In e na ional Jou nal o Cu en Science Resea ch and Re iew
ISSN: 2581-8341
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DOI: 10.47191/ijcs /V8-i11-33, Impac Fac o : 8.048
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Es ima ing The Numbe o In elligen Ex a e es ial Ci iliza ions:
A P obabilis ic App oach o he D ake Equa ion
H is o Dele 1, Todo ka L. Dimi o a2
1 MPHAC “Uni Hospi al”, adio he apy depa men Panagyu ish e, Bulga ia
2 Depa men o Physics, Facul y o Physics and Technology,
Uni e si y o Plo di “Paisii Hilenda ski”, Bulga ia
ABSTRACT: As obiology seeks o add ess some o humani y’s mos p o ound ques ions: A e we alone in he Uni e se? and Wha
a e he condi ions necessa y o li e o eme ge? One o he key heo e ical ools in his pu sui is he D ake Equa ion, o mula ed in
1961, which p o ides a p obabilis ic amewo k o es ima ing he numbe o in elligen ex a e es ial ci iliza ions in he Milky
Way. In his pape , we e isi he D ake Equa ion using upda ed as onomical and biological da a, along wi h simpli ied p obabilis ic
assump ions. By applying cu en obse a ional e idence o exoplane s, labo a o y s udies o p ebio ic chemis y, and es ima es o
s ella and plane a y habi abili y, we ob ain a en a i e alue o ~72 ci iliza ions capable o in e s ella communica ion ia adio
as onomy. The esul highligh s he pa adox i s iden i ied by En ico Fe mi -i in elligen li e is so p obable, why ha e we no ye
de ec ed i ? We discuss possible esolu ions o he Fe mi Pa adox, including dis ance, e olu iona y di e ences, and he possibili y
o sel -des uc ion. Finally, we ou line u u e di ec ions o as obiology, obse a ional as onomy, and SETI ha may e ine hese
es ima es and po en ially esol e one o he g ea es scien i ic mys e ies o ou ime.
KEY WORDS: As obiology, D ake Equa ion, Exoplane s, Fe mi Pa adox, SETI.
1. INTRODUCTION
The disco e y o housands o exoplane s o e he pas h ee decades has e olu ionized ou unde s anding o plane a y
sys ems and enewed in e es in he sea ch o ex a e es ial li e. A landma k momen occu ed in 1977, when a s ong na owband
adio signal was de ec ed a he equency o neu al hyd ogen (1.420 GHz), p ecisely whe e esea che s had heo ized an a i icial
signal migh appea . This signal, now amously known as he “Wow! Signal,” was aced o he egion o he globula clus e M55
(Ma el, 2001). Al hough i s o igin emains unexplained, i con inues o s imula e scien i ic deba e. Mo e ecen ly, in Decembe
2020, a po en ial new sou ce was sugges ed – s a 2MASS 19281982-2640123 (Caballe o, 2020) – ekindling in e es in he
possibili y o ex a e es ial adio ansmissions. The de ec ion o an a i icial adio signal would ep esen one o he mos
compelling pieces o e idence o he exis ence o in elligen ex a e es ial ci iliza ions.
Pa allel o adio as onomy, he sea ch o exoplane s has undamen ally ans o med ou knowledge o plane a y sys ems
beyond ou own. Mul iple de ec ion echniques ha e been de eloped, wi h he ansi me hod p o ing he mos e icien , accoun ing
o mo e han 70% o con i med disco e ies (NASA Exoplane A chi e, 2025). As o June 14, 2025, 5,921 exoplane s o bi ing
4,422 s a s ha e been con i med, wi h he Keple Space Telescope alone esponsible o de ec ing 3,328 o hem. Since he launch
o he T ansi ing Exoplane Su ey Sa elli e (TESS), he o al numbe o plane s disco e ed ia he ansi me hod has isen o 4,387,
yielding a success a e o app oxima ely 74.1%. This e iciency unde sco es why he ansi me hod has become he co ne s one o
mode n exoplane disco e y
Keple ’s mission, in pa icula , has yielded se e al g oundb eaking disco e ies. No able examples include Keple -186 -
he i s Ea h-sized plane ound wi hin he habi able zone o i s hos s a (Quin ana, 2014) – and Keple -16b, he i s con i med
ci cumbina y exoplane , o bi ing wo s a s (Doyle, 2011). Ano he in iguing case is KIC 8462852, also known as “Tabby’s S a ,”
which exhibi s i egula , ape iodic dimming e en s o up o 20% in he s ella lux (Simon, 2016). These unusual pa e ns ha e
spa ked conside able deba e, anging om na u al as ophysical explana ions o mo e specula i e hypo heses.
