Dark matter is a type of matter that does not emit, absorb, or reflectlight, making it invisible to telescopes and other instruments that detect electromagnetic radiation. It is also different from ordinary matter, such as the atoms that make up stars, planets, and living organisms.
Scientists have observed the gravitational effects of dark matter on the motions of galaxies and galaxy clusters. They have also studied the bending of light around massive objects, a phenomenon known as gravitational lensing, which provides indirect evidence for the presence of dark matter.
The universe is composed of approximately 5% ordinary matter (the stuff we can see and interact with), 27% dark matter, and 68% dark energy. Dark energy is another mysterious component that is responsible for the accelerating expansion of the universe.
The student demonstrates an understanding of the structure and properties of matter by classifying matter according to physical properties (i.e., color, size, shape, weight, texture, flexibility).