Sample Response: The big bang theory is supported by the observation that the spectrum of nearly all galaxies is red-shifted, implying that the universe is still expanding. It is also supported by the discovery of the cosmic microwave background radiation, which is leftover radiation from the big bang. Finally, the big bang theory is supported by the discovery that the composition of stars is 99% hydrogen and helium, the only two elements that could have existed shortly after the big bang.
According to astronomers, the whole universe is started with a giant explosion called as Big Bang. Big Bang theory shows that the universe is extended from high density state.
There are some evidence for big bang as :
(1) There are some red shifts of different galaxies which means that the universe is expanding.
(2) Due to the expanding of universe, some of the new elements are created like hydrogen, deuterium etc.
(3) Microwaves are detected by orbiting detectors.
All this parameters shows that big bang theory was correct.