When we peer up into the night sky and marvel at the shimmering stars, the brilliant Moon, or the distant planets, we are witnessing the grandeur of the Universe. This vast expanse is teeming with objects, all composed of something fundamental: matter. Matter is everywhere, from the tiniest grain of sand beneath our feet to the immense galaxies that twinkle above.
But did you know that matter has a secret superpower? It’s called gravity.
Imagine for a moment that everything you can touch, see, or feel has a hidden force gently tugging on everything else. This force isn’t visible, you can’t touch it, but it’s always there. This invisible hero is gravity. In simple terms, gravity is “an invisible force that pulls from all directions from anything that has mass.” It’s like an unseen thread that stitches the Universe together.
But how does this relate to the shape of celestial bodies like planets and stars? Why are they round instead of square or triangle? This is where gravity showcases its true might. Since gravity pulls from all directions, it pulls matter together into the most compact shape possible – a sphere. Just like when kids make a ball of clay by squeezing and shaping it in their hands, gravity moulds planets and stars into round shapes by pulling equally from all sides. This is why Earth, Mars, the Sun, and even distant stars are all round. It’s gravity at work, shaping and sculpting the Universe.
Of course, only some things in space are round. You have to be of a certain mass to achieve roundness. For example, the potato moons of Mars, Phobos and Deimos look like… potatoes. Some asteroids look like that, too. That is because they have not accreted (accumulated) enough mass.
Phobos and Deimos
When we explain gravity in this manner to young minds, it becomes a tangible concept, something that is both wondrous and relatable. It helps them understand why they stay grounded on Earth instead of floating away or why the Moon orbits our planet. Gravity is the superpower of matter, and it’s at the very heart of how our Universe functions. The next time you stand outdoors, gazing up at the vastness of space, remember the intricate dance of celestial bodies, all orchestrated by the mighty pull of gravity.
The featured image is a real image of the Sun, taken by Sam Leske.