Asteroid Impact Energy

Kinetic energy is mass times velocity squared, but mass itself scales with the CUBE of diameter (volume of a sphere grows with the radius cubed) while velocity only enters the energy formula squared. Practically, doubling an asteroid's diameter multiplies its energy by about 8x, while doubling its velocity only multiplies energy by about 4x -- so a small increase in size has a much larger effect on destructive potential than the same percentage increase in speed.

It is a simplified empirical scaling relationship, not a rigorous impact- physics model. Real crater size depends on factors this calculator does not capture, including impact angle (a shallow oblique impact carves a different crater than a vertical one), target material (solid rock, sediment, and water each couple energy differently), and atmospheric effects that can slow or fully disrupt smaller impactors before they reach the ground. Treat the figure as an order-of-magnitude illustration, not an engineering-grade prediction.

They translate the impact's energy, in megatons of TNT equivalent, into two widely recognized reference points: the Hiroshima atomic bomb (about 15 kilotons) and the Chicxulub impactor linked to the end-Cretaceous mass extinction (roughly 100 million megatons). The Hiroshima multiple shows how a relatively small object can already carry city-scale destructive energy, while the Chicxulub fraction shows how astronomically larger a mass-extinction-class event is than even a very large regional impact.

No -- it is a very rough statistical approximation of how often objects near the entered diameter are estimated to strike Earth, based on a simplified power-law relationship between size and impact frequency. Actual near-Earth object population estimates come from ongoing survey programs (like NASA's Center for Near-Earth Object Studies) that track discovered objects and model the undiscovered population; this calculator's figure is a coarse illustration of the general trend that larger impactors are dramatically rarer, not a substitute for that survey data.

Density determines how much mass a given diameter actually represents, and real near-Earth objects vary enormously: icy comets are roughly 1,000 kg/m3, rubble-pile asteroids (loose aggregates of rock and dust) around 1,500 kg/m3, solid rocky bodies near 3,000 kg/m3, and iron-nickel meteorites up to about 8,000 kg/m3. If you don't know the specific composition, 3,000 kg/m3 (rocky) is a reasonable general-purpose default, since most cataloged near-Earth asteroids are stony rather than metallic or icy.