Fact or Fiction | Common misconceptions about planet Earth

At first glance, the Earth appears to be a perfect sphere, especially when we observe it from space. However, upon closer examination, it becomes evident that its shape slightly deviates from a perfect sphere. The Earth is flattened at the poles and bulges at the equator, forming an ellipsoid that geodesists refer to as a geoid.

This seemingly minor difference in shape plays a significant role when conducting precise measurements on the planet's surface. If we consider the Earth to be a perfect sphere when calculating coordinates or distances, we will encounter inaccuracies that can be critical in navigation, geodesy, and other fields. For example, satellite navigation systems like GPS account for the Earth's ellipsoidal shape to provide high-precision location data.

The reason for this shape is the Earth's rotation around its axis. This rotation creates a centrifugal force that slightly "inflates" the planet in the equatorial region. Additionally, the Earth's mass is distributed unevenly, which also affects its shape and gravitational field.

At first glance, it might seem that as altitude increases, the air temperature constantly and uniformly decreases. And indeed, up to a certain point, this is true: for every kilometer climbed within the first 11 kilometers of the atmosphere, the temperature drops by about 6.5°C, reaching around –56.6°C at an altitude of 11 kilometers.

However, the Earth's atmosphere is not just a homogeneous layer of air but a complex system divided into several layers with different physical and chemical properties. After the 11-kilometer mark, the stratosphere begins, where temperature behaves differently. Between 11 and 25 kilometers, the temperature remains almost unchanged, staying stable.

Between 25 and 40 kilometers, something unexpected happens: the temperature starts to rise, from –56.5°C to +0.8°C. At an altitude of about 40 kilometers, it reaches approximately 0°C and remains at this level up to about 55 kilometers.

Then, in the mesosphere, the temperature drops again, decreasing by 0.25–0.3°C for every 100 meters climbed. At around 90 kilometers, the thermometer drops to –90°C, making it the coldest point in the vertical temperature distribution of the atmosphere.

But that's not the end of the temperature surprises. Above 90 kilometers, in the thermosphere, the temperature rises again, reaching impressive values of around 1,500 Kelvin (approximately +1226°C) at altitudes of 200–300 kilometers. After that, it remains almost unchanged at greater heights.

These temperature fluctuations are associated with different processes occurring in each layer of the atmosphere. For example, in the stratosphere, the temperature increase is due to the absorption of ultraviolet radiation by the ozone layer, while in the thermosphere, it is caused by the absorption of solar radiation by rarefied gases.

Understanding how temperature truly distributes with altitude not only dispels common misconceptions but also has practical significance. It's important for aviation, astronautics, and meteorology, helping to predict weather conditions and ensure flight safety. The Earth's atmosphere is a complex and dynamic system, full of unexpected changes and fascinating phenomena that continue to attract the attention of scientists and researchers.

It might seem logical that the deeper we go into the Earth's interior, the stronger gravity becomes. However, the opposite occurs: as we move toward the planet's center, gravity gradually decreases, and in the very center, there is a state of weightlessness. This is because the Earth's mass begins to surround you from all sides, and gravitational forces balance each other out.

Imagine the Earth as a perfect sphere with a uniformly distributed density. In this case, calculations show that gravitational force decreases linearly with depth. However, our planet is much more complicated. There are areas of higher density and voids in the Earth's crust, and the mantle is heterogeneous in composition and structure. Due to this, the Earth's center of gravity may be offset relative to its geometric center.

This means the zone of weightlessness is not exactly in the planet's center but slightly to the side—where its true center of mass is located. This offset affects the Earth's gravitational field and is considered in geophysical studies and when modeling the planet's internal processes.

Many believe that the changing of the seasons on Earth occurs because the planet either moves closer to or farther from the Sun. However, this is a common misconception. In reality, the cause lies in the tilt of the Earth's rotational axis relative to the plane of its orbit around the Sun.

The Earth's axis is tilted by approximately 23.5 degrees. This tilt remains almost constant as the Earth completes a full orbit around the Sun each year. It is due to this tilt that different hemispheres of the Earth receive varying amounts of sunlight and heat during different seasons.

When the Northern Hemisphere is tilted toward the Sun, summer arrives in that part of the planet. The Sun rises higher in the sky, the days become longer, and the surface receives more solar energy. At the same time, the Southern Hemisphere, tilted away from the Sun, experiences winter with shorter days and a lower Sun in the sky.

Six months later, the situation reverses: now the Southern Hemisphere is tilted toward the Sun, and summer occurs there, while winter sets in the Northern Hemisphere. Thus, the changing of the seasons is not determined by the distance to the Sun but by which part of the Earth is more illuminated due to the tilt of the axis.

Interestingly, in January, when it's winter in the Northern Hemisphere, the Earth is actually at its closest distance to the Sun—at the point of its orbit called perihelion. And in July, when it's summer in the Northern Hemisphere, the planet is at aphelion—the farthest distance from the Sun. But this difference in distance (about 5 million kilometers) doesn't have a significant impact on temperature because the distribution of solar energy mainly depends on the angle of the Sun's rays, which is related to the tilt of the axis.

