Rainbows form when sunlight hits water droplets in the air, bending and reflecting light to create a colorful arc. Roy G. Biv helps us remember the rainbow’s color order: red to violet. Rainbows are optical illusions and can also appear as fogbows in fog or moonbows at night. Sometimes, a double rainbow forms with reversed colors on the outer arc. Though we see arcs, rainbows are actually full circles, with only part visible from the ground.

Synanthropes are wild animals and plants that thrive alongside humans in cities and suburbs. Examples include raccoons, crows, cellar spiders, and dandelions. Unlike pets or livestock, they live independently but benefit from human activity. Many, like raccoons and crows, are clever scavengers. Some, like cellar spiders, may not survive without us. These urban species are all around—just remember to observe them safely from a distance.

Mosquitoes may be pesky, but they play important roles like pollinating plants and feeding animals. Only females bite, using scent and heat to find us. Bug sprays use ingredients like DEET, picaridin, and natural oils to mask our scent or repel insects. Insecticides kill bugs but can harm helpful species, while repellents keep bugs away safely. For outdoor fun, wear light clothes and apply bug spray properly for bite-free adventures.

Stars look tiny and twinkle because we see them from far away through Earth’s atmosphere, which bends their light. The sun looks bigger because it’s closer to us. Stars vary in size, with some much larger than the sun. Planets can also appear to twinkle as they reflect sunlight. For the best stargazing, head somewhere dark and open. Apps can help identify stars, and local events offer chances to explore the night sky.

Cicadas are loud insects with unique anatomy. They have an exoskeleton, six legs, four wings, antennae, compound eyes, and a beak for sipping plant juices. Males make sound using tymbals—ribbed organs that click when flexed. Air sacs amplify the sound, which can be as loud as a lawnmower. They call to attract mates, express distress, or say “leave me alone.” Despite no lungs or vocal cords, their body design makes them some of the loudest insects on Earth.

Plants may seem picky, but many survive in tough places like sidewalk cracks. Tiny roots find microscopic gaps in concrete, seeking water and soil. As roots grow, they widen cracks, letting in more water and helping the plant thrive. These hardy plants create mini-ecosystems for insects and pollinators. You can even watch root growth at home using seeds in a clear bag.

Earth is home to millions of species and is about 71% water. It’s not a perfect sphere, constantly changing shape due to tectonic activity and melting glaciers. Formed over 4.5 billion years ago, Earth won’t last forever as the sun will eventually die. The highest point is Mount Everest, the lowest is Challenger Deep. Earth’s name is unique among planets and its mantle is semi-solid, driving geological activity. Climate change threatens its ability to support life.

Birds sing early in the morning in what’s called the dawn chorus, mostly to attract mates and claim territory. Mornings are quieter and safer, helping their songs carry farther. Studies show birds improve their singing as the day goes on, suggesting morning songs are like vocal warmups. While male birds do most of the singing, some females sing too. In cities, the chorus may start earlier due to artificial light. Spring and summer are peak singing seasons.