Final answer:
Cosmic distances are measured using methods such as parallaxes for close stars, and luminous variable stars like cepheids for distant galaxies. The Andromeda galaxy is 2 million light-years from Earth, while the farthest known galaxy is 14 billion light-years away. Improved measurement techniques now offer around 10% accuracy for these vast distances.
Step-by-step explanation:
Understanding Cosmic Distances
Measuring cosmic distances is essential for understanding the scale of the universe. Astronomers use various methods such as parallaxes for nearby stars, the H-R diagram for star clusters, and luminous variable stars like RR Lyrae and cepheids for more distant objects. These methods have improved over time, allowing measurements with about 10% accuracy.
In our galaxy, distances are vast and measured in light-years. An average galaxy distance could be millions of light-years apart, with the nearest large galaxy to Earth, Andromeda, situated 2 million light-years away. Distances can reach up to 14 billion light-years for the farthest known galaxies.
Understanding the mass distribution in the universe also plays a role, with galaxies exhibiting high mass-to-light ratios, indicating the presence of dark matter. The application of these measures has allowed astronomers to reliably estimate the size of the universe, discovering galaxies akin to the Milky Way in size and content.