Why on Earth? Trivia Quiz

Answer: Because the Earth is spinning on its axis.

Almost everything in the universe, from the largest suns to the smallest particles, is spinning. The Earth is no exception. If we looked down at the Earth from above the North Pole, we would see it spinning counter clockwise. This is why the sun rises in the east and sets in the west. If the Earth were spinning the opposite way, the direction the sun travels across the sky would also be reversed.

It takes the Earth about 23 hours and 56 minutes to spin once on its axis. Why is it not an even 24 hours like our day length? Because the Earth is also moving around the sun, slowly changing where the sun is relative to the Earth. Those four extra minutes are to compensate for the Earth's travel, and bring the sun back to the same place in the sky.

The Earth spinning on its axis gives us our day. The Earth orbiting the sun gives us our year. The sun never goes out to recharge; it is always shining. We just can't see it when we're on the side of the Earth facing away. When the moon blocks out the sun, it is a rare event called a solar eclipse.

Answer: Because the Earth's axis is tilted relative to the orbital plane.

Most globes you see do not have the Earth spinning on an axis pointed straight at the ground. Usually it's angled at about 23 degrees. This is to better reflect reality, where the Earth has an axial tilt (most planets do, to varying degrees).

In the winter, the axis points away from the sun, and in the summer, the axis points towards the sun. This will change how much sun any given part of the Earth will experience during the day. It's also why the sun goes overhead in summer, while in winter it sometimes seems to barely get over the horizon. Near the equator, there is not much noticeable change. Farther away, the Earth experiences seasons and different amounts of daylight. It can become so extreme near the poles that in summer, daylight can last a whole month, and in winter there is a month-long night.

The opposite ends of the Earth experience the opposite effects. If it is winter in the northern hemisphere, then it is summer in the southern hemisphere. If the north is experiencing spring and getting ready for warm weather, then those in the south are going through fall, and are bundling up.

If the Earth did not have its tilt, then the weather and climate would not change throughout the year. It would always be hot at the equator and get gradually, predictably colder the closer you got to the poles.

Answer: Because the moon's gravity pulls the oceans towards it.

The reason the Earth's moon doesn't just fly away is because of gravity. The Earth is pulling the moon towards itself. However, we also know that every force has an equal and opposite force, which means the moon is also pulling the Earth towards itself. The moon is a lot smaller than the Earth, and so it doesn't have quite the same effect on the Earth, and cannot just pull the giant Earth around. However, the Earth is covered by a lot of water, which is a lot easier to pull than solid rock.

The moon pulls the Earth's water towards itself, creating a bulge on the part facing the moon. On the opposite side of Earth, inertia creates a second bulge. Because the Earth is rotating, the part that is facing the moon is always changing, and these bulges "move" around the Earth, creating the ebb and flow of tides


We get about two tides every day because the Earth rotates once per day and the moon stays (relatively) almost still. The moon does change slightly, orbiting the Earth about once a month, which throws off the calculations a bit.

Every celestial body affects every other one, but the smaller or father away they are, the less that effect is felt. The sun is much bigger, but also much farther away than the moon. It also plays a role in tides, although reduced. When the sun and the moon are aligned, the Earth experiences larger tides (King Tides). When the sun and moon are not aligned, the Earth experiences smaller tides.

Answer: Because the Earth's magnetic field guides charged particles.

The sun is constantly performing fusion reactions, releasing large amounts of energy every second. The high-energy charged particles are flung away by the sun in every direction (the solar wind). These particles would be dangerous to life on Earth if the Earth did not have a magnetic field. The Earth is a giant magnet, with its magnetic poles very near the poles of its axis. This means that magnetic field lines enter and exit the Earth near the poles, and wrap around the rest of the Earth, protecting it from the high-energy charged particles.

Because the the magnetic field lines travel towards the Earth near the poles, rather than across it, the high-energy particles are guided towards the Earth instead of away. These energetic particles interact with atoms in our atmosphere, and the energy released from those interactions is the auroras that can be seen near the north and south poles.

In the north, auroras are called aurora borealis, or the northern lights. In the south, they are called aurora australis.

Answer: Because the Earth is in the sun's habitable zone.

The habitable zone is often called the "Goldilocks zone" because it's not too warm and its not too cold. Too warm, and the water would vapourise. Too cold, and the water would freeze. The Earth sits at a distance from the sun that is not too hot or cold, but just right for liquid water to exist.

