Mark ChangMath 89SProfessor Hubert BrayPaper 3

Humans: Going Beyond the Living Boundaries of Earth

Introduction: Where else can we live?

We exist in the realm of environments that are sustainable of human life, which currently

is limited to the surface of our planet Earth. As we are vulnerable to slight changes in the

environment we live in, there are many questions that arise in whether we will ever be capable to

survive in atmospheres that are different to that of our planet. Evidently we cannot survive in

what the universe is mostly comprised of: the vacuum of space. Once exposed to the vacuum of

space – that of extremely low pressures – all the oxygen will escape out of our bodies in a matter

of seconds, and we will pass out due to the lack of oxygen transmitted to the brain and die as

body fluids boil in contact with the low pressures. As we search for places in the universe we

could possibly colonize, we consider planetary habitability and those atmospheres that will allow

ourselves to possibly adapt and sustain life on. However, before we look into the atmospheres

that seem habitable, we need to ask ourselves; what are the limits of human survival and how can

can we possibly sustain life in different environments?

I. The Human Boundaries

Survival depends on the ability to adapt to the surrounding environment and create an

“active equilibrium.” However, in order to reach this equilibrium, living organisms have to be

able to sustain life in in environments that differ in oxygen levels, temperature, water, and food.

Although humans are highly capable in adapting to perturbations in their surrounding

environments, there are still physical limits where conditions of survival are not met. The study

of these physical limits is known as limit physiology. These studies help to understand the

extreme conditions where humans will still be able to maintain a level of equilibrium with the

surrounding environment. Many living organisms are sensitive to slight changes in physical

surroundings, and their survival is limited to “niches.” Once conditions go beyond the limits of

these niches, the living organism are unable to maintain an equilibrium with the surrounding

environment, leading to extremely perilous situations for the whole species.

Organisms survive within their habitable environments, which are the limits where living

conditions are met. Once these boundaries are reached, organisms have to bear through the stress

levels until adaptation gradually occurs, or else they will no longer survive. As the stress levels

increase with the approaching of survival boundaries, it takes more effort to adapt, and the time

to compensate to the environment decreases, which is equivalent to the decrease of survival time.

This condition is portrayed through Figure 1, where the x-axis represents the time to death and

the y-axis shows the degree of stress on the organism through the environment. As adaptation

occurs within these boundaries, the curve will shift to the right because the organism will be able

to survive in these conditions for a longer period of time.

Figure 1

II. Sustainable Life-Support Systems

Humans are currently thriving within the habitable boundaries of the Earth, but once we

go beyond these limits of known survival, we stand no chance. As vulnerable as we are to the

changes in the environment, one of the most likely solutions to colonizing other planets is to

create some sort of life-support system that will provide us with the necessities, such as

uncontaminated and livable atmosphere, sufficient energy and protection from radiation, enough

food and water, and a system capable of controlling waste. The two types of systems of life-

support systems are open and closed systems. A complete open system does not recycle any of

the resources but supplies everything, and a complete closed system supplies and recycles all

resources. It would be ideal to create a closed system where a sustainable environment is created

with proper and complete recycling with only the initial supply of resources placed into the

system. Current technology does not allow the production of a complete closed system, because

we still are incapable of disposing waste completely and there are leaks within the closed system.

However, there seems to be possibility of technological developments in areas such as the

bioregenerative life-support systems (BLSS) that could mimic the closed ecosystem created and

maintained by the Earth. Figure 2 illustrates a condensed version of the BLSS model, which

shows a completely enclosed system where only light in the form of radiation enters to generate

energy for machinery and plant-growth lamps and only heat created by waste is released to

maintain life-sustaining temperature conditions. Edible portions of the plant can be eaten as a

source of food or be stored for future consumption. Furthermore, plants will intake carbon

dioxide and release oxygen, and this will allow the humans and plants to create a cycle of

exchanging CO2 and oxygen. Through enzymatic reactions, human waste can be oxidized to

create water, CO2 and minerals, and this self-sustaining system will be able to create a closed

life-support environment.

Figure 2

III. In Face of Sudden Extreme Conditions

Humans are frequently depicted in movies to survive through life threatening situations

with insufficient supplies and just the willpower to live. However, these situations are rarely true

in real life, especially in conditions that are beyond our environmental niche. In other words, it is

highly unlikely that one who has a stronger desire to live will survive in the burning desert with

no supplies and one who does not have a strong desire to live does not. At the end, the

equilibrium we create with the environment is the most important to survival, and its importance

cannot be stressed when we are searching for environments that are beyond our habitable

environments here on earth.

