Blood pressure is the force exerted upon the walls of our arteries (blood vessels) and is initiated by the pumping action of the heart. Contraction of the heart produces the highest (i.e. normally 120) while the relaxation of the heart reduces pressure to its lowest point. (i.e. normally 80).
There is no difference between a meteor, meteorite and a shooting star. Meteorites or shooting stars are just the large rocks that enter the atmosphere of our earth from outer space. They shine because the friction with the atmosphere makes them very hot and burns them.
Rainbows are seen usually after the rainfall because rain drops are necessary for the diffraction of sunlight into seven colours. The drops of rain that fall from the sky serve like prisms and the white light is broken down into a number of shades.
The age of a tree can be calculated by counting the annual rings or growth rings, which are seen in the cross section of its trunk. These rings are formed when new wood is added around the trunk just beneath the bark each year.
A boomerang has two arms, curved in opposite directions, similar to an airplane propeller. It is thrown with a special twisting movement and with force. It rotates when it flies through the air. The force of its own weight and the turning movement enables it to return to the place it started from.
