Science & Nature
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Play This Puzzle →A few sample clues
This invisible force, described by Newton's laws, pulls objects toward one another.
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This desert-dwelling mammal stores fat, not water, in the hump on its back.
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A tiny species of this insect-eating mammal, the Etruscan, is considered the smallest land mammal by weight.
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A biological molecule that speeds up chemical reactions in living things is called this.
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This large flightless African bird is both the largest bird and the fastest running bird alive.
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All 100 questions in this topic, with answers — use it to study, or just browse. Every actual play of the puzzle only pulls a random handful of these into one game, so knowing them all here won't spoil which ones show up or where they're hidden in the grid. Play it here.
A community of interacting organisms and their physical environment together form this.
ECOSYSTEMThe first vaccine ever developed, by Edward Jenner in 1796, protected against this deadly disease.
SMALLPOXThis physicist developed the theory of relativity, including E=mc².
EINSTEINA region of spacetime with gravity so intense that nothing, not even light, can escape is called a black '_ _ _ _.'
HOLEThis South American rainforest, the world's largest, produces roughly a fifth of the planet's oxygen.
AMAZONThis Arctic whale is nicknamed the "unicorn of the sea" for its long, spiraled tusk.
NARWHALThis slow-moving reptile holds the record for longest-lived land animal, with some individuals over 190 years old.
TORTOISEThis tree species, also in California, includes the largest trees on Earth by trunk volume: Giant '_ _ _ _ _ _ _.'
SEQUOIAThis colorful, dancing light display near the polar regions is caused by solar particles hitting the atmosphere.
AURORAThis distant object, once considered the ninth planet, was reclassified as a dwarf planet in 2006.
PLUTOThis layer of Earth beneath the crust is made of slowly flowing, semi-molten rock.
MANTLEThe organ that controls thought, memory, and the rest of the nervous system is this.
BRAINThe leading scientific theory for how the universe began is called the Big '_ _ _ _.'
BANGThis colorful crustacean can throw one of the fastest, most powerful punches in the animal kingdom: the Mantis '_ _ _ _ _ _.'
SHRIMPThis long-necked African mammal is the tallest living land animal.
GIRAFFEThe reticulated species of this legless reptile is the world's longest snake.
PYTHONThis absolute-zero-based temperature scale is named after a British physicist.
KELVINThis innermost layer of Earth is a solid ball of iron and nickel despite extreme heat.
COREThese extinct reptiles dominated Earth for over 150 million years before disappearing.
DINOSAURThis nocturnal bird of prey can rotate its head up to 270 degrees to see behind itself.
OWLThis Australian mammal is one of only a few that lay eggs instead of giving live birth.
PLATYPUSThe chemical symbol for this life-essential liquid is H2O.
WATERThis hormone, discovered in 1921, regulates blood sugar and is used to treat diabetes.
INSULINA layer of gas high in Earth's atmosphere that blocks most harmful ultraviolet radiation is called the '_ _ _ _ _' layer.
OZONEThis amphibian can breathe through its skin as well as its lungs.
FROGThe largest animal ever to exist on Earth is the Blue '_ _ _ _ _.'
WHALELarge biomolecules made of amino acid chains, essential for nearly every bodily function, are called this.
PROTEINThe basic physical unit of heredity, made of DNA, is called this.
GENESingle-celled microorganisms, some helpful and some harmful, found almost everywhere on Earth are called this.
BACTERIAA long period of significant temperature drop across the Earth is called an Ice '_ _ _.'
AGEThis tropical bird is instantly recognizable by its oversized, colorful beak.
TOUCANThis lightest and most abundant element in the universe powers stars through fusion.
HYDROGENThe scale most commonly used to measure the magnitude of an earthquake is named after this seismologist.
RICHTERThis ringed planet is the second-largest in the solar system.
SATURNThis English physicist and mathematician formulated the laws of motion and universal gravitation.
NEWTONThis tallest grass in the world can grow up to 3 feet in a single day.
BAMBOOThis three-letter molecule carries the genetic instructions for all known living organisms.
DNAThe preserved remains or traces of an ancient organism, often found in rock, are called this.
FOSSILThis naturalist developed the theory of evolution by natural selection after his voyage on the HMS Beagle.
DARWINThis diving bird of prey is the fastest animal on Earth, reaching over 240 mph in a hunting dive.
PEREGRINEThis lightweight noble gas, lighter than air, is used to make balloons float.
HELIUMThis big cat is the only one that can roar but cannot purr, unlike smaller cats.
LIONThis tropical plant produces the world's largest seed, weighing up to 40 pounds.
COCODEMERThis burrowing African mammal's name means "earth pig" in Afrikaans.
AARDVARKThis Mexican salamander can regenerate entire limbs, and even parts of its brain and heart.
AXOLOTLThis bird species undertakes the longest known migration of any animal, flying pole to pole each year.
TERNThis precious yellow metal does not tarnish or corrode, making it valuable for millennia.