The chances that we find a habitable environment within reach in our universe seems

highly unlikely in this point of time. Therefore, in order to adapt to these environments that are

beyond our survival boundaries, we need thorough preparation to decrease the potential exposure

to stress levels posed by the environment to increase the compensation time. There needs to be

clear foresight into the possibilities of failures in parts of the sustainable system, so that the

probability of death is minimized to a level of safety where a malfunction one part does not lead

to an extremely high chance of death. For example, a malfunctioning oxygen tank in the ascent

of the Himalayas could easily lead to death if there were no extra oxygen tanks in preparation for

this situation. This situation illustrates the “double failure” problem. The first problem occurred

when the hiker decided not to prepare the extra oxygen tanks and depend solely on the one

oxygen tank on him, and the second problem, that could have been quite insignificant with the

extra oxygen supplies, was the malfunctioning of the one oxygen tank the hiker took with him.

This double failure problem is essential in creating life-support systems in situations

where the failure of one part of the system may dramatically affect the probability of survival of

the entire human population living in closed environments. The double failure analysis can be

expressed through the condensed situation shown in Figure 3.

Figure 3

The diagram of survival probability is expressed by two independent events – (a) and (b)

– that individually, together, or neither occurs. Each event occurs in the probability 1 in 1000

with a 99 percent chance of survival. Therefore, the possibility of death for one of the events can

be calculated by the multiplication of the chance of the event occurring, 1:1000, and the

probability of death for the event, 0.01, which is 1 in 100,000. The chances of both of these

events to occur – represented by Pab is 1 in 1 million. However, it is set that if both of these

events occur, there is no chance of survival. If all of these events are taken into consideration, the

total probability of death, Pdeath(tot), equals 2.1 in 100,000, which is a reasonable risk to take.

In the case where event (a) already has occurred prior to event (b), shows how not

preparing for a situation can lower the probability of survival by a significant amount. As shown

through the bottom portion of Figure 3, (a) already occurred which makes its probability of

occurrence, Pa, equal to 1 but the probability of death, Pd, equal to zero. The probability of (b)

occurring, is same as the previous situation of 1 in 1,000, but the probability of death, Pd, equals

to 1 because (a) has already occurred. Consequently, the total probability of death for when (a)

occurs before the event, Pdeath(tot), turns out to be 1 in 1,000. It is clear that when event (a) occurs

prior to the event – similar to the situation where the hiker does not bring extra supplies of

oxygen – there is a much higher chance of death. When comparing the two probabilities, 2.1:

100,000 and 1: 1,000 we can clearly observe the difference preparation can make in the

probability of life or death. These probabilities have to be carefully analyzed, especially in

situations where the environment outside the closed life-support system is completely inhabitable

by humans.

This probability of survival can also be represented in a parallel system where in the case

event (a) occurs, event (b) can be intentionally put into action to decrease the chances of death.

The chances of death for each individual event is 1 in 1,000, but if both events are exercised, the

chances of death decrease exponentially to 1 in 1 million. An example of this situation is when

you are sailing on a boat alone, the chances of you surviving is 1 in 1,000, which is expressed

through probability Pa. Even with the life vest on, you are unable to stop the boat or catch up by

swimming, so the life-vest is insufficient. However, prior to falling off the boat, if you decide to

tie the safety vest to the boat, which is expressed through PB, there is a much decreased chance of

death to 1 in 1 million. This situation of a parallel system is shown through Figure 4. It is

essential to have these parallel events that could potentially decrease the probability of death

from 100 percent to a value much lower.

Figure 4

Conclusion

Humans are currently in the luxury of existing within the closed natural environment of

the Earth’s atmosphere. However, there is a chance that this environment will gradually exceed

our habitable niches, and we may be incapable of adapting to this new environment as the

intensity of stress on our bodies to create an equilibrium with the environment becomes too

great. Therefore, we need to develop sustainable life-support systems to perhaps one day be able

to live in completely closed systems on planets other than Earth. In order to make this system

truly sustainable, the risks of failure need to be extensively analyzed to make sure that the

chances of death of all the living organisms within the system are minimized. If the universe

does not offer us a second chance with a habitable planet like Earth, we need to create one

ourselves.

Works Cited

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Vera, Jean-Pierre De, and J. Seckbach. Habitability of Other Planets and Satellites. N.p.: n.p.,

n.d. Print.

Wolchover, By Natalie. "What Are the Limits of Human Survival?" LiveScience. TechMedia

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