Among he mos ascina ing exoplane s disco e ed o da e is K2-18b, which scien is s conside a p omising candida e in
he sea ch o li e beyond Ea h (Fo eman-Mackey e al., 2015; Benneke e al., 2017). In 2025, dime hyl sul ide (DMS) was de ec ed
in i s a mosphe e (Madhusudhan e al., 2025), a molecule o en conside ed a po en ial biosigna u e. Al hough his is no de ini i e
In e na ional Jou nal o Cu en Science Resea ch and Re iew
ISSN: 2581-8341
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p oo o li e, i makes K2-18b an exci ing a ge o u u e in es iga ions and highligh s he apid p og ess in iden i ying exoplane s
wi h condi ions po en ially sui able o li e.
1.1. D ake Equa ion
In 1961, he Ame ican as onome F ank D ake o Co nell Uni e si y p oposed a p obabilis ic ma hema ical amewo k o
es ima e he numbe o ex a e es ial ci iliza ions in ou galaxy capable o in e s ella communica ion. This amewo k, now
amously known as he D ake Equa ion, combines a se ies o measu able quan i ies and p obabili ies, such as he numbe o s a s
in he Milky Way and he likelihood ha plane s de elop li e. The equa ion also accoun s o he a e age li espan o ci iliza ions
capable o ansmi ing signals ac oss in e s ella dis ances (Maccone, 2010)
D ake’s objec i e was no o p o ide a de ini i e answe bu a he o s imula e scien i ic dialogue and encou age he
sys ema ic explo a ion o li e beyond Ea h. The D ake Equa ion is exp essed as ollows:
𝑁 = 𝑅∗𝑓
𝑝𝑛𝑒𝑓𝑙𝑓𝑖𝑓
𝑐𝐿, (1)
whe e 𝑅∗ is he a e age a e o s a s o ma ion in he Milky Way; 𝑓
𝑝 – he ac ion o s a s ha ha e plane a y sys ems; 𝑛𝑒 he
a e age numbe o he plane s pe sys em ha could suppo li e; 𝑓𝑙 – he ac ion o hose plane s on which li e ac ually eme ges;
𝑓𝑖 – he ac ion o plane s wi h li e ha de eloped in elligen beings; 𝑓
𝑐 – he ac ion o ci iliza ions, ha de eloped echnology
capable o in e s ella communica ion.; 𝐿 – he a e age li espan o such ci iliza ions. All pa ame e s excep R∗ and L ep esen
p obabili ies, e lec ing ou unce ain y abou he p ocesses ha lead o li e and in elligence. Consequen ly, he D ake Equa ion does
no yield a single de ini i e numbe bu highligh s whe e empi ical esea ch is mos u gen ly needed.
In his s udy, we p opose an app oach o cons aining he D ake Equa ion, s a ing wi h he bes -known pa ame e : he
numbe o s a s in he Milky Way, es ima ed a app oxima ely 400 billion. The subsequen s ep in ol es es ima ing he numbe o
plane s, an a ea in which ecen disco e ies, such as K2-18b, p o ide aluable insigh s. Obse a ions om mode n as onomical
ins umen s like he Keple and TESS space elescopes e eal ha plane a y sys ems a e common a he han excep ional. This
knowledge allows o mo e in o med es ima es o p han we e possible in D ake’s ime.
1.2. Exoplane s and he Sea ch o Biosigna u es
Among he mos in iguing exoplane disco e ies is K2-18b, a plane loca ed in he habi able zone o i s hos s a . I is
conside ed one o he mos p omising candida es in he sea ch o ex a e es ial li e (Fo eman-Mackey e al., 2015; Benneke e al.,
2017). In 2025, molecules o dime hyl sul ide (DMS) we e de ec ed in i s a mosphe e (Madhusudhan e al., 2025). On Ea h, DMS
is almos exclusi ely p oduced by biological p ocesses, making i a po en ial biosigna u e.
Al hough he de ec ion o such molecules does no cons i u e de ini i e p oo o li e, i signi ican ly in o ms he alues o
l ( he ac ion o plane s whe e li e eme ges) and po en ially i
( he ac ion o plane s whe e in elligence e ol es). Each new obse a ion educes unce ain y in hese pa ame e s, ans o ming
wha was once pu ely specula i e in o measu able science.
The disco e y o plane s like K2-18b demons a es he apid ad ancemen o exoplane a y esea ch. Wha D ake
o mula ed as a specula i e amewo k mo e han six y yea s ago is inc easingly being cons ained by obse a ional da a, b inging
humani y close o answe ing one o i s mos p o ound ques ions: A e we alone in he uni e se?
2. AN ATTEMPT TO SOLVE THE DRAKE EQUATION
Fo ou es ima ion, we u ilized da a om he Keple Space Telescope, NASA’s Exoplane A chi e (NASA Exoplane
Science Ins i u e, 2025), and he S ella ium so wa e (Zo i e al., 2021). Du ing i s p ima y mission, Keple con i med 2,781
exoplane s, and an addi ional 547 we e con i med du ing i s ex ended K2 mission (NASA Exoplane S a is ics, 2025), yielding a
o al o 3,328 con i med exoplane s a ibu ed o Keple .
Using S ella ium, we calcula ed ha Keple ’s ield o iew was app oxima ely 13.5° in declina ion and 14.1° in igh
ascension, co esponding o an a ea o 190.35 squa e deg ees, o 0.05798 s e adians (s ). Gi en ha he o al celes ial sphe e co e s
4π s , he a io be ween he ull sky and he egion obse ed by Keple is:
In e na ional Jou nal o Cu en Science Resea ch and Re iew
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𝛼 = 4𝜋
0,05798 =216.74 (2)
This indica es ha he en i e sky is oughly 217 imes la ge han he a ea obse ed by Keple . By ex apola ing Keple ’s
yield ac oss he ull sky, he expec ed numbe o de ec able exoplane s om Keple -like obse a ions is
𝑁ℎ𝑦𝑝=α∙3328 ≈721,311 (3)
Keple ’s mission concluded on Oc obe 30, 2018. As o June 2025, a o al o 5,921 con i med exoplane s in 4,422 plane a y
sys ems ha e been de ec ed using all me hods (NASA Exoplane A chi e, 2025). O hese, 4,378 plane s we e disco e ed ia he
ansi me hod, including con ibu ions om o he su eys such as TESS and NGTS. The emaining 1,043 plane s (17.6%) we e
de ec ed h ough non-Keple ansi me hods.
Thus, he es ima ed numbe o exoplane s de ec able using he ansi me hod alone is app oxima ely:
𝑁𝑡𝑟 ≈722,354 (4)
Al hough subs an ial, his numbe does no accoun o he o al expec ed popula ion o plane s in he Milky Way. To
imp o e ou es ima e, we in oduce he mul iplici y coe icien .
2.1. The Mul iplici y Coe icien
F om cu en s a is ics, he a io o con i med exoplane s (N0) o hos s a s (S0) is:
𝑘 = 𝑁0
𝑆0=5921
4422 ≈ 1.34 (5)
This “mul iplici y coe icien ” k indica es ha on a e age , each s a wi h plane s hos o 1.34 plane s. O e he pas 5 yea s,
he alue o k has a ied by less han 1%, so i can be ea ed as app oxima ely cons an o la ge scale es ima es.
