Within auroral ovals, some 100 to 1,000 km (62 to 620 mi) over our heads, high-energy electrons from solar plasma collide with
air molecules in Earth's upper atmosphere.
Neutrinos entering the detector collide with
water molecules, generating light patterns that are monitored by the 11,000 photomultiplier tubes in the cylinder's wall.
According to one theory, some massive, dark-matter particles occasionally collide with
each other and either generate gamma rays or produce particles that decay into gamma rays.
If the components of these "contact binary asteroids" pull apart but remain gravitationally bound, traveling together as they collide with
a planet, they might produce the double craters detected on Earth, the moon, and, most recently, Venus.
One near-Earth asteroid more than 1 kilometer across may collide with
the sun every 100,000 years or so, report Paolo Farinella of the University of Pisa in Italy and his colleagues in the Sept.
Higher-energy neutrinos from outside the solar system, however, occasionally do collide with
atoms inside the planet.
Like the energetic electrons before them, these exiting particies collide with
atoms in the chromosphere, creating a faint glow of gamma rays that can last for hours after the main flare peters out.
astronomers predicted that if downward-moving proton beams were indeed the carriers, these particles would collide with
hydrogen atoms to produce a brief but telltale type of ultraviolet radiation.
The team finds that while high-speed fullerenes bounce back when they collide with
silicon surfaces, those with metal atoms inside do not rebound as readily.
8 kilometers per second, the free-floating oxygen atoms that collide with
the shuttle hit their target quite fast.
The third stage, due in 1995, will be a second 3-TeV beam to collide with