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শিক্ষাবর্ষঃ ২০০৮-২০০৯ || বাংলাদেশ প্রকৌশল ও প্রযুক্তি বিশ্ববিদ্যালয় (বুয়েট) || 2008
English
English
in a fix
fan the flames
effective
at six and seven
keep the ball rolling
fan the flames
tighten one's belt
jump on the bandwagon
snake in the grass
tall story
tower of strength
villain of the piece
to carry coal to Newcastle
up to the elbow
nobody's fool
a heart to hear
We believe that the earth is about 4.6 billion years old. At present, we are forced to look to other bodies in the solar system for hints as to what the early history of the earth was like. Studies of our moon, Mercury, Mars and the large satellites of Jupiter and Saturn have provided ample evidence that all these large celestial bodies were bombarded by smaller objects in a wide variety of sizes shortly after the larger bodies have formed. This same bombardment must have affected the earth as well. The lunar record indicates that the rate of impacts decreased to its present low level of about 4 billion years ago. On earth, subsequent erosion and crustal motions have obliterated the craters that must have formed during this epoch, Scientists estimate the earth's age by measuring the ratios of various radioactive elements in rocks. The oldest earth rocks tested thus far are about 31/3 billion years old. But no one knows whether these are the oldest rocks on earth. Tests on rocks from the moon and on meteorites show that these are about 4.6 billion years old. Scientists believe that this is the true age of the solar system and probably the true age of the earth.
Earth's age
Studying the records of moon
Examining the rocks
The crustal motion
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