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  2. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    In frequency (and thus energy), UV rays sit between the violet end of the visible spectrum and the X-ray range. The UV wavelength spectrum ranges from 399 nm to 10 nm and is divided into 3 sections: UVA, UVB, and UVC. UV is the lowest energy range energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions.

  3. Brightness temperature - Wikipedia

    en.wikipedia.org/wiki/Brightness_temperature

    For a black body, Planck's law gives: [8] [11] = where (the Intensity or Brightness) is the amount of energy emitted per unit surface area per unit time per unit solid angle and in the frequency range between and +; is the temperature of the black body; is the Planck constant; is frequency; is the speed of light; and is the Boltzmann constant.

  4. Special relativity - Wikipedia

    en.wikipedia.org/wiki/Special_relativity

    A 20-year round trip for them (5 years accelerating, 5 decelerating, twice each) will land them back on Earth having travelled for 335 Earth years and a distance of 331 light years. [71] A full 40-year trip at 1 g will appear on Earth to last 58,000 years and cover a distance of 55,000 light years.

  5. Orders of magnitude (illuminance) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude...

    Factor ()Multiple Value Item 0 0 lux 0 lux Absolute darkness 10 −4: 100 microlux 100 microlux: Starlight overcast moonless night sky [1]: 140 microlux: Venus at brightest [1]: 200 microlux

  6. Orders of magnitude (frequency) - Wikipedia

    en.wikipedia.org/.../Orders_of_magnitude_(frequency)

    Acoustic – frequency of G −7, the lowest note sung by the singer with the deepest voice in the world, Tim Storms. His vocal cords vibrate 1 time every 5.29 seconds. 10 0: 1 hertz (Hz) 1 to 1.66 Hz: Approximate frequency of an adult human's resting heart beat: 1 Hz: 60 bpm, common tempo in music 2 Hz: 120 bpm, common tempo in music ~7.83 Hz

  7. Apparent magnitude - Wikipedia

    en.wikipedia.org/wiki/Apparent_magnitude

    Absolute magnitude is defined as the apparent magnitude that a star or object would have if it were observed from a distance of 10 parsecs (33 light-years; 3.1 × 10 14 kilometres; 1.9 × 10 14 miles). Therefore, it is of greater use in stellar astrophysics since it refers to a

  8. Relativistic Doppler effect - Wikipedia

    en.wikipedia.org/wiki/Relativistic_Doppler_effect

    In the non-relativistic case, the light ahead of the observer is blueshifted to a wavelength of 300 nm in the medium ultraviolet, while light behind the observer is redshifted to 5200 nm in the intermediate infrared. Because of the aberration of light, objects formerly at right angles to the observer appear shifted forwards by 42°.

  9. Magnitude (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Magnitude_(astronomy)

    Apparent magnitude, the brightness of an object as it appears in the night sky. Absolute magnitude, which measures the luminosity of an object (or reflected light for non-luminous objects like asteroids); it is the object's apparent magnitude as seen from a specific distance, conventionally 10 parsecs (32.6 light years).