An atmosphere (from Greek ἀτμός (atmos), meaning 'vapour', and σφαῖρα (sphaira), meaning 'sphere'[1][2]) is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low. The atmosphere of Earth
Earth is composed of nitrogen (about 78%), oxygen (about 21%), argon (about 0.9%) with carbon dioxide and other gases in trace amounts. Oxygen
Oxygen is used by most organisms for respiration; nitrogen is fixed by bacteria and lightning to produce ammonia used in the construction of nucleotides and amino acids; and carbon dioxide is used by plants, algae and cyanobacteria for photosynthesis. The atmosphere helps to protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays
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In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium.[1][2] This includes:electromagnetic radiation, such as radio waves, microwaves, visible light, x-rays, and gamma radiation (γ) particle radiation, such as alpha radiation (α), beta radiation (β), and neutron radiation (particles of non-zero rest energy) acoustic radiation, such as ultrasound, sound, and seismic waves (dependent on a physical transmission medium) gravitational radiation, radiation that takes the form of gravitational waves, or ripples in the curvature of spacetime. Radiation
Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules, and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms
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The number e is a mathematical constant, approximately equal to 2.71828, which appears in many different settings throughout mathematics. It was discovered by the Swiss mathematician Jacob Bernoulli while studying compound interest,[1] where e arises as the limit of (1 + 1/n)n as n approaches infinity
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In physics, a force is any interaction that, when unopposed, will change the motion of an object.[1] A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force
Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F. The original form of Newton's second law
Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time
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A cryptographic hash function is a special class of hash function that has certain properties which make it suitable for use in cryptography. It is a mathematical algorithm that maps data of arbitrary size to a bit string of a fixed size (a hash) and is designed to be a one-way function, that is, a function which is infeasible to invert. The only way to recreate the input data from an ideal cryptographic hash function's output is to attempt a brute-force search of possible inputs to see if they produce a match, or use a rainbow table of matched hashes
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In science and engineering, the weight of an object is related to the amount of force acting on the object, either due to gravity or to a reaction force that holds it in place.[1][2][3] Some standard textbooks[4] define weight as a vector quantity, the gravitational force acting on the object. Others[5][6] define weight as a scalar quantity, the magnitude of the gravitational force. Others[7] define it as the magnitude of the reaction force exerted on a body by mechanisms that keep it in place: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero
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Ultraviolet
Ultraviolet (UV) is an electromagnetic radiation with a wavelength from 100 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present in sunlight constituting about 10% of the total light output of the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Suntan and sunburn are familiar effects of over-exposure of the skin to UV, along with higher risk of skin cancer
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Photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities (energy transformation). This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", and σύνθεσις, synthesis, "putting together".[1][2][3] In most cases, oxygen is also released as a waste product. Most plants, most algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs
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As of 2014[update] the taxonomy was under revision[1][2]Chroococcales Chroococcidiopsidales Gloeobacterales Nostocales Oscillatoriales Pleurocapsales Spirulinales Synechococcales Incertae sedis†Gunflintia†OzarkcolleniaSynonymsMyxophyceae Wallroth, 1833 Phycochromaceae Rabenhorst, 1865 Cyanophyceae Sachs, 1874 Schizophyceae Cohn, 1879 Cyanophyta Steinecke, 1931 Oxyphotobacteria Gibbons & Murray, 1978 Cyanobacteria
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Cyanobacteria /saɪˌænoʊbækˈtɪəriə/, also known as Cyanophyta, are a phylum of bacteria that obtain their energy through photosynthesis,[4] and are the only photosynthetic prokaryotes able to produce oxygen.[5] The name "cyanobacteria" comes from the color of the bacteria (Greek: κυανός, translit. kyanós, lit. 'blue').[6][7] Cyanobacteria
Cyanobacteria (which are prokaryotes) used to be called "blue-green algae"
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Algae
Algae (/ˈældʒi, ˈælɡi/; singular alga /ˈælɡə/) is an informal term for a large, diverse group of photosynthetic organisms that are not necessarily closely related, and is thus polyphyletic. Included organisms range from unicellular microalgae genera, such as Chlorella
Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length. Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomata, xylem, and phloem, which are found in land plants. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra
Spirogyra and the stoneworts. No definition of algae is generally accepted
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A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure
Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis to help find surface troughs, high pressure systems and frontal boundaries. Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be transported from place to place matching the atmospheric pressure to the corresponding altitude, while a barometer is kept stationary and measures subtle pressure changes caused by weather
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Amino acids
Amino acids are organic compounds containing amine (-NH2) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid.[1][2][3] The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids. About 500 naturally occurring amino acids are known (though only 20 appear in the genetic code) and can be classified in many ways.[4] They can be classified according to the core structural functional groups' locations as alpha- (α-), beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other categories relate to polarity, pH level, and side chain group type (aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.)
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A molecule is an electrically neutral group of two or more atoms held together by chemical bonds.[4][5][6][7][8] Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions. In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are monoatomic molecules.[9] A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with oxygen (O2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (H2O)
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Nucleotides are organic molecules that serve as the monomer units for forming the nucleic acid polymers deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules in all life-forms on Earth. Nucleotides are the building blocks of nucleic acids; they are composed of three subunit molecules: a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and at least one phosphate group. They are also known as phosphate nucleotides. A nucleoside is a nitrogenous base and a 5-carbon sugar. Thus a nucleoside plus a phosphate group yields a nucleotide. Nucleotides also play a central role in life-form metabolism at the fundamental, cellular level
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Nitrogen
Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia (NH3) or other molecules available to living organisms.[1] Atmospheric nitrogen or molecular dinitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds. The fixation process frees nitrogen atoms from their triply bonded diatomic form, N≡N, to be used in other ways. Nitrogen
Nitrogen fixation is essential for some forms of life because inorganic nitrogen compounds are required for the biosynthesis of the basic building blocks of plants, animals and other life forms, e.g., nucleotides for DNA and RNA, the coenzyme nicotinamide adenine dinucleotide for its role in metabolism (transferring electrons between molecules), and amino acids for proteins. Therefore, as part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer
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The surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface. The surface gravity may be thought of as the acceleration due to gravity experienced by a hypothetical test particle which is very close to the object's surface and which, in order not to disturb the system, has negligible mass. Surface gravity is measured in units of acceleration, which, in the SI system, are meters per second squared
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