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

---

	entire Web this site

P Cygni profile
P wave
Pace, Norman
pacemaker
Pacioli, Luca (1445-1517)
packed cell volume
packetizing
packing
pad abort
pad deluge
paddlewheel satellite
Paedocypris
PAET (Planetary Atmospheric Entry Test)
Pageos (Passive GEOS)
pahoehoe
PAHs
Paine, Thomas (1737-1809)
Paine, Thomas O. (1921-1992)
Pal, George (1908-1980)
Palapa
palate
paleocontact hypothesis
Paleozoic era
palimpsest
palindrome
palindromic number
Palisa, Johann (1848-1925)
palisade parenchyma
Pallas (minor planet 2)
pallasite
Palmachim
Palmer, Raymond (Arthur) (1910-1977)
Palomar Observatory
Palomar Observatory Sky Survey (POSS)
Palomar Testbed Interferometer
palpitations
Pan
pancreas
pancreatic cancer
pancreatic cancer treatment
pancreatic polypeptide
pandiagonal magic square
pandigital number
Pandora
Panel on Extraterrestrial Life
Panel 2 on Extraterrestrial Life
Pangea
pangram
panspermia
Paperclip, Operation
Pappus of Alexandria (lived c. AD 300)
parabola
parabolic flight
parabolic orbit
parabolic reentry
parabolic velocity
paraboloid
parachute
paradox
parallactic angle
parallactic displacement
parallax
parallel
parallel circuit
parallel operation of engines
parallel postulate
parallel staging
parallel universe
parallelepiped
parallelogram
parallelogram of forces
parallelogram of velocities
paralysis
paramagnetism
parameter
parametric amplifier
Paranal Observatory
paranasal sinus
parasite
parasitic disease
PARASOL (CNES satellite)
parathyroid gland
parathyroid hormone
paratyphoid fever
parenchyma
paresis
parent star
parietal bone
Paris Gun
Paris Observatory (Observatoire de Paris)
parity
Parkes Observatory
Parkes Radio Telescope
parking orbit
Parkinson's disease
Parmenides (fl. c. 475 BC)
Parrondo's Paradox
parsec (pc)
partial derivative
partial differential equation
partial eclipse
PARTICLE PHYSICS
partition number
parton
Parus
pascal (Pa)
Pascal, Blaise (1623-1662)
Pascal's mystic hexagon
Pascal's triangle
Paschen-Back effect
Pasiphaë
passive satellite
Pasteur, Louis (1822-1895)
pasteurization
patent ductus arteriosus
Pathfinder
pathogen
pathological curve
Patrick Air Force Base
Patroclus (minor planet 617)
Paul Wild Observatory
Paulet, Pedro E. (1874-1945)
Pauli exclusion principle
PAW ascent
payload
Payload Assist Module (PAM)
payload integration
payload ratio
payload specialist
payoff
Payne-Gaposchkin, Cecilia Helena (1900-1979)
P-class asteroid
Peano, Giuseppe (1858-1932)
Peano curve
Pearce, Joseph Algernon (1893-1988)
Pearls of Sluze
Pease, Francis Gladheim (1881-1938)
pectin
peculiar galaxy
peculiar motion
peculiar star
pedal curve
pedal triangle
Peekskill meteorite
Peenemünde
Peewee-1 (nuclear reactor)
peg solitaire
51 Pegasi
51 Pegasi-type planets
Pegasus (launch vehicle)
Pegasus Dwarf Spheroidal (Peg dSph, DDO 216)
Pele's hair
Pele's tears
Pelican Nebula (IC 5070)
Pell equation
Pell numbers
pellagra
Peltier effect
pelvis
Pendred syndrome
pendulum
penetration probe
penicillin
penis
Penning Trap
