Main article: Design of experiments

That the independent variable is the only factor that varies systematically in the experiment; in other words, that the experiment is appropriately controlled - that confounding variables are eliminated; and That the dependent variable truly reflects the phenomenon under study (a question of validity) and that the variable can be measured accurately (i.e., that various types of experimental error, such as measurement error can be eliminated). Nature, in the broadest sense, is the natural world, physical universe, material world or material universe. "Nature" refers to the phenomena of the physical world, and also to life in general. Manufactured objects and human interaction are, in common usage, not considered part of nature unless qualified in ways such as "human nature" or "the whole of nature". The letter A' is the first letter in the Latin alphabet. Its name in English is a^[1] (pronounced /eɪ/), plural As, As, as, or a's.^[2] The letter A can be traced to a pictogram of an ox head in Egyptian hieroglyph or the Proto-semitic alphabet.^[3] Modern generally means something that is "up-to-date", "new", or from the present time. The term was invented in the early 16th century to describe recent trends.^[1] Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe. Astronomy is one of the oldest sciences. Knowledge is defined (Oxford English Dictionary) variously as (i) expertise, and skills acquired by a person through experience or education; the theoretical or practical understanding of a subject, (ii) what is known in a particular field or in total; facts and information or (iii) awareness or familiarity gained by experience of a fact or situation. Philosophical debates in general start with Plato's formulation of knowledge as "justified true belief". There is however no single agreed definition of knowledge presently, nor any prospect of one, and there remain numerous competing theories. Systematic meansrelating to or consisting of a system2: presented or formulated as a coherent body of ideas or principles <systematic thought>3 a: methodical in procedure or plan <a systematic approach> <a systematic scholar> b: marked by thoroughness and regularity <systematic efforts>. Practice is the act of rehearsing a behavior over and over, or engaging in an activity again and again, for the purpose of improving or mastering it, as in the phrase "practice makes perfect". Sports teams practice to prepare for actual games. Playing a musical instrument well takes a lot of practice. Scientific method refers to the body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. It is based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning.^[1] A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses.^[2]

Research is a human activity based on intellectual investigation and is aimed at discovering, interpreting, and revising human knowledge on different aspects of the world. Research can use the scientific method, but need not do so.

Scientific research relies on the application of the scientific method, a harnessing of curiosity. The word originates from Latin substantia, literally meaning "standing under". The word was used to translate the Greek philosophical term ousia. Originally a term coined by Michael Faraday to provide an intuitive paradigm, but theoretical construct (in the Kuhnian sense), for the behavior of electromagnetic fields, the term force field refers to the lines of force one object (the "source object") exerts on another object or a collection of other objects. An object might be a mass particle or an electric or magnetic charge, for example. The lines do not have to be straight, in the Euclidean geometry case, but may be curved. In physics, particularly in quantum physics, a system observable is a property of the system state that can be determined by some sequence of physical operations. For example, these operations might involve submitting the system to various electromagnetic fields and eventually reading a value off some gauge. In systems governed by classical mechanics, any experimentally observable value can be shown to be given by a real-valued function on the set of all possible system states. The Universe is most commonly defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term "universe" may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world or Nature. Astronomical observations indicate that the universe is 13.73 ± 0.12 billion years old and at least 93 billion light years across. In physics, velocity is defined as the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. In the SI (metric) system, it is measured in metres per second: (m/s) or ms^-1. In physics, acceleration is defined as the rate of change of velocity, or as the second derivative of position (with respect to time). It is then a vector quantity with dimension length/time². In SI units, acceleration is measured in meters/second² (m·s^-2).

• Particle displacement, a measurement of distance of the movement of a particle in a medium as it transmits a wave. Displacement field (mechanics), an assignment of displacement vectors for all points in a body that is displaced from one state to another. Fundamental meansof or relating to essential structure, function, or facts : radical <fundamental change>; also : of or dealing with general principles rather than practical application <fundamental science> adhering to fundamentalism of, relating to, or produced by the lowest component of a complex vibration of central importance : principal <fundamental purpose> belonging to one's innate or ingrained characteristics : deep-rooted <her fundamental good humor>. Quantity is a kind of property which exists as magnitude or multitude. It is among the basic classes of things along with quality, substance, change, and relation. Quantity was first introduced as quantum, an entity having quantity. An operational definition is a showing of something — such as a variable, term, or object — in terms of the specific process or set of validation tests used to determine its presence and quantity. Properties described in this manner must be publicly accessible so that persons other than the definer can independently measure or test for them at will. An operational definition is generally designed to model a conceptual definition. Measurement is the estimation of the magnitude of some attribute of an object, such as its length or weight, relative to a unit of measurement. Measurement usually involves using a measuring instrument, such as a ruler or scale, which is calibrated to compare the object to some standard, such as a meter or a kilogram. In science, however, where accurate measurement is crucial, a measurement is understood to have three parts: first, the measurement itself, second, the margin of error, and third, the confidence level -- that is, the probability that the actual property of the physical object is within the margin of error. Distance is a numerical description of how far apart objects are at any given moment in time. In physics or everyday discussion, distance may refer to a physical length, a period of time, or an estimation based on other criteria (e.g. "two counties over"). In mathematics, distance must meet more rigorous criteria.

  In mathematics the dimension of a manifold (a type of abstract topological space) is roughly defined as the mimimum number of coordinates needed to specify every point within it^[1][2]. In the physical world the theory of relativity suggests there are four dimensions: three in space and one in time. Dimensions can be thought of as the axes in a Cartesian coordinate system, which in a three-dimensional system run left-right, up-down and forward-backward. In physics, a physical body (sometimes called simply a body or even an object) is a collection of masses, taken to be one. For example, a cricket ball can be considered an object but the ball also consists of many particles (pieces of matter). Specifically, a physical body is an object which can be described by the theories of classical mechanics, or quantum mechanics, and experimented upon with physical instruments.