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  2. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    Simplifying the units of the generalized form reveals that H 0 specifies a frequency (SI unit: s −1), leading the reciprocal of H 0 to be known as the Hubble time (14.4 billion years). The Hubble constant can also be stated as a relative rate of expansion.

  3. Demographics of Rwanda - Wikipedia

    en.wikipedia.org/wiki/Demographics_of_Rwanda

    32.7 65.94 2018 12 532 000 391 000 78 000 313 000 31.2 6.2 24.9 3.99 32.0 66.25 2019 12 835 000 395 000 79 000 316 000 30.8 6.1 24.6 3.94 31.0 66.44 2020 ...

  4. Demographics of the Czech Republic - Wikipedia

    en.wikipedia.org/wiki/Demographics_of_the_Czech...

    The erection of bilingual signs has technically been permitted since 2001, if a minority constitutes 10% of the population of a municipality. The requirement that a petition be signed by the members of minority was cancelled, thus simplifying the whole process. [30]

  5. Urea - Wikipedia

    en.wikipedia.org/wiki/Urea

    The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.

  6. Color rendering index - Wikipedia

    en.wikipedia.org/wiki/Color_rendering_index

    Calculate the special (i.e., particular) CRI using the formula = [15] [16] Find the general CRI (R a ) by calculating the arithmetic mean of the special CRIs. Note that the last three steps are equivalent to finding the mean color difference , Δ E ¯ U V W {\displaystyle \Delta {\bar {E}}_{UVW}} and using that to calculate R a {\displaystyle R ...

  7. Vacuum tube - Wikipedia

    en.wikipedia.org/wiki/Vacuum_tube

    Later thermionic vacuum tubes, mostly miniature style, some with top cap connections for higher voltages. A vacuum tube, electron tube, [1] [2] [3] [thermionic] valve (British usage), or tube (North America) [4] is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.