L series (Japanese rockets)
L1551 (IR5)
L5 Society
La Silla Observatory
La Superba (Y Canum Venaticorum)
Lacaille, Abbé Nicolas Louis de (1713–1762)
Lacaille 9352
LACE (Low-power Atmospheric Compensation Experiment)
Lacerta (constellation)
lacrimal gland
Lacrosse
lacteal
lactic acid
lactose
laevorotatory
Lageos (Laser Geodynamics Satellite)
Lagoon Nebula (M8, NGC 6523)
Lagrange, Joseph Louis de (1736–1813)
Lagrangian orbit
Lagrangian points
lahar
L'Aigle meteorite shower
Laika
Laing-Garrington effect
Lake Vida
Lake Vostok
Lalande 21185
Lalande, Joseph Jérôme Le Français de (1732–1807)
Lamarck, Jean Baptiste (Pierre Antoine) de Monet (1744–1829)
Lambda Bootis star
lambda calculus
Lambda Eridani star
Lambert, Johann Heinrich (1728–1777)
Lamé curve
laminar flow
lamination
Landsat
Langley, Samuel Pierpont (1834–1906)
Langley Research Center
Langley's adventitious angles
Langton's ant
lanolin
lanthanide
lanthanum
lapilli
Laplace, Pierre Simon, Marquis de (1749–1827)
Large Binocular Telescope (LBT)
Large Hadron Collider
large intestine
Large Magellanic Cloud (LMC)
Large Millimeter Telescope (LMT)
large numbers
Large Southern Array (LSA)
large-scale structure
largest Kuiper Belt objects
Larissa
Larmor precession
larva
laryngeal nerve
larynx
laser
laser propulsion
Lassell, William (1799–1880)
Lasswitz, Kurd (1848–1910)
Last and First Men
late heavy bombardment
latent heat
lateral
lateral meristem
late-type galaxy
late-type star
Latin square
latissimus dorsi
latitude
latitude variation
lattice
lattice path
lattice point
lattice theory
latus rectum
launch
launch control center
launch pad
LAUNCH SITES
launch support and hold-down arm
launch umbilical tower
launch vehicle
launch window
launcher deflector
lava
lava delta
lava flow
lava fountain
lava lake
lava tube
Lavoisier, Antoine Laurent (1743–1794)
Lawrence, Ernest Orlando (1901–1958)
lawrencium
laws of reflection
laxative
LBT
LDEF (Long Duration Exposure Facility)
Le Chatelier's principle
Le Gentil, Guillaume Joseph Hyacinthe Jean Baptiste (1725–1792)
Le Prieur, Yves Paul Gaston (1885–1963)
lead (Pb)
leading hemisphere
leaf
leaf primordium
league
leap second
leap year
Leasat (Leased Satellite)
least common multiple
least upper bound
Leavitt, Henrietta Swan (1868–1921)
Lebedev, Valentin V. (1942–)
Lebesgue, Henri Leon (1875–1941)
Lebombo bone
Leda
Lederberg, Joshua (1925–2008)
Leeuwenhoek, Anton van (1632–1723)
legionnaire's disease
legume
Leibniz, Gottfried Wilhelm (1646–1716)
Leibniz harmonic triangle
Leinster, Murray (1896–1975)
leishmaniasis
Lem, Stanislaw (1921–2006)
Lemaître, Georges Édouard (1894–1966)
lemma
lemniscate of Bernoulli
Lemonnier, Pierre Charles (1715–1799)
lens
lens (eye)
Lense-Thiring effect
lenticel
lenticular galaxy
LEO (low Earth orbit)
Leo (constellation)
Leo I
Leo II
Leo III
Leo Minor (constellation)
Leonard Euler Telescope
Leonardo da Vinci (1452–1519)
Leonids
Leonov, Alexei Archipovich (1934–)
leprosy
lepton
lepton flavor violation
Lepus (constellation)
LES (Lincoln Experimental Satellite)
lesion
Leucippus
leucoplast
leukemia
leukemia treatment
leukocyte
Leurechon, Jean (c.1591–1670)
Leuschner Observatory
leveled thrust
lever
Leverrier, Urbain Jean Joseph (1811–1877)
Levin, Gilbert (1925–)
Levin's hypothesis, about the active nature of the Martian soil
Levy, David H. (1948–)
Lewis, C(live) S(taples) (1898–1963)
Lewis and Clark
Lewis Research Center
Lexell, Comet (D/1770 L1)
Ley, Willy (1906–1969)
Lhote, Henri (1903–1991)
Liais, Emmanuel
Liar paradox
Libra (constellation)
libration
lichen
Lick Observatory
lidar (light detection and ranging)
Lie, Marius Sophus (1842–1899)
Lie algebra
Lie group
Liebig, Justus von (1803–1873)
Life, article on UFOs (1952)
life, classification
life, detection
life, extraterrestrial
life, in space
life, nature
life, origin
life, variety
Life, Conway's Game of
Life Finder
life support
life zone
lifetime, of extraterrestrial civilizations
lift
lift-drag ratio
lifting-body
liftoff
ligament
ligand
ligase
light
light barrier
light cone
light curve
light echo
light element
light flash phenomenon
light pollution
light pressure
light time
lightning
light-year (ly)
lignin
Lilienthal, Otto (1848–1896)
Lilly, John Cunningham (1915–2001)
limaçon of Pascal
limb
limb correction
limb darkening
limbic system
