Since 2019, defined as the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second, where the second is defined by a hyperfine transition frequency of caesium.
Lower bound of the (possibly infinite) radius of the universe, if it is a 3-sphere, according to one estimate using the WMAP data at 95% confidence[50] It equivalently implies that there are at minimum 21 particle horizon-sized volumes in the universe.
According to the laws of probability, the distance one must travel until one encounters a volume of space identical to our observable universe with conditions identical to our own.[51][52]
1.6 × 10−5 quectometres (1.6 × 10−35 metres) – the Planck length (Measures of distance shorter than this do not make physical sense, according to current theories of physics.)
1 qm – 1 quectometre, the smallest named subdivision of the metre in the SI base unit of length, one nonillionth of a metre.[54]
To help compare different orders of magnitude, this section lists lengths between 10−13m and 10−12 m (100 fm and 1 pm).
570 fm – typical distance from the atomic nucleus of the two innermost electrons (electrons in the 1s shell) in the uranium atom, the heaviest naturally-occurring atom
300nm – greatest particle size that can fit through a HEPA (high efficiency particulate air) filter (N100 removes up to 99.97% at 0.3 micrometres, N95 removes up to 95% at 0.3 micrometres)[citation needed]
To help compare different orders of magnitude, this section lists lengths between 10−4m and 10−3 m (100μm and 1mm). The term myriometre (abbr. mom, equivalent to 100 micrometres; frequently confused with the myriametre, 10 kilometres)[79] is deprecated; the decimal metric prefix myrio-[80] is obsolete[81][82][83] and was not included among the prefixes when the International System of Units was introduced in 1960.
100 μm – 1/10 of a millimetre
100 μm – 0.00394inches
100 μm – smallest distance that can be seen with the naked eye
To help compare different orders of magnitude, this section lists lengths between one metre and ten metres. Light, in vacuum, travels 1 metre in 1⁄299,792,458, or 3.3356409519815E-9 of a second.
1.63 m – (5 feet 4 inches) (or 64 inches) – height of average U.S. female human as of 2002[update] (source: U.S. Centers for Disease Control and Prevention (CDC))
1.75 m – (5 feet 8 inches) – height of average U.S. male human as of 2002[update] (source: U.S. CDC as per female above)
2.5 m – height of a sunflower
2.72 m – (8 feet 11 inches) – tallest-known human (Robert Wadlow)[30]
3.63 m – the record wingspan for living birds (a wandering albatross)
13 metres – length of a giant squid and colossal squid, the largest living invertebrates
15 metres – approximate distance the tropical circles of latitude are moving towards the equator and the polar circles are moving towards the poles each year due to a natural, gradual decrease in the Earth's axial tilt
18 metres – height of a Sauroposeidon, the tallest-known dinosaur
20 metres – length of a Leedsichthys, the largest-known fish to have lived
21 metres – height of High Force waterfall in England
33 metres – length of a blue whale,[105] the largest animal on earth, living or extinct, in terms of mass
39 metres – length of a Supersaurus, the longest-known dinosaur and longest vertebrate[106]
66km – diameter of Naiad, the innermost of Neptune's moons
100 kilometres
A length of 100 kilometres (about 62 miles), as a rough amount, is relatively common in measurements on Earth and for some astronomical objects. It is the altitude at which the FAI defines spaceflight to begin.
986 Mm – Diameter of HD 100546 b's surrounding disk
1 gigametre
; lower part: their darker mirror images (artist's interpretation).
The gigametre (SI symbol: Gm) is a unit of length in the metric system equal to 1000000000metres (109m). To help compare different distances this section lists lengths starting at 109metres (1 gigametre (Gm) or 1 billion metres).
5.0 Gm – Closest approach of Comet Halley to Earth, happened on 10 April 837
5.0 Gm – (proposed) Size of the arms of the giant triangle shaped Michelson interferometer of the Laser Interferometer Space Antenna (LISA) planned to start observations sometime in the 2030s.
