This article, the second of two parts, by physicist Eric Hedin, is reprinted with permission from Evolution News. Here’s the first part?

Reducing the mass of a spaceship doesn’t exactly solve the distance problem for space travel. Suppose we trade our 747-sized spacecraft for an economy model about the size of a Winnebago camper trailer, having a much smaller mass of 4,500 kg. That’s 89 times less mass than the original spacecraft. Unfortunately, this means that the energy required to get there is still 54 times the total U.S. energy consumption for an entire year.

OK, so we just need a lot of energy, and apparently nothing we currently use for generating energy will come even close to meeting our needs for interstellar space travel. But what’s to say we couldn’t develop a super-charged energy supply? The gold standard for producing energy from mass comes from the total annihilation of matter, converting it 100 percent to energy according to Einstein’s famous equation, E=mc². How much mass, then, would we need to convert to pure energy to meet our original estimate of 140 quadrillion kWh? The answer turns out to be a little over 5.6 million kg of matter. That’s about 14 times more mass than the mass of the fully-loaded 747-sized spacecraft.

Now it becomes more complicated, but we’d definitely end up needing more than just the 5.6 million kg of matter to convert to energy, since the extra matter that has to be carried along as fuel for the spaceship would require even more energy to accelerate. A rough estimate suggests that the mass of the fuel needed to accelerate the spaceship plus the fuel would be closer to 1,400 times the original mass of the spaceship. This begins to appear impractical, but maybe not impossible. 

However, since according to known physics, the only way to accomplish the conversion of matter to pure energy is to combine it with an equal amount of antimatter, our space travelers would also need to carry an equal amount of antimatter. Although a better solution would be to find a way to easily convert matter to antimatter, that can’t be done, directly. In conclusion, accelerating matter to move through space at high speeds is prohibitively energy intensive. 

Moving with Space?

Perhaps instead of trying to move through space, one could find a way to move with space. Here, we draw upon results from Einstein’s theory of general relativity. In this model, space itself flows into masses at a speed that is proportional to the strength of the gravitational field around the mass. In the extreme limit of a black hole, the flow rate of space into the black hole becomes equal to the speed of light, as one approaches the boundary around the hole known as the event horizon. Since nothing can move through space faster than the speed of light, this is why there’s no way anything can ever escape from inside the event horizon of a black hole.

How could we use the flow of space for space travel? One useful concept is that we could do so by falling into a black hole; that is, by flowing with space towards the event horizon of the black hole, you could attain movement at the speed of light without expending any external energy.

Now, falling into a black hole is a one-way “down the drain” experience, but physicists have mathematically explored the concept of a wormhole, a theoretical construct of spacetime that connects two disparate points in spacetime. Under certain conditions, it is theorized that matter could traverse a wormhole and effectively take a shortcut through hyperspace to facilitate travel to a distant point in the universe (or even into another universe!). However, while serving their purpose as plot props for science fiction stories, wormholes remain distantly removed from scientific reality.

First of all, even with the many existing descriptions of constructions of traversable wormholes, we are nowhere close to actually creating one, or at least to imagining an experiment which would, once put into practice, bring into existence such an object. Moreover, no wormholes have been observed so far in the Universe.

Borrowing from the imagination of science fiction, one of the more intriguing possibilities for interstellar travel involves nullifying the inertia of the entire spaceship. From a physics perspective, we have no idea how this could be done, but if it could, and if relativistic limitations somehow didn’t apply, the result would be marvelous. With the inertialess spaceship having effectively zero mass, its cruising speed would only be limited by the balance between its rocket thrust and the friction the spaceship encounters as it moves through the near-vacuum of the interstellar medium. In the science fiction series utilizing this creative technology, the science-literate author estimated that the touring speed of a spaceship would be about 300 light-years per hour. In this fictional world, a trip to Gliese 12b from Earth would take only about 8 minutes! 

Children of Light

The dream of interstellar space travel suffers from a reality check according to the physics we know due to the nearly unfathomable distances separating us from other stars. To put it in perspective, the farthest distance humans have traveled from Earth is to the moon. The distance to our own sun is 400 times farther than to the moon, and the distance to a star system 40 light years away is over 2.5 million times farther away than our sun! 

The human yearning to explore finds it hard to accept that travelling to the stars may be physically impossible. But viewing the heavens beyond our reach causes us to look up and stretch our imaginations to envision a realm vastly greater than our own. Travel to the stars may intrigue and fascinate us because we were originally created for a destiny that included accessing this realm. 

In the biblical narrative, God is Spirit and light, and in him we are called “children of light” (Ephesians 5:8). To do the impossible may require that we ourselves become beings of light. Light needs no outside energy source to travel between stars, and in the time frame of reference of light, no time is needed to make the trip, even from one side of the universe to the other!

Here’s the first part of this two-part series: Interstellar travel: Fantasy or destiny?