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  2. Spacetime diagram - Wikipedia

    en.wikipedia.org/wiki/Spacetime_diagram

    Unlike a regular distance-time graph, the distance is displayed on the horizontal axis and time on the vertical axis. Additionally, the time and space units of measurement are chosen in such a way that an object moving at the speed of light is depicted as following a 45° angle to the diagram's axes.

  3. Accelerating expansion of the universe - Wikipedia

    en.wikipedia.org/wiki/Accelerating_expansion_of...

    The timeline in this schematic diagram extends from the Big Bang/inflation era 13.8 billion years ago to the present cosmological time. Observations show that the expansion of the universe is accelerating, such that the velocity at which a distant galaxy recedes from the observer is continuously increasing with time.

  4. Redshift - Wikipedia

    en.wikipedia.org/wiki/Redshift

    The largest-observed redshift, corresponding to the greatest distance and furthest back in time, is that of the cosmic microwave background radiation; the numerical value of its redshift is about z = 1089 (z = 0 corresponds to present time), and it shows the state of the universe about 13.8 billion years ago, [62] and 379,000 years after the ...

  5. Proper motion - Wikipedia

    en.wikipedia.org/wiki/Proper_motion

    The first is the direction of the proper motion on the celestial sphere (with 0 degrees meaning the motion is north, 90 degrees meaning the motion is east, (left on most sky maps and space telescope images) and so on), and the second is its magnitude, typically expressed in arcseconds per year (symbols: arcsec/yr, as/yr, ″/yr, ″ yr −1) or ...

  6. Spacetime - Wikipedia

    en.wikipedia.org/wiki/Spacetime

    In physics, spacetime, also called the space-time continuum, is a mathematical model that fuses the three dimensions of space and the one dimension of time into a single four-dimensional continuum. Spacetime diagrams are useful in visualizing and understanding relativistic effects, such as how different observers perceive where and when events ...

  7. Acceleration (special relativity) - Wikipedia

    en.wikipedia.org/wiki/Acceleration_(special...

    In order to find out the transformation of three-acceleration, one has to differentiate the spatial coordinates and ′ of the Lorentz transformation with respect to and ′, from which the transformation of three-velocity (also called velocity-addition formula) between and ′ follows, and eventually by another differentiation with respect to and ′ the transformation of three-acceleration ...

  8. Gravitational redshift - Wikipedia

    en.wikipedia.org/wiki/Gravitational_redshift

    Indeed, in a frame moving (in direction) with velocity relative to the rest frame, the clocks at a nearby position are ahead by (/) (/) (to the first order); so an acceleration (that changes speed by / per time ) makes clocks at the position to be ahead by (/) (/), that is, tick at a rate

  9. Galilean invariance - Wikipedia

    en.wikipedia.org/wiki/Galilean_invariance

    An inertial frame is a reference frame in relative uniform motion to absolute space. All inertial frames share a universal time. Galilean relativity can be shown as follows. Consider two inertial frames S and S' . A physical event in S will have position coordinates r = (x, y, z) and time t in S, and r' = (x' , y' , z' ) and time t' in S' .