7.9 Gm – Diameter of Gamma Orionis, a blue dwarf or blue giant
1.83 Tm – 12.2 au – Diameter of HR 5171 A, the largest-known yellow hypergiant star although the latest research suggests it is a red hypergiant with a diameter about 2.1 Tm (14 au)[164][165]
7.5 Pm – 50,000 AU – Possible outer boundary of Oort cloud (other estimates are 75,000 to 125,000 or even 189,000 AU (1.18, 2, and 3 light-years, respectively))
9.5 Pm – 63,241.1 AU – One light-year, the distance traveled by light in one year
260 Pm – 27 light-years – Distance to Chara, a star approximately as bright as the Sun. Its faintness gives an idea how the Sun would appear when viewed from this distance.
The exametre (SI symbol: Em) is a unit of length in the metric system equal to 1018metres. To help compare different distances this section lists lengths between 1018m (1Em or 105.7 light-years) and 1019m (10Em or 1,057 light-years).
To help compare different orders of magnitude, this section lists distances starting at 10 Ym (1025m or 1.1 billion light-years). At this scale, expansion of the universe becomes significant. Distance of these objects are derived from their measured redshifts, which depends on the cosmological models used.
13 Ym – 1.37 billion light-years – Length of the South Pole Wall
13 Ym – 1.38 billion light-years – Length of the Sloan Great Wall
To help compare different orders of magnitude, this section lists distances starting at 100 Ym (1026m or 11 billion light-years). At this scale, expansion of the universe becomes significant. Distance of these objects are derived from their measured redshifts, which depend on the cosmological models used.
260 Ym – 27.4 billion light-years – Diameter of the observable universe (double LTD)
440 Ym – 46 billion light-years – Radius of the universe measured as a comoving distance
590 Ym – 62 billion light-years – Cosmological event horizon: the largest comoving distance from which light will ever reach us (the observer) at any time in the future
886.48 Ym – 93.7 billion light-years – The diameter of the observable universe (twice the particle horizon); however, there might be unobserved distances that are even greater.
To help compare different orders of magnitude, this section lists distances starting at 1 Rm (1027m or 110 billion light-years). At this scale, expansion of the universe becomes significant. Distance of these objects are derived from their measured redshifts, which depend on the cosmological models used.
>1 Rm - >105.7 billion light-years – Size of universe beyond the cosmic light horizon, depending on its curvature; if the curvature is zero (i.e. the universe is spatially flat), the value can be infinite (see Shape of the universe) as previously mentioned
↑ The diameter of human hair ranges from 17 to 181 μm Ley, Brian (1999). Elert, Glenn (ed.). "Diameter of a human hair". The Physics Factbook. Retrieved 8 December 2018.
↑ 10115 is 1 followed by 115 zeroes, or a googol multiplied by a quadrillion. 1010115 is 1 followed by a quadrillion googol zeroes. 101010122is 1 followed by 1010122 (a googolplex10 sextillion) zeroes.
The astronomical unit is a unit of length defined to be exactly equal to 149,597,870,700 m. Historically, the astronomical unit was conceived as the average Earth-Sun distance, before its modern redefinition in 2012.
In physics and general relativity, gravitational redshift is the phenomenon that electromagnetic waves or photons travelling out of a gravitational well lose energy. This loss of energy corresponds to a decrease in the wave frequency and increase in the wavelength, known more generally as a redshift. The opposite effect, in which photons gain energy when travelling into a gravitational well, is known as a gravitational blueshift. The effect was first described by Einstein in 1907, eight years before his publication of the full theory of relativity.
Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the International System of Units (SI) system the base unit for length is the metre.
The micrometre as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer, also commonly known by the non-SI term micron, is a unit of length in the International System of Units (SI) equalling 1×10−6 metre ; that is, one millionth of a metre.
In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings. Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ). The term "wavelength" is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids.
