the distance of the distant universe

The great human spacecraft Voyagers 1 and 2 left the solar system for the first time into interstellar space around 2018, more than 40 years after it was launched in 1977. Humans celebrated the great feat with excitement. Voyagers, who had expected to die early, are still alive and communicating to Earth. It is almost 50 years now.

They are about 150 AU away from Earth and keep moving away. Considering that the distance to Neptune, the farthest planet in the solar system, is 30 AU, it’s a very, very long way to go.

It’s as if a dementia patient who is about to die is saying something unknown, but Voyager 2 is sending communication to Earth discontinuously. They’ve gone so far that it takes a considerable amount of time for their communication to reach Earth. It takes about 20 hours after Voyager sends communication to reach Earth.

Wait! How much is it? About 20 hours? Then a day?
Radio waves travel at the same speed as light, so in other words, Voyager 2 is one light day away from Earth, which is 1/365 light year away.

Reaching a light day’s distance in almost 50 years? Then it takes 18,000 years to get to a light year, and about 80,000 years to get to the three bodies, which are 4.3 light years away.

80,000 years. It was about 60,000 to 70,000 years ago that homo sapiens began to move out of Africa into the Old World. If it takes 80,000 years to get to the nearest star system, then it’s out of the question that mankind will explore and interact with other worlds outside of our solar system.

The speed of modern spacecraft is about one-hundred-thousandth of the speed of light, or 0.001%. If you put people or equipment on it, it becomes much slower.

Because technology develops exponentially, spacecraft will speed up quickly, so sooner or later, time will be drastically shortened. This is the common idea. By the way, 50 years after the launch of the Voyager, the speed of human-made spacecraft has not improved at all. In the past 50 years, when technology has developed exponentially.

In addition, the speed of spacecraft is fundamentally limited by the theory of general relativity. The mass of an object increases dramatically as it approaches the speed of light, so the faster it gets, the greater the limit.

Let’s say that science and technology have developed to create a space battleship that emits 1% of the speed of light, just like the novel Three Body. Currently, no planets have been found that can support life, not only the three bodies but also Sirius, the third closest to us. So, an exoplanet that has the potential to contain life is at least 30 light years away. It takes 3,000 years to achieve 30 light years at 1% of the speed of light.

The distance of the universe is really far,
It would be impossible for mankind to interact with other aliens. Likewise, no matter who is far away, they would not dare to come to us.