Earth & Space Flashcards
tidal / jean and jefferey’s hypothesis
it was propunded by jean and jeffery in 1917 AD. according to this, a big star revolving arounf the sun finally approached the sun and a large mass was ejected in the form of tide. that tidal matter fragmented into small pieces and with time it changed into planets, satellites and other heavenly bodies.
nubular hypothesis
it was propounded by kant a german philosopher in 1755 AD and laplace a french mathematician modified it in 1796 AD. according to this hypothesis whole solar system was in the form of nebula and it began to contrac due to its own gravity. with time, an outer ring was detached from the central core and started revolving aroung it. the masses collided and broke into small pieces forming everything there is in this solar system.
planetesimal/ geroge buffin’s hypothesis
george buffon propunded this hypothesis in 1749 AD. the earth and other bodies in this solar system was formed when revolving around the universe then collided with the sun billions of years ago.
formation of solar system from the milky way
according to this the sun was formed by the accumulation of small dust particles present in the milky way due to its gravitation. other bodies also were formed by the same process.
causes of evolution of life ont he earth
- the earth has sufficient amount of life supporting gases in its air.
- it has sufficient amount of water required for survival of life.
- the eath has suitable temperature for the survival.
changes in position of the eath and the sun
- days and nights are nor equal except in the equatoral region.
- the sunrise and sunset donot take place from the same place.
- the changes of seasons take place
the height of sun from the earth in the afternoon changes everyday. - the rays of sun doesnot fall perpendicularly in a place all the time.
changes of seasons
the dueation of one year four seasons occurs: sumer, winter, sutumn and spring. when the northern hemisphere is tilted towarsa the sun, we experience summer and the people in the southern experience winter. spring and sutumn seasons occur when earth lies in between these two positions.
longest night and the shortest day of the year
june 21 (8th of asar) is the longest day and the shortest night in teh northern hemisphere.
march 21 (chaitra 8) days and nights are equal in all parts of the earth. spring occurs in the northern hemisphere
shortest night and longest day of the year
december 22 (poush 7) is the shortest day and longest night in the norhtern hemisphere.
september 23 (asoj 7) days and nights are equal. autumn occurs in the northern hemisphere.
phases of moon
the gradual increas in the bright disc of the moon is called waxing of the moon.
the gradual decrease in the bright disc of the moon is called the waining of the moon.
the waxing and waining of the disc of the moon, as the moon revolves around the earth is called the phases of the moon.
syndomic month and sidereal month
syndomic month: it is the suration between 2 consecutive full moons or new moons. its duration is 29.5 days.
sideral month: it is the duration that the moon completes one revolution around the earth. its duration is 27 days, 7 hours, 43 minutes and 11 seconds.
