Interstellar Ship

Interstellar Ship

Let us spend a moment thinking about an interstellar ship. The Earth gravitationally attracts us with a certain force, which if we are falling we experience as an acceleration. Where we to fall out of a tree – and many of our proto-human ancestors must have done so – we would plummet faster and faster, increasing our fall speed by ten meters (thirty-two feet) per second, every second. This acceleration, which characterizes the force of gravity holding us to the Earth surface, is called 1g, g. for Earth gravity. We are comfortable with accelerations of 1 g; we have grown up with 1 g. If we lived in an interstellar spacecraft that could accelerate at1 g., we would find ourselves in a perfectly natural environment. In fact, the equivalence between gravitational forces and the forces we 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 we would be traveling very close to the speed of light (0,01 km/sec2) x (3×10(7) sec) = 3 x 10(5) km/sec).

Suppose that such a spacecraft accelerates at 1g, approaching more and more closely to the speed of light until the midpoint of the journey; and then is turned around and decelerates at 1 g until arriving at its destination. For most of the trip the velocity would be very close to the speed of light and time would slow down enormously. A nearby mission objective, a sun that may have planets, is Barnard’s Star, about six light-years away. It could be reached in about eight years as measured by clocks aboard the ship; the center of the Milky Way, in twenty-one years; M31, the Andromeda galaxy, in twenty-eight years.

Of course, 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 we got home, few of our friends would be left to greet us. In principle, such a journey, mounting the decimal points ever closer to the speed of light, would even permit us to circumnavigate the known universe in some fifty-six years ship time.

We would return tens of billions of years in our future = to find the Earth a charred cinder and the Sun dead. 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.

The designs for Orion, Daedalus and the Bussard Ramjet are probably farther from the actual interstellar spacecraft we will one day build than Leonardo’s models are from today’s supersonic transports. But if we do not destroy ourselves, Carl Sagan believed that we would one day venture to the stars.

When our solar system is all explored, the planets of other stars will beckon. Image: As Space Art meets Science by © Megan Jorgensen (Elena)

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.

Interstellar ship. When the Solar system is all explored, the other stars and galaxies will beckon. Image: Spaceship traveling near star by © Elena

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 things 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, 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 civilizations, 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, Human civilization can start using it today. Financially… well, financially it is another matter.