The Gravitational Pull of the Sun is one of the key factors that has helped the Solar System remain stable for billions of years. However, an intriguing phenomenon is occurring: the planets, including Earth, are continuously drifting away from the Sun. This might sound contradictory, especially when many people understand that gravity acts as a pulling force towards the center.
In fact, Earth is moving away from the Sun at a rate of about 1.5 cm per year. Although this number is very small and does not have a significant impact in the short term, it raises the question: why is this happening?
Many might think that the expansion of the universe is the cause. However, this is not the case. The expansion of the universe—driven by dark energy—only affects regions not bound by gravitational forces. The Solar System, with its planets under the gravitational influence of the Sun, is not affected by this process. The planets are not being “pushed away” by the expanding universe; rather, the true cause lies in their own dynamics and how the Sun operates.
The planets, including Earth, are continuously drifting away from the Sun.
To understand why the planets do not fall straight into the Sun, we first need to look at their motion. The planets are not stationary; they are moving at very high speeds horizontally around the Sun. Earth, for example, is traveling at speeds of up to 107,826 km/h. This speed is the result of momentum that the planets acquired during their formation from the protoplanetary disk billions of years ago. It is this horizontal motion that creates a circular or elliptical orbit, preventing the planets from being pulled into the Sun.
So why are the planets drifting away from the Sun instead of maintaining a stable orbit? The answer lies with the Sun itself. Over time, the Sun is gradually losing mass. The fusion process in the core of the Sun, where hydrogen is converted into helium, continuously releases energy in the form of radiation and particles, causing the Sun’s mass to decrease. Additionally, solar wind—a stream of charged particles emitted from the Sun’s surface—also carries away a small amount of material into space. Although this mass loss occurs very slowly, at about 10⁻¹³ times the Sun’s mass each year, it is sufficient to slightly weaken the gravitational pull. As the gravitational force weakens, the orbits of the planets gradually expand, leading to an increasing distance between the planets and the Sun.
However, this phenomenon does not mean that Earth and the other planets will continue to drift away from the Sun indefinitely without any risk. In the distant future, as the Sun enters its final stages, the story will change completely. When the Sun exhausts the hydrogen in its core, it will enter the red giant phase. The core will collapse, temperature and pressure will rise, causing helium to begin fusing into carbon. This process will push the outer layers of the Sun outward, causing it to expand. During this phase, the outer layers of the Sun may expand to the point of engulfing the inner planets, including Mercury, Venus, and potentially Earth. Nevertheless, we do not need to worry about this, as it will not happen for at least another 5 billion years.
The drift of the planets away from the Sun is a natural phenomenon, a consequence of the long-term evolution of the Solar System. Although the change is very slow and insignificant in the short term, it still provides us with profound insights into how gravity and dynamics operate in space. And while the planets are drifting away, their ultimate fate—especially that of Earth—will still be intertwined with the changes of their parent star in the billions of years to come.
