The U.S. Environmental Protection Agency (EPA) has launched an investigation into Make Sunsets, a two-man startup from Silicon Valley that releases weather balloons filled with sulfur dioxide to cool the Earth. The practice, which aims to combat climate change, raises concerns about potential air pollution and health risks. Critics argue that geoengineering could have unforeseen effects on weather patterns. Although Make Sunsets claims its actions comply with the Weather Modification Act of 1976, the EPA's scrutiny highlights the regulatory challenges of climate modification. The company has raised $750,000 from notable investors.