Could a massive cloud of cold, interstellar gas have pushed the sun’s protective heliosphere away from Earth two to three million years ago, causing an ice age? Astronomers know for certain the arrival of the cold cloud caused important changes in our atmosphere’s chemistry and subjected it to more radiation. Thankfully, the sun and the cold cloud continued moving through the universe in different directions and eventually separated, allowing the heliosphere to snap back into place. That left Earth and its inhabitants safely under the sun’s protection again. The “heliosphere is our protective bubble, our home in the galaxy,” she realized, meaning it could have seriously affected Earth’s development.