Science or imagination?

A large part of the "scientific" research currently being developed, rather than being science, is just an exercise of the imagination of "scientists." It seems that we must consider as scientists all those who do mathematical speculations that have little or nothing to do with reality. And naturally, everything a scientist does is “science”. At least, scientific journals and high-profile media consider it as such.

Will traveling to the stars be possible?

Will interstellar travel be possible? At the current level of our technology, the answer is clearly no. Will it be possible in the future? It is always dangerous to make predictions: reality often strays from what was supposed to happen. But it doesn't look like interstellar travel is going to become feasible anytime soon. Of course, in the scientific literature, both serious and imaginative, various methods have been proposed, some of which we’ll review in this and future posts, by analyzing the relative probabilities of each one.

Many writers consider interstellar travel the next frontier of human spread, and the only guarantee to avoid our extinction, either accidental, if a cosmic catastrophe occurs, or caused by ourselves with a nuclear war. The problem is, a trip to the stars would be much more difficult than planet exploration in the solar system. Apart from the sun, the closest star to us is 4.27 light-years away, just over 40 trillion kilometers. With our current technique, speeds of the order of one million kilometers per day can be reached, so a trip to that star would last more than one hundred thousand years. Taking advantage of the gravitational pull of giant planets, like Jupiter, it would be possible to triple the speed, but even so we are talking about tens of thousand years.

Wormholes

Science fiction novels make it clear that, even if we were able to reach relativistic speeds (close to the speed of light), our need to personally explore the universe wouldn’t be satisfied. We’d like to travel to other stars with the same ease with which we cross the Atlantic today. We’d like to measure in days, if not hours, the time of a trip to the center of the galaxy (which probably contains a large black hole). Is there any chance of this happening?

To do this, we should discover in the future some property of the universe, now unknown, that would help us break the speed limit of light, which seems firmly established, and which would make us spend thousands of years on trips to most stars, except the nearest.

To solve the problem, science fiction authors have used essentially two different procedures:

Science or speculation?

Merging of two black holes

In December 2013 several media made reference to an article published in the journal Physical Review Letters, in the field called quantum gravity, a set of mutually incompatible theories that in the last 30 years have scarcely formulated a single testable prediction, although they are usually presented as the latest in physics and give rise to news broadly popularized by the general media. This scientific news was presented by some media with this title: quantum entanglement causes the appearance of wormholes. Some of the reviews contained important mistakes. I’ll cite two:

1.      The group showed that, by creating two black holes intertwined, later separated, a wormhole appeared, a “shortcut”' through the universe, connecting the two distant black holes to one another.

Comment: the group did not show that. It just found some equations that suggest that this might happen (or not, because mathematics is not the same as physics). Moreover, these theoretical speculations are based on string theory, which is just one among several alternative proposals of quantum gravity existing today.

What does physics tell us about time travel?

In the previous article we considered a few paradoxes that could bring us to doubt the possibility of time travel. But what does physics say about this? Is there any theory that would make time travel possible? Is it true, as some say, that Einstein’s special theory of relativity implies that it will be possible to travel in time?

First of all, we must refute a fairly widespread misconception. We often hear people saying something like this:

If it were possible to travel at speeds greater than the speed of light, we would travel backwards in time, because the passage of time would become negative.

Is this true? Consider the equation that defines the relationship between proper time and external time for a body moving with a uniform rectilinear speed, according to the special theory of relativity:

Where t is the time experienced by travelers who move at speed v; t₀ is the equivalent external time (the time experienced by an object at rest); and c is the speed of light. 

We can see that, for v < c, the term inside the square root is positive and less than 1, its root would also be less than 1, and therefore t < t₀ (the time experienced by the travelers is shortened).