Perhaps many people, when they were young, looked up at the sky and saw the twinkling stars, wondering: Will they ever fall? What would happen if they did fall and touched the Earth?
Curiosity is the first step in human advancement. Scientists conduct research through such questions, and the answer to this question is: they will not fall! But what is the principle behind this?
The planets will not fall.
“Big Bang Cosmology”
To understand the mystery of the planets’ hovering, we must first understand how planets are born. There has always been much debate about the origin of the universe, and what most scientists agree on is the cosmological model of the “Big Bang.”
In March 1949, British astronomer Fred Hoyle proposed the idea, and the discovery of cosmic microwave background radiation in 1964 later became critical evidence supporting the Big Bang theory.
According to observations made by the Planck satellite in 2015, the Big Bang occurred approximately 13.8 billion years ago, subsequently expanding to reach the state of the universe as we know it today.
Based on the origins and evidence of the Big Bang model, the universe was initially composed of high-temperature, high-pressure matter that was uniform and isotropic, and rapid expansion and cooling occurred in the early stages.
You can imagine the explosion process like a pressure cooker filled with water and rice, where the steam escape hole is blocked, causing the gas to expand without any outlet, leading to an ever-increasing pressure until the cooker cannot withstand it and eventually explodes.
At the end of this process, fundamental particles were created, and as the universe cooled dramatically, planets, stars, galaxies, and even the first forms of life were born.
The birth of planets.
Most of the stars we can see with the naked eye in our daily lives are stars. Stars form when high-density regions of molecular clouds collapse into spherical plasmas, all of which are inseparable from the Big Bang.
This is the initial process of star formation.
Some of the stars you see when you look up may have been shining for billions of years since you were five years old. As you grow up and look up at the sky again, some of the stars from your childhood may have disappeared. This is a wonder of nature that captivates and amazes humanity.
Exploring “Cosmic Gravity”
In 1687, Isaac Newton first published the law of universal gravitation in “Mathematical Principles of Natural Philosophy,” which can well explain the interaction between objects, part of classical mechanics.
The reason why stars can hover in the air is closely related to the influence of gravitational force.
But what exactly is gravitational force?
Gravitational force prevents stars from falling.
If we use the definition provided by Newton, gravity refers to the attractive force between two particles, proportional to the product of their masses and inversely proportional to the square of the distance between them.
A simple summary of this is: the greater the mass, the greater the gravitational force; the farther apart, the weaker the gravitational force. In daily life, we can see many things that exist due to gravity, such as the more vegetables we buy, the heavier they become, or how things flow from high to low, like apples falling down.
Some may ask, does gravity also exist in our bodies? Why don’t we feel its strong effects in daily life?
This is because the mass of a person is too small, and the gravitational force between a person and an object is too weak to notice. However, the gravitational force between the Earth and a person is very strong; we have adapted to and become accustomed to it over a long evolutionary process, so we usually do not feel any special strong force.
To prove this, there is a very simple example: in our lives, we have never seen anyone jump and fly straight into space, right? You’ve never seen anyone fly directly from the South Pole to the North Pole? It is the existence of gravity that pulls us to the surface of the Earth, allowing us to live normally.
Why don’t stars fall?
So what is the relationship between gravity and planets?
Each planet is not only affected by the gravitational force created by one planet but also by forces from all directions. These forces work together to keep the planet in a state of uniform but relatively balanced motion.
The stars we can see when we look up have a very large mass, but they are actually very far from Earth.
In 1915, Scottish astronomer Robert Innes discovered Proxima Centauri in South Africa, which is the closest star to the Sun and is 4.22 light-years away from Earth.
A light-year is the distance that light travels in a vacuum in one year. One light-year is approximately 9.46 trillion kilometers. If the Earth’s equator is used as a standard, this means that one light-year could circle the Earth’s equator 236.5 million times. If you traveled at a speed of 120 km/h, it would take you 9 million years to travel one light-year!
In general, stars are very unlikely to fall due to the gravitational pull of the Earth, which is why they remain suspended in the universe.
So what about the meteors we see? Are they falling planets?
Meteors refer to a meteorite traveling in interstellar space, often composed of space materials such as cosmic dust and solid chunks. When it gets close to Earth, it is attracted by the Earth’s gravitational force, thus entering the Earth’s atmosphere and rubbing against it to create a glowing trail. The color will vary depending on its burning intensity.
It is important to note that meteors are not planets, let alone falling planets. If you look up and see a shooting star, don’t worry about it being a falling star; instead, enjoy its brilliance and maybe make a wish as per the legend.
Meteors falling to Earth.
Conclusion: The journey of exploring the universe is endless
Throughout history, humanity has always had a curiosity and desire to explore the sky and the infinite universe. During the Ming Dynasty, Tao Chengdao, known as Wanhu, once constructed 47 rockets and tied them to a chair, then sat on the chair himself, igniting the rockets, hoping to soar into the sky.
Today, with the continuous development and advancement of science and technology, humans have built spacecraft, the International Space Station, space suits, and are increasingly gaining a deeper understanding of the mysteries of the universe.
With ongoing extensive knowledge, when we look up at the sky, we have freed ourselves from the fear of the unknown that existed in primitive times.
Currently, the pace of exploration continues, with human-made spacecraft exploring the Moon and even Mars. The mysteries of the universe are silently waiting to be discovered.
