Astronomy 101 -- Worksheet #10LIFE ON EARTH and LIFE IN THE UNIVERSE1) Life has been present on the Earth for at least ________________ years.2) Ureyand Miller (1953) showed that electrical discharges applied to a primitive atmosphere can lead tothe formation of ___________________ in only a fewdays. From this, theyconcluded the the primitiveoceans on the Earth contained ______________________________.3) Life could presumable develop anywhere in the galaxy given____________________.4) The number of civilizations in the MilkyWay depends first on the number of _____________ in ourGalaxy,and the fraction of these which are the right type. The right type means not too hot and not toocool.5) Life is not likely to develop on a planet orbiting stars which are _____________________ or_______________________________.6) The number of civilizations in the MilkyWay also depends on the fraction of stars which have_____________, and the fraction of these which develop life.7) The most uncertain variable in determining the number of civilizations in the MilkyWay at the presenttime is the ______________________________ of a ______________________________.8) The trapping of sunlight by certain gases in the atmosphere is known as the ____________________.The particular gas which is responsible for trapping ∼50% of the heat in our atmosphere is____________________.9) Overall, human beings have increased the total amount of carbon dioxide in the atmosphere by_____________ in less than 200 years, primarily from burning fossil fuels and from deforestation.10) At the present time, scientists are debating whether the increase in the concentration of____________________ in the atmosphere is the direct cause of warmer temperatures, or global warm-ing, on the planet. In fact, the past decade includes the warmest years everrecorded on the Earth. Inde-pendent of the cause of the global warming, the gases in the atmosphere which trap the heat and con-tribute to the greenhouse effect are harmful because of air pollution, acid rain, and ozone depletion.11) In 1985, the world population was close to ________________ people, and still growing. Because ofthe growing population, the rate of ____________________ is also growing.12) Worldwide, the present energy supply is based primarily on the use of ________________, with lessthan 1/5th of the energy based on renewable sources.13) The environmentally benign power sources available to us are ________________,________________, and ________________.-2-14) The _____________ is a nuclear power plant located at a safe distance of 93,000,000 miles from us.At the Earth, we receive anamount of energy equivalent to _______________ of sunlight on every squaremeter of surface.15) There are twodifferent ways of generating power using solar energy.One, based on the collecting ofsunlight to use as a heat source, is called ____________________. The other,based on using sunlight tocreat a current in a semi-conductor such as silicon, is called ________________.16) In areas of the world where solar or wind energy are the most favorable sources of power available,excess energy could be exported to other parts of the world. One waytostore and then export the energyis to convert (electrolyze) _______________ into its component elements, which are then stored in tanksfor transporting. One of these elements, _______________, could be used to power our automobiles, andthe byproduct of the combustion would be _______________.17) The total world fossil fuel consumption could be replaced with ________________ as the source ofenergy.The necessary amount could be produced using solar energy as the source of electricity on only500,000 km2,or__________% of the