Pennsylvania State Pulsar Group
Penrose, Roger (1931-)
Penrose diagram
Penrose stairway
Penrose tiling
Penrose triangle
penta-
pentomino
pentose
penumbra
pepsin
peptide
peptide bond
peptide nucleic acid
peptidoglycan
Perelman, Yakov Isidorovitch (1882-1942)
perennial
perfect cube
perfect number
perfect power
perfect square
perianth
periapsis
periastron
pericardial cavity
pericarditis
pericardium
pericycle
periderm
peridotite
perigalacticon
perigee
perigee kick motor
perigee propulsion
perihelion
perilune
perimeter
period
period, of a decimal expansion
period-age relation
periodic
periodic attractor
periodic table
periodic tiling
period-luminosity relation
period-mass relation
period-spectra relation
peripheral arterial disease
peripheral nervous system
periphery
peristalsis
peritoneal cavity
peritoneum
peritonitis
perivisceral cavity
Perkin, William Henry (1838-1907)
permafrost
permeability
Permian period
Permian period
permittivity
permutation
pernicious anemia
peroxides
peroxisome
perpendicular
Perrin sequence
Perrotin, Henri (1845-1904)
Perseids
Perseus Arm
Perseus Cluster (Abell 426)
Perseus-Pisces Supercluster
Persinger, Michael
persistent train
perturbation
PET (positron emission tomography) scanning
petal
petiole
Petit-Prince
Petri dish
petrochemical
petroleum
petroleum-based propellant
Petrov, Boris N. (1913-1980)
PFS (Particles and Fields Subsatellite)
PG 1159 star
pH
Phaethon (minor planet 3200)
phage
phagocytosis
Phair, Venetia (1919-)
phalange
pharynx
phase
phase angle
phase change
phase equilibria
phase space
phase transition
phaser
phenol
phenotype
phenylalanine
phenylketonuria
PHILOSOPHY
Phillips, Hubert (1891-1964)
Phillips, Samuel C. (1921-1990)
phloem
phlogiston
Phobos
Phocaea group
Phoebe
Phoebus (nuclear reactor series)
Phoenix, Project
Phoenix Dwarf
Phoenix Lander
Pholus
phosphate
phospholipid
phosphorescence
phosphoric acid
phosphorus
phosphorus-based life
PHOTINT
photoautotrophs
photochemical
Photocorynus spiniceps
photodissociation
photoelectric cell
photoelectric effect and Einstein
photographic magnitude
photoionization
photolysis
photometer
photometry
photon
photon propulsion
photopolarimeter
photoreceptor cell
photosphere
photosynthesis
photosynthetic
photosynthetic gas exchanger
photosynthetic pigments
phototropism
phreaking
phreatic eruption
Phutball
phycobilin
phylogeny
phylum
PHYSICAL CHEMISTRY
physical chemistry
physical map
PHYSICISTS
physiological acceleration
physiological factors
phytoplankton
pi
pia mater
Piazzi, Guiseppe (1746-1826)
Piccard, Auguste (1884-1962) and Jean Félix (1884-1963)
Pic-du-Midi Observatory
Pickering, Edward Charles (1846-1919)
Pickering, William Henry (1858-1938)
Pickering, William H. (1910-)
picket ship
Pick's theorem
picosat
picric acid
Pierce, John R. (1910-2002)
piezo-electric effect
pig iron
piggyback search
pigment
Pigott, Edward (1753?-1825)
pillow lava
pilus
pinch effect
pineal gland
pinna
pinocytosis
Pinwheel Galaxy
pion
Pioneer 6
Pioneer 7
Pioneer 8
Pioneer 9
Pioneer 10
Pioneer 11
Pioneer anomaly
Pioneer plaque
