A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

R association
R Coronae Borealis star
R Leonis
R Sculptoris
R Scuti
"R" series of Russian missiles
Rabi, Isidor Isaac (1898–1988)
rabies
racemic mixture
rad
radar
RADARSAT
radial artery
radial engine
radial nerve
radial pulsation
radial symmetry
radial velocity method
radian
radiant
radiation
radiation pressure
radiation temperature
radiation therapy
radical
radicle
radio
radio astronomy
RADIO ASTRONOMY AND COMMUNICATIONS
radio galaxy
radio telescope
radio waves
radioactive series
radioactivity
radioglyph
radioisotope
radioisotope heater unit (RHU)
radioisotope thermoelectric generator (RTG)
radiolarian
radiometer
radionuclide
radionuclide scanning
radioresistant
radiosonde
radium
radius
radius (arm bone)
radius of gyration
radon
Radose
Raduga
radula
RAE (Radiation Astronomy Explorer)
railroad
railways, early history
rain
rainbow
raised beach
Raman, Chandrasekhar Venkata (1888–1970)
Raman effect
Raman spectroscope
Ramanujan, Srinivasa Aaiyangar (1887–1920)
ramjet
ramjet, interstellar
Ramo, Simon (1913–2016)
Ramsay, William (1852–1916)
Ramsden disk
Ramsey theory
ramus
random
random drift
random number
random walk
range (math.)
range finder
range safety officer
Ranger
Rankine, William John Macquorn (1820–1872)
Rankine scale
ranunculoid
Raoult's law
rare earth elements
Rasalhague (Alpha Ophiuchi)
Ra-Shalom
ratchet
ratio
rational number
rationalism
rattlesnake
Rauschenbach, Boris Viktovich (1915–2001)
raven paradox
Rayleigh, John William Strutt, Third Baron (1842–1919)
Rayleigh criterion
Rayleigh scattering
Rayleigh-Taylor instability
Raynaud's disease
reactance
reaction control system
reaction engine
reaction mass
Reaction Research Society
reaction wheel
reactionless drive
real analysis
real number
realism
Reber, Grote (1911–2002)
receptor-mediated endocytosis
recessive
reciprocal
recombination
reconnaissance satellite
Recorde, Robert (c. 1510–1558)
recovery (of a spacecraft)
rectangle
rectangular coordinates
rectifier
rectum
rectus abdominis
recursion
recursive function
recursively enumerable set
red algae
red dwarf
red giant
red rain of Kerala
Red Rectangle
Red Spider Nebula (NGC 6537)
Red Square
red supergiant
red tide
Redi, Francesco (1626–1697)
redox reaction
redshift
Redstone
reducing agent
reduction
reductionism
redundancy
reentry
REENTRY PHYSICS AND TERMINOLOGY
reentry thermal protection
reentry vehicle
Rees, Eberhard Friedrich Michael (1909–1998)
refining
reflecting binary
reflecting telescope
reflection
reflection nebula
reflector
reflex
reflex arc
refracting telescope
refraction
refractive index
refractor
refractory
refrigeration
refugium
regenerated disk
regeneration
regenerative cooling
regimes of flight
regmaglypt
Regnault, Henri Victor (1810–1878)
regolith
regression of nodes
regular expression
regular polyhedron
Regulus
relative atomic mass
relative molecular mass
relative permeability
relatively prime
relativistic beaming
relativistic effects
relativity theory
relaxation
Relay
relief
rem
Remek, Vladimir (1948–)
Remote Manipulator System
remote sensing
remote sensing satellite
renal dialysis
renin
repdigit
replicator
reproduction
reproduction in flowering plants
reproductive system
rep-tile
reptile
reptiles, early
reptiles and amphibians, unusual
reptiles in the Mesozoic
rep-unit
RESEARCH FACILITIES AND ESTABLISHMENTS
resin
resistance, electrical
resistivity
resistojet
Resnik, Judith A. (1949–1986)
resolution
resolution bandwidth
resonance (in acoustics and physics)
resonance (in chemistry)
resonance (orbital)
resorcinol
respiration
respiratory disease
respiratory distress syndrome
respiratory failure
respiratory system
restless legs syndrome
Resurs
reticular formation
reticulite
reticulo-endothelial system
Reticulum (constellation)
retina
retort
retrograde (motion)
