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  2. Accelerating expansion of the universe - Wikipedia

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

    Spectral lines of their light can be used to determine their redshift. For supernovae at redshift less than around 0.1, or light travel time less than 10 percent of the age of the universe, this gives a nearly linear distance–redshift relation due to Hubble's law. At larger distances, since the expansion rate of the universe has changed over ...

  3. Spectrophotometry - Wikipedia

    en.wikipedia.org/wiki/Spectrophotometry

    The names are due to the geometry of the light source, observer and interior of the measurement chamber. Scientists use this instrument to measure the amount of compounds in a sample. If the compound is more concentrated more light will be absorbed by the sample; within small ranges, the Beer–Lambert law holds and the absorbance between ...

  4. Absorption spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Absorption_spectroscopy

    Absorption spectroscopy is employed as an analytical chemistry tool to determine the presence of a particular substance in a sample and, in many cases, to quantify the amount of the substance present. Infrared and ultraviolet–visible spectroscopy are particularly common in analytical applications. Absorption spectroscopy is also employed in ...

  5. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    The γ factor approaches infinity as v approaches c, and it would take an infinite amount of energy to accelerate an object with mass to the speed of light. The speed of light is the upper limit for the speeds of objects with positive rest mass, and individual photons cannot travel faster than the speed of light. [39]

  6. Spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Spectroscopy

    Spectroscopy is a branch of science concerned with the spectra of electromagnetic radiation as a function of its wavelength or frequency measured by spectrographic equipment, and other techniques, in order to obtain information concerning the structure and properties of matter. [4]

  7. Eddington experiment - Wikipedia

    en.wikipedia.org/wiki/Eddington_experiment

    The earliest parameterizations of the post-Newtonian approximation were performed by Eddington (1922). The parameter concerned with the amount of deflection of light by a gravitational source is the so-called Eddington parameter (γ), and it is currently the best-constrained of the ten post-Newtonian parameters.

  8. Observer effect (physics) - Wikipedia

    en.wikipedia.org/wiki/Observer_effect_(physics)

    A common example is checking the pressure in an automobile tire, which causes some of the air to escape, thereby changing the amount of pressure one observes. Similarly, seeing non-luminous objects requires light hitting the object to cause it to reflect that light.

  9. Astronomical spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Astronomical_spectroscopy

    The Star-Spectroscope of the Lick Observatory in 1898. Designed by James Keeler and constructed by John Brashear.. Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects.