Drake Essay (2)

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Kaeden Caldwell ASTR 170B1 Partake In Drake Have you ever looked up at the stars in the night sky and wondered what else could be possibly out there? Or, if you are anything like me at all, you watch various amounts of different youtube videos listening to what conspiracy theories sound the most interesting. Whichever way you think about the universe, there is always one question that lingers. What is the estimated number of how many different civilizations are trying to communicate with us in our Milky Way Galaxy? To have any attempt in estimating the number, we first need to understand what Fermi Thinking is. Enrico Fermi, an Italian-American physicist, first came up with the thinking when the atomic bombs were first being tested back in 1945. After the bomb was dropped. Fermi was able to conclude that the atomic bomb was equivalent to 10 thousand tons of TNT being detonated at once. After several weeks of conducting the exercise, it was discovered that Fermi’s instant estimate had been correct. People wondered how Fermi was able to estimate the nuclear bomb and its reaction, Fermi broke down the difficult problem into different smaller problems making it easier to manage. When the problem was broken down into subproblems, without the help of references or the internet, an estimate can be made that can come close to the exact solution. “Fermi’s belief was the ability to make educated guesses when facing unknown or complex problems was a crucial skill, not just in science but across many domains.” However, when trying to find out how many different civilizations are trying to communicate with us in our galaxy, I will be using both Fermi’s method with the Drake equation as well. The Drake equation will represent the odds of finding intelligent life in the Milky Way. I believe that the drake equation and Fermi’s method have a lot in common. Both methods are based on an estimate of numbers put together and trying to find the closest answer. While the Drake equation is a list of specific numbers meant to only find one answer; you can use fermi’s method and use your numbers and certain products in your equation to give you an estimate of your answer. I will be using Fermi’s method by using my

numbers and products and implementing them into the Drake equation giving me an estimate of how many civilizations are trying to communicate with us. Before I get into how the Drake equation works, we must understand how certain exoplanets and stars are discovered and what techniques are used by astronomers. The first technique that we must understand is the doppler effect. The Doppler Effect occurs when sounds waves, or light waves, travel between two different objects. When the light waves are leaving a source that can be detected, the Doppler Effect causes the frequency to differ between the received frequency and the source. This effect is observed by astronomers as it is easier to detect if there is a motion that is increasing or decreasing between the distances of the source and the receiver. When the distance is increased between the two objects, we see that the wave frequency becomes lower the further the objects move apart. When the distance is decreased between the two objects, the frequency of the waves has the frequency of the received waveform will be higher than the source waveform. However, if the distances between the receiver and sources remain unchanged, the waves would be set to a consistent rate between both objects. The next method astronomers use to discover exoplanets is the Transit Method. The transit method occurs when a planet is in front of its star during its orbit, which then causes the brightness of the star to dim. The Transit Methods measures the luminosity of the stars which can only be measured for a short period and is difficult to catch. This is when astronomers can detect an exoplanet as even the slightest change in the star’s brightness can be beneficial. The method can also be used in a variety of different ways. It can be used to help determine certain characteristics of the exoplanet, for example, you can determine the size of the exoplanet’s orbit, how long it takes to orbit, and lastly the size of the actual planet. Another aspect we can learn about is the exoplanet’s atmosphere through transit. During the transit, the light will be emitted through the atmosphere which can be analyzed and determine what kind of elements are presented throughout the atmosphere. We students aren’t the only ones who are curious about what lies throughout our galaxy and what kind of potential it holds. The National Aeronautics and Space Administration (NASA) has launched several missions into space but two, in particular, have used the transit method and have attempted to

