1. It reflects off the ocean.
   When oxygen interacts with nitrogen, it turns blue.
2. Blue light scatters more than other colors.
   When moonlight mixes with sunlight, it turns blue.

Light comes from the sun and although it may seem white, it is actually made up of every color of the rainbow. All the particles in the Earth's atmosphere then absorb those colors, but since blue light is a shorter and choppier wavelength than other colors, it gets scattered around the sky.

1. Andromeda
   Milky Way
2. Messier 81
   Canis Major

A galaxy is a collection of space particles, gases and stars all held together by gravity. A solar system is a system of planets and objects orbiting the Sun. There are at least 100 billion galaxies in the universe. Our galaxy is called the Milky Way.

1. Neptune
   Saturn
2. Earth
   Jupiter

Jupiter is half a billion miles away from the Sun and is the largest planet in our solar system. It is more than double the size of all other planets in the solar system combined and has 79 moons. It takes 12 years for Jupiter to orbit the Sun.

1. A seed
   Soil
2. A tree
   Bacteria

Soil is not a living thing but is home to many living things. A seed is a living thing that is in a dormant state, and inside a seed is a plant embryo. All living things require nutrients, and all living things excrete waste. Rivers, mountains and dirt are nonliving.

1. 2 hydrogen atoms bonded to 1 oxygen atom
   1 hydrogen atom bonded to 1 oxygen atom
2. 1 hydrogen atoms bonded to 2 oxygen atoms
   2 hydrogen atoms bonded to 2 oxygen atoms

Hydrogen loves bonding to oxygen, and when two hydrogen atoms bond to one oxygen atom, water forms. The formula for water is H2O and water can be created in many different ways, both naturally and artificially.

1. Gases
   Liquids
2. Solids
   A mixture of all three

Clouds are made of dry air (gas), water droplets (liquid) and ice (solid). Not all clouds are made of all three states of matter, but all clouds are made of dry air. Dry air makes up about 95% of a cloud, but intense storm clouds might contain a higher percentage of water vapor.

1. A large meteorite began perfectly orbiting the sun.
   Gravity pulled gases and particles together.
2. A piece of the sun broke off.
   Five asteroids smashed into each other.

Over the course of about 10 billion years, gravity pulled gases and particles together until molecular clouds were formed. One of these clouds collapsed and formed the sun and a ring of particles formed around it. Then gravity took another 20 million years to pull enough gases and particles together to form Earth.

1. 1 day
   1 week
2. 1 month
   1 year

It takes 365.25 days for Earth to orbit the sun, which is one year. Every four years we have a leap year that consists of 366 days. It takes about one month for the moon to orbit Earth and about one day for Earth to complete one full rotation on its axis.

1. Shark
   Platypus
2. Seal
   Dolphin

Sharks are fish and not mammals, but some of them do give birth the same way mammals do. Most fish lay eggs and most mammals give birth to live young. The duck-billed platypus and some anteaters are the only mammals that lay eggs.

1. Sight
   Touch
2. Itching
   Hearing

Humans have five basic senses but we also have others like proprioception, which is the sense of space. This allows people to move a fork to their mouth without having to watch their hand the whole way. Our vestibular sense lets us know whether we're sitting down or standing up, or sitting in a moving car or a parked car.

1. Iron and nickel
   Aluminum
2. Carbon and nitrogen
   Silicon

The Earth's inner core is at the center of the planet and is about 4,000 miles deep, so we haven't actually obtained a sample. It is estimated to be made of an iron and nickel alloy and is about 10,000 degrees Fahrenheit, which is the same as the Sun's surface temperature.

1. Nitrogen
   Carbon
2. Hydrogen
   Oxygen

The most abundant element in the universe is hydrogen, which makes up about 75% of all baryonic matter in space. Hydrogen is atomic number one on the periodic table of elements, meaning its nucleus only has one proton.

1. Double helix molecule
   Deoxyribonucleic acid
2. Divided nucleus acids
   Double nucleic acid

Deoxyribonucleic acid (DNA) is the double-helix molecule that codes the identity of every living thing. It is one of, if not the, most complex molecule in the universe and isn't fully understood. It was first discovered by a Swiss biologist in 1869.

1. K2
   Mt. Everest
2. Manaslu
   Makalu

Mount Everest rises higher above sea level than any other mountain on Earth, at 29,000 feet tall. The tallest mountain in the world, base to summit, is Mauna Kea, which only rises 13,000 feet above sea level, but also extends 20,000 feet below sea level.

1. Pacific Ocean
   Atlantic Ocean
2. Indian Ocean
   Arctic Ocean

The Pacific Ocean is the largest ocean in the world at more than 60 million square miles, although all the oceans do connect with each other. The Pacific is also the deepest ocean in the world and reaches about seven miles deep at its deepest point.

1. Russia
   China
2. India
   The United States

Russia is the largest country in the world by land size at more than 6 million square miles, which is bigger than Antarctica. It is only the ninth largest country in terms of population with 144 million residents, which is less than half of the U.S.

1. First
   Fourth
2. Second
   Third

Mercury, Venus, Earth and Mars are the first four planets from the Sun in order. The third position is apparently the perfect distance from the sun, as Earth is the only planet that sustains life as we know it.

