#193 Dark Energy (B)

The rest of the universe appears to be made of a mysterious, invisible [1] called dark matter 25 percent and a force that repels gravity known as dark energy 70 percent. Scientists have not yet [2] dark matter directly. It doesn't interact with baryonic matter; it's completely invisible to light and other forms of electromagnetic radiation, making dark matter [3] to detect with current instruments. But scientists are confident it [4] because of the gravitational effects, it appears to have on galaxies and galaxy clusters.