Sub ac ing plane s de ec ed by ansi s (4,378) om he o al con i med (5,921), gi es he numbe o non- ansi plane s
de ec ed:
𝑁1=1543 (6)
The co esponding numbe o s a s hos ing hese plane s is:
𝑆1=𝑁1
𝑘≈1151 𝑠𝑡𝑎𝑟𝑠 (7)
The a io be ween he o al numbe o he s a s in he Milky Way (SMW≈4x1011) and his sample is:
𝑝 = 𝑠𝑚𝑤
𝑠1= 3.48 ×108 (8)
Ex apola ing his o he whole Galaxy, he numbe o non- ansi plane s is:
𝑁2= 𝑝 ∗ 𝑁1≈ 5.36 ×1011 (9)
Thus, he o al numbe o exoplane s in he Milky Way is:
𝑁𝛴= 𝑁2+𝑁𝑡𝑟 ≈ 5.36 ×1011 (10)
Thus, ou app oach es ima es app oxima ely 536 billion exoplane s in he Milky Way, consis en wi h independen
as ophysical es ima es anging om 100–400 billion plane s (Cassan e al., 2012; Winn & Fab ycky, 2015). His inding suppo s
he hypo hesis ha plane s a e a leas as nume ous as s a s in ou galaxy.
2.2. Beyond Plane s: Moons and In e s ella Objec s
Some la ge moons could be conside ed “plane -like” i hey o bi ed s a s di ec ly. Among he 211 na u al sa elli es in he
Sola Sys em, h ee – Ganymede, Ti an, and Callis o -a e compa able in size o Me cu y. Fo example, Callis o has a adius o 2,410
km, whe eas Me cu y’s adius is 2,440 km. This indica es ha app oxima ely 1.4% o moons a e la ge enough o quali y as plane -
sized bodies. While no exomoons ha e been conclusi ely con i med o da e, se e al candida es ha e been p oposed. ALMA
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obse a ions, o ins ance, sugges a possible moon- o ming disk a ound he young exoplane PDS 70c, wi h a po en ial sa elli e
mass o 0.03 Ea h masses (Benis y e al., 2021). The sea ch o exomoons has hus become a g owing sub ield wi hin exoplane a y
science (Ru io, 2023).
In addi ion o moons, wo in e s ella objec s ha e been obse ed passing h ough he Sola Sys em: ʻOumuamua in 2017
and 2I/Bo iso in 2019. Spec oscopic s udies o Bo iso e ealed ola ile compounds such as CO, C₂, and CN (Bodewi s e al.,
2020; Ka e a e al., 2020), con i ming ha o ganic p ecu so s o li e exis e en in in e s ella bodies. ʻOumuamua, wi h i s unusual
ajec o y and elonga ed shape, spa ked deba e o e whe he i could ha e an a i icial o igin (Loeb, 2022), al hough mos s udies
suppo a na u al explana ion (T illing e al., 2018).
These indings highligh ha he in en o y o po en ially habi able o biologically ele an bodies ex ends beyond
adi ional exoplane s o include moons and in e s ella objec s, expanding he scope o as obiological explo a ion.
3. RESULTS AND DISCUSSION
Ha ing calcula ed he app oxima e numbe o plane s in he Milky Way (~5.36×1011),, we can now es ima e he likelihood
o in elligen ex a e es ial ci iliza ions using he D ake Equa ion. As no ed ea lie , his es ima e canno be aken as exac , since
many pa ame e s a e p obabili ies a he han di ec ly measu ed alues. Ne e heless, hese p obabili ies a e inc easingly in o med
by obse a ional and expe imen al da a om space elescopes, plane a y p obes, and labo a o y expe imen s (Dele & Dim o a,
2025).
