SD

Our Planet

  • Earth differentiates:

    • contains life

      • (we) modified earth and made it “different” from other planets

    • a small but habitable planet: reason

      • a star that is just the right size, 0.75-1.5 as big as the sun

        • large stars burn too fast, too small of a star would produce less heat (gradually cools down)

      • a planet about the size of ours

        • too small =

      • has to be terrestrial = has to be made up of rock (for chm reactions & things to grow upon), not gas

      • lots of water = liquid water (between 0 & 100C)

      • planet has to be js the right distance from the sun, 15-20C

        • too close: water will be steam

        • too far: water will be ice

      • needs to be a relatively circular orbit

        • reason: planet is warmed up evenly

      • have to rotate on its axis relatively frequently

        • 24 hours

          • spin of planet = constant temp

    components of the earth

    • Hydrosphere - the worlds oceans

      • covers 55% of surface

    • Atmosphere-gas that is held by the surface of gravity (thin layer)

      • ex: mars has a thin atmosphere=weight down

      • ex:

    • Lithosphere - the rock

    • Biosphere - the area of the 3 above that contain life

  • Planterary Atmosphere (Mole Percent)

    • H, He, CO2, N2, O2, AR (six main elements in atmosphere)

    • sun contains 89 % Hydrogen, 11% Helium

    • venus contains 96% carbon dioxide and 4% nitrogen (as a result = very hot)

    • earth contains 78%nitrogen, 21% oxygen, 0.9 argon

    • mars has 95% carbon dioxide, 3%nitrogen

    • jupiter contains 90% hydrogen & 10%helium (gas planet)

    • saturn contains 96% hydrogen & 4% helium

    • uranis 85%(H) & 15%(He)

    • Neptuen 85%(H) & 15%(He)

    • *ex question: which is the main element of uranus? hydrogen

  • milestones in our history

    • 13.9 ×10^9 years ago = Big Bang

    • 5 × 10^9 years ago = Sun Forms

    • 4.6×10^9 = Earth forms

    • 3.7×10^9 = oldest fossil - photosynthesis starts

    • 5×10^8 vertebrates in fossil record (backbone)

    • 4× 10^8 ozone forms - life on land possible

    • 3.5 × 10^8 mammals & reptiles

      • last 10% = about 350 million years ago (they formed)

    • 6.5 × 10^7 dinos extinct (except birds)

      • mammals coule come out more prominently

    • 2.5 × 10^6 early homo ancestors

    • 5 × 10^4 homo sapiens (sole homonoid)

    • 1×10^4 recorded history

      • oral history, tablets

    • 1×10² high technology

      • ex: horse & buggy to space shuttle

    • 0.4 × 10² large scale environmental issues