161 Science Riddles With Answers
Science riddles reward knowing how the world works. The answer is usually an everyday phenomenon described in unfamiliar terms - ice, a shadow, sound, gravity, your own heartbeat.
They are a natural fit for a science lesson, because solving one requires exactly the move science asks for: matching a description of behaviour to the thing that behaves that way.
Every riddle here has its answer and an explanation of the science behind it.
Where are the most sweat glands located?
While we notice underarm sweat, the highest density of glands is on the hands and feet.
How many vertebrae in the human spine?
The spine consists of 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal vertebrae.
First vaccine developed for which disease?
Edward Jenner used cowpox to immunize against smallpox in 1796.
How many chambers in the human heart?
The human heart has two atria (top) and two ventricles (bottom).
What does the gallbladder secrete?
Bile is produced by the liver and stored/concentrated in the gallbladder.
What does DNA stand for?
DNA is the hereditary material in humans and almost all other organisms.
Average weight of a newborn baby?
The average birth weight is between 5.5 and 10 pounds.
How long is the large intestine?
The large intestine is wider but much shorter than the small intestine (which is ~20ft).
How many taste buds are on the tongue?
Taste buds are located in the papillae of the tongue and decrease as you age.
How many skin cells shed every minute?
Humans shed their entire outer layer of skin every 2-4 weeks.
What is the heaviest internal organ?
The liver is the largest and heaviest internal organ, weighing about 3-3.5 lbs.
How many bones are in the human body?
Humans are born with more bones (~300) which fuse together as they grow to reach ~206.
Who created the first polio vaccines?
Salk developed the inactivated virus vaccine; Sabin developed the oral attenuated one.
How much blood is in the human body?
Blood volume is roughly 7-8% of total body weight.
What is the rarest blood type?
Rh-null has no Rh antigens at all; only about 50 people worldwide have it.
What is the largest organ in the human body?
The skin protects the body and regulates temperature; it can weigh up to 20 lbs.
World’s largest Hydroelectric Power Plant?
The Three Gorges Dam in China has the world's largest installed capacity.
What is the deepest part of the ocean?
Challenger Deep is about 10,935 meters (35,876 ft) deep.
How much does a cubic foot of water weigh?
Water density changes slightly with temperature; it is densest at 4°C.
What is the pH of water?
Pure water is neutral on the pH scale, which ranges from 0 (acidic) to 14 (basic).
How much water do Americans use daily?
The average American uses 80-100 gallons per day, but indoor use is around 50.
How long can a human live without water?
While you can live weeks without food, water is essential for life processes after a few days.
How often is the air's water replenished?
The atmosphere's water content is small but cycles extremely rapidly.
What provides 90% of atmospheric water?
Evaporation is the primary way water moves from the surface to the atmosphere.
How much of Earth’s water is saltwater?
Less than 4% of Earth's total water is fresh; the rest is saline.
Where is most freshwater located?
Over 68 percent of the world's fresh water is locked up in ice and glaciers.
How much water is stored in oceans?
About 96.5 percent of all Earth's water is held in the oceans as saltwater.
How much of Earth is covered in water?
Approximately 71% of Earth is water-covered, primarily by oceans.
How many bones are in a giraffe’s neck?
Like humans and most mammals, giraffes have only seven cervical vertebrae, but they are very large.
What is the smallest mammal on Earth?
The Etruscan shrew is the smallest mammal by mass, weighing about 1.8 grams.
What animal has the longest lifespan?
The glass sponge (Hexactinellid) can live for over 10,000 years.
What do you call a female elephant?
Adult male elephants are called bulls, while females are called cows.
What do you call a group of flamingos?
A group of flamingos is called a 'flamboyance' because of their bright colors.
How long can beavers hold their breath?
Beavers have physiological adaptations that allow them to stay submerged for long periods.
What are sea monkeys?
Sea-Monkeys are a hybrid breed of brine shrimp sold as novelty aquarium pets.
What animal kills the most humans each year?
Mosquitoes kill over 700,000 people annually by spreading diseases like malaria.
Largest mammal in North America?
The American Bison can weigh up to 2,000 pounds and stand 6 feet tall.
Which animal did Australia go to “war” with?
The Great Emu War of 1932 was a nuisance wildlife management military operation in Australia.
Length of the largest blue whale measured?
The largest recorded blue whale was a female measuring nearly 111 feet.
Average distance between Earth and the moon?
The average distance is ~384,400 km or 238,855 miles.
What planet is closest in size to Earth?
Venus is often called Earth's twin due to its similar size, mass, and composition.
Where does the asteroid belt lie?
The belt is located between the orbits of the inner rocky planets and the outer gas giants.
Who was the first American woman in space?
Sally Ride became the first US woman in space in 1983 on the STS-7 mission.
How long for the ISS to orbit the Earth?
The ISS travels at 17,500 mph, completing about 15.5 orbits per day.
How long to drive to the nearest star at 70 mph?
Proxima Centauri is 4.2 light-years away; 70 mph is incredibly slow for interstellar travel.
How long would it take to walk to the moon?
At a steady walking pace without stopping, it would take about 9 years to cover the distance.
What is the coldest planet in our solar system?
Uranus has the coldest atmosphere, with temperatures reaching as low as -224°C.
How many orbits has Neptune made since discovery?
Neptune takes ~165 years to orbit; it was discovered in 1846 and finished its first orbit in 2011.
