Life in the Universe

1. Life in the Universe

2. FACT: At present, there is no evidence of life forms other than on the planet Earth.

3. Astronomers… are split on whether or not life is probable elsewhere in the universe.

4. The earth is about 4.6BY old. Fossils of the first life forms appear in rocks about 3.5 BY This means there have been simple life forms here for much of the planets history. More complex forms appear in rocks about 600 MY ago.

5. Our species, Homo Sapiens, has existed for about 500,00years—only one-ten thousandth of the age of the planet.

6. The Earth’s life forms • are made of the same elements as the earth is made of. • There is remarkable commonality among the building blocks (e.g. amino acids, proteins, DNA) of the earth’s diverse life forms.

7. The scientific position is that life on Earth evolved fairly rapidly from common origins (complex organic molecules)

8. Under controlled conditions, • It is possible to stimulate compounds thought to be common in the Earth’s early atmosphere methane, Ammonia) to produce organic molecules and amino acids.

9. Organic material so produced • has been found to spontaneously generate structures which isolate sections of the sample (primitive cell wall?)

10. Complex organic molecules are also found in interstellar clouds and some meteorites.

11. While no experiments have produced cells which can reproduce They have produced RNA strands which can replicate themselves.

12. It is a common scientific belief That life originated on earth spontaneously. Other astronomers hold that life originated elsewhere and was transported to earth.

13. PANSPERMIA The position that life on earth descended from organisms created elsewhere in the universe. e.g. as bacteria transported in dust particles. (Not generally supported today)

14. EVIDENCE FOR OTHER WORLDS: The “Drake Equation” (Frank Drake) • There are 1010 stars like the Sun in the Milky Way. • If one in ten has a life-sustaining planet, the total would decrease to 109 • 1 in 100 provided the conditions for the spontaneous development of life, the total would be 107

15. The Drake Equation, continued • If one in a thousand potential life-supporting worlds gave rise to a technical civilization, there would be 104 or 10,000 technical civilizations in the Milky Way.

16. Why don’t they call? • With the radius of the Milky Way being 50,000LY, and assuming 10,000 technical civilizations, the average distance between civilizations would be 1000LY.

17. Soooo, • If a society learned to use radio waves at the same time as the Earth, (late nineteenth century), their first messages would not get to us until the year 2900.

18. Even if there are other technical civilizations, We would most likely hear from them if: • They wanted to communicate • They had mastered space flight and communication

19. The Gaia (guy-uh) Hypothesis James Lovelock/Lynn Margulis, 1974) The planet Earth and its life forms are in a symbiotic relationship (they change/affect each other)

20. Life forms… • Adapt to the environment, AND the environment changes as a result of the actions of life forms.

21. In the classic example: • Early plants produced oxygen, which created an ozone layer, which protected the plants from U-V radiation. • The life forms (plants) changed the planet.

22. If the planet gets too cold, • Plants will die off, so less carbon Dioxide is scrubbed from the atmosphere. • Since CO2 is a greenhouse gas, the global temperature might rise.

23. If the planet gets too warm… • More plants would grow, so more carbon dioxide would be removed from the atmosphere—less greenhouse effect.

24. CONCLUSION? • The “numbers” imply that life COULD exist elsewhere…. • But there is NO direct evidence of that life as of 2012.