The distances of supernova are measured by measuring the amount of red light they emit. This is done by analyzing the spectrum of the supernova. The more redder the light appears the faster the star are getting away from us. By measuring how fast the galaxy is getting away from us we can calculate the speed of the expansion of our universe. It is done by comparing the velocities of galaxies with their distances. These data can help to find out when our universe will stop expanding and start shrinking. Or this may lead to some other possibility.