In Part 1 & 2 on the fate of humanity due to over population I have hinted at the possibilities of colonizing other worlds.
We shall continue this fascinating topic at some challenges a space traveller will face by briefly outlining whatever that flows my mind.
We shall look at the scale of the problem - why reaching even the nearest stars is a monumental challenge. First, we shall look at the fuel and propulsion problems. Conventional chemical rocket propulsion is inadequate for interstellar distances.
The use of nuclear propulsion such as the idea of nuclear thermal and
nuclear pulse propulsion (e.g., Project Orion, Project Daedalus) is an option, but nuclear power is too heavy, and risky.
Exploring the feasibility of using solar energy and light pressure, ion propulsion and solar sails are better alternatives, although solar energy will diminish as we leave the Solar System.
Theoretical energy sources, such as fusion and antimatter propulsion could power a star ship.
I think for fuel and propulsion there are breakthrough
star shot and laser propulsion, concepts like using Earth-based lasers to push
lightweight probes at near-light speeds.
However, in order to manage vast distances and time, we may use warp drives and wormholes or Einstein-Rosen bridge (I shall shortly explain wormholes in detail) are theoretical concepts from physics, such as the Alcubierre drive and traversable wormholes that are short cut paths across immensely vast, vast distances that may possibly take an interstellar journey only a few seconds instead of thousands, millions, billions or trillions of years to arrive.
For the management of aging, according to Einstein's Special Theory of Relativity, a space traveller moving at a speed close to the speed of light would experience time dilation. This means that time passes more slowly for the traveller compared to someone who is stationary on Earth. To put this in another way - the space traveller ages slower on the spaceship compared to someone on Earth.
When the spaceship is moving close to the speed of
light, time dilation occurs, meaning that time for the traveller on the
spaceship passes more slowly than time for someone who is stationary on Earth.
So, if the traveller spends, say, 10 years on the spaceship, those 10 years
would feel like much less time for the traveller due to time dilation. This
phenomenon is directly related to the Lorentz factor:
gamma (γ) = 1 /√ (1 / v2 / c2)
where,
v = speed moving observer
c = speed of light in a vacuum
which mathematically describes how much time dilation
occurs at a given velocity; essentially, the higher the speed, the greater the
Lorentz factor, and the more time slows down for the moving object relative to
a stationary observer.
For someone on Earth, however, the passage of time would be normal, so they would age the typical amount. In fact, when the traveller returns to Earth, they would have aged less than the people who stayed behind. Let's have a look numerically here.
If we enter the values into the Lorentz factor
(γ) of an object travelling at 2 % the speed of light
Given by the above equation:
gamma (γ) = 1 /√ (1 / v2 / c2)
the Lorentz factor is approximately
1.0002
Interpretation:
This means that, for an object traveling at 2% of the
speed of light, relativistic effects such as time dilation are extremely small.
The time experienced by a moving observer (the "moving clock") would
be only slightly slower than the time experienced by a stationary observer (the
"stationary clock").
For example, if 1 second passes for an observer at
rest, only about 1.00021 seconds would pass for the moving observer. The
difference is so small that it is practically negligible at this low speed.
In terms of time dilation: the time difference would be
imperceptible at 2% of the speed of light, which is typical for everyday
speeds. Relativistic time effects only become noticeable at speeds that are a
significant fraction of the speed of light.
For example, if the traveller moves at 99 % the speed
of light, what would be the Lorentz factor, and what does that mean to the
traveller, compared to someone at rest?
Let's now re-calculate the Lorentz factor for an object
traveling at 99% of the speed of light.
We’ll use the same formula for the Lorentz factor:
gamma (γ) = 1 /√ (1 / v2 / c2)
If we calculate this out, this works out to be ≈
7.09
Interpretation:
The Lorentz factor is approximately 7.09 when the
object is moving at 99% of the speed of light.
What does this mean? This means time for the traveller
will slow down relative to someone at rest. Specifically, for every second that
passes for someone at rest, only about 1 / 7.09 ≈ 00.141 seconds will
pass for the traveller.
In terms of time dilation, the traveller’s clock would
be moving about 7.09 times slower than the clock of an observer at rest. This
means that time would appear to pass much more slowly for the traveller
compared to someone who is stationary.
For example, if the traveller spends 7.09 seconds
traveling at 99% the speed of light, someone at rest would observe that 1
second has passed for the traveller.
A practical example is, if the traveller moves at 99%
the speed of light for 7.09 years, only 1 year would pass for an observer at
rest.
This level of time dilation becomes significant at high
speeds like 99% of the speed of light and shows just how much time is affected
at relativistic velocities!
