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Unformatted text preview: ISP209s9 Lecture 231 Today Announcements: HW#9 is due April 15 at 8am Exam 3 on April 30 (Thursday) Final exam will be on CAPA like exam 2 Black holes, Worm holes, and White holes Life in the Universe Are we alone? ISP209s9 Lecture 232 Einstein Equations predict Black holes A hole so deep that even light can not escape. www.ifa.hawaii.edu/~barnes/ast110_06/bhaq.html A huge mass in a tiny spacetime region warps it so strongly that it has infinite curvature aka a spacetime singularity develops. Einstein didnt believe in them. He thought it was an artifact of the mathematics. ISP209s9 Lecture 233 How we detect black holes if we cant see them Nearby dust/gas gets pulled towards the Black hole by its gravity. As the particles speed/heat up, they emit xrays 1) Xray emissions 2) Gravitational Lensing Intense gravity bends light. 3) Stars orbiting nothing ISP209s9 Lecture 234 Einstein Equation also predicts Wormholes This could be the basis for a time machine. Wormholes emerge as mathematical consequence of Einsteins Equations. Unlike Black Holes, there is ZERO evidence or hint that they are real. ISP209s9 Lecture 235 Wormholes Wormholes are a possible solution to Einsteins equations. Wormholes are not stable. Some type of exotic material (that acts as antigravity) is necessary to keep one end open. If there are wormholes, there must be white holes. No white hole has ever been observed. We think a white hole is not stable since material would collect near the opening and collapse the white hole to a black hole. ISP209s9 Lecture 236 Back to time travel We need some mysterious type of material to keep the wormholes stable. One type would be exotic matter that is repelled (not attracted) by gravity The wormhole entrance has to be big enough so tidal forces (recall the NOVA video) are not too large. One end of the wormhole must be flown at near the speed of light for some time. Perhaps these are just technical difficulties an advance civilization can overcome. ISP209s9 Lecture 237 What is the Fate of the Universe? The current age of the Universe is 13.7 billion years (or about 10 10 years). 10 100 years: All stars will have used up their nuclear fuel. 10 100 to 10 150 years: The Dark Ages 10 150 years: All black holes will have evaporated....
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 Fall '07
 Sherrill

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