Galactic Distances and Speeds

The distances in the Universe are mind-boggling. On the one hand, these in molecules and atoms are so small that we can’t even see or experience them. On the other hand, the distances between planets, stars and galaxies are so huge we can’t even reach them in our lifetimes. In this short article, I’m going to give you a sense of large distances that are not possible on Earth but only in space and extremely high speeds we need to cover them.

We rarely run in our homes to reach any corner, as we can just walk and reach any point in a few seconds. We also walk in streets to a nearby park or shop in a few minutes. If our destination is a bit far away, we use vehicles to reach them usually with some speed, say, 40 KMPH (kilometers per hour). If we want to reach another city, we may go at a higher speed, say, an 80 KMPH, depending on the type of the road and the vehicle you use. If we walk, it may take hours, days, weeks or months to reach another city. If we want to reach much faster, we may want to travel by a car, bus, train or airplane. However, to reach planets, one needs to use spacecrafts or spaceships that use rockets for propelling through space with speeds of thousands of kilometers per hour.

Now, to give you a sense of distances, we start with the distances to the Moon, then to Mars and to a nearby star in our home galaxy, the Milky Way, and the nearby Andromeda galaxy. We will also find out the speeds the spaceships need to travel over such large distances, and the reasonable times they should take to reach the destinations for any meaningful journeys.

Average distance of the Moon from Earth is 384,400 KM. We need speed of 48,000 KMPH to reach in 8 hours, or 16,000 KMPH to reach in 24 hours or 5,400 KMPH to reach in 3 days. Of course, these are point-to-point times. Apollo 11, with Neil Armstrong, Edwin Buzz Aldrin and Michael Collins, reached orbit around the Moon on July 19, 1969 in 76 hours after travelling for 386,242.56 KM.

The speed used for reaching the Moon is hardly sufficient to reach other planets in a reasonable time. Even the light speed, which is considered impossible to achieve, is only sufficient to reach one of the nearby stars, Alpha Centauri, in a few years. We need light year speeds to reach the star in a few hours. I wonder if we ever reach speed even close to the light speed in the near future, though we do reach even light-year speeds in my sci-fi novel (see at the end of the article for more information)!

Speed of light is 299,792.458 kilometers per second, which is 1.08 billion kilometers per hour. In one year, light travels a distance of 9.46 trillion kilometers called light-year. Our solar system diameter is only about 2 percent of the light-year.

Here is a table of destinations and speeds of spacecrafts or spaceships required to reach them in a reasonable time:

KM : Kilometers, KMPH: Kilometers per hour, MKM: Million kilometers, MKMPH: Million KMPH, LY : Light Year, MLY: Million LYs, LYPH: Light-year per hour.

As the table indicates, we need speeds of a few million kilometers per hour to reach planets in our solar system for a meaningful journey. To travel to any star, speed of a few light-years per hour is not good enough but thousands of times that speed for any successful journey. Of course, such speeds are next to impossible to achieve at the moment. If you like fantasy and would like to travel from Earth to Mars and various exoplanets in the Milky Way, the Andromeda and the Triangulum galaxies, read my novel “Escape to the Galaxies” available on various online stores. Some of the stores are as following:

Notion Press:


Amazon India:

Amazon USA:

Amazon UK:

A software professional with interests in database systems, web applications, NLP, AI, space, travel and trekking. Author of Escape to the Galaxies.