The destruction of a missile or meteor strike is easy to see on the surface but, until now, no one has taken a good look at the results underground where the brunt of the impact is felt.

Physicists at Duke University simulated high speed impacts using artificial soil and sand and then used high speed cameras to record the strikes. The impacts could then be played back in super slow-motion or frame by frame.

The results, appearing this week in Physical Review Letters, show that the harder sand and soil are struck the harder they become. That means that the faster a projectile is moving, the greater the resistance it encounters.

The research was funded by the Defence Threat Reduction Agency in the hope of gaining better control over “earth-penetrating” missiles.

To simulate the impact the researchers dropped a pointed metal projectile, from a seven-foot-high ceiling into a pit of beams. The kinetic energy from the projectile dissipated as the beads collided below the surface.

Beads used of clear plastic were used to better visualize the impact. Light shined through the beads shifted as they were compressed by the impact. When viewed through polarizing filters, the light showed up in “force chains”, branching chains of light that travel from one bead to the next during impact “like lightning bolts snaking their way across the sky,” according to a statement.

The projectiles were dropped at a rate of only about 15 miles per hour, but by varying the hardness of the beads, the team was able to simulate impacts at a variety of speeds ranging upward to 670 miles per hour.

Each impact was recorded with a high-speed video camera at a rate of 40,000 frames per second, then played back in slow motion. This allowed researchers to see, in great detail, how the impact spread through the beads.

The pattern of the force chains variety widely with the speed of each impact. Low speed impacts resulted in a sparse network of beads carrying the brunt of the impact according to Robert Behringer of Duke University, a co-author of the study.

The faster the impact the more extensive the force chain, which means that high speed impacts caused energy to move rapidly away from the point of impact.

The other thing that happened at very high speeds was a hardening of the material as new contacts form between the beads.

“Imagine you’re trying to push your way through a crowded room. If you try to run and push your way through the room faster than the people can rearrange to get out of the way, you’re going to end up applying a lot of pressure and ramming into a lot of angry people,” said study co-author Abram Clark, currently a postdoctoral researcher in mechanical engineering at Yale University.