Stellar parallax is a measurement technique developed by Friedrich Bessel to measure far away objects in deep space. The process of stellar parallax involves measuring an object from two separate vantage points hinging upon the fact that the object being observed will appear to move a lot more than objects further behind it (e.g. if an observer closes one eye and views their finger in front of a building, and then repeats this act with their second eye closed and the first eye open, the observers finger will appear as though it has moved much further left or right, relative to the other objects behind it). Because Bessel developed a method of calculation to take advantage of this phenomena, astronomers now have the ability to map grand distances with relative accuracy. Bessel worked out that if an observer took an image of a star when the Earth was at either side of its orbit around the sun, it would be possible to observe the star shifting in its position. By knowing how much a star shifts, it is possible to calculate the distance the star is from its observation point on Earth. Bessel surmised that the relatively close star 61 Cygni must be 100,000,000,000,000 (100 trillion) kilometers away from the Earth because of his parallax distance method. This technique unfortunately is severely limited as the diameter of the Earth’s orbit is only 300,000,000 (300 million) kilometers which means that the parallax method can only measure objects up to a factor of 1,000,000x (1 million) the Earths orbital rotation, allowing for a maximum distance of 300,000,000,000,000 (300 trillion) kilometers which is only a tiny fraction of the size of the Milky Way Galaxy or the universe as a whole
