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Space and Time Can Warp Your Mind

Space and Time Can Warp Your Mind. Frank Summers Space Telescope Science Institute June 3, 2003. Fundamental Framework. Space. What is space? Gridwork for measuring distances Everything – planets, stars, galaxies, and the universe Is space infinite?. Time. What is time?

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Space and Time Can Warp Your Mind

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  1. Space and Time Can Warp Your Mind Frank Summers Space Telescope Science Institute June 3, 2003

  2. Fundamental Framework

  3. Space • What is space? • Gridwork for measuring distances • Everything – planets, stars, galaxies, and the universe • Is space infinite?

  4. Time • What is time? • The constant drumbeat of existence • “Time is what happens when nothing else does.” • Measured with atomic clocks to one part in 1015 • One second since the demise of the dinosaurs • Does time have a beginning? An end?

  5. Motion • Change of position in space over time • Change in space • Change in time • Motion through space variable • Motion through time constant • Change within fixed framework

  6. Motion is Relative • Motion measured compared to fixed frame of reference • Which frame is fixed? Which is moving? • Why you can’t sit still • Earth’s rotation – 800 mph • Earth’s orbit – 65,000 mph • Sun’s orbit – 450,000 mph • Milky Way’s motion – 1,300,000 mph

  7. Speed of Light

  8. Speed of Light • Finite • 186,000 miles per second • 670 million mph • Light travel distances • Earth-Sun distance is 93 million miles • 500 seconds of light travel time • 1 light-year = 186,000*60*60*24*365.25 • 1 light-year = 6 trillion miles

  9. Time-Warped View • Proxima Centauri – 4.2 ly • Center of Milky Way – 27 thousand ly • Andromeda galaxy – 2.5 million ly • Fornax cluster – 65 million ly • Most distant objects – 13 billion ly • Looking out in space = back in time

  10. Observable Universe • Finite speed of light • Finite age of the universe • Finite volume observable • Properties • Spherical • Centered on the observer • Horizon, not edge

  11. Special Theory of Relativity

  12. Special Theory of Relativity • Speed of light is an absolute - c • Physics is the same to all observers • Observer at rest • Observer in motion • Inertial reference frame • Our reference frame has considerable motion

  13. Non-relativistic Motion • Velocities add together 2 mph 20 mph Total 22 mph

  14. Relativistic Motion • Motions don’t add linearly 0.1 c 0.95 c Total 1.05 c - WRONG (0.1 + 0.95) c Relativistic sum = 0.96 c (1 + 0.1*0.95)

  15. Special Theory of Relativity • Thought experiments • Deduce relativistic behavior • Observer at rest vs. observer in motion • Speed of light is constant • Change in space different • Change in time different

  16. Thought Experiment - rest mirror • Measure distance • Measure time • Calculate speed of light light

  17. Thought Experiment - motion mirror • Measure distance • Measure time • Calculate speed of light light

  18. Shrinking Space • Length contraction • The length of an object appears shorter when measured by a moving observer • Spaceship pilot flying at 0.99c would measure football field as 14 yards long • Crowd would measure spaceship to be 1/7 as long as pilot thinks • Relativistic diet tip: If you move fast, other people think you’re thinner

  19. Stretching Time • Time dialation • Time appears to slow down when measured by a moving observer • Travel to Proxima Centauri at 0.99 c would take 4.25 years • Pilot would only age (4.25/7) years, about 7 months • One way time travel to the future

  20. Light doesn’t exist? • At speed of light, lengths go to zero • At speed of light, time stands still • Photon of light doesn’t experience space or time • Emitted • Instantaneously crosses any amount of space • Absorbed • In its own frame of reference, light doesn’t exist in space or time

  21. Special Theory of Relativity One’s view of space and time depends on one’s motion

  22. General Theory of Relativity

  23. General Theory of Relativity • Matter warps space • Re-interpret gravity as geometry • Straight paths, but in curved space • Geodesic • Extends special relativity to handle non-inertial frames of reference