limestone
limit (mathematics)
limit load
limit pressure
limiting magnitude
limping triangle
limu
LINCOS
Lindblad, Bertil (1895–1965)
Lingbergh, Charles Augustus (1902–1974)
Lindsay, David (1878-1945)
Lindsay-Shapley Ring (AM0644-741)
line
line blanketing
line broadening
line displacement
line of nodes
line profile
line ratio
line spectrum
line width
lineament
linear (mathematics)
LINEAR (Lincoln Near Earth Asteroid Research) program
LINEAR, Comet (C/1999 S4)
linear algebra
linear accelerator
linear energy transfer
linear group
linear programming
linear system
LINER (low-ionization nuclear emission-line region)
linkage
Liouville number
lip
lipase
lipid
lipid bilayer
lipofuscin
Lippershey, Hans (c.1570–c.1619)
Lippincott, Sarah Lee
Lippisch Ente
LiPS (Living Plume Shield)
liquefaction of gases
liquid
liquid-air cycle engine
liquid hydrogen
liquid oxygen (LOX)
liquid propellant
liquid-fueled rocket
liquid-propellant rocket engine
LISA (Laser Interferometer Space Antenna)
Lissajous figure
Lissajous orbit
Listeners, The
Lister, Joseph (1827–1912)
lithium (Li)
lithium depletion boundary
lithium hydroxide
lithium-rich star
lithopanspermia
lithosphere
lithotrophs
Little Dipper
Little Dumbbell Nebula (M76, NGC 650 and 651)
Little Gem Annular Nebula (NGC 6818)
"little green men"
Little Joe
little LEO
littoral cone
Littrow, Joseph Johann von (1781–1840)
lituus
liver
liver cancer
liver cancer treatment
LMC
load factor
loading
Lobachevsky, Nikolai Ivanovich (1793–1856)
lobe
Local Bubble
Local Group
local horizon
local hour angle (LHA)
Local Interstellar Cloud (LIC)
local standard of rest
Local Supercluster
local time
local vertical
localized solution
Loch Ness monster
Locke, John (1632–1704)
Locke, Richard Adams (1800–1871)
Lockheed Martin
Lockman Hole
Lockyer, (Joseph) Norman (1836–1920)
loculus or Archimedes
locus
lodranite
logarithm
logarithmic spiral
logic
logical depth
logical positivism
Lo'ihi Underwater Volcanic Vent Mission Probe
Lomonosov, Mikhail Vasilievich (1711–1765)
long bone
Long March
long QT syndrome
longitude
longitude at the epoch
longitude of perihelion
longitude of the ascending node
longitudinal axis
long-period comet
long-period variable
Longshot, Project
loop
loop prominence
Lorenz, Edward Norton (1917–)
Lorenz system
Lorentz, Henrik Antoon (1853–1928)
Lorentz contraction
Lorentz force turning
"Los Angeles Air Raid"
Losat-X (Low Altitude Satellite Experiment)
Lost City meteorite
Lost In Space
lost languages
Lousma, Jack Robert (1936–)
Lovejoy, Arthur Onck (1873–1962)
Lovelace, William Randolph, II (1907–1965)
Lovell, (Alfred Charles) Bernard (1913–)
Lovell, James Arthur, Jr. (1928–)
Lovell Telescope
Lovelock, James E. (1919–)
Low, Archibald Montgomery (188–1956)
low Earth orbit (LEO)
low surface brightness galaxy
Lowell, Percival (1855–1916)
Lowell Observatory
lower back pain
lower transit
low-gain antenna
low-velocity star
loxodrome
Loyd, Sam (1841-1911)
lozenge
LSA
LSAT
L-system
Lubbock Lights
Lucas, (François) Edouard (Anatole) (1842–1891)
Lucas sequences
Luch
Lucian of Samosata (AD c.120–180)
Lucid, Shannon Matilda Wells (1943–)
Lucky 13
lucky number
Lucretius (c.99–55 BC)
Ludolph's number
lumbar puncture
lumbar vertebra
lumen (lm)
luminosity
luminescence
luminosity class
luminosity function
luminous flux
luminous intensity
luminous mass
Lump Star (NGC 2023)
Luna
Lunan, Duncan (Alasdair) (1945–)
lunar eclipse
Lunar Landing Research Vehicle (LLRV)
Lunar Orbiter
lunar parallax
lunar phases
lunar polarization
Lunar Prospector
Lunar Receiving Laboratory
Lunar Reconnaissance Orbiter
Lunar Roving Vehicle (LRV)
Lunar-A
lunarian
lunar-orbit rendezvous (LOR)
lunation
Lundin, Bruce T. (1919–2006)
lune
lung cancer
lung cancer treatment
lung function tests
lung ventilation-perfusion scan
lungs
Lunik
Lunine, Jonathan
lunisolar
Lunney, Glynn S. (1936–)
Lunokhod
lupus
Lupus (constellation)
luteinizing hormone
lutetium
lux (lx)
Luyten, Willem Jacob (1899–1994)
Luyten 726-8 (UV Ceti)
Luyten 789-6
Lyapunov fractal
Lyapunov orbit
Lyman series
Lyman-alpha
Lyman-alpha forest
lymph
lymph node
lymphangioleiomyomatosis (LAMS)
lymphatic organ
lymphatic system
lymphatic vessel
lymphocyte
lymphoma
Lyndon B. Johnson Space Center
Lynx (constellation)
Lyra (constellation)
Lysithea
lysosome
lysozyme