Although distances are expressed in the same units, many different measurement methods can be used. When we want to measure our height, a tape measure is enough. But it is impossible to measure the radius of subatomic particles. The radius of an electron can be determined using a different method with the help of the periodic table, but never with a tape measure. The more impossible it is to measure the distance between the Sun and the Earth with a tape measure. So how are distances measured in the universe?
Distance Measurements in the Solar System
The solar system is very small compared to the universe. Distance measurements here are similar to radar technique. First, a light wave is sent to the object whose distance is to be measured. The transmitted light hits the object and some of it is reflected back to Earth. The reflected light travels the distance to be measured twice. The travel time is recorded and the distance of objects in the Solar system from the Earth is calculated, taking into account the speed of light at 300,000 km per second.
Distance Measurements of Nearby Stars
The closest star to Earth is Proxima Centauri. Its distance from Earth is 4.2 light years. So the light from Proxima Centauri reaches Earth in 4.2 years. If the radar method had been used, the light from Proxima Centauri would have lasted about 8.4 years. At this point, the radar method is insufficient to measure distant objects from the Earth. The parallax method allows measuring objects up to 100 light-years away.
The Parallax Method:
When we align our finger to a distant object and look first with our left and then with our right eyes, we see that the object changes position relative to our finger. This change in position increases as the finger gets closer to the eyes. There is a trigonometric relationship between the distance of the distant object to the new positions and the distance of our finger to our eye. From this relationship, and angle changes, the Earth’s distance from the stars can be calculated.
Of course, the universe is not just composed of Gubeş and stars. Scientists have even tried to calculate the distance of the Earth to the galaxies. But they haven’t found any method that works at distances more than 1 billion light-years away. In this article, I talked about how the distance to the Sun and the stars is measured. More detailed information can be found here. Don’t lose your way to Earth while exploring far distances in the universe 😉