Earth isn’t getting bigger. It’s actually getting smaller! Decaying vegetation does pile up across the planet, but not everywhere equally. Wind and rain erode the ground over time, and even where leaves and other vegetation do gradually accumulate, like peat bogs and river deltas, that material doesn’t add to Earth’s bulk.
But Earth’s size isn’t quite constant. Space around Earth is dusty; it’s full of asteroid debris, comet trails and ionized particles streaming away from the sun. And as our planet flies through that dust, our gravity vacuums it up. This steady flow of dust — along with occasionally larger chunks in the form of meteorites — adds about 43 tons of mass to Earth every day.
Moreover, and in spite of the added space dust, the planet is actually losing mass over all, because our atmosphere leaks. Gravity does a decent job of keeping Earth’s air wrapped around us, but a faint stream of lightweight gasses — mostly hydrogen, but also helium and oxygen — is continually escaping from the fringes of our atmosphere. Thanks to our leaky atmosphere, Earth loses several hundred tons of mass to space every day, significantly more than what we’re gaining from dust. So, overall, Earth is getting smaller.
