Earth is our one and only home. But, is it possible for humanity to leave its home and visit other stars (or other stars that have planets, actually) in the future?

Our galaxy, “The Milky Way is a barred spiral galaxy (a spiral galaxy with a central bar-shaped structure composed of stars) some 100,000-120,000 light-years in diameter, which contains 100-400 billion stars. It may contain at least as many planets as well.

Our Sun (the Solar System) is located within the disk, about 27,000 light-years away from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm.

The nearest star, Proxima Centauri (Latin proxima, meaning “next to” or “nearest to”) is a red dwarf about 4.24 light-years from the Sun.

As a guide to the relative physical scale of the Milky Way, if it were reduced to 100 meters in diameter, the Solar System, including the hypothesized Oort cloud, would be no more than 1 millimeter in width, about the size of a grain of sand. The nearest star, Proxima Centauri, would be only 4.2 mm distant.

Alternatively visualized, if the Solar System out to Pluto were the size of a US quarter (25 mm in diameter), the Milky Way would have a diameter of 2,000 kilometers, an area approximately one-third the size of the United States.

As Douglas Adams pointed out, “Space is big. Really big. You just won’t believe how vastly, hugely, mind-bogglingly big it is.”

So, will we ever leave our home planet and visit other stars in the future?

Video: Will We Ever Visit Other Stars?

The video published by Michael Stevens (popularly known as the Vsauce) below contains some possible answers to that very question.

Spoiler: most likely, humans will never be able to go beyond the solar system.

Will We Ever Visit Other Stars? Note: Voyager 1 flew beyond the heliopause and entered interstellar space on August 25, 2012, making it the first human-made object to explore this new territory. Voyager 2 entered interstellar space on November 5, 2018.

Wait calculation problem: When should our interstellar journey start?

One of the main problems in interstellar travel is the wait calculation, which tries to determine the optimal time to wait for technological progress to improve spaceship speeds, before committing to the journey.

In Michael’s words: leave too soon, your spaceship can be passed by astronauts who left Earth hundreds, even thousands of years after you (because of the improvements in space travel).

American physicist and science fiction writer Robert L. Forward (August 15, 1932 – September 21, 2002) has argued that an interstellar mission that cannot be completed within 50 years should not be started at all. Instead, assuming that civilization is still on an increasing curve of propulsion system velocity and not yet having reached the limit, the resources should be invested in designing a better propulsion system.

In his study titled “Interstellar Travel – The Wait Calculation and the Incentive Trap of Progress”, Andrew Kennedy calculated that given the pace of our current progress, the soonest human civilization might ever reach Bernard star, which is 6 light-years away, is 1,104 years from 2006 (the year 3110).

And even this number can be optimistic because Kennedy’s only concern was speed. We need to also solve problems like “how to survive interstellar radiation for decades?” or “how to avoid collisions with interstellar material at very high speeds?”

Milky Way. Will we ever visit other stars?
Our galaxy, the Milky Way contains between 100-400 billion stars. But, in the distant future maybe, will we be able to reach any of them? Will we ever visit other stars? Photo by Oliver Griebl – Imported from 500px. CC BY 3.0, Link

The Fermi Paradox: Why “other stars” didn’t visit us?

At the end of the video, Michael also talks about the “Fermi Paradox”.

The Fermi paradox (or Fermi’s paradox) is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilization and humanity’s lack of contact with, or evidence for, such civilizations. The basic points of the argument, made by physicists Enrico Fermi and Michael H. Hart, are:

  • The Sun is a typical star, and relatively young. There are billions of stars in the Milky Way galaxy that are billions of years older.
  • Almost surely, some of these stars will have Earth-like planets. Assuming the Earth is typical, some of these planets may develop intelligent life.
  • Some of these civilizations may develop interstellar travel, a technology Earth is investigating even now (such as the 100-Year Starship).
  • Even at the slow pace of currently envisioned interstellar travel, the galaxy can be completely colonized in a few tens of millions of years.

According to this line of thinking, the Earth should already have been colonized or at least visited. But no convincing evidence of this exists. Furthermore, no confirmed signs of intelligence (see Empirical resolution attempts) elsewhere have yet been spotted in our galaxy or (to the extent it would be detectable) elsewhere in the observable universe. Hence Fermi’s question, “Where is everybody?”

You can also read a very good article that contains all possible answers to the Fermi Paradox on waitbutwhy.com.

In a nutshell, here are the possible solutions to the Fermi Paradox:

  • Rare Earth Hypothesis: This hypothesis suggests that Earth may be a rare planet where the conditions necessary for the evolution of complex life are very uncommon. The hypothesis argues that while the universe may contain many habitable planets, the conditions that allow for the evolution of intelligent life are so rare that Earth may be the only planet in the galaxy where complex life has evolved. The Rare Earth Hypothesis is based on several factors that are thought to be necessary for the development of complex life. For example, the hypothesis suggests that the planet must be located in a habitable zone, which is the region around a star where conditions are just right for liquid water to exist. This is considered to be a crucial factor, as water is essential for life as we know it. The Rare Earth Hypothesis also suggests that a planet must have a stable orbit and a large moon to stabilize its rotation, which in turn, provides a stable climate that supports life. Additionally, the planet must have a strong magnetic field to protect it from solar wind and cosmic radiation, which can damage the planet’s atmosphere and life forms. Other factors that are considered to be necessary for the evolution of complex life include plate tectonics, which provides the necessary nutrients for life to thrive, and a stable atmosphere that provides protection from harmful radiation.
  • The Great Filter Hypothesis: This hypothesis suggests that there is some sort of filter that prevents intelligent life from reaching a certain stage of development. The filter could be in the form of a natural disaster, a hard-to-achieve evolutionary jump, self-destruction due to technological progress, or other factors.
  • The Zoo Hypothesis: This hypothesis suggests that intelligent civilizations are aware of us, but have chosen not to make contact. They may be observing us from afar or have imposed some sort of quarantine to prevent contamination.
  • The Simulation Hypothesis: This hypothesis suggests that our reality is a simulation created by a highly advanced civilization. Therefore, any evidence of extraterrestrial life may be a programmed illusion.
  • Interstellar Travel is Difficult: This hypothesis suggests that the distances between stars are simply too vast, and the energy required to travel between them is prohibitively high. Therefore, other intelligent civilizations may exist, but they are too far away to contact us.
  • We are alone: This hypothesis suggests that there are no other intelligent civilizations in the universe.
  • Communications Barrier: This hypothesis suggests that other civilizations may be trying to communicate with us, but their methods of communication are so different from ours that we are unable to recognize them. See: Are we alone in the Universe? Probably. Like the others.

These are just a few of the many possible solutions to the Fermi Paradox. It’s important to note that there is no definitive answer to the Fermi Paradox, and it remains one of the most intriguing mysteries in the field of astrobiology.

But, there’s a very high probability that if the aliens of other stars didn’t visit us, we also won’t (can’t) visit them.

Sources

  • Wait/walk dilemma on Wikipedia
  • Interstellar travel on Wikipedia
  • Study: “Interstellar Travel – The Wait Calculation and the Incentive Trap of Progress”, A. Kennedy. Link
M. Özgür Nevres
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