Venus is closer to the sun, and comparable to the Earth in size. It also has an atmosphere, but experienced a runaway greenhouse effect, and is incredibly hot. Liquid water cannot exist on Venus because it would instantly vapourise.

Mars is a planet farther away from the sun, and so far only frozen ice has been found on it.

There are other factors at play, but the habitable zone is arguably the most important. If the Earth did not have a magnetic field, it might lose its atmosphere, or be bombarded by the sun's energy without any shielding, which would affect its ability to retain liquid water.

Mars does not have a thick atmosphere or magnetic field thought to be required to sustain water. Mars may have once had a magnetic field, atmosphere, and liquid water, which is often what scientists are seeking evidence of with their Mars missions. Liquid water is considered a probable requirement for life forming, and would be very interesting to find on Mars.

Answer: Because tectonic plates push into each other.

Almost all mountains on Earth appear near tectonic plate boundaries, and are a result of the movement of those plates. When two plates press against one another, one will go down under the other in a process called subduction. The result is that the other plate, many kilometers thick, will get pushed towards the sky, creating mountains. There are a few nuances distinguishing different types of mountain formation, but almost all involve the movement of tectonic plates.

Animals can create large mounds of dirt, but not the large solid rock formations we know as mountains. Wind can create sand dunes, which slowly migrate, but cannot crush sand into solid rock. The moon's gravity is strong enough to move the Earth's water about slightly, but has no effect on mountain formation.

Answer: Because hot spots of magma under the crust melt through and spew out lava.

Magma is hot (it is liquid rocks). Sometimes, some parts of the mantle (the layer just below the crust) can become abnormally hot, and can start to melt through the crust. This is what happened with Hawaiian islands. A hot spot formed in the middle of the Pacific plate and melted through.

As it melted through, magma came through the hole and solidified. As magma kept coming up and solidifying, an island was formed. As the pacific plate slowly moved across the the hot spot over hundreds of thousands of years, a chain of islands formed, with the oldest in the north-west, and the newest in the south-east.

Answer: Because the Earth has an ozone layer.

Electromagnetic radiation can have different effects on use depending on its energy. The radiation we are most concerned with is ionizing radiation, which is ultraviolet or stronger (x-ray, gamma ray, etc.). The sun does produce radiation along the entire spectrum, but thanks to Planck's Law, it produces only small amounts of the really dangerous stuff. The sun does still output a lot of UV, though, which can be dangerous to humans (and most organisms). Thankfully, the Earth has the ozone layer.

Ozone is a chemical, made up of three oxygen atoms. It is an unstable molecule (oxygen usually exists as just two oxygen atoms) and is toxic to humans. When ozone is created, it will naturally move up to an altitude of about 25km (a quarter of the way to "space"), where it will accumulate in what we know as the ozone layer.

While we most certainly don't want to be around ozone ourselves, it does provide an excellent shield against ultraviolet light, absorbing upwards of 95% of all incoming UV rays. Depleting the ozone layer will mean more UV can get through, which will lead to increased risks of skin cancer, among other complications.

Answer: Because underground water flows erode underlying rock and soil

Sinkholes appear all over the world, including underwater. In fact, the deepest sinkholes are found in the ocean, and are often explored by scuba divers (though they are not nearly as deep as ocean trenches).

Sinkholes are often formed when water can trickle through the ground and erode and wash away underlying rocks and soil a little bit at a time. Over years, enough of the underlying structure can be washed away that the top layer can no longer be supported, and the structure caves in.

Sinkholes are often tourist attractions for scuba divers and cave explorers, and can host very interesting formations and ecosystems. However, we most often see sinkholes when they form in urban centres, often causing public health and safety risks, and immense damage to local infrastructure. An example of this happening was in Guatemala City in 2007 and 2010.

Answer: Because the Earth has a jetstream.

The jet streams are actually multiple wobbly air currents that circle the Earth. They exists in both the north and south, though are absent near the equator and poles. They usually exist at an altitude of 10 to 15 kilometers. Commercial passenger jets usually fly around 10km up. Those flying in the direction of the jet stream will often fly a bit higher to take advantage of the extra speed. Those flying in the opposite direction will often fly lower so they don't have to use extra fuel to fly against the winds.

If the Earth's rotation were to assist airplanes flying faster, we would expect to see the planes flying towards to west to be faster. Instead, we see the opposite.