The Mille -U ey expe imen (Mille , 1953) demons a es ha unde condi ions simila o Ea h’s ea ly a mosphe e, o ganic
compounds such as amino acids. This indica es ha he basic building blocks o li e can eme ge na u ally unde plane a y condi ions,
o e en in in e s ella en i onmen . Fu he mo e, he hypo hesis o panspe mia sugges s ha li e o p ebio ic molecules migh be
ans e ed be ween plane a y sys ems ia come s, as e oids, o in e s ella dus . F om he la e we conclude he p obabili y o
inding li e-suppo ing plane s is high enough. Fo ou model we sugges he ac o :
𝑛𝑒= 0.67 (11)
Mul iplying his ac o by he o al numbe o plane s gi es us o al numbe o :
𝑁𝑙= 3.59.1011 li e-suppo ing plane s (12)
3.1. P obabili y o Li e and he Eme gence o In elligen Ci iliza ions
The nex pa ame e in he D ake Equa ion is he p obabili y o li e eme ging on plane s si ua ed wi hin habi able
en i onmen s, deno ed as l. Fo li e o a ise, plane a y condi ions mus be a o able, which equi es conside a ion o bo h he S ella
Habi able Zone (SHZ) and he Galac ic Habi able Zone (GHZ).
The SHZ e e s o he o bi al egion a ound a s a whe e liquid wa e can exis on a plane ’s su ace, a key p e equisi e o
li e as we know i (Kas ing, Whi mi e, & Reynolds, 1993). The GHZ, in con as , encompasses a b oade galac ic con ex , including
ac o s such as s ella me allici y, supe no a equency, and ambien adia ion le els (Linewea e , Fenne , & Gibson, 2004). Plane s
loca ed oo close o he Galac ic cen e a e exposed o in ense adia ion and g a i a ional pe u ba ions, which may hinde he
eme gence o li e. Con e sely, plane s in he ou e Galac ic disk o wi hin globula clus e s o en exhibi low me allici y, educing
he abundance o hea y elemen s such as i on, magnesium, and calcium, which a e c i ical o plane a y di e en ia ion and
biochemis y.
O ganic molecules ha e been de ec ed in a wide ange o en i onmen s, including in e s ella molecula clouds, come s,
and icy moons wi hin he Sola Sys em (Eh en eund & Cha nley, 2000; Öbe g, 2009). Howe e , he me e p esence o o ganic
compounds does no cons i u e de ini i e e idence o li e. Ne e heless, he his o y o Ea h demons a es ha li e can eme ge
ela i ely quickly once a o able condi ions a e es ablished. The classic Mille –U ey expe imen p o ided expe imen al e idence
ha amino acids— he building blocks o li e—can o m unde p ebio ic condi ions (Mille , 1953). Mo e ecen s udies ha e
con i med ha complex o ganic molecules can o m in in e s ella ices unde ul a iole i adia ion (He bs & an Dishoeck, 2009).
Fu he mo e, li e is highly adap i e and capable o su i ing ex eme en i onmen s, anging om hyd o he mal en s o
high- adia ion dese s (Cockell, 2015). Based on hese conside a ions, and acknowledging he inhe en unce ain ies, a conse a i e
alue o he p obabili y o li e eme ging on a habi able plane is adop ed as:
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𝑓𝑙= 0.1 (13)
This esul s ha he es ima ed numbe o plane s in he Milky Way ha could hos simple li e o ms is equal o:
𝑁𝑖𝑛𝑡 ≈ 3.59 ×1010 (14)
plane s wi h hos ing simple li e o ms
3.2. E olu ion o In elligen Li e
The nex ac o in he D ake Equa ion, deno ed as i, ep esen s he p obabili y ha li e e ol es in o in elligen , complex
o ganisms. On Ea h, unicellula li e domina ed o app oxima ely h ee billion yea s be o e mul icellula li e eme ged, e en ually
gi ing ise o species capable o complex cogni ion (Knoll, 2015). The e olu ion o in elligence appea s o equi e mul iple
e olu iona y “leaps,” o en igge ed by en i onmen al changes such as oxygena ion e en s, clima e shi s, o mass ex inc ions.
Howe e , Ea h p o ides only a single da a poin , and al e na i e e olu iona y pa hways may exis elsewhe e in he galaxy.
In elligence is no an ine i able ou come o li e, and e en when i a ises, echnological capabili y may no necessa ily ollow.
Cul u al, ecological, and physiological ac o s could in luence whe he a species de elops echnologies capable o in e s ella
communica ion.