By the way, the word “climate” is directly related to this phenomenon. It comes from the ancient Greek word “κλίμα” (klima), which means “tilt” or “slope.” This emphasizes the importance of the Earth's axial tilt in shaping the planet's climate conditions.

Astronomers distinguish several types of days, and the concept of a “day” is not as constant as it may seem.

Solar days, which we use in everyday life, are defined as the time it takes for the Earth to complete one full rotation around its axis relative to the Sun. This is the period between two consecutive solar culminations—the moments when the Sun is at its highest point in the sky. However, true solar days are not strictly constant. Throughout the year, their duration changes slightly due to the Earth's elliptical orbit and the tilt of its axis. This causes solar days to lengthen or shorten by small intervals.

Additionally, there is the concept of sidereal days. If we take a distant "stationary" star as the reference point instead of the Sun, the Earth's rotation period relative to this star will be slightly shorter. A sidereal day is approximately 23 hours, 56 minutes, and 4 seconds, which is 3 minutes and 56 seconds less than the average solar day. This occurs because, during one complete rotation on its axis, the Earth moves slightly along its orbit around the Sun. Therefore, the Earth needs to rotate a little more than 360 degrees for the Sun to return to the same position in the sky.

This difference between solar and sidereal days is significant in astronomy and navigation. For example, sidereal days are used for accurate positioning of telescopes and satellites, as well as for creating star maps.

Therefore, the familiar division of time into 24 hours in a day, 60 minutes in an hour, and 60 seconds in a minute is a simplified model that is convenient for everyday life but does not reflect the complexity of our planet's movement. Time is a relative concept, and its measurement depends on the chosen reference point and various astronomical factors. Understanding these nuances reveals fascinating aspects of how the universe works and allows us to appreciate the accuracy and complexity of the systems we use daily.

There is a widespread myth that the Great Wall of China is the only man-made object visible from space with the naked eye. However, in reality, seeing it from Earth's orbit is nearly impossible without special instruments. The Wall is built from materials that blend with the surrounding landscape, and its width does not exceed a few meters, making it invisible from great heights.

Astronauts from the International Space Station, located about 400 kilometers above Earth's surface, note that even under ideal weather conditions and knowing the exact location of the Wall, it's extremely difficult to spot it. This requires the use of powerful telescopes or high-resolution cameras.

Interestingly, other man-made objects are much easier to spot from space. The runways of international airports, with their long straight lines and contrasting surfaces, stand out against the surrounding terrain. The Egyptian pyramids, located against the light sands of the desert, are also clearly distinguishable from space due to their shape and contrast with the environment.

Many believe that the driest place on Earth is the Sahara Desert, known for its scorching temperatures and endless sand dunes. However, if we measure dryness by annual precipitation, this title rightfully belongs to... Antarctica!

Yes, you heard that right. On the coldest continent of the planet are three unique regions known as the Dry Valleys of McMurdo. These valleys are astonishing because they have not experienced rain or snow for at least two million years! Surrounded by mountains that block moisture and exposed to constant strong winds, these valleys are almost entirely devoid of ice and snow, making them the driest places on Earth.

Read more about the driest places on our planet in our article "Where is the driest place on Earth?"

Many of us are accustomed to thinking that forests produce the majority of oxygen in the atmosphere. While green plants do play a significant role in the process of photosynthesis, absorbing carbon dioxide and releasing oxygen, forests are not the only and not even the primary contributors to this process.

In fact, the main supplier of oxygen on Earth is microscopic algae living in the seas and oceans—phytoplankton. These tiny organisms, invisible to the naked eye, are responsible for producing more than half of all atmospheric oxygen. The planet's vast bodies of water provide ideal conditions for their reproduction and photosynthesis, making them indispensable participants in the global gas exchange.

Read more about this in our article "Which plants produce the majority of the oxygen on the planet"

Many people believe that the water vortex in a sink swirls in one direction in the Northern Hemisphere and in the opposite direction in the Southern Hemisphere. This misconception is linked to the Coriolis effect, described by French mathematician Gustave Coriolis in 1833. Coriolis forces indeed influence the movement of large masses of water and air on our planet. For example, they explain why rivers in the Northern Hemisphere more often erode their right banks, while in the Southern Hemisphere, they erode the left banks, and why cyclones rotate in different directions in different hemispheres.

However, when it comes to small volumes of water, such as in a sink or bathtub, the Coriolis forces become virtually negligible. At these scales, the direction of the water vortex depends on many other factors: the shape and symmetry of the sink, the position of the drain hole, the initial movement of the water during draining, and even the slightest surface irregularities. Even minor random influences can determine which way the water swirls.

Thus, regardless of whether you are in the Northern or Southern Hemisphere, the water in your sink can swirl either clockwise or counterclockwise. The Coriolis effect only plays a noticeable role on larger scales, such as ocean currents or atmospheric phenomena.