GOLDThis element forms the chemical basis of all known life on Earth.
CARBONThis Australian marsupial sleeps up to 22 hours a day, largely due to its low-nutrient eucalyptus diet.
KOALAAlexander Fleming's accidental 1928 discovery of an antibiotic mold gave us this drug: Peni'_ _ _ _ _ _.'
CILLINThis tropical cyclone, called a typhoon in the Pacific, is fueled by warm ocean water.
HURRICANEA slow-moving mass of dense ice, formed over long periods of snow accumulation, is called this.
GLACIERThe green species of this South American snake is the world's heaviest, especially after a big meal.
ANACONDAThis marine mammal has the largest brain of any animal on Earth, even larger than an elephant's — it's also known by an older whaling-era nickname.
CACHALOTKitti's hog-nosed species of this flying mammal is the smallest in the world by body length.
BATThis ancient, horseshoe-shaped arthropod has existed largely unchanged for 400 million years and has blue blood used in medical testing: Horseshoe '_ _ _ _.'
CRABThis nearly indestructible microscopic creature, able to survive the vacuum of space, is nicknamed the water '_ _ _ _.'
BEARThis deep-sea fish family uses a glowing lure dangling from its head to attract prey in total darkness.
ANGLERA massive, gravitationally bound system of stars, gas, and dust — like our own Milky Way — is called this.
GALAXYThis ancient tree species, found in California's White Mountains, includes individuals over 4,800 years old: Bristle'_ _ _ _' pine.
CONEThe basic signaling cell of the nervous system, which transmits electrical impulses, is called this.
NEURONThis second planet from the sun is the hottest in the solar system due to its thick atmosphere.
VENUSThis lightweight, corrosion-resistant metal is the most abundant metal in Earth's crust.
ALUMINUMThis natural satellite phenomenon occurs when Earth passes directly between the sun and the moon.
ECLIPSEEarth's only natural satellite, visible at night, is simply called this.
MOONThis African beetle is one of the heaviest insects on Earth, weighing over three ounces as a larva.
GOLIATHThis eight-armed sea creature has three hearts and blue-colored blood.
OCTOPUSThis scale, based on water's freezing point at 0 degrees and boiling point at 100, is used by most of the world.
CELSIUSSound cannot travel through this: the near-total absence of matter found in outer space.
VACUUMThis element, essential for human respiration, makes up about 21% of Earth's atmosphere.
OXYGENThis trunk-bearing mammal is the largest living land animal.
ELEPHANTThe largest living structure on Earth, visible from space off Australia's coast, is the Great Barrier '_ _ _ _.'
REEFThis scientist won Nobel Prizes in two different sciences — physics and chemistry: Marie '_ _ _ _ _.'
CURIEThis flowering plant, native to Indonesia, produces the largest single flower in the world and smells of rotting flesh.
RAFFLESIAThis carnivorous plant snaps shut on insects that trigger tiny hairs on its leaves: Venus '_ _ _ _ _ _ _.'
FLYTRAPThis lizard can rotate its eyes independently and change color to match its mood or surroundings.
CHAMELEONThis unit measures the loudness of sound, named after the inventor of the telephone.
DECIBELThis violent, rapidly rotating column of air, common in the central US, can level buildings in seconds.
TORNADOA microscopic infectious agent, smaller than bacteria and unable to reproduce without a host cell, is called this.
VIRUSThis largest planet in the solar system is a gas giant with a Great Red Spot storm.
JUPITERThis liquid metal is the only metal that's liquid at room temperature, once used in thermometers.
MERCURYThis South American rodent, often kept as a pet, is the largest living rodent in the world.
CAPYBARAEarth's crust is broken into large, slowly shifting pieces called tectonic '_ _ _ _ _ _.'
PLATESThis Antarctic seabird cannot fly but is an exceptional swimmer, some species diving over 500 meters deep.
PENGUINThis gemstone, formed from extreme heat and pressure on carbon, is the hardest known natural material.
DIAMONDThis insect can lift objects many times its own body weight, proportionally among the strongest animals alive.
ANTThis big cat is the fastest land animal, capable of speeds over 60 mph in short bursts.
CHEETAHThis fourth planet from the sun is nicknamed the "Red Planet" for its rusty, iron-oxide surface.
MARSAn opening in Earth's crust that releases molten rock, ash, and gases is called this.
VOLCANOThis fungus, found underground and prized by chefs, can sell for thousands of dollars per pound.
TRUFFLEThe muscular organ that pumps blood throughout the body is this.
HEARTThis natural phenomenon, caused by sunlight refracting through raindrops, produces a multicolored arc in the sky.
RAINBOWThis towering California tree species includes the tallest living trees on Earth.
REDWOODThis Italian astronomer improved the telescope and provided key evidence for a sun-centered solar system.
GALILEOA massive object from space, believed to have triggered the extinction of the dinosaurs, is this.
ASTEROID