Gi en he unce ain ies associa ed wi h he eme gence o in elligence, a conse a i e es ima e is adop ed:
𝑓𝑖= 0.001 (15)
Applying his pa ame e yields an es ima ed numbe o plane s hos ing in elligen li e in he Milky Way:
𝑁𝑖𝑛𝑡 ≈ 3.59 ×107 (16)
plane s wi h in elligen li e.
This es ima e unde sco es he a i y o in elligence ela i e o he p e alence o li e in habi able en i onmen s and highligh s
one o he c i ical bo lenecks in he eme gence o echnologically ad anced ci iliza ions
3.3. Technological Ci iliza ions and Communica ion
E en i in elligence e ol es, no all ci iliza ions de elop echnologies capable o in e s ella communica ion. The
pa ame e c ep esen s he ac ion o in elligen ci iliza ions ha achie e his s age. Fo example, humani y de eloped adio
as onomy only in he pas ~200 yea s, a small ac ion o i s exis ence. Cul u al, social, o en i onmen al cons ain s could p e en
many in elligen species om de eloping adio echnologies a all (Ta e , 2001; W igh e al., 2018).
Fo ou model, we again adop a conse a i e alue:
𝑓
𝑐= 0.001 (17)
This yields an es ima ed numbe o echnologically capable ci iliza ions:
𝑁𝑐𝑖𝑣 ≈ 3.59 ×104 (18)
3.4. Li espan o Ci iliza ions (L)
The inal ac o , L, ep esen s he a e age du a ion o e which a ci iliza ion emains capable o in e s ella communica ion.
This pa ame e is highly unce ain. Human ci iliza ion has conduc ed adio as onomy o less han 200 yea s, compa ed o Ea h’s
age o app oxima ely 4.5 billion yea s, gi ing a ac ion o :
200
4.5×109≈ 4.4 × 10−8 (19)
I mos ci iliza ions endu e o only b ie pe iods be o e sel -des uc ion, L emains e y small. Howe e , i is plausible
ha some ci iliza ions pe sis much longe , s abilizing hei socie ies and echnologies. Ci iliza ions a ound olde main-sequence
s a s, pa icula ly wi hin he Galac ic Habi able Zone (GHZ), may ha e exis ed o millions o yea s (Ći ko ić, 2004). Fo his
calcula ion, we assume a modes p obabili y:
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𝐿 = 2 × 10−4 (20)
By combining he es ima ed ac ions o echnological ci iliza ions and hei li espan, he expec ed numbe o ac i e
communica i e ci iliza ions in he Milky Way is:
𝑛 = 𝑁𝑐𝑖𝑣 ∙ 𝑙 ≈ 72 (21)
3.5. In e p e a ion
Ou es ima e sugges s ha dozens o ci iliza ions in he Milky Way may cu en ly be capable o in e s ella communica ion.
Al hough small ela i e o he o al numbe o plane s, his numbe is scien i ically signi ican and jus i ies con inued sea ches by
SETI p og ams.
This analysis also highligh s c i ical bo lenecks in he D ake Equa ion. While habi able plane s may be abundan , he p obabili ies
o in elligence eme ging, ci iliza ions de eloping communica ion echnology, and he long- e m su i al o hose ci iliza ions
emain highly unce ain. Fu u e obse a ions wi h he James Webb Space Telescope (JWST), he planned LUVOIR mission, and
nex -gene a ion Ex emely La ge Telescopes (ELTs) could help e ine hese es ima es by de ec ing biosigna u es and
echnosigna u es in exoplane a y a mosphe es (Seage , Bains, & Pe kowski, 2016; Madhusudhan, 2019).
4. THE FERMI PARADOX
F om he D ake Equa ion, we es ima ed ha app oxima ely 72 ex a e es ial ci iliza ions in he Milky Way may cu en ly
be capable o in e s ella adio communica ion. This leads o a na u al ques ion, amously posed by En ico Fe mi in 1950: “Whe e
is e e ybody?” (Ha , 1975; B in, 1983). Despi e decades o sys ema ic sea ches, no con i med signals om ex a e es ial
ci iliza ions ha e been de ec ed. This appa en con adic ion be ween he high p obabili y o ex a e es ial ci iliza ions and he
lack o obse a ional e idence is known as he Fe mi pa adox (Sandbe g, 2018).
