Is it possible for the Humans to reach another galaxy? Well, the answer is not simple.
If the Humans lived in an interstellar spacecraft that could accelerate at 1 g., they would find themselves in a perfectly natural environment. In fact, the equivalence between gravitational forces and the forces the Earthlings would feel in an accelerating spaceship is a major feature of Einstein’s later general theory of relativity. With a continuous 1 g acceleration, after one year in space an interstellar ship would be traveling very close to the speed of light.
Well, now suppose that such a spacecraft accelerates at 1 g, approaching gradually to the speed of light until the midpoint of the journey. Then the spacecraft turns around and decelerates at 1 g until arriving at its destination.
We can see thus that for most of the trip the velocity would be close to the speed of light. According to the Einstein’s theory, time would slow down enormously.
In this case, a nearby mission objective, f.i. the Barnard’s Star, located about six light-years away, could be reached in about eight years as measured by clocks aboard the spaceship.
The Humans thus could reach the center of the Milky Way, in twenty one years and the Andromeda Galaxy (M31) in twenty-eight years only! In principle, such a journey, mounting the decimal points ever closer to the speed of light, would even permit a crew to circumnavigate the known universe in some fifty-six years ship time.
Unfortunately, people left behind on Earth would see thing differently. Instead of twenty-one years to the center of the Galaxy, they would measure an elapsed time of 30,000 years. When the interstellar ship got home, the Humanity would change for the better or for the worse and even the mission would be obliterated.
After the trip to Andromeda Galaxy, the ship would return tens of billions of years in the future, to find the Earth a charred cinder and the Sun dead.
The conclusion is thus obvious: Relativistic spaceflight makes the universe accessible to advanced civilisations, but only to those who go on the journey. There seems to be no way for information to travel back to those left behind any faster that the speed of light.
Is there a way to break the rule? No! But… But there exists a perfect and incredible easy way to bend it! Technically, the Human civilisation can start using it today. Financially… well, winancially it is another matter.
When the Solar system is all explored, the other stars and galaxies will beckon. Image: Spaceship traveling near star by © Megan Jorgensen