The Drake Equation

N = N* fp ne fl fi fc fL

N* represents the number of stars in the Milky Way Galaxy

Question: How many stars are in the Milky Way Galaxy?

Answer: Current estimates are 100 billion.

fp is the fraction of stars that have planets around them

Question: What percentage of stars have planetary systems?

Answer: Current estimates range from 20% to 50%.

ne is the number of planets per star that are capable of sustaining life

Question: For each star that does have a planetary system, how many planets are capable of sustaining life?

Answer: Current estimates range from 1 to 5.

fl is the fraction of planets in ne where life evolves

Question: On what percentage of the planets that are capable of sustaining life does life actually evolve?

Answer: Current estimates range from 100% (where life can evolve it will) down to close to 0%.

fi is the fraction of fl where intelligent life evolves

Question: On the planets where life does evolve, what percentage evolves intelligent life?

Answer: Estimates range from 100% (intelligence is such a survival advantage that it will certainly evolve) down to near 0%.

fc is the fraction of fi that communicate

Question: What percentage of intelligent races have the means and the desire to communicate?

Answer: 10% to 20%

fL is fraction of the planet's life during which the communicating civilizations live

Question: For each civilization that does communicate, for what fraction of the planet's life does the civilization survive?

Answer: This is the toughest of the questions. If we take Earth as an example, the expected lifetime of our Sun and the Earth is roughly 10 billion years. So far we've been communicating with radio waves for less than 100 years. How long will our civilization survive? Will we destroy ourselves in a few years like some predict or will we overcome our problems and survive for millennia? If we were destroyed tomorrow the answer to this question would be 1/100,000,000th. If we survive for 10,000 years the answer will be 1/1,000,000th.

When all of these variables are multiplied together when come up with:

N, the number of communicating civilizations in the galaxy.

The real value of the Drake Equation is not in the answer itself, but the questions that are prompted when attempting to come up with an answer. Obviously there is a tremendous amount of guess work involved when filling in the variables. As we learn more from astronomy, biology, and other sciences, we'll be able to better estimate the answers to the above questions. Many of these questions will be addressed in depth in future issues of Enigma.

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Frank Drake

Drake Equation atau persamaan Drake adalah persamaan yang digunakan untuk memperkirakan potensi jumlah peradaban luar bumi di Galaksi bima sakti. 

Persamaan ini digunakan dalam bidang exobiology dan Search for Extraterrestrial Intelligence (SETI). 

Persamaan ini dibuat oleh Frank Drake pada 1961. 

Drake merumuskan persamaan ini untuk persiapan menghadiri pertemuan Green Bank yang diadakan di Green Bank, West Virginia. 

Pertemuan ini didirikan oleh SETI yang dihadiri oleh astronom, fisikawan, ahli biologi, ilmuwan sosial, dan para pemimpin industri yang datang bersama untuk membahas kemungkinan untuk mendeteksi kehidupan cerdas di luar planet bumi.

Green bank merupakan tempat pertemuan pertama dimana persamaan Drake dibahas, dan menjadi topik utama pembicaraan pada pertemuan SETI berikutnya.

N = jumlah peradaban di galaksi kita dengan mana komunikasi antara kita mungkin terjadi

R* = tingkat rata-rata per tahun formasi bintang di galaksi kita

ƒp = fraksi dari bintang-bintang yang memiliki planet

ne = jumlah rata-rata planet yang berpotensi dapat mendukung kehidupan per bintang yang memiliki planet

ƒℓ = fraksi yang digunakan untuk mengembangkan kehidupan dibeberapa aspek

fi = fraksi yang digunakan untuk mengembangkan kehidupan cerdas

ƒc = fraksi peradaban yang mengembangkan teknologi untuk melepaskan tanda-tanda keberadaan mereka ke ruang angkasa

L = waktu yang digunakan untuk melepaskan sinyal yang bisa di deteksi diluar angkasa

Hasil penelitian ini belum membuahkan hasil. 

Selama enam jam per harinya sejak April hingga Juli tahun 1961, proyek ini baru menangkap sinyal yang awalnya di duga berasal dari bintang Tau Ceti dan Epsilon Eridani. Namun sayang, ternyata sinyal itu tak lebih dari alarm yang salah dari sinyal proyek militer rahasia.