1) firstly how many of you know that our universe is expanding day by day?
2)if so why? according to some space scientists our present universe is expanding day by day.coming to the point why the universe is expanding? In 1929 Edwin Hubble, working at the Carnegie Observatories in Pasadena, California, measured the redshifts of a number of distant galaxies. He also measured their relative distances by measuring the apparent brightness of a class of variable stars called Cepheids in each galaxy. When he plotted redshift against relative distance, he found that the redshift of distant galaxies increased as a linear function of their distance. The only explanation for this observation is that the universe was expanding.
take a keen look at this.this would do the understanding.