Black Holes

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Full list of words from this list:

words only definitions & notes
  1. space-time
    the four-dimensional coordinate system (3 dimensions of space and 1 of time) in which physical events are located
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red
  2. singularity
    the quality of being one of a kind
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red
  3. black hole
    a region of space resulting from the collapse of a star
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red
  4. neutron star
    a star that has collapsed under its own gravity
    This is only a factor of a few smaller than the radius of a neutron star, which is 10 km for a 1.4 solar mass object.
  5. metric
    based on a decimal unit of measurement
    The little black triangles in the diagram are the local lightcones, and they trace out the metric structure of this space-time.
  6. radius
    a straight line from the center to the perimeter of a circle
    In particular, the radius of a black hole can not be defined as the distance from the central singularity to the event horizon, because observers trying to measure this would inevitably fall into the singularity.
  7. magenta
    a primary subtractive color for light
    The boundary between these two regions in space-time is the magenta curve.
  8. diagram
    a drawing intended to explain how something works
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red curves are future lightcones from events where light cannot escape.
  9. coordinate
    of equal importance, rank, or degree
    The coordinates used in this diagram are the Kerr metric coordinates for times later than the creation of the singularity.
  10. analytic
    using or skilled in using analysis
    Before the creation of the singularity a simple analytic form is used instead of the exact solution for a collapsing sphere of pressureless matter.
  11. curve
    the trace of a point whose direction of motion changes
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red curves are future lightcones from events where light cannot escape.
  12. rotate
    turn on or around an axis or a center
    The Kerr metric describes a rotating black hole, but the rotation is set to zero here.
  13. neutron
    a subatomic particle with zero charge
    This is only a factor of a few smaller than the radius of a neutron star, which is 10 km for a 1.4 solar mass object.
  14. horizon
    the line at which the sky and Earth appear to meet
    This boundary of the trapped region is the event horizon of the black hole.
  15. hypothesis
    a tentative insight that is not yet verified or tested
    The cosmic censorship hypothesis states that this is always true, but this hypothesis appears to be false in general, even though it is correct for this space-time and for all (or almost all) physically plausible space-times.
  16. solar
    relating to the sun or utilizing the energies of the sun
    Numerically it is 3 km for a 1 solar mass object.
  17. collapse
    break down, literally or metaphorically
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red curves are future lightcones from events where light cannot escape.
  18. infinity
    time without end
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red curves are future lightcones from events where light cannot escape.
  19. cosmic
    pertaining to or characteristic of the universe
    The cosmic censorship hypothesis states that this is always true, but this hypothesis appears to be false in general, even though it is correct for this space-time and for all (or almost all) physically plausible space-times.
  20. rotation
    the act of turning as if on an axis
    The Kerr metric describes a rotating black hole, but the rotation is set to zero here.
  21. event
    something that happens at a given place and time
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red curves are future lightcones from events where light cannot escape.
  22. circumference
    the length of the closed curve of a circle
    But if one measures the circumference of the event horizon and divides by 2*pi, one gets RS = 2GM/c2, which is called the Schwarzschild radius.
  23. triangle
    a three-sided polygon
    The little black triangles in the diagram are the local lightcones, and they trace out the metric structure of this space-time.
  24. plausible
    apparently reasonable, valid, or truthful
    The cosmic censorship hypothesis states that this is always true, but this hypothesis appears to be false in general, even though it is correct for this space-time and for all (or almost all) physically plausible space-times.
  25. creation
    the act of starting something for the first time
    The coordinates used in this diagram are the Kerr metric coordinates for times later than the creation of the singularity.
  26. zero
    the mathematical symbol 0 denoting absence of quantity
    The Kerr metric describes a rotating black hole, but the rotation is set to zero here.
  27. physically
    in accord with physical laws
    The cosmic censorship hypothesis states that this is always true, but this hypothesis appears to be false in general, even though it is correct for this space-time and for all (or almost all) physically plausible space-times.
  28. define
    show the form or outline of
    In particular, the radius of a black hole can not be defined as the distance from the central singularity to the event horizon, because observers trying to measure this would inevitably fall into the singularity.
  29. inevitably
    in such a manner as could not be otherwise
    In particular, the radius of a black hole can not be defined as the distance from the central singularity to the event horizon, because observers trying to measure this would inevitably fall into the singularity.
  30. definition
    a brief explanation of the meaning of a word or phrase
    Space-time is strongly curved near a black hole, so one has to be very careful about definitions.
  31. defined
    showing clearly the outline or profile or boundary
    In particular, the radius of a black hole can not be defined as the distance from the central singularity to the event horizon, because observers trying to measure this would inevitably fall into the singularity.
  32. region
    the extended spatial location of something
    The boundary between these two regions in space-time is the magenta curve.
  33. divide
    a serious disagreement between two groups of people
    But if one measures the circumference of the event horizon and divides by 2*pi, one gets RS = 2GM/c2, which is called the Schwarzschild radius.
  34. sphere
    a round three-dimensional closed surface
    Before the creation of the singularity a simple analytic form is used instead of the exact solution for a collapsing sphere of pressureless matter.
  35. factor
    anything that contributes causally to a result
    This is only a factor of a few smaller than the radius of a neutron star, which is 10 km for a 1.4 solar mass object.
  36. measure
    determine the dimensions of something or somebody
    In particular, the radius of a black hole can not be defined as the distance from the central singularity to the event horizon, because observers trying to measure this would inevitably fall into the singularity.
  37. solution
    a homogeneous mixture of two or more substances
    Before the creation of the singularity a simple analytic form is used instead of the exact solution for a collapsing sphere of pressureless matter.
  38. future
    the time yet to come
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red curves are future lightcones from events where light cannot escape.
  39. structure
    a complex entity made of many parts
    The little black triangles in the diagram are the local lightcones, and they trace out the metric structure of this space-time.
  40. solid
    not soft or yielding to pressure
    Formation of a Black Hole
    The space-time diagram at right shows matter in blue collapsing to form a singularity [the solid black line], while the green curves are the future lightcones from events where light can escape to infinity, while the red curves are future lightcones from events where light cannot escape.
  41. object
    a tangible and visible entity
    Numerically it is 3 km for a 1 solar mass object.
  42. describe
    give a statement representing something
    The Kerr metric describes a rotating black hole, but the rotation is set to zero here.
  43. trace
    an indication that something has been present
    The little black triangles in the diagram are the local lightcones, and they trace out the metric structure of this space-time.
  44. surround
    extend on all sides of simultaneously; encircle
    Note that the event horizon forms before the singularity and entirely surrounds it, so there is not a naked singularity in this space-time.
  45. local
    of or belonging to or characteristic of a particular area
    The little black triangles in the diagram are the local lightcones, and they trace out the metric structure of this space-time.
  46. simple
    having few parts; not complex or complicated or involved
    Before the creation of the singularity a simple analytic form is used instead of the exact solution for a collapsing sphere of pressureless matter.
Created on Mon Dec 13 11:15:25 EST 2010 (updated Mon Dec 13 11:16:24 EST 2010)

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