In optics, the Arago spot, Poisson spot, or Fresnel spot is a bright point that appears at the center of a circular object's shadow due to Fresnel diffraction. This spot played an important role in the discovery of the wave nature of light and is a common way to demonstrate that light behaves as a wave.
In computer networking, Gigabit Ethernet is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use in 1999, and has replaced Fast Ethernet in wired local networks due to its considerable speed improvement over Fast Ethernet, as well as its use of cables and equipment that are widely available, economical, and similar to previous standards. The first standard for faster 10 Gigabit Ethernet was approved in 2002.
Clementine was a joint space project between the Ballistic Missile Defense Organization and NASA, launched on January 25, 1994. Its objective was to test sensors and spacecraft components in long-term exposure to space and to make scientific observations of both the Moon and the near-Earth asteroid 1620 Geographos.
Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. It is used in optics applied to light waves, in antenna theory applied to radio waves, and in acoustics applied to sound waves. The colloquial use of the term "resolution" sometimes causes confusion; when an optical system is said to have a high resolution or high angular resolution, it means that the perceived distance, or actual angular distance, between resolved neighboring objects is small. The value that quantifies this property, θ, which is given by the Rayleigh criterion, is low for a system with a high resolution. The closely related term spatial resolution refers to the precision of a measurement with respect to space, which is directly connected to angular resolution in imaging instruments. The Rayleigh criterion shows that the minimum angular spread that can be resolved by an image forming system is limited by diffraction to the ratio of the wavelength of the waves to the aperture width. For this reason, high resolution imaging systems such as astronomical telescopes, long distance telephoto camera lenses and radio telescopes have large apertures.
A helium–neon laser or He-Ne laser is a type of gas laser whose high energetic medium gain medium consists of a mixture of ratio of helium and neon at a total pressure of approximately 1 Torr inside a small electrical discharge. The best-known and most widely used He-Ne laser operates at a wavelength of 632.8 nm, in the red part of the visible spectrum.
A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.
In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when plane waves are incident on a diffracting object, and the diffraction pattern is viewed at a sufficiently long distance from the object, and also when it is viewed at the focal plane of an imaging lens. In contrast, the diffraction pattern created near the diffracting object and is given by the Fresnel diffraction equation.
A diode-pumped solid-state laser (DPSSL) is a solid-state laser made by pumping a solid gain medium, for example, a ruby or a neodymium-doped YAG crystal, with a laser diode.
Chirped pulse amplification (CPA) is a technique for amplifying an ultrashort laser pulse up to the petawatt level, with the laser pulse being stretched out temporally and spectrally, then amplified, and then compressed again. The stretching and compression uses devices that ensure that the different color components of the pulse travel different distances.
Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine.
Multi-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Multi-mode links can be used for data rates up to 800 Gbit/s. Multi-mode fiber has a fairly large core diameter that enables multiple light modes to be propagated and limits the maximum length of a transmission link because of modal dispersion. The standard G.651.1 defines the most widely used forms of multi-mode optical fiber.
The absorption of electromagnetic radiation by water depends on the state of the water.
A laser beam profiler captures, displays, and records the spatial intensity profile of a laser beam at a particular plane transverse to the beam propagation path. Since there are many types of lasers—ultraviolet, visible, infrared, continuous wave, pulsed, high-power, low-power—there is an assortment of instrumentation for measuring laser beam profiles. No single laser beam profiler can handle every power level, pulse duration, repetition rate, wavelength, and beam size.
The angstrom or ångström is a metric unit of length equal to 10−10 m; that is, one ten-billionth (US) of a metre, a hundred-millionth of a centimetre, 0.1 nanometre, or 100 picometres. Its symbol is Å, a letter of the Swedish alphabet. The unit is named after the Swedish physicist Anders Jonas Ångström (1814–1874).
↑ Nave, Carl R. "Neutron Absorption Cross-sections". HyperPhysics. Retrieved 4 December 2008. (area for 20 GeV about 10 × 10−42 m2 gives effective radius of about 2 × 10−21 m; for 250 GeV about 150 × 10−42 m2 gives effective radius of about 7 × 10−21 m)
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↑ Stewart, Robert. "Dr". Radiobiology Software. Archived from the original on 30 June 2010. Retrieved 20 May 2015.
