| KILOMETRE: | 1000 METRES, 0.621371 MILES |
| AU, ASTRONOMICAL UNIT: | 149,597,910 KILOMETRES (1 AU=DISTANCE FROM SUN TO EARTH) |
| C, CELSIUS: | 33.8� FAHRENHEIT |
| K, KELVIN: | -272� CELSIUS |
| LIGHT YEAR: | TIME TRAVELLED BY LIGHT IN 1 YEAR, 9.45 MILLION MILLION KILOMETRES |
| MEGAPARSEC: | 3.26 MILLION LIGHT YEARS |
| THERMONUCLEAR FUSION: | THIS IS THE PROCESS THROUGH WHICH STARS OUTPUT THEIR TREMENDOUS ENERGY. IT INVOLVES THE COMBINING OF ELEMENTS OF HYDROGEN, RELEASING HUGE AMOUNTS OF POWER FOR ONLY A SMALL AMOUNT OF MATTER |
| BIG BANG: | A GIANT EXPLOSION WHICH IS BELIEVED TO HAVE MARKED THE BEGINNING OF THE UNIVERSE AS WE KNOW IT. THE BIG BANG IS ESTIMATED TO HAVE OCCURED 13.5 BILLION YEARS AGO. |
| BLACK HOLE: | AN AREA OF SPACE IN WHICH THE GRAVITATIONAL PULL IS SO GREAT THAT NOT EVEN LIGHT CAN ESCAPE IT, BLACK HOLES ARE THE REMINANTS OF GIANT STARS AFTER THEY HAVE COLLAPSED. BLACK HOLES MAY BE AT THE CENTRE OF THE GALAXIES |