During an approaching gravity storm, the first symptom people feel is sluggishness. This triggers the panic response that sends them running to gravity shelters. Within a short time, the heaviness grows until a person becomes incapable of any movement. As the weight of all objects in the path of the gravity storm increases, the sky grows ominously black, shooting violent scarlet bolts that strike the ground. This is when most objects, including people who are not protected by a gravity shelter, increase in density and are crushed under their own weight. Perhaps most unnerving is the gravity storm's eerie silence. Even sound waves get crushed.