Pioneer series
Pipe Nebula
Pirs Docking Compartment (ISS)
Pisces Cloud (NGC 379, 380, 382-5)
Pisces Dwarf (LGS-3)
pistil
Pistol Star
pit
pit crater
pitch (chemical)
pitch (movement)
pitch (musical)
pitch drop experiment
pitchover
pith
pituitary gland
placenta
place-value system
plage
plagioclase
plague
Plancius, Petrus (1552-1622)
Planck
Planck and the origins of quantum theory
Planck constant
Planck length
Planck time
Planck's quantum principle
plane
PLANE CURVES
plane partition
planet
PLANET (Probing Lensing Anomalies Network)
Planet- (Japanese spacecraft)
Planet Imager
planet migration
planet swallowing
Planet X
planetary features
planetary nebula
planetary protection
planetary protection test
Planetary Society
planetary system
planetary systems, formation
planetesimals
planetocentric coordinates
planets, as living beings
PLANETS AND MOONS
planisphere
plankton
plano-concave lens
plano-convex lens
plant
plant cell
plant root
plant stem
Plaskett, John Stanley (1865-1941)
Plaskett's Star (V640 Mon)
plasma (blood)
plasma (physics)
plasma detector
plasma frequency
plasma membrane
plasma sheath
plasma sheet
plasma wave detector
plasma-based life
plasmasphere
plasmid
plasmodesmata
plastic
plastic number
plastid
plate tectonics
Plateau, Joseph Antoine Ferdinand (1801-1883)
Plateau curves
Plateau's problem
platelet
platinum group
Plato
Platonic solid
Platonic year
Platonism
pleated surface
Pleiades (M45)
Pleione (28 Tauri)
Pleistocene epoch
plenitude, principle of
Plesetsk Cosmodrome
pleura
pleural cavity
pleural effusion
pleurisy
plinean eruption
Pliocene epoch
plug-hole vortex
Plum Brook Research Station
plume
plumule
pluralism
plurality of worlds
Plutarch
Pluto
Pluto, moons of
plutoid
Pluto-Kuiper Express
pluton
plutonium
PMG (Plasma Motor/Generator)
PNA
pneumonia
Poe, Edgar Allan (1809-1849)
POES (Polar Operational Environmental Satellite)
Poggendorff illusion
pogo effect
Pogue, William R. (1930-)
poikilotherm
Poincaré, (Jules) Henri (1854-1912)
Poincaré conjecture
Poincaré disk
Poinsot, Louis (1777-1859)
point
Point Mugu
point source
point-set topology
Poisson, Siméon Denis (1781-1840)
Polar
Polar BEAR (Polar Beacon Experiment and Auroral Research)
polar coordinates
polar distance
polar molecule
polar orbit
polar ring galaxy (PRG)
polar solvent
polar wandering
polarimeter
polarimetry
Polaris (Alpha Ursae Minoris)
Polarissima Borealis (NGC 3172)
polarization
polarized light
polarography
pole
pole star
poliomyelitis
pollen tube
pollination
Pollux (Beta Geminorum)
Polyakov, Valery Vladimirovich (1942-)
Pólya's conjecture
polychoron
polycube
polycyclic aromatic hydrocarbons (PAHs)
polycythemia vera
polyextremophile
polygon
polygonal number
polyhedron
polyiamond
polymerase
polymerase chain reaction (PCR)
polymerization
polymers
polymorphism
polynomial
Polyot
polyp
polypeptide
polysaccharide
polystyrene
polythene
polytope
Poncelet, Jean Victor (1788-1867)
Poncelet's theorem
Ponnamperuma, Cyril
pons
Pons, Jean Louis (1761-1831)
Pony Puzzle
Pope, Gustavus W. (1829-?)
