物体が地球から離れ去っていくときには、その物体から発せられる光はより波長の長いものとして（赤っぽい色に）見えます。物体が地球に向かってくるときは、その物体から発せられる光はより波長の短いものとして（青っぽい色に）見えます。の英語

When an object moves away from Earth, the light that it is giving off is seen in longer wavelengths. When an object moves toward Earth, the light that it is giving off is seen in shorter wavelengths.

By looking at an object's electromagnetic spectrum, scientists can determine if an object is moving away from Earth or towards Earth.

the action of producing a monochromatic beam of light by exciting electrons to a higher energy level and causing them to radiate energy, called a laser

either of two fine mutually perpendicular lines that cross in the focus plane of an optical instrument and are use for sighting or calibration

As for the air, there is always some moisture in the atmosphere, but when the amount increases a great deal, it affects the light waves.

fuel consisting of the remains of organisms preserved in rocks in the earth's crust with high carbon and hydrogen content

the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate)

a chemical bond in which one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion

a chemical bond consisting of a hydrogen atom between two electronegative atoms (e.g., oxygen or nitrogen) with one side be a covalent bond and the other being an ionic bond

an inactive substance that is a vehicle for a radioactive tracer of the same substance and that assists in its recovery after some chemical reaction

used of a compound (especially of carbon) containing atoms sharing more than one valence bond

characteristic of or relating to the physical properties of solid materials especially electromagnetic or thermodynamic or structural properties of crystalline solids

used of organisms (especially of different species) living together but not necessarily in a relation beneficial to each

a vacuum tube in which a hot cathode emits a beam of electrons that pass through a high voltage anode and are focused or deflected before hitting a phosphorescent screen

a thin fluid layer next to the surface of a stationary body in which fluid flows at a much slower velocity than elsewhere

The rapid spin of the Earth along with the liquid, hot metallic core causes a magnetic field to surround the Earth.

The retina detects light with two types of cells: cone cells in the light, and rod cells in the dark.

shiny substance that resemble enamel and is secreted by the corium of certain fishes (especially ganoid fishes) and composes the outer layer of their scales

atmospheric electricity (lasting 10 msec) appearing as globular flashes of red (pink to blood-red) light rising to heights of 60 miles (sometimes seen together with elves)

a phenomenon in which, when associating an electrified body with a conductor the side of the conductor facing the electrified body takes on the same electric charge as the electrified body and the side opposite to electrified body takes

of or relating to a defect in the eye or in a lens caused by a deviation from spherical curvature which prevents light rays from meeting at a common focus and so results in distorted images

a colored glassy compound (opaque or partially opaque) that is fused to the surface of metal or glass or pottery for decoration or protection

a physical theory of relativity based on the assumption that the speed of light in a vacuum is a constant and the assumption that the laws of physics are invariant in all inertial systems

formed by blending unlike elements especially by reducing one element to particles and dispersing them throughout another substance

an electric cell that cannot be recharged after its contents have been chemically changed

the three traditional states of matter are solids (fixed shape and volume) and liquids (fixed volume and shaped by the container) and gases (filling the container)

a chemical reaction in which a completely new substance is created by altering the atomic makeup of the two or more substances used in the reaction

an electrically charged particle built up from polymeric molecules or ions and occurring in certain colloidal electrolytic solutions like soaps and detergents

the condition of a picture that is blurred by the difference in wave length when light focuses into image

a white crystalline peroxide used in bleaching (flour or oils or fats) and as a catalyst for free radical reactions