Space is big, really really big. Let’s do some math: Earth has a diameter at the Equator of 7,926 miles. If one astronomical unit (AU) is 92,955,807.3 miles, and the distance between the Sun and the Heliopause is about 123 AU, that’s 11,433,564,297.9 miles ÷ 7,926 miles = 1,442,539…That means 1.4 million Earth’s could fit in a line from the Sun to the Heliopause. The Heliopause is the last boundary between material from the Sun vs other stars from interstellar space. After 35 years of travel, Voyager 1 crossed the Heliopause and entered interstellar space on August 25, 2012. Voyager 1 was launched by NASA on September 5, 1977.