What shape is the moon?
The moon is slightly elongated due to Earth's gravity, making it lemon-shaped.
When was our solar system formed?
It formed from a giant interstellar molecular cloud about 4.6 Gya.
Which two planets have no moons?
The inner-most planets, Mercury and Venus, are the only ones without natural satellites.
What is the hottest planet in our solar system?
Venus's thick CO2 atmosphere creates a runaway greenhouse effect, reaching 464°C.
How long for one orbit around the galactic center?
This vast period of time is often called a 'Cosmic Year'.
How fast does the solar system orbit the Milky Way?
We are traveling at over half a million miles per hour around the galaxy's center.
What color is the sunset on Mars?
Dust in the Martian atmosphere scatters blue light more effectively near the sun.
How many stars are in the universe?
There are an estimated 1,000,000,000,000,000,000,000 stars (1 septillion).
How long to fly a plane to Pluto?
Pluto is billions of miles away; even a fast plane would take centuries to arrive.
Atoms with different masses but same element?
Isotopes have the same number of protons but different numbers of neutrons.
Element named after "greenish-yellow"?
Chlorine comes from the Greek 'chloros', meaning pale green.
Who is the father of modern chemistry?
Lavoisier established the law of conservation of mass and named oxygen and hydrogen.
What element is a diamond composed of?
Diamonds are a solid form of pure carbon with its atoms arranged in a crystal structure.
Particles that make up protons and neutrons?
Quarks are elementary particles that combine to form composite particles called hadrons.
When was the first Nobel Prize in chemistry awarded?
Jacobus van 't Hoff won the first prize in 1901 for his work on chemical dynamics.
What are helium, neon, and argon called?
Noble gases are inert because they have a full outer shell of electrons.
When was the modern periodic table introduced?
While Mendeleev created the first in 1869, the version based on atomic numbers came in 1912.
At what temp are Celsius and Fahrenheit equal?
At -40 degrees, both temperature scales intersect and read the same value.
What is the newest element on the periodic table?
Oganesson (118) was officially named in 2016, completing the 7th row.
Periodic element named after Albert Einstein?
Einsteinium (atomic number 99) was discovered in the debris of the first hydrogen bomb.
Most abundant element in the Earth’s crust?
Oxygen accounts for about 46% of the Earth's crust by weight.
What is hydrogen oxide?
Hydrogen oxide (or dihydrogen monoxide) is simply the chemical name for water.
What is a solid changing directly into a gas called?
Sublimation occurs when a substance skips the liquid phase (e.g., dry ice).
What scale measures the hardness of minerals?
The Mohs scale ranks minerals from 1 (talc) to 10 (diamond).
What is the splitting of atomic nuclei called?
Nuclear fission releases a huge amount of energy by splitting heavy atoms.
What does a conchologist collect?
Conchology is the study and collection of mollusk shells.
What is the red pigment that transports oxygen?
Hemoglobin in red blood cells binds to oxygen to transport it through the body.
How long is the memory of a goldfish?
Studies show goldfish can remember things for months, debunking the 3-second myth.
Which is the only rock that floats?
Pumice is a volcanic rock full of air bubbles, giving it a density lower than water.
How long does sun light take to reach Earth?
Light travels at ~300,000 km/s; the Sun is ~150 million km away.
What is the largest desert in the world?
A desert is defined by low precipitation; Antarctica is the world's largest cold desert.
What are the most common elements in the human body?
O, C, H, and N make up the vast majority of human biological molecules.
What does a Geiger counter measure?
Geiger counters detect ionizing radiation like alpha, beta, and gamma rays.
How many bones do sharks have?
Sharks have skeletons made entirely of cartilage, not bone.
What element did Joseph Priestley discover in 1774?
Priestley isolated oxygen by heating mercuric oxide.
Are the sun and moon the same size?
The Sun is 400x larger but also 400x further away, creating an illusion of equal size.
Who is credited with the theory of evolution?
Charles Darwin published 'On the Origin of Species' in 1859.
What country has the most tornadoes?
The U.S. experiences around 1,200 tornadoes per year due to its unique geography.
What do you call molten rock before it has erupted?
Magma is below the surface; once it breaks the surface, it's called lava.
How do you determine the age of a tree?
Each ring typically represents one year of growth in a tree's life.
What element is used to create nuclear energy?
Uranium-235 is the primary fuel used in nuclear power plants.
What do you call a volcano that’s not currently erupting?
A dormant volcano is one that hasn't erupted for a long time but could again.
Which is the most abundant element in the universe?
Hydrogen makes up about 75% of the elemental mass of the universe.
What is the study of fungi called?
Mycology is the branch of biology concerned with the study of fungi.
How many colors are in the rainbow?
The rainbow consists of 7 colors: Red, Orange, Yellow, Green, Blue, Indigo, Violet.
What do you call the study of weather and atmosphere?
Meteorology focuses on atmospheric conditions and weather forecasting.
What do you call an animal that eats both plants and animals?
Omnivores, like humans and bears, consume both plant and animal matter.
How many elements are on the periodic table?
There are 118 confirmed elements, from Hydrogen to Oganesson.
What are the three layers of the Earth?
The Earth consists of the outer crust, the thick mantle, and the central core.
What is the fastest animal on land?
The cheetah can reach speeds up to 70 mph (112 km/h).
What is the largest planet in our solar system?
Jupiter is the gas giant with the largest mass and volume in our solar system.
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