A wide ange o hypo heses, has been p oposed o explain his pa adox . below we discuss h ee p ima y classes o
explana ions: dis ance and communica ion limi s, e olu iona y dispa i y, and sel -des uc ion.
4.1. Dis ance and Communica ion Cons ain s. The simples explana ion is spa ial sepa a ion. The nea es s a sys em,
P oxima Cen au i, lies 4.24 ligh -yea s away. A adio signal ansmi ed om Ea h would ake mo e han , 4 yea s o a eply o
e u n. Fo s a s loca ed hund eds o housand o ligh -yea s away, communica ion becomes inc easing imp ac ical, equi ing
millennia o a wo-way exchange (Ta e , 2001).
Mo eo e , he de ec abili y o adio signals dec eases wi h dis ance due o he in e se-squa e law o elec omagne ic
adia ion. Ci iliza ions using di ec ed beams a he han iso opic b oadcas s would u he limi he p obabili y o de ec ion (W igh
e al., 2018). I is also possible ha ad anced ci iliza ions no longe ely on adio communica ion a all, ins ead using echnologies
beyond ou comp ehension, such as quan um communica ion o neu ino-based signaling (Messe schmi , 2015).
4.2. E olu iona y Dispa i y. Ano he explana ion is he di e ence in e olu iona y s ages be ween ci iliza ions. Mo e
ad anced ci iliza ions may employ communica ion me hods ha a e indis inguishable om na u al cosmic noise o us, o may
delibe a ely a oid con ac , conside ing humani y oo p imi i e o wa an a en ion (Ći ko ić, 2009). In his con ex , he Zoo
Hypo hesis sugges s ha ex a e es ial ci iliza ions in en ionally a oid in e ac ing wi h Ea h o allow o na u al cul u al and
biological e olu ion (Ball, 1973).
Con e sely, i is possible ha humani y is among he i s e ol ed ci iliza ions in ou galaxy. In his case, he appa en
silence is no pa adoxical bu e lec s he a i y o long-li ed echnological socie ies (Tiple , 1980; Hanson, 1998). Ano he a ian ,
he Da k Fo es Hypo hesis, a gues ha ad anced ci iliza ions may delibe a ely emain silen o a oid de ec ion by po en ially
hos ile neighbo s (Liu, 2008).
4.3. Sel -Des uc ion and he G ea Fil e . One o he mos sobe ing explana ions o he Fe mi Pa adox is he sel -
des uc ion hypo hesis, closely ela ed o he G ea Fil e heo y (Hanson, 1998; Bos om, 2008). This iew sugges s ha while
in elligen li e may eme ge ela i ely equen ly, ci iliza ions end o des oy hemsel es be o e de eloping s able in e s ella
communica ion o expansion. The isks o sel -des uc ion include nuclea wa , uncon olled a i icial in elligence, ecological
collapse, o global pandemics (Rees, 2003; O d, 2020).
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This scena io is connec ed wi h he Ka dashe scale (Ka dashe , 1964), which ca ego izes ci iliza ions by hei ene gy
consump ion (Ka dashe , 1964). Humani y is cu en ly a Type I ci iliza ion candida e, ha es ing ene gy on he plane a y scale.
P og essing o Type II (s ella ene gy usage) o Type III (galac ic ene gy usage) would equi e echnological leaps ha migh also
inc ease exis en ial isks. G ay (2020) expanded he Ka dashe amewo k o inco po a e social and ecological s abili y,
emphasizing ha he su i al o ci iliza ions is no gua an eed by echnological ad ancemen alone.
None heless, in elligence may also os e esilience. Ci iliza ions capable o ecognizing exis en ial isks migh ansi ion
owa d sus ainable and coope a i e u u es, ex ending hei li espan and inc easing hei de ec abili y ac oss cosmic imescales being
ex ended in 2020 (G ay, 2020) and he so-called G ea il e . The main idea o his hypo hesis is ha while e ol ing, ci iliza ions
ge in elligen enough o de elop ocke y, nuclea powe and nuclea weapons. Thus, inc easing he chance o sel -des uc ion.
