Two spaceships a and 8 are moving in opposite directions. each measures the speed of the other to be (3js)e. they pass alongside each other and each sets its clocks to zero at that instant. ship a receives a light-message at time t = 320 hours on its clocks that there has been an explosion in 8 that destroyed 8's oxygen generating plants and also left them unable to alter their velocity. the occupants of8 know that they have only enough oxygen to survive 1000 hours (on 8 's clocks). ship a, immediately upon receiving the message, sends rescue ship c to b. the velocity ofc, as measured by a, is (4js)e. assume that 8 sent the message simultaneously with the explosion and that c was dispatched simultaneously with the receipt of the message by a. (a) how long must the crew of8 wait for rescue, according to a, from the time of the explosion to the time that c arrives? (b) how long is this time interval according to the clocks of 8? were they rescued or not? hint: start by drawing a sequence of four pictures in a's rest frame, each picture representing an important event in the story.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

-first use of geothermal energy occurred more than 10,000 years ago in north america by american paleo-indians

-the first industrial use of geothermal energy began near pisa, italy in late 18th century

-in 1904, italian scientist piero ginori conti invented the first geothermal electric power plant in which steam was used to generate the power

-with the above experiment, the first geothermal plant in usa started in 1922 with a capacity of 250 kilowatts

-however, in 1946 first ground-source geothermal heat pump installed at commonwealth building in portland, oregon

-during the 1960’s, pacific gas and electric began operation of first large scale geothermal power plant in san francisco, producing 11 megawatts

-in 1973, when oil crisis began many countries began looking for renewable energy sources and by 1980’s geothermal heat pumps (ghp) started gaining popularity in order to reduce heating and cooling costs

-as effect of climate change started showing results, governments of various countries joined hands to fight against it, for which kyoto protocol was signed in japan in 1997, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it

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