1. Lungs
   Gills
2. Fins
   Ears

Water is two parts hydrogen and one part oxygen, so fish are able to take in water through their mouths and then their gills are used to absorb oxygen from the water. Once absorbed, fish expel carbon dioxide and excess water through their gills

1. Avocado
   Celery
2. Eggplant
   Tomato

Avocados, eggplants and tomatoes are all fruits that are commonly mistaken as vegetables. To make things more complicated, chefs sometime consider them vegetables because of their savory tastes, but botanically, they are fruits. Celery is a vegetable

1. Kinetic energy
   Nuclear energy
2. Solar energy
   Sonic energy

There are many types of energy humans can harness from natural sources, and solar energy might be the cleanest source of renewable energy in the universe. Solar energy absorbs sunlight and converts it into usable energy.

1. Great Barrier Reef
   Florida Reef
2. Andros Coral Reef
   Red Sea Coral Reef

The Great Barrier Reef is a system of about 3,000 coral reefs that extend for about 1,500 miles in the Coral Sea off the coast of Australia. It is the longest reef in the world. The New Caledonian barrier reef is the longest continuous reef in the world.

1. 22
   40
2. 32
   58

A full set of adult teeth includes four molars that may or may not have been removed at some point in your life. If you have all your teeth, you should have 32 teeth. Teeth are the hardest parts of the human body but there are plenty of ways they can still break.

1. 40
   46
2. 23
   17

Humans have 23 pairs of chromosomes to total 46 individual chromosomes. Chromosomes are the building blocks of identity and the first 22 pairs of chromosomes are identical in both males and female humans. The 23rd set controls the reproductive organs.

1. Sirius
   Polaris
2. Betelgeuse
   The sun

The sun is the Earth's nearest star as it's only 93 million miles away. It takes just eight minutes for light to travel from the sun to Earth. The North Star (Polaris) is 323 light years away, meaning when you look at it, you are seeing what it looked like 323 years ago.

1. Colossus of Rhodes
   Great Pyramid of Giza
2. Temple of Artemis at Ephesus
   Lighthouse of Alexandria

The Great Pyramid of Giza is both the oldest Ancient Wonder of the World and the only one that is largely intact. It was built in 2500 BC and is more than 400 feet tall. The first ancient wonder to be destroyed was the Temple of Artemis in 356 BC.

1. A global system of connected computers
   A browser that allows you to search anything
2. A gigantic database of information
   The World Wide Web

The internet is a system of interconnected computers that can communicate and share with each other. The World Wide Web is not the internet. It is an information system hosted on the internet. You need to use the internet to access the World Wide Web.

1. An underwater tornado
   Gravitational pull
2. Sudden motion on the ocean floor
   A hurricane in the ocean

Normal waves rise and fall with the tide and are caused by the sun and Moon's gravitational pull. A tsunami or seismic wave isn't formed by gravity, but by a displacement of water caused by a sudden motion on the ocean floor. Above-water disturbances can also cause tsunamis, but underwater earthquakes, eruptions and explosions are the usual cause.

1. Gas
   Wood
2. Solid
   Liquid

Wood is not a state of matter. It is a solid. The three basic states of matter are solids, liquids and gases, but there are other states of matter in science. Degenerate matter and plasma are a couple of the less-popular states of matter.

1. 10
   4
2. 8
   12

Earth's atmosphere is five layers thick and Earth itself is four layers thick. The surface of Earth is the crust, which is about 1,800 miles deep. The second layer is the mantle, the third is the outer core, and the center of Earth is called the inner core, which is about 85% iron.

1. 2
   4
2. 6
   8

Helium is the second most abundant element in the universe and also has an atomic number of two, which means its nucleus only has two protons. Although helium is extremely abundant, it is so light that it easily escapes Earth's gravitational pull, so mining it isn't the easiest.

1. Homeostasis
   Photosynthesis
2. Evolution
   Metamorphosis

Metamorphosis is when an animal goes through distinct stages of life, like a caterpillar turning into a butterfly. Not all animals go through metamorphosis. Humans are born small and then grow, but tadpoles don't grow into bigger tadpoles, they morph into frogs.

1. Galileo Galilei
   Louis Pasteur
2. Nicholas Copernicus
   Isaac Newton

In 1687, Isaac Newton published his research that outlined the discovery of gravity. He's also known for his Three Laws of Motion, which are the basis of a lot of physics.

1. Oxygen
   Carbon
2. Nitrogen
   Helium

The atmosphere is almost 80% nitrogen and 20% oxygen with about 5% of the atmosphere being comprised of other gases. The five layers of the atmosphere are the exosphere, thermosphere, mesosphere, stratosphere and troposphere.

1. Silicon
   Lithium
2. Carbon
   Hydrogen

Cellphones use rechargeable lithium-ion batteries that were first created in the 1970s. North America only has one known lithium mine and doesn't produce much of the element. Lithium is mostly produced in Australia, Chile and China.

1. Homo Erectus
   Neanderthals
2. Panthera Tigris
   Homo Sapiens

Modern humans are part of the genus called Homo and the species called Sapiens. All humans that have ever roamed Earth, including Neanderthals, are part of the Homo genus, but Sapiens are the only species still on Earth today.