Earth and space

Earth and space

1. The Big Bang Theory

   • the current model of the early development of the Universe which expanded from a small point in which the Universe were concentrated into with high density and pressure singularity which expanded outward and still expanding
   • Evidence
     • All the galaxies are moving away
     • the further away the galaxy is the faster it is moving
     • Cosmic background microwave radiation
   • Steady state model state that the density of galaxies remains more or less constant as Universe expand with no refrence to CMBR

2. Doppler effect is the change of frequency or wavelength of a wave when there is relative motion between the source and observer

   • when the source is moving away from observer, the wavelength increase and frequency decrease
   • when the source is moving toward the observer the wavelength decrease and frequency increase

3. Red-shift is the increase in wavelength of electromagnetic light radiation of photons of moving objects and galaxies as they move away so the pattern of the absorption line spectrum is shifted toward the red region

   • elements absorb the light spectrum for energy
   • the further the star is the more its light is red-shifted, so distant galaxies are moving away at faster speeds
   • Hubble law states that the distance to a galaxy is proportional to the speed with which it is moving away from us
     • Velocity = Hubble constant X Distance from earth

4. Microwave background radiation is the cooled remnant of the hot Big bang that fills the entire Universe with radiation

   • space was saturated with high energy gamma photons when the universe was young and hot, the expansion stretched the wavelength of these high energy photons to be red-shifted to microwave according to doppler shfted effect

5. Difficult to predict the universe future as it s difficult to measure accurately the distances involved and the uncertainty with respect to the part that is not yet observed and the dark matter

   • Mass of universe is small --> open universe --> expand forever. Mass of universe is big --> flat --> expansion will stop. Mass of universe is very big --> closed --> big crunch

6. The life cycle of a star

   • Due to tiny variation in the nebula denser regions form so gravity pulls in more dust and gas increasing pressure and temperature as gravitational energy is eventually transfered to thermal energy. When it is hot enough around 15 million kelvin a protostar is formed
     • Fusion reaction start in the core of the protostar
       • the temperature rise need to be very large to overcome the repulsion force between the two positive nuclei
     • when the outward expansion force is equal and balanced with the compressing inward gravity force the star is stable in a main sequence
       • how long it stay depends on the size of the star
         • Massive stars are only stable for short time as they are much hotter than smaller stars so they have faster rate of reaction and run out of fuel first
       • Stars with Low mass between 0.5 M and 10 M
         • they run low on hydrogen fuel in the core so gravitational force is greater so the core starts to collapse increasing the pressure enough to start fusion reaction in a shell around it. As these layers expand they cool down giving the red color red giants stars
           • when the layers drift of into the space the hot core is left behind emitting energy because it leaks photons so it form a white dwarf
             • when al the photons are leaked it form a black dwarf
       • More Massive stars more than 10 M
         • the changes in the core cause the star to expand forming a Red Supergiant star where the temperature and pressure are high enough to fuse massive nuclei forming a series of shells until an inert iron core
           • this makes the str very unstable to withstand the crushing gravitational forces causing the implosion of the layers that bounces off the solid core in a Supernova explosion
             • in Neutron stars, is the remnants of supernova which is very high in density and made up of closely packed neutrons
             • Black holes have a strong gravitational field

7. Exo planet is a planet outside the solar system

8. Extra-terrestrial life is the existence of life outside of Earth determined by water and oxygen supply

   • There is no evidence to indicate that extra-terrestrial life exists
     • this research is important to answer questions

9. Telescopes

   • it enable scientists to gather more information about our Universe for better understanding and predictions using telescopes, manned and unmanned space missions
   • Optical telescope for electromagnetic radiation
     • Refractors using lenses. Reflectors using mirrors. Or both
     • Magnified by using an eyepiece
   • Earth based optical telescope observe visible light to view the night sky only when the sky is totally clear and clean.
     • the quality of image is degraded as light passes through Earth atmosphere and suffer from its interference (absorption, scattering and bluring)
       • the effect of atmosphere distortion is reduced by building them on high mountains so less absorption of light and less air to pass through
   • Radio telescopes detect radio waves which can be used in bad weather of cloudy nights as radio waves are not blocked so it have less distortion and can be used anytime
     • Radio signals from space are very weak so they have large dishes to gather as much energy so they are expensive. X-rays are partially blocked by the atmosphere so they are paced in high altitudes
   • Space telescopes based on space platforms can detect different electromagnetic radiation that are blocked by the atmosphere (Hubble, Chandra, Herschel) so they collect sharper images with unlimited field of view
     • they are difficult and expensive to launch as only atronauts can fix them

10. space agencies

    • NASA
    • ESA
    • CNSA
    • RFSA