Free Astronomy Magazine July-August 2022 ARABIC VERSION

The arbitrary average value initially attributed to L c was around 10,000 years, perhaps even optimistic con- sidering that the apex of the so- called “Cold War” was reached at the very beginning of the 1960s, when the use of nuclear weapons seemed close. After 60 years, the same scenario and threat has re- turned, “enriched” by a pandemic and the beginning of a climatic up- heaval, whose developments we can- not predict. These are just some of the threats that, in extreme cases, could plunge humanity to a pre-tech- nological level. Fortunately, there are no concrete reasons to believe that our civilization is representative of all possible alien civilizations ex- isting in the galaxy. If there are oth- ers, they could aspire to longevity im- measurably greater than ours. Suppose, however, that hu- manity comes to its senses as soon as possible and is able to fully exploit the vital time span that the Sun guarantees to the Earth, then another 1-2 bil- lion years. Today, as well as in that distant future, L t remains smaller than L b because both are linked to a specific planet, on which biology has a much longer history than technology. Long before the Sun, in its red giant phase, engulfs the Earth, humanity will have already moved elsewhere, and hav- ing an almost infinite future ahead, it could happen that at some point L t becomes greater than L b . It can be deduced that if technosignatures are not al- ready in excess compared to biosignatures today, they will probably be in the future. Anyway, we cannot rule out that humanity as a whole be- comes so stupid as to annihi- late itself, unleashing a nuclear war, creating lethal viruses or irreparably compromising the ecosystem. If this happens within a very short geo- logically time, another technological civilization could evolve after a pause of a few million years, a new civilization that would still have an im- mense time at its disposal to spread its technology throughout the galaxy, hopefully without making the same mistakes as ours. Curiously, just as we can- not quantify the L t /L b ratio for the future, we cannot quantify it for the past. In fact, although our civilization is having an indelible impact on geo- logical records (in a word: Anthropocene), in mil- lions of years the causes of the changes we are responsible for will not be distinguishable from the ef- fects of natural processes and phe- nomena. If there had existed on Earth a technological civilization be- fore ours, perhaps tens of millions of years ago, the chances of finding di- rect evidence of its passage would be feeble. We would be more likely to detect indirect evidence, such as anomalies in the chemical composi- R search scientist at NASA Goddard avi Kumar Kopparapu is a re- Space Flight Center, Greenbelt, MD. M partment of Aerospace, Physics and anasvi Lingam is a member of the De- Space Sciences, Florida Institute of Technol- ogy. [Photo by Mia B. Frothingham] S Fellow at the SETI Institute, working on techno- ofia Z. Sheikh is an NSF-ASCEND Postdoctoral