Liri looked at her own point in the window glass. Left and right – exactly the same.
A shape has line symmetry if an imaginary line – the line of symmetry – divides it into two exactly equal halves. If you fold the paper along this line, both sides lie exactly on top of each other.
A butterfly is a classic example: the red dashed line is the line of symmetry.
On the right, click the squares that mirror the pattern on the left – that makes a symmetrical picture:
Plane shapes are flat (2D): square, rectangle, triangle, circle. Solids are three-dimensional (3D) – they have depth and do not fit onto a sheet of paper.
Planets are almost perfect spheres – shaped by their own gravity.
Many satellites are shaped like a cuboid, with fold-out solar panels.
Some constellations look almost symmetrical if you draw an imaginary line through their middle.
A square and a cube are often mixed up – but a square is flat (2D), a cube is three-dimensional (3D) and is even made of six squares!
Tip: can you pick it up and look at it from all sides? Then it is a solid (3D), not a plane shape.
Liri looked at her star map once more – this time with a trained eye for shapes and reflections.
Liri now recognises reflections and knows which shapes planets, moons and satellites have.