Howe e , being in elligen enough, hey may s op using hese echnologies wi h bad in en ions and u n hem in o in ensions, capable
o de eloping he ci iliza ion u he .
4.4 Summa y
In summa y, he Fe mi Pa adox highligh s he ension be ween he appa en abundance o habi able en i onmen s in he
Milky Way and he absence o obse ed ex a e es ial con ac . Possible esolu ions ange om simple communica ion ba ie s o
p o ound exis en ial il e s limi ing he longe i y o ci iliza ions. Whe he humani y is alone, ea ly, o simply oo p imi i e o de ec
he signals o o he s emains an open and deeply consequen ial scien i ic ques ion.
5. CONCLUSION
As obiology is a apidly de eloping in e disciplina y ield o mode n as onomy ha seeks o add ess some o he mos
p o ound scien i ic ques ions: A e we alone and whe e do we come om?”,; “Wha is li e and how did i eme ge?; Unde wha
condi ions can li e exis elsewhe e?. In his wo k, we applied basic ma hema ics and obse a ional da a, including esul s om
NASA a chi es, o explo e an inno a i e app oach o one o he mos endu ing p oblems in as obiology – he D ake Equa ion.
By adop ing pa ame e es ima es g ounded in plane a y science, chemis y, and e olu iona y biology, we calcula ed ha
app oxima ely 72 ci iliza ions in he Milky Way may cu en ly possess he abili y o communica e ia adio wa es. Al hough ou
chosen coe icien s ep esen easonable app oxima ions, i is impo an o emphasize ha each ac o in he D ake Equa ion is
subjec o signi ican unce ain y. Al e na i e assump ions can yield alues anging om ze o o millions, and he e o e no single
solu ion should be ega ded as de ini i e.
This unce ain y na u ally leads in o he Fe mi Pa adox: i he Galaxy should hos dozens o e en housands o echnological
ci iliza ions, why ha e we no ye de ec ed hem? Po en ial explana ions include as in e s ella dis ances and communica ion
limi a ions, dispa i ies in e olu iona y de elopmen , delibe a e silence, o he sel -des uc ion o ci iliza ions be o e hey can
achie e in e s ella con ac . Concep s such as he Zoo Hypo hesis, he Da k Fo es Hypo hesis, and he G ea Fil e illus a e he
wide spec um o possible esolu ions, each ca ying p o ound implica ions o ou own u u e as a ci iliza ion.
Despi e his silence, he e ha e been in iguing anomalies, such as he WOW! signal de ec ed in 1977 o he unusual ligh
luc ua ions o KIC 8462852 (Tabby’s S a ), which emain unexplained and con inue o inspi e deba e. While no one p o ide
de ini i e e idence o ex a e es ial in elligence, hey se e as eminde s ha ou sea ch is a om comple e.
Ul ima ely, sol ing he D ake Equa ion is no abou p oducing a inal numbe bu abou aming he scien i ic p oblem and
e ining ou unde s anding as new da a become a ailable. Wi h he apid ad ancemen o obse a ional echnologies -nex -
gene a ion elescopes, mo e sensi i e adio a ays, and ad anced biosigna u e de ec ion echniques -we a e mo ing close o
add essing one o humani y’s oldes and mos p o ound ques ions. Whe he he Uni e se is eeming wi h li e o we a e uly alone,
he pu sui o his answe con inues o expand bo h ou scien i ic ho izons and ou philosophical pe spec i e on humani y’s place in
he cosmos.
In summa y, while ou cu en es ima ion yields app oxima ely 72 po en ial ci iliza ions capable o adio communica ion
in he Milky Way, his numbe emains highly en a i e. The coming decades p omise ans o ma i e disco e ies, as obse a ional
echnologies ma u e and in e disciplina y esea ch s eng hens he ounda ions o as obiology. Con inued explo a ion—bo h
obse a ional and heo e ical -will be essen ial in add essing he Fe mi Pa adox and in e ining ou unde s anding o humani y’s
place in he Uni e se.
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