signature searches with the Allen Telescope Array. ﻛـﺎن ﻣﺘﻮﺳـﻂ اﻟﻘﻴﻤـﺔ اﻟﺘﻌﺴــﻔ ﻴﺔ اﳌﻨﺴــﻮﺑﺔ ) إﱃ Lc( ﺣـﻮاﱄ ١٠,٠٠٠ ﻋـﺎم ، ورﲟـﺎ ﻛـﺎن ﺗﻔـﺎﺋﻼً ﺑـــﺎﻟﻨﻈﺮ إﱃ أن ذروة ﻣـــﺎ ﻳﺴـــﻤﻰ ﺑــــ " اﳊـــﺮب اﻟﺒــــﺎردة " ﻗــــﺪ ﰎ اﻟ ﻮﺻــــﻮل إﻟﻴﻬــــﺎ ﺑﺪاﻳــــﺔ اﻟﺴـ ﻴ ﻴﺎت ﻋﻨـﺪﻣﺎ ﺑـﺎت اﺳـﺘﺨﺪام ا ﻷﺳـﻠﺤﺔ اﻟﻨﻮوﻳــﺔ ﻗﺮﻳﺒًـــﺎ ، ﺑﻌـــﺪ ٦٠ ﻋﺎﻣًـــﺎ ، ﻋـــﺎد ﻧﻔـــﺲ اﻟﺴ ﻨﺎرﻳﻮ واﻟﺘﻬﺪﻳﺪ إﱃ إﺛﺮاء " " اﻟﻮﺑﺎء وﺑﺪاﻳـﺔ ﻣﻨ اﺛﺎر ﺎﺧﻴـﺔ ﻻ ﳝﻜﻨﻨـﺎ اﻟﺘ ﺒـﺆ ﺑﺘﻄﻮراﺗﻬـﺎ ﻫـﺬه ﻟﻴﺴـــﺖ ﺳـــﻮى ﺑﻌـــﺾ اﻟﺘﻬﺪﻳـــﺪات اﻟـــﱵ اﳊــــﺎﻻت اﻟﻘﺼـــﻮى ﳝﻜـــﻦ أن ﺗــــﺪﻓﻊ اﳊﻀــﺎرة اﻟﺒﴩــ ﻳﺔ إﱃ ﻣﺴــﺘﻮى ﻣــﺎ ﻗﺒـــﻞ اﻟﺘﻜﻨﻮﻟﻮﺟﻴـــﺎ ، ﳊﺴـــﻦ اﳊـــﻆ ﻻ ﺗﻮﺟﺪ أﺳﺒﺎب ﻣﻠﻤﻮﺳﺔ ﻟﻼﻋﺘﻘﺎد ﺑـﺄن ﺣﻀــــﺎرﺗﻨﺎ ﲤﺜــــﻞ ﺟﻤﻴــــﻊ اﳊﻀــــﺎرات اﻟﻔﻀــــﺎ ﺋﻴﺔ اﳌﺤﺘﻤﻠــــﺔ اﳌﻮﺟـــــﻮدة اﳌ ، ﺠـــــﺮة إذا ﻛـــــﺎن ﻫﻨـــــﺎك آﺧــــــﺮون ﻓﻴﻤﻜﻨﻬﻢ أن ﻳﻄﻤﺤﻮا إﱃ ﻃﻮل اﻟﻌ أﻛـﱪ ﺑﻜﺜـﲑ ﻣــﻦ ﻋ ﻧــﺎ ، ﻟﻨﻔــﱰض ﻣـﻊ ذﻟﻚ أن اﻟﺒﴩﻳﺔ ﺗﻌﻮد إﱃ رﺷﺪﻫﺎ أﴎع وﻗـــــﺖ ﳑﻜـــــﻦ وﻗـــــﺎدرة ﻋـــــﲆ اﻻﺳــــﺘﻔﺎدة اﻟﻜﺎﻣﻠــــﺔ ﻣــــﻦ اﻟﻔــــﱰة اﻟﺰﻣﻨﻴـــــﺔ اﳊﻴﻮﻳـــــﺔ اﻟـــــﱵ ﺗﻀـــــﻤﻨﻬﺎ اﻟﺸـﻤﺲ ﻟـﻸرض ، ﰒ ١-٢ ﻣﻠﻴـﺎر ﺳـﻨﺔ أﺧـــــﺮى . اﻟﻴـــــﻮم وﻛـــــﺬﻟﻚ ذ ﻟـــــﻚ اﳌﺴﺘﻘﺒﻞ اﻟﺒﻌﻴﺪ ، ﻻ ﻳﺰال )Lt( أﺻـﻐﺮ ) ﻣـــــﻦ Lb( ﻷن ﻛﻼﻫﻤـــــﺎ ﻣﺮﺗﺒﻄـــــﺎن ﺑﻜﻮﻛــﺐ ﻣﻌـــﲔ ، ﺣﻴـــﺚ ﻟﻠﺒﻴﻮﻟﻮﺟﻴـــﺎ ﺗﺎرﻳﺦ أﻃـﻮل ﺑﻜﺜـﲑ ﻣـﻦ اﻟﺘﻜﻨﻮﻟﻮﺟﻴـﺎ ﻗﺒﻞ وﻗﺖ ﻃﻮﻳﻞ ﻣﻦ اﺑﺘﻼع اﻟﺸﻤﺲ ﻣﺮﺣﻠﺘﻬـﺎ اﻟﻌﻤـﻼق اﻷ ﻸرضﻟـ ﺣـ ﺳﺘﻜﻮن اﻟﺒﴩﻳﺔ ﻗﺪ اﻧﺘﻘﻠﺖ ﺑﺎﻟﻔﻌـﻞ إﱃ ﻣﻜـــﺎن آﺧـــﺮ ، وﻟـــﺪﻳﻬﺎ ﻣﺴـــﺘﻘﺒﻞ ﺑﺒ ﺐ راﻓﻲ ﻮﻣﺎر ﻮ ﺎراﺑﻮ ﻋـﺎﻟﻢ أﺑﺤـﺎثﻓـﻲﻣﺮﻛـﺰ ﺟﻮدارد ﻟﺮﺣﻼت اﻟﻔﻀﺎء اﻟﺘﺎﺑﻊ ﻟﻨﺎﺳﺎ ﻣﻨــﺎز ﻒ ﻟ ﻨﻐــﺎم ﻋﻀـــﻮﻓـــﻲﻗﺴـــﻢﻋﻠـــﻮم اﻟﻔﻀـــﺎء ــﺎ ـﺎء واﻟﻔﻀـﺎء ، ﻣﻌﻬـﺪ ﻓﻠﻮر ــﺪا ﻟﻠﺘﻜﻨﻮﻟﻮﺟ واﻟﻔ . [Photo by Mia B. Frothingham] ﺻﻮﻓ ﺎ ﺷﻴﺦﻫﻲزﻣ ﻠﺔ ﻣﺎ ﻌﺪ اﻟـﺪﻛﺘﻮراﻩ ﻓـﻲﻣﻌﻬـ ﺪ SETI ، وﺗﻌﻤـﻞ ﻋﻠـﻰ ﺎﺳـﺘﺨﺪام أﺑﺤـﺎث اﻟﺘﻮﻗﻴـﻊ اﻟﺘﻘـ ﻣﺼﻔﻮﻓﺔ Allen Telescope. ﻣﺠﻠﺔ Astronomy ﺎﻟﻌﺮ ﺔ ﻳﻮﻟﻴﻮ – أﻏﺴﻄﺲ 2022 ٣٩ ﻏﲑ ﳏﺪود ﺗﻘﺮﻳﺒًﺎ ، ﳝﻜـﻦ أن ﻳﺤـﺪث ﻣﺮﺣﻠــﺔ ﻣــﺎ أن ﻳﺼــﺒﺢ Lt) ( أﻛــ ﱪ ﻣــﻦ Lb) ( ﳝﻜـﻦ أن ﻧﺴـ ﻨﺘﺞ أﻧـﻪ إذا ﱂ ﺗﻜـﻦ اﻟﺒﺼــﻤﺎت اﻟﺘﻘﻨﻴـــﺔ ﺟـــﺎﻫﺰة ﻟﻠﺰﻳـــﺎدة ﻣﻘﺎرﻧـــﺔ ﺑﺎﻟﺒﺼـــﻤﺎت اﳊﻴﻮﻳـــﺔ اﻟﻴـــﻮم ﻓﻤـﻦ اﳌﺤﺘﻤـﻞ أن ﺗﻜـﻮن اﳌﺴـﺘﻘﺒﻞ ﻋﲆ أي ﺣﺎل ، ﻻ ﳝﻜﻨﻨـﺎ أن ﻧﺴـ ﺒﻌﺪ أن ﺗﺼﺒﺢ اﻟﺒﴩﻳﺔ ﻛ ﻜﻞ ﻏﺒﻴﺔ ﻟﺪرﺟﺔ أﻧﻬﺎ ﺗــﺪﻣﺮ ﻧﻔﺴــﻬﺎ وﺗﻄﻠــﻖ اﻟﻌﻨــﺎن ﳊــﺮب ﻧﻮوﻳــﺔ أو ﺗﺨﻠــﻖ ﻓﲑوﺳــﺎت ﻗﺎ ﺗﻠــﺔ أو ﺗﻌﺮض اﻟﻨﻈـﺎم اﻟﺒ ـﱩ ﻟﻠﺨﻄـﺮ ﺑﺸـﻜﻞ ﻻ ﳝﻜـــﻦ إﺻـــﻼﺣﻪ إذا ﺣـــﺪث ﻫـــﺬا وﻗﺖ ﺟﻴﻮﻟـﻮﴂ ﻗﺼـﲑ ﺟـﺪًا ، ﳝﻜـﻦ أن ﺗﺘﻄﻮر ﺣﻀﺎرة ﺗﻜﻨﻮﻟﻮﺟﻴﺔ أﺧﺮى ﺑﻌـﺪ ﺗﻮﻗــﻒ ﻟﺒﻀــﻌﺔ ﻣﻼﻳــﲔ ﻣــﻦ اﻟﺴــ ﲔ ﺣﻀـﺎرة ﺟﺪﻳـﺪة ﻻ ﻳـﺰال ﻟـﺪﻳﻬﺎ اﻟ ﻮﻗـﺖ اﻟﻬﺎﺋﻞ ﻟﻠﻘﻴﺎم ﺑ ﻨﴩ ﺗﻘﻨ ﺘﻬﺎ ﺟﻤﻴﻊ أﻧﺤــــﺎء اﳌﺠــــﺮة وﻧﺄﻣــــﻞ أن ﻻ ﺗﻔﻌــــﻞ ﺑﺑﺑ ـــــ ﺑ ﻨﻔﺴﻬ ﺎ أﺧﻄﺎﺋﻨﺎ . ﻣﻦ اﻟﻐﺮﻳﺐ ﲤﺎﻣًﺎ ﻛﻤـﺎ ﻻ ﳝﻜﻨﻨــــــﺎ ﺗﺤﺪﻳــــــﺪ ﻧ ﺴــــــﺒﺔ (Lt)/(Lb) ﻟﻠﻤﺴــــﺘﻘﺒﻞ و ﻻ ﳝﻜﻨﻨــــﺎ ﺗﺤﺪﻳــــﺪﻫﺎ اﳌــﺎﴈ . اﻟﻮاﻗــﻊ ، ﻋــﲆ اﻟــﺮﻏﻢ ﻣــﻦ أن ﺣﻀـــــﺎرﺗﻨﺎ ﻟﻬـــــﺎ ﺗـــــﺄﺛﲑ ﻻ ﳝـــــﴛ ﻋـــــﲆ اﻟﺴـــــﺠﻼت اﳉﻴﻮﻟﻮﺟ ) ﻴـــــﺔ ﺑﺎﺧﺘﺼــــــﺎر : اﻷﻧﱶوﺑﻮﺳﲔ ، ﻓﻼ ( ﳝﻜﻦ ﻓﺼـﻞ أﺳـﺒﺎب اﻟﺘﻐــﲑات اﻟــﱵ ﻧﺘﺤﻤــﻞ ﻣﺴــﺆوﻟﻴﺘﻬﺎ ﻣﻼﻳـﲔ اﻟﺴـ ﲔ ﻋـﻦ ﺗـﺄﺛ ﲑات اﻟﻌﻤﻠﻴـﺎت واﻟﻈــﻮاﻫﺮ اﻟﻄﺒﻴﻌﻴــﺔ ، إذا ﻛﺎﻧــﺖ ﻫﻨــﺎك ﺣﻀـــﺎرة ﺗﻜﻨﻮﻟﻮﺟﻴــﺔ ﻋــﲆ اﻷرض ﻗﺒـــﻞ رﲟـ ﺎ ﺣﻀـﺎرﺗﻨ ﺎ ﻗﺒـﻞ ﻋﴩـات اﳌﻼﻳـﲔ ﻣـﻦ اﻟﺴــ ﲔ ﻓــﺈن ﻓــﺮص اﻟﻌﺜــﻮر ﻋــﲆ دﻟ ﻴــﻞ ﻣﺒــﺎﴍ ﻋــﲆ ﻣﺮورﻫــﺎ ﺳــﺘﻜﻮن ﺿــﻌﻴﻔﺔ ﻣﻦ اﳌ ﺮﺟﺢ أن ﻧﻜﺘﺸﻒ أدﻟﺔ ﻏﲑ ﻣﺒـﺎﴍة ﻣﺜـﻞ اﻟﺸـﺬوذ اﻟﱰﻛﻴـﺐ اﻟﻜﻴﻤ ﻴـﺎﰄ أو اﻟﻨﺴﺐ اﻟﻨﻈﲑﻳﺔ ﻟﻠﺮواﺳﺐ ﻟﻜﻦ ﻻ ﳝﻜﻨﻨﺎ اﺳـــــ ﺒﻌﺎد اﻷﺳــــــﺒﺎب اﻟﻄﺒﻴﻌﻴــــــﺔ وراء ــــ ﺑ ﺒ ﺒﺐ