Mark Chang

Math 89S

Professor Hubert Bray

Paper 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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