population
Population I
Population II
population types
pore
porosity
porphin
porphyria
porphyrins
Portia
posigrade motion
posigrade rocket
positional angle
positional cloning
positive g
positron
positron emission tomography (PET) scanning
positronium
Post, Wiley Hardeman (1898-1935)
postage stamp problems
posterior
potassium
potential difference
potential energy
potential theory
potentially hazardous asteroid
potentiometer
Potok
power (mathematics)
power (physics)
power law
power series
power tower
powered landing
powerful number
Poynting-Robertson effect
p-process
practical number
Praesepe (M44, NGC 2632)
pragmatism
praseodymium
prebiotic
prebiotic evolution
Precambrian
preceding
precessing orbit
precession
prednisone
pregnancy
prelaunch
prelaunch test
pre-main-sequence object
presbyopia
pre-Socratic philosophy
presolar grains
pressure
pressure broadening
pressure feed system
pressure ionization
pressure limit
pressure ridges
pressure suit
pressurized-water reactor
prevalve
Príbram meteorite
Priestley, Joseph (1733-1804)
primary
primary endosperm nucleus
primary growth
primary immunodeficiency
primary mirror
primate
PRIME (Precision Recovery Including Maneuvering Entry)
Prime Directive
prime focus
prime meridian
prime number
primer
primitive material
primitive root
primitive root of unity
primorial
primordial atmosphere
Prince Rupert's problem
principal quantum number
principle of equivalence
prisoner's dilemma
Private (rocket)
probability
probability theory
Probing Lensing Anomalies Network (PLANET)
procambium
Proclus Diadochus (c. AD 410-485)
Proctor, Richard Anthony (1837-1888)
Procyon (Alpha Canis Minoris)
progesterone
prograde
Progress
progressive burning
Project Apollo
Project Argus
Project BETA
Project Blue Book
Project Cyclops
Project Daedalus
Project Gemini
Project Grudge
Project Longshot
Project Manhigh
Project Mercury
Project META
Project Mogul
Project Orbiter
Project Orion
Project Ozma
Project Phoenix
Project Prometheus
Project Rover
Project Sentinel
Project Sign
Project Skyhook
Project Stargazer
Project Twinkle
projectile
projective geometry
projective plane
prokaryote
prokaryotic
prokaryotic cell
prolactin
prolate
prolate spheroid
Prometheus
Prometheus, Project
promethium
prominence
promoter
prompt neutron
prone g
pronic number
pronucleus
proof
propanol
propellant
propellant mass ratio
propellant storage
propellant utilization
PROPELLANTS
proper motion
PROPERTIES OF MATTER
prophase
proplastid
proplyd
proportional
proportional counter
propulsion
propulsion system
Propulsive Small Expendable Deployer System (ProSEDS)
prosimian
Prospector
Prospero (moon of Uranus)
Prospero (UK artificial satellite)
prostaglandin
prostate cancer
prostate cancer treatment
prostate gland
prosthetic group
protease
proteinoids
proteins
Proteus
protists
protactinium
protobiological
protobionts
protocells
Proton (rocket)
proton (particle)
proton flare
proton-proton chain
protoplanet
protoplanetary disk
protoplanetary nebula
protoplasm
protostar
protostellar core
protozoan
Proxima Centauri (Gliese 551)
proximal
Przybylski's Star (HD 101065)
pseudocrater
pseudogene
pseudopodium
pseudoprime
pseudosphere
PSLV (Polar Satellite Launch Vehicle)
PSR 1257+12
PSR B1620-26
psychic teleportation
psychrophiles
PTI
Ptolemaic system
Ptolemy (c. 100-168)
Ptolemy's Cluster (M7, NGC 6475)
Ptolemy's theorem
puberty
Puck
puerperal fever
pulley
pulmonary arterial hypertension
pulmonary artery
pulmonary embolism
pulsar
pulsar planets
pulsar timing noise
pulsar wind nebula
pulsating variable
pulse detonation engine
pulse oximetry
pulsed plasma thruster (PPT)
pulse-jet
pumice
punctuated equilibrium
pupil
Puppis A
Purcell, Edward M. (1912-)
pure mathematics
purge
purines
Purkinje effect
pursuit curve
pus
puzzle jug
puzzle rings
PV Telescopii star
pyramid
pyramidal number
Pyrex
pyridine
pyrimidines
pyrite
pyroclastic
pyroclastic flow
pyroxene
pyrrole
pyruvic acid
Pythagoras (c. 569- c. 500 BC)
Pythagoras's theorem
Pythagorean triangle
Pythagorean triplet