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Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
Do Aliens Exist
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Do Aliens Exist


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Theories to prove existence of aliens... An outline of how to determine whether aliens exist in outer space, and reasons behind speculations that aliens do exist...

Theories to prove existence of aliens... An outline of how to determine whether aliens exist in outer space, and reasons behind speculations that aliens do exist...

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  • 1. R. Sandeep Rajkumar 31709214037
  • 2. THE NEED TO SEARCH FOR EXTRATERRESTRIAL LIFE In the past couple of decades, the study of life on Earth has revealed the existence of life in “extreme” environments that were generally thought to be uninhabitable. The organic chemicals needed for life as we know it are found pervasively in and between the stars of the galaxy. In the past decade we have been detecting more and more planets orbiting other stars. Hence, a compelling question arises as to whether we are alone in this universe or not. Tube worms near deep ocean hydrothermal vent Star forming region Sun-like star with Earth-like planet Artist concept
    • Many theories have been proposed on whether extraterrestrial life exists and attempts have been made to prove them.
    • The most important theories are:
    • * Fermi’s Paradox
    • * Drake’s Equation
    • Enrico Fermi in 1950
    • Conflict between an argument of scale and probability and a lack of evidence .
    • Definition:
    • The apparent size and age of the universe suggests that many technologically advanced extraterrestrial civilizations ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.
  • 5. DRAKE EQUATION N = R * f p n e f l f i f c L R* = rate of formation of stars suitable for the development of intelligent life. f p = fraction of those stars with planetary systems. n e = number of planets, per solar system, with an environment suitable for life. f l = fraction of suitable planets on which life actually appears. f i = fraction of life bearing planets on which intelligent life emerges. f c = fraction of civilizations that develop a technology that releases detectable signs of their existence into space. L = length of time such civilizations release detectable signals into space. N = estimated number of civilizations in the Milky Way Galaxy whose electromagnetic emissions are detectable.
    • R * = 7/year
    • f p = 0.5
    • n e = 2
    • f l = 0.33
    • f i = 0.01
    • f c = 0.01
    • L = 10000 years
    • N = 7 × 0.5 × 2 × 0.33 × 0.01 × 0.01 × 10000 = 2.31
  • 7. CRITERIA FOR A PLANET TO SUPPORT LIFE Evidence of oxygen Presence of liquid water Analysis of reflected light from the planet to see if the planet has an atmosphere Signs of biological activity (ex): Methane
  • 8. ORIGIN OF LIFE IN THE UNIVERSE BIG BANG Sun & planets forming LIFE! Habitable worlds Heavier elements needed for life created in massive stars and spewed into the galaxy via supernova explosions Organic materials
  • 9. IMPACT OF LIFE ON ITS ENVIRONMENT Presence of ozone (O 3 ) and water vapor in the spectrum of Earth’s atmosphere is an indirect evidence of life
    • Life needs a suitable environment to flourish. It also feeds back and changes its environment.
    • The way life changes its environment is known as a biosignature – a sign of presence of life.
    • Oxygen in Earth’s atmosphere is a biosignature of life, inferred from the presence of photosynthetic life if there is atmospheric oxygen.
    • Most of the life on Earth is made up of microbes, not animals or plants.
    • Animals and humans make up only 1% of life on Earth.
  • 11. SEARCH FOR EXTRATERRESTRIAL LIFE What are scientists doing?
    • Astrobiology: Studying life on Earth to aid the search for life beyond Earth — microbial life in “extreme environments”
    • Planetary Exploration: Exploring planets in our solar system with robots — Mars rovers seeking signs of past surface water
    • Finding Extra-solar planets: Searching for Earth-like planets orbiting distant stars — NASA’s Kepler Mission.
    • Looking for Signs of Life: Learning how to measure the composition of the atmospheres of extra-solar planets to detect signs of life.
    • SETI: Seeking electromagnetic signals from a technological civilization.
    Mars rover Parkes Radio Telescope Kepler
    • The search for extraterrestrial life is the central theme of astrobiology.
    • This includes a search for signs of other intelligent civilizations, which may be using EM radiation or other means of communication.
    • The only practical method of investigating the extra-Solar System universe is by spectral analysis of the radiation reaching Earth from such systems.
    • These include the familiar visible spectrum, other wavebands of the EM spectrum and occasionally, particles of matter.
    • The latter may range in size from protons to meteorites and comets.
    • Robotic probes are being used to survey the Solar System, with great efficacy.
    • Beyond the Solar System, time and distance factors make them impractical.
  • 14. NASA’S TERRESTRIAL PLANET FINDER In a decade or so, TPF's spectroscopy should allow atmospheric chemists and biologists to use the relative amounts of gases like carbon dioxide, water vapor, ozone & methane to find whether an extra-solar planet may support life. NASA’s Terrestrial Planet Finder (TPF) Spacecraft
  • 15. SETI
    • SETI – Search for Extra Terrestrial Intelligence
    • The SETI Institute uses radio and optical telescopes to search for signals that might be emitted by technologically advanced life.
    • The Allen Telescope Array is being developed at Hat Creek, CA to greatly expand the SETI search.
    Allen Telescope Array Dish Parkes Radio Telescope
    • As of today, no unequivocal evidence has been obtained for the existence of extraterrestrial life within or outside of the Solar System whether primitive or advanced; but the search continues.
    • Our biosphere was enabled to appear, evolve, and persist for 3.7 Gy as a result of a rare combination of dynamic, cosmic and geological factors.
    • Earth’s environment is unstable and easily upset.
    • Biosphere perturbations may be caused by changing geological and cosmic forces, and also by biological factors, including those resulting from human activity.
    • Human colonization of other star systems does not seem possible at this time.
    • For the foreseeable future, Earth will be our only home.
  • 17.
    • So ultimately, there are only two possibilities:
    Maybe we’re alone… Or… Maybe we’re not…
  • 18.