  24. Warped Space

  25. Warped Space • Matter tells space how to curve • Curved space tells matter how to move

  26. Gravitational Lenses • More mass, more warp • Warped space can act like a glass lens

  27. Slowing Time • Gravitational time dilation • Clocks run slower in a larger gravitational field • Tested by flying atomic clock in plane • Slower due to special relativity • Faster due to general relativity • Today’s atomic clocks can measure altitude difference of 1 yard

  28. General Theory of Relativity One’s view of space and time depends on how much matter is around and how it is distributed

  29. Expansion of Space

  30. Einstein’s Greatest Mistake • Equations for the universe unstable • Einstein added an energy of space (cosmological constant) term to create stable solution • Missed predicting the expansion of the universe Energy of motion Energy of matter Energy of space = +

  31. Expansion of Space • Hubble measured motions of galaxies • All appear to move away from us • Cosmic cooties? • Expansion through space - WRONG • Galaxies moving away from center • No measurements show a center • Copernican hypothesis underlies astronomy, and all science

  32. Expansion of Space • Expansion of space • Galaxies at rest • Space between galaxies expanding • All galaxies see every other galaxy moving away • No center • Different kind of relative motion • Observers at rest • Reference frame in motion

  33. Big Bang • The Universe has expanded … • from small to big • from hot to cold • from dense to rarified • Standard framework of cosmology • Only hypothesis that fits observations • Scientific theory

  34. Big Bang Observation • Cosmic Microwave Background • Remnant glow from hot early universe • Seen in every direction on the sky\ • Perfect thermal spectrum • Time: half a million years after big bang • Temperature: 3000 degrees • Size: 1/1000th present size • Observational evidence that the universe was smaller, denser, and hotter in the past

  35. Expansion of Space One’s view of space and time depends on when in the history of the universe one is observing

  36. Cosmology

  37. It’s Too Perfect • Universe looks the same in all directions • Cosmic Microwave Background • Uniform across the entire sky to about one part in a hundred thousand • Not enough time to achieve uniformity

  38. Inflation • Idea to create a smooth universe • Hyper-expansion • Regions previously in contact become widely separated • Details • Universe larger by factor of 1043 • Occurs in 10-32 of a second • Universe 1026 degrees, supercools, reheats • Knowledge of pre-inflation universe is lost

  39. Inflation Physics • Blame the particle physicists • Energy is relative • Cooling universe looks for energy minimum • Briefly finds false energy minimum • Energy of space drives inflation • Release of energy from false minimum to true minimum provides reheating

  40. Faster than Light Expansion? • Inflation expands space much faster than the speed of light • Doesn’t this violate relativity? • No … • Matter is not moving through space • Space is growing, and carrying matter along for the ride • Superluminal expansion is part of Big Bang

  41. What’s the matter? • Expansion – motion vs matter • Measure motion • Measure matter • Too much motion or too little matter • Dark Matter • About 10 times more than ‘normal’ matter • 90% of the matter is unobserved • Conspiracy theory: Space and time controlled by unseen matter

  42. Too Much Space • Measure expansion rate of the universe • Distant supernovae • Amount of expansion between then and now • Expansion is accelerating • Cosmic concordance • Other observations agree • Age: 13.7 billion years • Matter: 4.4% • Dark Matter: 22% • Dark Energy: 73%

  43. The Fate of the Universe • Dark Energy dominates universe • Energy of space accelerates expansion • Einstein’s “mistake” triumphs • Universe expands ever faster • Eventually faster than speed of light • Objects disappear from observable universe • Fabric of space-time stretched apart Energy of motion Energy of matter Energy of space = +

  44. Fire and Ice - Robert Frost SOME say the world will end in fire, Some say in ice. From what I’ve tasted of desire I hold with those who favor fire. But if it had to perish twice, I think I know enough of hate To know that for destruction ice Is also great And would suffice.

  45. The Ultimate Free Lunch? • Where does one get all this energy? • Expansion  more space • More space  more dark energy • More dark energy  more expansion … • What physics? • Somewhat like inflation …

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