SPECTRUM   :   

The distribution of wavelengths and frequencies.

SPICULES   :   

The grass-like patterns of gas seen in the solar atmosphere.

STARCH   :   

The major complex carbohydrate of caloric value from plant products. Starch is a polymer made of thousands of glucose units.

STATIC ELECTRICITY   :   

Describes the situation where objects carry a charge at rest and interactions between them.

STATISTICS   :   

The mathematical procedure to describe probabilities and the random or non-random distribution of matter or occurrence of events.

STEM CELL   :   

Stem cells are specialized cells of animals and plants that have the ability to grow and divide by mitosis. Cell division results in self-regeneration as well as differentiation. This means that stem cells can maintain their characteristic as stem cells (self-regeneration), but also change into a different cell type (differentiation).

STEM CELLS   :   

Stem cells are found in many different organs and tissues of the body, including bone marrow, liver and skin. Adult stem cells are able to divide and form a few types of cell. For example, blood stem cells, usually extracted from bone marrow can become red blood cells or white blood cells.

STISHOVITE   :   

A dense, high-pressure phase of quartz that has so far been identified only in shock-metamorphosed, quartz-bearing rocks from meteorite impact craters.

STOCK   :   

In ecological cycles and models, the amount of a material in a certain medium or reservoir.

STOMATA   :   

Tiny openings or pores, found mostly on the under-surface (epidermis) of a plant leaf, and used for gas exchange.

STRATIGRAPHIC RECORD   :   

Sequences of rock layers. Correlating the sequences of rock layers in different areas enables scientists to trace a particular geologic event to a particular period.

STRATOSPHERE   :   

The cold region of a planetary atmosphere above the convecting regions (the troposphere), usually without vertical motions but sometimes exhibiting strong horizontal jet streams.

SUBDUCTION   :   

The process in which one plate is pushed downward beneath another plate into the underlying mantle when plates move towards each other.

SUBLIME   :   

Sublimation occurs when a substance changes directly from a solid to a gas without becoming liquid.

SUCCESSION   :   

A fundamental concept in ecology that refers to the more or less predictable and orderly changes in the composition or structure of an ecological community.

SULCUS   :   

Subparallel furrows and ridges.

SULFUR DIOXIDE   :   

A colorless, extremely irritating gas or liquid (SO2), used in many industrial processes, especially the manufacture of sulfuric acid. In the atmosphere it can combine with water vapor to form sulfuric acid, a major component of acid rain.

SULFURIC ACID   :   

A heavy, corrosive, oily, dibasic strong acid H2SO4 that is colorless when pure; it is a vigorous oxidizing and dehydrating agent.

SUNSPOT   :   

An area seen as a dark spot on the photosphere of the Sun. Sunspots are concentrations of magnetic flux, typically occurring in bipolar clusters or groups. They appear dark because they are cooler than the surrounding photosphere.

SUPER CONDUCTIVITY   :   

The flow of electricity without any resistance at certain temperatures near absolute zero in certain temperatures is known as super conductivity.

SUPERIOR PLANETS   :   

The planets Mars, Jupiter, Saturn, Uranus, Neptune and Pluto are superior planets because their orbits are farther from the Sun than Earth's orbit.

SYNAPSIS   :   

When crossing over occurs during the pairing of homologous chromosome pairs during prophase of the first meiotic division is known as synapsis.

SYNCHRONOUS ORBIT RADIUS   :   

The orbital radius at which the satellite's orbital period is equal to the rotational period of the planet. A synchronous satellite with an orbital inclination of zero (same plane as the planet's equator) stays fixed in the sky from the perspective of an observer on the planet's surface. These orbits are commonly used for communications satellites.

SYNCHRONOUS ROTATION   :   

A satellite's rotational period is equal to its orbital period; this causes the same side of a satellite to always face the planet. Synchronous rotation occurs when a planet's gravity produces a tidal bulge in its satellite. The gravitational attraction and bulge acts like a torque, which slows down the satellite until it reaches a synchronous rotation.

SYNERGISM   :   

The result obtained with the help of two agents that work together which could not have been possible by independent agents is known as synergism.

SYNGAMY   :   

The sexual reproduction by the union of gametes or fertilization is known as syngamy.

SYNTENY   :   

The state where two or more genes are located on the same chromosome even thought there may or may not be any demonstrable linkage between them is known as synteny.

SYNTHETIC-APERTURE RADAR   :   

SAR is a side-looking imaging system that uses the Doppler effect to sharpen the effective resolution in the cross-track direction.