1 Planck length =
SI units
16. 163×10−36 m16. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International 163×10−27 nm
Natural units
11. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a In Physics, natural units are Physical units of Measurement defined in terms of universal Physical constants, such that some chosen physical 706 lS305. In Physics, natural units are Physical units of Measurement defined in terms of universal Physical constants, such that some chosen physical 43×10−27 a0
US customary / Imperial units
53. In the Bohr model of the structure of an Atom, put forward by Niels Bohr in 1913 Electrons orbit a central nucleus. US customary units, also known in the United States as English units or Imperial units (in reference to the British Empire) (but see English Imperial units or the Imperial system is a collection of units first defined in the British Weights and Measures Act of 1824 027×10−36 ft636. A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit 32×10−36 in

The Planck length, denoted by $\scriptstyle\ell_P \$, is the unit of length approximately 1. Inches redirects here To see the Les Savy Fav album see Inches. Length is the long Dimension of any object The length of a thing is the distance between its ends its linear extent as measured from end to end 6 × 10−35 metres, 6. 3 × 10−34 inches, or about 10−20 times the diameter of a proton. Inches redirects here To see the Les Savy Fav album see Inches. It is in the system of units known as Planck units. Planck units are Units of measurement named after the German physicist Max Planck, who first proposed them in 1899 The Planck length is deemed "natural" because it can be defined from three fundamental physical constants: the speed of light, Planck's constant, and the gravitational constant. In Physics, natural units are Physical units of Measurement defined in terms of universal Physical constants, such that some chosen physical The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. The gravitational constant, denoted G, is a Physical constant involved in the calculation of the gravitational attraction between objects with mass

## Value

The Planck length equals [1][2]

$\ell_P =\sqrt\frac{\hbar G}{c^3} \thickapprox 1.616 252 (81) \times 10^{-35} \mbox{ metres}$

where:

• c is the speed of light in vacuum;
• G is the gravitational constant;
• $\hbar$ (pronounced h-bar) is Dirac's constant, Planck's constant divided by 2π . The gravitational constant, denoted G, is a Physical constant involved in the calculation of the gravitational attraction between objects with mass The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta.

The two digits between the parentheses denote the uncertainty in the last two digits of the value. Brackets are Punctuation marks used in pairs to set apart or interject text within other text

In SI units, the Planck length is approximately 1. 6 × 10−35 metres. The estimated radius of the observable universe (4. In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that 4 × 1026 m or 46 billion light-years) is 2. 7 × 1061 Planck lengths.

## Physical significance

The physical significance of the Planck length is somewhat abstract. Because it is the only length (up to a constant factor) obtainable from the constants c, G, and $\hbar$, it is expected to play some role in a theory of quantum gravity. Quantum gravity is the field of Theoretical physics attempting to unify Quantum mechanics, which describes three of the fundamental forces of nature In some theories or forms of quantum gravity, it is the length scale at which the structure of spacetime becomes dominated by quantum effects, giving it a discrete or foamy structure, but in other theories of quantum gravity there are no such effects predicted. Quantum foam, also referred to as spacetime foam, is a concept in Quantum mechanics, devised by John Wheeler in 1955. If there are large extra dimensions (such as those implied by string theory), the measured strength of gravity may be much smaller than its true (small-scale) value; in this case the Planck length would have no physical significance, and quantum gravitational effects would appear at much larger scales. In Particle physics, the ADD model, also known as the model with large extra dimensions, is an alternative scenario to explain the weakness of Gravity relative String theory is a still-developing scientific approach to Theoretical physics, whose original building blocks are one-dimensional extended objects called strings

This thought experiment draws on both general relativity and the Heisenberg uncertainty principle of quantum mechanics. General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 Werner Heisenberg (5 December 1901 in Würzburg &ndash1 February 1976 in Munich) was a German theoretical physicist best known for enunciating the In Quantum physics, the Heisenberg uncertainty principle states that locating a particle in a small region of space makes the Momentum of the particle uncertain Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Combined, these two theories imply that it is impossible to measure position to a precision shorter than the Planck length, or duration to a precision to a shorter time interval than a Planck time. In Physics, the Planck time ( tP) is the unit of Time in the system of Natural units known as Planck units. These limits may apply to a theory of quantum gravity as well. Quantum gravity is the field of Theoretical physics attempting to unify Quantum mechanics, which describes three of the fundamental forces of nature [3][4]

## History

Max Planck was the first to propose the Planck length, a base unit in a system of measurement he called natural units. In Physics, natural units are Physical units of Measurement defined in terms of universal Physical constants, such that some chosen physical By design, the Planck length, Planck time, and Planck mass are such that the physical constants c, G, and $\hbar \$ all equal 1 and thus disappear from the equations of physics. In Physics, the Planck time ( tP) is the unit of Time in the system of Natural units known as Planck units. The Planck mass is the unit of Mass, denoted by m P in the system of Natural units known as Planck units. A physical Constant is a Physical quantity that is generally believed to be both universal in nature and constant in time Although quantum mechanics and general relativity were unknown when Planck proposed his natural units, it later became clear that at a distance equal to the Planck length, gravity begins to display quantum effects, whose understanding would seem to require a theory of quantum gravity. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons Quantum gravity is the field of Theoretical physics attempting to unify Quantum mechanics, which describes three of the fundamental forces of nature Note that at such a distance scale, the uncertainty principle begins to intrude on one's ability to make any useful statements about what is actually happening. In Quantum physics, the Heisenberg uncertainty principle states that locating a particle in a small region of space makes the Momentum of the particle uncertain

## References in science fiction

• In Hyperion by Dan Simmons, Planck length is referred to as "the shortest length possible". For the novel 'Hyperion' written by Friedrich Hölderlin see Hyperion (Hölderlin Hyperion is a Hugo Award Dan Simmons (born April 4, 1948 in Peoria, Illinois) is an American Author most widely known for his Hugo Award
• Many objects in Xenosaga are compressed to a 'planck-scale size'. --> TC --> is primarily a series of Science fiction
• A modified Planck length is used as a wish-fulfillment device in Rudy Rucker's Master of Space and Time. Rudolf von Bitter Rucker (born March 22, 1946 in Louisville Kentucky) is an American Computer scientist and Science fiction Master of Space and Time is a 1984 novel by Rudy Rucker that centers on an inventor Harry Gerber who discovers a way to create his own tailor-made universe