why do they sweep the ice in curling

They sweep the ice in curling to control how far and how straight the stone travels by reducing friction and slightly changing the ice surface in front of the rock.

Quick Scoop: What Sweeping Actually Does

• Reduces friction: Fast brushing creates friction heat, which very slightly warms and melts the “pebbled” ice, leaving a thin film of water under the stone.

• Makes the stone go farther: With less friction, the stone slows down less and can travel several extra feet compared with a shot that isn’t swept.

• Straightens the line: Sweeping typically makes the stone “curl” less, so it runs straighter along its path.

• Fine‑tunes the curl: At high levels, sweepers can even influence how much the stone bends by which side of the running path they work on and how hard they sweep.

• Cleans the path: Sweeping also removes dust or debris (“picks”) that could grab the stone and make it jump off line or stop early.

In other words, the thrower decides the basic speed and curl, and the sweepers act like in‑flight controllers , tweaking distance and path after the stone is released so it ends up in exactly the right scoring spot.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.