↑ Langevin, Dominique (2008). "Chapter 10: DNA-Surfactant/Lipid Complexes at Liquid Interfaces". In Dias, Rita S; Lindman, Bjorn (eds.). DNA Interactions with Polymers and Surfactants. Hoboken, NJ: John Wiley & Sons, Inc. p.265. doi:10.1002/9780470286364.ch10. ISBN978-0-470-25818-7. DNA has 20 elementary charges per helical turn over the corresponding length of 3.4nm
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1 2 3 4 According to The Physics Factbook, the diameter of human hair ranges from 17 to 181μmLey, Brian (1999). "Width of a Human Hair". The Physics Factbook.
↑ Duncan, Martin (2008). "16"(PDF). Physics 216 – Introduction to Astrophysics. Archived from the original(PDF) on 17 December 2008. Retrieved 14 November 2008.
↑ Annis, Patty J. October 1991. Kansas State University. Fine Particle POLLUTION. Figure 1. (tobacco smoke: 10 to 1000nm; virus particles: 3 to 50nm; bacteria: 30 to 30000nm; cooking oil smoke: 30 to 30000nm; wood smoke: 7 to 3000nm)
↑ Eninger, Robert M.; Hogan, Christopher J.; Biswas, Pratim; Adhikari, Atin; Reponen, Tiina; Grinshpun, Sergey A. (2009). "Electrospray versus Nebulization for Aerosolization and Filter Testing with Bacteriophage Particles". Aerosol Science and Technology. 43 (4): 298–304. Bibcode:2009AerST..43..298E. doi:10.1080/02786820802626355. S2CID93465533.
↑ Ramel, Gordon. "Spider Silk". Archived from the original on 4 December 2008. Retrieved 4 December 2008. garden spider silk has a diameter of about 0.003 mm ... Dragline silk (about 0.00032 inch (0.008 mm) in Nephila)
1 2 Roberts, Richard W. (1 June 1975). Metric System of Weights and Measures – Guidelines for Use. US: Director of the National Bureau of Standards. Federal Register FR Doc.75-15798 (18 June 1975). Accordingly, the following units and terms listed in the table of metric units in section 2 of the act of 28 July 1866, that legalized the metric system of weights and measures in the United States, are no longer accepted for use in the United States: myriameter, stere, millier or tonneau, quintal, myriagram, kilo (for kilogram).
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↑ "long wave". Oxford Dictionaries. Archived from the original on 1 March 2019. Retrieved 12 March 2011. wavelength above one kilometre (and a frequency below 300 kHz)
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↑ Haugen, Einar, Norwegian English Dictionary, 1965, Oslo: Universitetsforlaget and Madison: University of Wisconsin Press, s.v. mil
↑ "FAQ-Alaska Highway Facts". The MILEPOST. Archived from the original on 29 September 2007. Retrieved 25 August 2007. 1,390 miles ... Alaska Route 2 and often treated as a natural extension of the Alaska Highway
↑ Richichi, A.; Roccatagliata, V.; Shultz, Matt; Williamson, Michael H.; Moya, Andres (2005). "Aldebaran's angular diameter: How well do we know it?". Astronomy & Astrophysics. 433 (1): 305–312. arXiv:astro-ph/0502181. Bibcode:2005A&A...433..305R. doi:10.1051/0004-6361:20041765. S2CID119414301. They derived an angular diameter of 20.58±0.03 milliarcsec, which given a distance of 65 light-years yields a diameter of 61 million km.
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↑ Szpir, Michael (May–June 2001). "Bart Bok's Black Blobs". American Scientist. Archived from the original on 29 June 2003. Retrieved 19 November 2008. Bok globules such as Barnard 68 are only about half a light-year across and weigh in at about two solar masses
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