82 FAQs about Relativity (The Astronomy Cafe)

Relativity Links and FAQs Relativity UseNet, Chris Hillmans Page

Primers Stanford Linear Accelerator , Relativity Tutorial

Quantum gravity: Penrose Spin Networks,

String Theory The Official Web Site!

Experimental Tests General Relativity

Gravitational Lens Cluster Hubble Space Telescope

 Back to the Astronomy Cafe - 365 of the most popular questions since 1996. Over 1 million page requests!

Beginner:

 

  1. What is it like to be in a place with no gravity?
  2. How do you explain Einstein's relativity theory to a 12 year old?
  3. If a marshmallow traveled at 99.99 percent the speed of light hit the Earth, what would happen?
  4. Could you tell me the name of the NASA astronomer who discovered two gaps in time?
  5. How is it said that relativity is tested billions of times a year, when there are only a few accelerator labs on Earth?
  6. Does gravity travel faster than the speed of light?
  7. What is a space anomaly?
  8. If I shined a flashlight into the sky, would someone in another galaxy eventually see it?

Intermediate:

  1. According to relativity, how much younger are astronauts in earth-orbit after 6 months?
  2. What would happen if the speed of light were 10 times faster?
  3. If we traveled 100 light years into space, would we really see the Earth as it was 100 years ago?
  4. How are scientists trying to detect gravity waves?
  5. Has it been experimentally proven that the speed of light is the fastest?
  6. If nothing can travel faster than light, why does gravity take affect instantly?
  7. What binary star is producing gravity waves?
  8. Can light be altered by a magnetic field?
  9. What would a universe be like with two time dimensions?
  10. Has the constancy of the speed of light been measured?
  11. Can you exceed the speed of light by manipulating space-time in some way?
  12. If an object approached the speed of light, would it be transformed into light?
  13. Are we gravitationally affected by where an object is now, or where it was when the light we see started its journey to us?
  14. What is time?
  15. What visual distortions occur as you approach the speed of light?
  16. Is the speed of light a barrier of the same kind as the speed of sound?
  17. What studies have been made for gravity waves?
  18. Does 'now' have a size instead of being a point in spacetime?
  19. Can gravity affect the speed of light?
  20. Is it possible to exceed the speed of light?
  21. Is it difficult to know what is happening now if it takes light time to get here?
  22. If we could travel faster than light, could we go back in time?
  23. Does gravity travel at the speed of light?
  24. Could an astronaut use a wrist watch to measure relativistic time dilation?
  25. What objects have we seen traveling near the speed of light either natural or man-made?
  26. Do gravitational fields produce their own gravity?
  27. How can matter just appear out of nowhere?
  28. Does space have more than 3 dimensions?
  29. Why can't we travel faster than light?

Advanced:

 

  1. Are there any other astronomical systems where general relativity can be tested other than the Hulse-Taylor binary pulsar?
  2. What is the simplest evidence that there are more than 4 dimensions?
  3. What prevents densities higher than the so-called Planck Limit from happening?
  4. If gravity is a distortion in space-time, why do we call it a force?
  5. How do you really know that the limits to general relativity for strong fields are set inside black holes?
  6. Can information between pairs of particles travel faster than light?
  7. Is there a theory that predicts the velocity of light?
  8. Why is the gravitational field of the universe another name for space-time?
  9. Don't objects steadily evaporate over time by emitting gravity waves?
  10. Does anyone really understand general relativity well enough to have an intuitive grasp of the universe?
  11. Why can't a rigid body exist?
  12. What does the equation look like that shows how gravitational radiation is lost from the binary pulsar system?
  13. Under what circumstances can a particle exceed the speed of light?
  14. Why is time so different from space in the way we experience it?
  15. How does a body actually bend space-time?
  16. What the ding dang are gravitons?
  17. Is gravity the exchange of gravitons, or the curvature of space-time?
  18. When a photon falls in a gravitational well, does its speed exceed 'c'?
  19. Does matter really get infinitely compressed in a singularity?
  20. How does gravity propagate through space?
  21. What is it that physically prevents faster than light speeds?
  22. How are electromagnetic fields and space-time related, and can electromagnetic fields exert a force on space- time?
  23. How do you reconcile classical quantum mechanics with general relativity?
  24. Why isn't it possible to travel in time?
  25. Is the constancy of the speed of light dictated by special relativity invalidated by the expansion of the universe?
  26. If a photon travels at the speed of light, why isn't its mass infinite?
  27. If you travel near the speed of light, do you enter another dimension?
  28. If you traveled at the speed of light, would the universe appear instantaneous?
  29. What happens to the fabric of space-time when an object moves through it near the speed of light?
  30. Does 'now' have a size instead of being a point in spacetime?
  31. Do electrons interact with past and future representations of themselves?
  32. Is there such a thing as hyperspace?
  33. How do we know that the speed of light is the same in every galaxy?
  34. How do you actually use Einstein's famous equation E = mc-squared?
  35. Is anti-matter the same as negative mass?
  36. Why is the speed of light a constant?
  37. How do astronomers tell the difference between the different kinds of redshifts?
  38. Does the star DI Herculis prove that general relativity is breaking down?
  39. Can space exist by itself without matter or energy around?
  40. What happens in the space between gravitating bodies?
  41. What is a brane?
  42. Are all the postulates in General Relativity accepted or does there exist room for alternatives to General Relativity with different outcomes?
  43. Is space really quantized?

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