One of the most fascinating aspects of gravity, from a scientific perspective, is its universality. It acts on everything with mass, from the tiniest particles to the most massive galaxies, binding the universe together in a cosmic dance. We often ask students, if you are made of “something”, does that mean you have gravity? The fact that the same force that causes an apple to fall from a tree also governs the motions of celestial bodies billions of light-years away is a testament to the elegance and coherence of the physical laws of the universe.
Just like there are 92 naturally occurring chemical elements that make up the visible Universe, the laws of physics and chemistry are universal. They apply no matter which planet, star or galaxy you are on.
Because the laws of physics and chemistry are universal – which is a grand claim but not an exaggeration, we can understand in return how the Universe works.
Here are some of our favourite gravity facts in our solar system and galaxy that perhaps students might find intriguing:
The Tug of War with the Sun and Moon: Our ocean tides on Earth are influenced by gravity! When the moon is overhead, its gravitational pull causes the oceans to bulge out a little, creating a high tide. The Sun also plays a role, but its effect is weaker because it’s much farther away. When the gravitational pulls of the Sun and the Moon combine during full and new moons, we get especially high tides called “spring tides.”
Planetary Dances: Gravity keeps the planets orbiting the Sun. Think of it like an invisible string that the Sun uses to pull the Planets close. If there was no gravity, planets would simply fly off into space.
The Tail of a Comet: Have you ever seen pictures of comets with their beautiful tails? Those tails actually point away from the Sun, no matter the direction the comet is travelling. It’s the Sun’s gravity and radiation that causes these tails to form!
Black Holes: These are places in space where gravity is so strong that not even light can escape from them. They’re like cosmic vacuum cleaners, pulling everything close enough into them.
Galactic Dance: Our whole solar system is orbiting the centre of the Milky Way galaxy. Why? You guessed it: gravity! There’s a supermassive black hole at the centre of our galaxy, and its immense gravitational pull influences the motion of all the stars and other structures in the Milky Way.
Saturn’s Rings: One of the most iconic sights in our solar system, Saturn’s rings, exists thanks to gravity. The rings are made of countless chunks of ice and rock. Saturn’s gravity keeps these pieces close and ensures they orbit the planet in this beautiful, flat formation.
Shooting Stars Aren’t Stars: When you see a “shooting star” or meteor streaking across the night sky, it’s actually a small space rock burning up in Earth’s atmosphere. The Earth’s gravity pulls these rocks toward it, and as they speed up and enter our atmosphere, they heat up and glow, creating the streak of light we see.
Space-time Fabric: Advanced but fascinating! Scientists often describe gravity as the bending of “space-time.” Imagine a trampoline and placing a heavy ball (like a bowling ball) in the centre. It will create a dip or curve. Now, if you roll a smaller ball onto the trampoline, it will move towards the heavier ball because of the curve it created. That’s a bit like how gravity works in space!
Weightlessness in Space: Astronauts appear to float in space not because there’s no gravity there (there is, though weaker) but because they’re in continuous free fall towards the Earth. They’re moving forward so fast that they keep missing it even as they get pulled towards Earth by its gravity!
Neptune’s Discovery: The planet Neptune was discovered in a unique way. Astronomers noticed weird movements in the orbit of Uranus and suspected that another unseen planet’s gravity was affecting it. By doing the math and understanding gravity’s influence, they predicted where this mystery planet should be, and voila, they found Neptune!
Sam’s favourite thing about gravity: It keeps you grounded!
Sharing these facts can help students appreciate the pervasive influence of gravity not just on Earth but throughout our solar system and the vast galaxy beyond.