detect exoplanets. The Kepler spacecraft was launched into space on March 9, 2009, with the sole purpose to search and detect any exoplanets within our Milky Way Galaxy. On November 15, 2018, NASA had announced that the Kepler space scope was retired completing its nine-year-long mission. In its time, the Kepler spacecraft was nothing but extraordinary as it discovered more than 2,600 exoplanets over 500,000 stars had been observed. Another example of a spacecraft that used the transit method to detect exoplanets is the TESS mission, which launched on April 18, 2018. Astronomers can study the atmosphere of these planets and reveal the planet’s compositions. However, unlike the Keppler spacecraft, TESS (Transiting Exoplanet Survey Satellite) will study stars that are 30 to 100 times brighter than those the Kepler mission and K2 follow-up surveyed, which will enable far easier follow-up observations with both ground-based and space-based telescopes. Astronomers and scientists believe the mission will catalog thousands of planet candidates and vastly increase the current number of known exoplanets. Understanding what we know we can now incorporate the Drake equation as astronomers and scientists try to break down the famous equation. The Drake equation consists of seven different elements, N = R* · fp · ne · fl · fi · fc · L, the first element I will be breaking down is the mean rate of star formation (R*). After reviewing the table on each spectral type and the percentage of all main sequence stars, I believe the only stars that are suitable are types B, A, F, and G. These stars I believe provide a good luminosity level and have a radius similar to earth. However, all have a low percentage of being on the main sequence; with that being said I believe that there are 0.138 solar masses found per year, (0.013+0.006+0.03+0.076)2. The second factor in the Drake equation is the fraction of new stars that host planets. (fp) Over the years this estimate can be more accurate based on what we have learned about space so far. With the Doppler effect, Transit effect, and the use of Microlensing during the Kepler mission, we were able to get a projected number of terrestrial planets around main sequence stars in the Milky Way. My estimate for the fraction of new stars that host planets is 0.5.

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The third factor in the Drake equation is the number of Earth-like planets in the habitable zones of those stars. (ne) With the help of Kepler, scientists were looking for planets similar to Earth’s features; such as its temperate, rocky, and orbiting sunlike stars. After observing the planet’s basic surface features, we know to look at certain characteristics such as magnetic fields, atmospheres, water content, and plate tectonics all play a crucial role. With this, we can get an estimate of 0.5% of Earth-like planets in the habitable zone. The next factor presented in the Drake equation is the fraction of habitable planets that develop life (fI). For planets to be labeled as habitable, many factors are factored into this. For example, the planet must orbit a star that remains stable in output for billions of years, be a perfect distance away from the star which results in the surface water remaining in a liquid form rather than freezing, and must have a circular orbit around its star. This space is also referred to as the “Goldilocks Zone” where life can be habitable and all the conditions have been achieved. However, astronomers have discovered that Earth is a special planet and some have stated “So far, we haven’t seen anything else like it.” With Earth being the perfect example of being a habitable planet, it is a hard planet to come across on, making this part of the equation a low estimate. With there being 4,878 confirmed exoplanets I believe the percentage of habitable planets that develop life is only 0.1%. The fifth factor that is brought up in the Drake Equation is the fraction of the planet with life that becomes intelligent (fi). A question I asked myself before coming up with my estimate is, What does it mean for a planet to have intelligent life? Or what classifies intelligent life? After researching I believed the most important factors are sustainability, communication, and the ability to adapt. These factors I think are required for intelligent life, however intelligent life could be rarer than we think. Life can arise on planets but can intelligent life be guaranteed? With all these unanswered questions it is difficult to say how rare is intelligent life, however, my estimate for the probability for intelligent life developing is 1/152 chance (0.66%). (38 planets that can support life / 1:4 probability) The sixth factor given in the equation is the fraction of intelligent life that wants to communicate (fc). The factor that we must realize is that intelligent life on a planet is still not enough for us to

communicate. For us to communicate with other civilizations, both sides would need the correct technology and resources that can reach each other light-years away. There are many risks and decisions to be made when attempting to communicate; some civilizations might believe it is too risky to reveal their location, or some have yet to invent radio telescopes (which we humans didn’t accomplish until the 20th century), or perhaps simply are not interested in trying to communicate. This will be another low estimate with having only a 10% chance with other intelligent life trying to communicate with us. The seventh and final factor presented in the Drake Equation is the typical lifetime of communicating civilizations (L). I believe this is the most unknown factor out of the Drake Equation since we know nothing about other civilizations. However, we can get an estimate by basing this factor off on their access to technology and how advanced it is. Their technology may be much more advanced than ours, which would likely make their lifespan longer than ours. My estimate for the typical lifetime for communicating civilizations is 500 years. I think this is the perfect estimate as it is enough time for civilizations to create technology that is capable of reaching us. Factor R* Fp Ne FI Fi Fc L Estimate 0.138 0.3 0.5 0.1 0.06 0.10 500 The last step that will complete the Drake is multiplying all seven variables together to get our answer of how many intelligent civilizations are trying to communicate with us within our galaxy. After multiplying all seven values we get a value of 0.00621. After rounding the numbers, I believe that within our galaxy 0.006 civilizations are attempting to communicate with us. Enrico Fermi, not only created his famous ways of being able to estimate values all within his head but also created the Fermi Paradox. Fermi Paradox is simple, where are the aliens right now. Another hypothesis that can be used to help determine alien life is the Rare Earth Hypothesis. This hypothesis argues how unlikely alien life is and states why the Earth is rare and complex throughout our