Let me put it another simpler term. For the traveller
on the spaceship, they experience time more slowly while traveling near the
speed of light, so they age slower. For someone on Earth, time passes at the
normal rate, so they age faster in comparison to the traveller.
This is the core idea of the twin paradox. The
traveling twin (the one on the spaceship) will be younger than the twin who
stays on Earth after they reunite. This effect becomes more pronounced as the
speed of the spaceship approaches the speed of light. At light speed,
theoretically, time would stop completely for the traveller, but traveling at
that speed is impossible because it would require infinite energy.
Therefore, if the traveller returns to Earth after
their high-speed journey, they would have aged much less than those who stayed
on Earth.
The relativistic time dilation may solve the limits of
human lifespans in high speeds travels in space.
According to Einstein’s theory of special relativity, time dilation occurs when an object moves at speeds approaching the speed of light. For a space traveller moving at such velocities, time in their frame of reference slows down relative to an observer on Earth. As a result, if the traveller embarks on an extended journey at relativistic speeds and subsequently returns to Earth, significantly less time would have elapsed for them compared to those who remained on the planet.
Depending on the duration and
velocity of the journey, centuries may have passed on Earth, leading to the
demise of multiple generations, while the traveller themselves would have aged
only by a fraction of that time. This effect is a direct consequence of the
Lorentz factor, which mathematically describes how time dilates as velocity
approaches the speed of light.
If this explanation is difficult to understand, let me
rewrite it in a simpler way
When a space traveller moves at speeds close to the
speed of light, time for them slows down relative to an observer on Earth. This
is a direct consequence of Einstein’s theory of relativity, specifically time
dilation. If the traveller embarks on a journey at near-light speed and later
returns to Earth, they would have aged only a little, whereas much more time
would have passed on Earth—potentially centuries. As a result, the traveller
may find that entire generations have passed away while they themselves have
barely aged.
One theoretical way to short cut long, long journeys is to use worm holes passages. A wormhole, as theorized in Einstein’s general relativity, is a hypothetical tunnel-like structure that connects two separate points in spacetime, potentially allowing for instantaneous travel between them.
A useful analogy involves imagining space as a two-dimensional sheet of
paper. If we mark two points, A and B, on this sheet, a conventional journey
between them requires traveling along the surface, much like drawing a line
between the points. The longer the line, the more time it takes.
However, if we bend or fold the paper so that points A
and B touch, we effectively reduce the spatial separation to zero. By then
piercing a hole through these touching points with a needle, we create a
shortcut - analogous to a wormhole, that allows for near-instantaneous
traversal between the two locations. In the context of general relativity, such
a wormhole would be a solution to Einstein’s field equations, often modelled by
the Einstein-Rosen bridge, though its stability remains a theoretical challenge.
Besides the problem of horrendously vast
distances, staggering amount of energy is needed for high-speed
interstellar travel already briefly written, there is also the problem with
cosmic hazards such as space debris, radiation, and other dangers of traveling
at relativistic speeds.
There are also communication delays with the challenge
of maintaining contact with Earth over light-years of distance.
Besides that, we also have another problem with human
adaptation to biological and psychological effects of long-duration space
travel.
What are the potential solutions to overcome challenges
then? One solution is to use generation ships. This means sending
multi-generational crews to settle distant star systems.
Another method is cryogenic sleep and biostasis, the
idea of hibernating travellers for long journeys. We also need Artificial Intelligence and robotics by
sending autonomous probes before human explorers. If safe, AI need to accompany
us in the journey.
The future of humanity among the stars also depends on
ethical and philosophical implications of interstellar colonization.
In one of my many technical forum discussions at the University of Oxford when I did my postdoctoral there, I proposed, we need to search for the nearest habitable exoplanets, where we might go first instead of going to the stars, much, much further away. We shall briefly go into our search of exoplanets in Part 4 of this series of essays. How interstellar travel might change human civilization I am not sure.
What about extra-terrestrial intelligence should we encounter alien beings halfway through our journey or when we landed in another world? I am unsure how to answer that! It can be very frightening especially when you are alone in isolation out there in the darkness and void of deep outer space with only a few crew members, and I dare not discuss this here.
Meantime, we need to explore the importance of continued scientific advancements in making it a future possibility.
The potential and obstacles of interstellar travel
remains one of the greatest challenges of human exploration.
As I have suggested, we can search for habitable exoplanets, where might we go first? We shall try to explore some newly discovered exoplanets (planets that lie outside our Solar System) if life exists there and how we can get there in the future – food for thought.
We shall write on this later, but before that, we shall try to solve one of our greatest problems and requirements of all - how are we going get air, water and food out there in the darkness and void of outer space? We shall answer in dilemma in Part 4
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