the figure was as high as 90 per cent.

    While the odd feeling is widespread, it does not seem to be considered a grave problem. Dr. Rosenberger said: "It's not actually a syndrome in a technical sense. That's just the name that's got stuck to it." He added," Only 2 per cent of people consider it a problem."

    While this phenomenon is widespread, the scientific community has not yet invested much effort in getting to the bottom of why we suffer phantom calls.

    Dr. Rosenberger said: "People are guessing it has something to do with nervous energy. The cognitive(认知的)scientists are talking about brain chemistry, cognitive pathways changing. But it's not like they have brain scans to go on." He said: "We have a phone call in our pocket all the time and it becomes sort of an extension of ourselves. We have this sort of readiness to experience a call. We feel something and we think, OK, that could be a call."

Many scientists today are convinced that life exists elsewhere in the universe—life probably much like that on our own planet. They reason in the following way.

    As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.

    Life requires the right amount and kind of atmosphere. This eliminates(除去) all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.

    Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.

    Finally, life could evolve(进化) only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.

    If we suppose that every star in the universe has a family of planets, then how many planets might support life? First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.

    This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.