galaxy. Or the hypothesis could argue the opposite and explain how complex life is typical and occurs commonly throughout our galaxy. However, understanding both thinkings, I believe that there is intelligent alien life that wishes to communicate with us. Since our Milky Way galaxy is 52,850 light- years, the possibilities are endless and we have yet to explore even a fraction of it yet. I feel that my answer does not support Fermi Paradox, Fermi believed that aliens existed and questioned why haven’t we made contact yet. My estimate shows that there is little to no alien life attempting to communicate with us right now. Having the technology is one thing, having the money to create the technology is another problem to deal with. The Search for Extraterrestrial Intelligence, (SETI) is an organization that attempts to seek the answer to a question we will be asking for years to come, are we alone within our universe. I would invest in organizations like these as I am also curious to find out if we are truly alone within our universe. Bibliography Pat Brennan. “What’s a transit?” January 6, 2021 https://exoplanets.nasa.gov/faq/31/whats-a-transit/ Lauren Fuge. “Precision Planet Detection” August 5, 2021 https://cosmosmagazine.com/space/precision-planet-detection/ “What is the Doppler effect?” https://www.qrg.northwestern.edu/projects/vss/docs/communications/3- what-is-the-doppler-effect.html Chris Mann “Fermi Thinking: Creating a framework for navigating uncertainty” July 2, 2020 https://sportsology.pro/fermi-thinking-creating-a-framework-for-navigating-uncertainty-sport/

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#:~:text=Named%20after%20Enrico%20Fermi%2C%20the,calculations%20with%20little%20concrete %20information Pat Brennan “Kepler's legacy: discoveries and more” September 24, 2020 https://exoplanets.nasa.gov/keplerscience/ Rob Garner “About TESS” August 24, 2020 https://www.nasa.gov/content/about-tess Marcia Rieke “Properties of the Planets and Habitable Zones” November 26, 2021 http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/habzone.htm Abel Mendez “Goldilocks Worlds: Just Right For Life?” October 15, 2014 https://www.nationalgeographic.com/astrobiology/goldilocks-worlds/#:~:text=Of%20the %201%2C780%20confirmed%20planets,too%20cold%20to%20support%20life. Marcelo Gleiser “What Scientific Concept Would You Improve Everybody’s Cognitive Toolkit?” March 28, 2011 https://www.edge.org/response-detail/11331 Emily Calandrelli “How Do You Define Intelligent Life” May 23, 2014 https://www.thespacegal.com/blog/2014/5/23/how-do-you-define-intelligent-life Ethan Siegel “Life Might Be Common In The Universe, But Intelligence Is Likely Rare” May 21, 2020 https://www.forbes.com/sites/startswithabang/2020/05/21/life-might-be-common-in-the-universe-but- intelligence-is-likely-rare/?sh=752779464ee6 Andy Tomaswick “The First Civilization We Contact Will Have Been Around Much Longer Than Humanity” November 20, 2020 https://www.universetoday.com/148869/the-first-civilization-we-contact-will-have-been-around-much- longer-than-humanity/ Bynadia Drake “How Many Alien Civilizations Are Out There? A New Galactic Survey Holds a Clue” November 2, 2020 https://d2l.arizona.edu/d2l/le/content/1049349/viewContent/11724962/View

Chris Impey “Fraction of stars with planetary systems, fp, 1961 to the present” July 5, 2015 https://www.cambridge.org/core/books/abs/drake-equation/fraction-of-stars-with-planetary-systems-fp- 1961-to-the-present/71DDE7F46C63543C4C0FD79A0DA4027D Elizabeth Howell “Fermi Paradox: Where are the aliens?” April 26, 2018 https://www.space.com/25325-fermi-paradox.html#section-what-could-the-answer-be

Drake Essay (2)

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