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California Gives Green Light to Space Solar Power
Energy beamed down from space is one step closer to reality,now that California has given the green
light to an agreement that would see the Pacific Gas and Electric Company buy 200 megawatts（兆瓦）of power
beamed down from solar-power satellites beginning in 2016.But some major challenges will have to be
overcome if the technology is to be used widely.
A start-up company called Solaren is designing the satellites,which it says will use radio waves to beam
energy down to a receiving station on Earth.
The attraction of collecting solar power in space is the almost uninterrupted sunshine available in geo-
synchronous（与地球同步的）orbit. Earth-based solar cells , by contrast , can only collect sun light during day-
time and when skies are clear.
But space-based solar power must grapple（努力克服）with the high cost per kilogram of launching things in-
to space,says Richard Schwartz of Purdue University in West Lafayette,Indiana."if you're talking about it being
economically viable for power of the Earth,it's a tough go,"he says.
Cal Boerman,Solaren's director of energy services,says the company designed its satellites with a view
to keeping launch costs down."We knew we had to come up with a different,revolutionary design,"he says.
A patent the company has won describes ways to reduce the system's weight,including using inflatable mir-
rors to focus sunlight on solar cells,so a smaller number can collect the same amount of energy.
But using mirrors introduces other challenges,including keeping the solar cells from overheating,says
Schwartz."You have to take care of heat dissipation（散发）because you're now concentrating a lot of energy
in one place,"he says.According to the company's patent,Solaren's solar cells will be connected to radia-
tors to help keep them cool.
Though Boerman says the company believes it can make space-based solar power work,it is not expec-
ting to crowd out other forms of renewable energy.Laws in California and other states require increasing use
of renewable energy in coming years,he points out."To meet those needs,we're going to need all types of
renewable energy sources,"he says.
Space-based solar power will rule out other forms of renewable energy sources.
A.Right
B.Wrong
C.Not mentioned
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Learn about Light
1 .Ancient civilizations were amazed by the existence of light for thousands of years. The Greek philosophers believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision. However,Empedocles and a Dutch scientist named Christian Huygens believed that light was like a wave. According to them,light spread out and travelled like a straight line. This theory was accepted during the 19th century.
2 .In 1905,Albert Einstein published a research paper in which he explained what is re-ferred to as the photoelectric effect. This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us to see things around us.
3 .Things that give off light are known as sources of light. During the day,the primary source of light is the sun. Other sources of light include stars,flames,flashlights,street lamps and glowing gases in glass tube.
4 .When we draw the way light travels we always use straight lines. This is because nor-mally light rays travel in a straight line. However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）, etc.
5 .Physicists have attempted to measure the speed of light since the early times. In 1849, Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel,number of wheel's teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second. In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second. This is about a million times faster than the speed of an airplane.
Stars,flames,flashlights are some examples of______.
A.sources of light
B.the speed of light
C.the path of light
D.a straight line
E.a beam of light
F.a form of energy
