Expansion of Universe

The fact that the universe is expanding was established using the Doppler shift of light from different galaxies. Light emitted by star falls in continuous spectrum and as it passes through different stars the continuous spectrum is lost. Edwin Hubble, an American astronomer confirmed the existence of many galaxies other than Milkyway. He concluded that the galaxies are moving away from the earth and farther away the galaxy is from us, more is the speed. This can be established using a three dimensional coordinate system considering that the earth is at origin while the other coordinates represent various galaxies. Since universe is expanding, it is clear that the distance between galaxies and earth is also increasing. This increase is at a constant ratio k for a particular time t. Thus, it is clear that more the distance of the galaxy from earth more is its speed as compared to the galaxy nearby to it. This can be clearly explained by giving a simple example of inflating a football. If we mark different points on the football and inflate it with air, each point will find the other points moving away from it, and farther the point is, greater is the separation.


By: MOLLA RAMIZUR RAHMAN