retrovirus
Reuleaux Triangle
Reutersvärd, Oscar (1915-2002)
revolution
REX (Radiation Experiment)
Reynaud, Jean (1806–1863)
Reynolds number
Rh incompatibility
Rhea
rhenium
rheostat
rhesus factor
RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager)
Rheticus (1514–1574)
rheumatic fever
rheumatoid arthritis
Rhind papyrus
rhinitis
rhizome
Rho Cassiopeiae
Rho Coronae Borealis
Rho Ophiuchi Nebula
rhodium
rhodopsin
rhomboid
rhombus
rhynchocephalia
rhyolite
rib
rib-cage
riboflavin
ribonucleic acid
ribose
ribosomal DNA
ribosomal RNA
ribosome
ribozymes
Riccioli, Giovanni Battista (1598–1671)
Richards, Theodore William (1868–1928)
Richardson, Owen Willans (1879–1959)
richest field telescope
Richter, Hermann Eberhard (1808–1876)
Richter scale
Rickettsia
Ride, Sally Kristen (1951–2012)
Riedel, Klaus (1901–1944)
Riemann, (Georg Friedrich) Bernhard (1826–1866)
Riemann hypothesis
Riemann surface
Riemann zeta function
rift valley
rift zone
Rigel (Beta Orionis)
right ascension
rigidity
rille
rima glottidis
ring (mathematics)
ring (planetary)
Ring Nebula (M57, NGC 6720)
Ringworld
ringworm
Ritchey-Chrétien telescope
Rithmomachia
Ritter, Johann Wilhelm (1776–1810)
Rittenhouse, David (1732–1796)
river
river-crossing problems
riveting
RME (Relay Mirror Experiment)
RNA (ribonucleic acid)
Robby the Robot
Robert's Quartet
Robinson, Abraham (1918–1974)
robot
Roche limit
Roche lobe
Rochon prism
rock
rock cycle
rocket
ROCKET ENGINE TYPES
ROCKET ENGINEERS AND SPACE SCIENTISTS
rocket equation
rocket launch terminology
rocket plane
rocket propellants
rocket sled
ROCKETRY, HISTORY
ROCKETRY, TERMINOLOGY
ROCKETS, MISSILES, AND LAUNCH VEHICLES
rockoon
Rockot
rod cell
Roddenberry, (Eu)Gene Wesley (1921–1991)
Rodentia
rogue planet
rogue star
Rohini
Rolle's theorem
Rolls-Royce Thrust-measuring Rig ("flying bedstead")
Roman numerals
Rømer, Ole (1644–1710)
Ronchi test
Röntgen, Wilhelm Carl (1845–1923)
röntgen (unit)
rooks problem
Roosa, Stuart A. (1933–1994)
root (mathematics)
root (botany)
rope
rope-around-the-Earth puzzle
Roque de los Muchachos Observatory
rorqual whale
RORSAT (Radar Ocean Reconnaissance Satellite)
Rosalind
Rosamund's Bower
ROSAT (Roentgen Satellite)
rose curve
Rosen, Milton W. (1915–2014)
Rosetta
Rosette Nebula (NGC 2237-2239, 2246)
Rosny, J. H. (the Elder) (1856–1940)
Ross, Frank Elmore (1874–1960)
Ross, H(arry) E.
Ross, Ronald (1857–1932)
Ross 128
Ross 154
Ross 248
Rosse, Third Earl of (William Parsons) (1800–1867)
Rossi, Bruno Benedetto (1905–1993)
rostrum
Roswell incident
rotating variable
rotation
rotation curve
rotation period
rotator cuff
rotavirus infection
Rothrock, Addison M. (1903–1971)
Roton
rotor
roulette
round
round window
round-trip light time
roundworm
Roux, Pierre Paul Émile (1853–1933)
Rover, Project
Royal Astronomical Society
Royal Greenwich Observatory
Royal Institution
RP-318
r-process
RR Lyrae star
RS Canum Venaticorum star
RS Ophiuchi
RTG
R-type asteroid
rubber
rubble-pile asteroid
rubella
rubidium
Rubik's Cube
ruby
Rucker, Rudy (1946–)
rudaceous
Rudolph, Arthur L. (1906–1996)
Ruggieri, Claude (fl. early 19th century)
ruled surface
Rumford, Benjamin Thompson, Count (1753–1814)
ruminant
runaway star
runner
R.U.R. (Rossum's Universal Robots)
Russell, Bertrand Arthur William (1872–1970)
Russell, Henry Norris (1877–1957)
Russian launch sites
Russian launch vehicles
Russian manned lunar programs
Russian multiplication
Russian Space Agency (RKA)
Russian Space Research Institute (IKI)
rust
Rutan, Elbert L. "Burt" (1943–)
ruthenium
Rutherford, Ernest (1871–1937)
Rutherford's experiment and atomic model
rutherfordium
rutile
Ruzicka, Leopold Stephen (1887–1976)
RV Tauri star
RXTE (Rossi X-ray Timing Explorer)
Rydberg, Johannes Robert (1854–1919)
Ryle, Gilbert (1900–1976)
Ryle, Martin (1918–1984)
Rynin, Nikolai Alexsevitch (1887–1942)
Ryusei