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Interstellar Travel

Interstellar Travel. By: David Rodriguez Astro 5: Life in the Universe Winter 2008. Motivation: Fermi’s Paradox. If the chances of developing a technological civilization are 1 in a million: 100,000 civilizations in the galaxy

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Interstellar Travel

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  1. Interstellar Travel By: David Rodriguez Astro 5: Life in the Universe Winter 2008

  2. Motivation: Fermi’s Paradox • If the chances of developing a technological civilization are 1 in a million: • 100,000civilizationsin the galaxy • This is an application of the Drake Equation, but ignoring the Lifetime of civilizations If these are spread over the lifetime of the Galaxy, the time between civilizations is about 50,000 years

  3. Fermi’s Paradox • With such a long time, a civilization might be able to colonize the Galaxy or at least make its presence known • They could at least send self-replicating machines

  4. Solutions to Fermi’s Paradox • There are three solutions to Fermi’s Paradox: • We are alone • A galactic civilization exists, but it remains hidden from us • Other civilizations exist, but none have colonized the galaxy. Why? • No interest in doing so • Self-annihilation • Technological difficulties

  5. Introduction • In order to travel to the stars, colonize other worlds, and establish an Everlasting Galactic Empire, we will need interstellar travel

  6. Rocket Science • Current rockets use chemical fuels • These can be solids, liquids, or gases • Efficiency of a rocket measured with the mass ratio = • Mass with fuel / Mass without fuel

  7. Rocket Science • To escape the gravity of the Earth need a mass ratio of ~39 • Single stage rockets have mass ratios of ~15 or less • This is not enough, so we can’t leave the Earth • Or can we?

  8. Multistage Rockets

  9. Distances to Stars • The nearest star system (Alpha Centauri) is 4 light-years away (40 trillion km) • At 60mph, this would take… 44 million years • At 17,000mph, this would take just 160,000 years At this speed, it would take a billion years to reach the center of our Galaxy

  10. What can we do? • We need to go faster! • It’s all a mater of getting higher efficiency from our fuel I can make 0.5 past light speed!

  11. Nuclear Rockets • Use fission to heat hydrogen gas, which provides the thrust • Fuse small pellets of hydrogen, the energy released moves it forward • Set off a nuclear bomb behind you

  12. Ion Drives • Shoot out ions from light-weight gases • Little thrust, but can work for longer times and therefore get large velocities

  13. Solar Sails • Use the pressure from photons of light to push the craft forward- like wind on a sail. • Can also use lasers

  14. Antimatter Engines • Antimatter is like regular matter but with opposite charge • When antimatter and matter meet, they completely annihilate each other producing energy

  15. Ramjets • Like the solar sail, an interstellar ramjet carries no fuel • Take hydrogen from space and fuse it

  16. To Infinity, and Beyond! • These new technologies allow light-weight space craft to reach very high speeds with very little fuel. • In order to go faster we just need to run the engine for a longer time

  17. But then this guy came along… Image credit: Kevin Hainline

  18. A Maximum Speed • The speed of light in a vacuum is always a constant with respect to any observer. • This speed, c, is • 300,000 km/s • 186,000 miles/s • 1.8 terra furlongs/fortnight • Nothing can travel faster than light

  19. Special Relativity • All motion is relative • Many weird effects will happen when special relativity is applied, but I’ll only mention a few: • Moving clocks run slower as seen by a stationary observer  time dilation • Distances are contracted along the direction of motion of a moving object  length contraction

  20. Special Relativity • At 99.99% of c, to go to Vega (25 light-years away) and back: • Space ship frame: 8 months • Earth (stationary) frame: 50 years • But light takes 50 years to travel 50 light-years, yet you do this in 8 months: • Length contraction: you travel 0.4 light-year rather than 25 light-year

  21. General Relativity to the Rescue?

  22. Wormholes • A highly curved region of space could intersect another region of space and form a hole between them • These wormholes are unstable and collapse if anything goes through them

  23. The Alternative: Interstellar Arks • Use conventional technology, but be prepared to wait a very long time • The original travelers will die and new ones will be born before reaching the destination Or you could place everyone in suspended animation for thousands of years

  24. Questions ?

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