Let’s look at the evidence. Gavin Schmidt took five minutes to bring me up to speed.
Schmidt is director of the NASA Institute for Space Studies named after Goddard (also called GISS), a scientific institution for world-class climatology research. Once, last year, I came to GISS with an unusual proposal. Being an astrophysicist, I began to study global warming from the “astrobiological point of view.” That is, I was trying to find out whether any civilization that appears on any planet provokes its own version of climate change through its activities. I came to GISS that day in the hope of gaining some knowledge of climatology and, possibly, finding partners for this work. That’s how I ended up in Gavin’s office.
When I talked enthusiastically about my research plan, Gavin interrupted me.
“Wait a second,” he said, “but how do you know that we are the only civilization that ever existed on our planet?”
It took me a few seconds to lift the fallen jaw from the floor. Of course, I walked into Gavin’s office ready to roll my eyes when mentioning “exo-civilizations.” But the civilizations he asked about could exist many millions of years ago. Sitting here and looking inwardly at the huge evolutionary telescope on Earth’s past, I felt something like a temporary dizziness. “Yes,” I muttered, “is it possible that we have already had an industrial civilization here so long ago?”
We did not return to the question of other civilizations. But from this first conversation a new study began, which we recently published in the International Journal of Astrobiology. And although none of us understood this at that moment, Gavin’s deep question opened the window not only to the past of the Earth, but also to our own future.
We used to represent extinct civilizations in the form of sunken statues and underground ruins. Such kind of artifacts left from past human societies are good if you are interested in a time frame of only a few thousand years. But as soon as you rewind time back for hundreds of millions of years, things get much more complicated.
When it comes to direct evidence of the existence of industrial civilizations – such as cities, factories and roads – geological footprints are traced no further than the so-called Quaternary period, which began 2.6 million years ago. For example, the oldest section of the ancient earth’s surface is in the Negev desert. She is “only” 1.8 million years old. Sites of the more ancient land surface can usually be found in a section, for example, where there is something like a rock break or where a rock is being developed. If you want to go deeper much further than the quad period, you’ll find that everything has turned to dust and mixed up.
And if we go so far, there will be no more talk about human civilizations. A reasonable person appeared on the planet not earlier than 300 thousand years ago or something like that. This means that our problem concerns other species, so Gavin called it the “Silurian hypothesis”, in honor of one of the episodes of the old TV series “Doctor Who”, where there were reasonable reptiles.
So, can researchers find clear evidence that some ancient species created a relatively short-lived industrial civilization that existed long before ours? For example, it is possible that some early mammal during the Paleocene epoch (about 60 million years ago) quickly developed and formed a civilization. Of course, there are fossils. But the fossil remains of life are always small, and they vary greatly depending on the time and place of living of living things. Therefore, to miss an industrial civilization that existed only 100 thousand years, can be very simple, but meanwhile, this is 500 times longer than our present civilization has existed to the present day.
Considering that all direct evidence will go into oblivion in many millions of years, what evidence can still be found now? It is best to answer this question, figuring out what we will leave after ourselves, if the human civilization collapses at this stage of development.
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Seychas, kogda nasha industrial’naya tsivilizatsiya stala po-nastoyashchemu global’noy, kollektivnaya deyatel’nost’ chelovechestva ostavlyayet posle sebya razlichnyye sledy, kotoryye uchenyye smogut obnaruzhit’ v budushchem, cherez 100 millionov let. Aktivnoye ispol’zovaniye udobreniy, naprimer, pozvolyayet kormit’ sem’ milliardov chelovek, no takzhe eto oznachayet, chto azotnyye zapasy planety perenapravlyayutsya na proizvodstvo produktov pitaniya. Budushchiye issledovateli dolzhny uvidet’ eto po kharakteristikam azota, otlagayushchegosya v osadochnykh porodakh nashey epokhi. To zhe samoye kasayetsya i nashey neutolimoy zhadnosti do redkozemel’nykh elementov, ispol’zuyemykh v elektronnykh gadzhetakh. Seychas namnogo bol’she ikh atomov nakhodyatsya na poverkhnosti zemli, chem eto bylo by bez nas. Ikh tozhe mozhno budet nayti v budushchikh otlozheniyakh. Yeshche my nastol’ko aktivno proizvodim i ispol’zuyem sinteticheskiye steroidy, chto i ikh mozhno budet obnaruzhit’ v geologicheskikh sloyakh cherez 10 millionov let.
Zatem ves’ etot plastik. Issledovaniya pokazali, chto vse bol’sheye kolichestvo plastikovogo i polietilenovogo «morskogo musora» otkladyvayetsya na morskom dne povsyudu ot pribrezhnykh rayonov do glubokovodnykh vpadin i dazhe v Arktike. Veter, solntse i volny razmalyvayut krupnyye predmety iz etogo materiala, i zapolnyayut morya mikroskopicheskimi plastikovymi chastitsami, kotoryye mogut osest’ na morskoye dno, obrazovav ustoychivyy geologicheskiy sloy.
Bol’shoy vopros, odnako, kak dolgo vse eti sledy sushchestvovaniya nashey tsivilizatsii sokhranyatsya. V khode nashego issledovaniya my obnaruzhili, chto u kazhdogo iz nikh yest’ shans sformirovat’ budushchiye otlozheniya. Po ironii sud’by, odnako, samym perspektivnym markerom sushchestvovaniya chelovechestva kak prodvinutoy tsivilizatsii mogut byt’ produkty toy yego deyatel’nosti, kotoraya bol’she vsego yemu zhe i ugrozhayet.
Kogda my szhigayem iskopayemoye toplivo, my vypuskayem uglerod, kotoryy kogda-to byl chast’yu zhivykh tkaney, obratno v atmosferu. Odin iz trekh vidov etogo drevnego ugleroda, odin iz izotopov etogo elementa, ischerpyvayetsya. Chem bol’she iskopayemogo topliva my szhigayem, chem bol’she sdvigayetsya balans etikh izotopov. Uchenyye, zanimayushchiyesya atmosferoy, nazyvayut eto effektom Susse, i izmeneniye izotopnogo sootnosheniya ugleroda iz-za szhiganiya iskopayemogo topliva legko prosledit’ v techeniye poslednego stoletiya. Povysheniye temperatury takzhe ostavlyayet izotopnyye signaly. Eti izmeneniya budut ochevidny dlya lyubogo uchenogo budushchego, kto stanet analizirovat’ obnazhivshiyesya sloi gornoy porody nashey epokhi. Naryadu s etim indikatorami, geologicheskiye sloi antropotsena mogut takzhe otrazhat’ korotkiye skachki kontsentratsii azota, soderzhat’ nanochastitsy plastika i dazhe sinteticheskiye steroidy. Tak yesli vse eti sledy nashey tsivilizatsii ostanutsya v budushchem, mozhet byt’, takiye zhe «signaly» v gornoy porode seychas tozhe tol’ko i zhdut, chtoby rasskazat’ nam o davno ushedshey tsivilizatsii?
56 millionov let nazad Zemlya perezhila paleotsen-eotsenovyy termicheskiy maksimum (PETM). Vo vremya PETM srednyaya temperatura na planete podnyalas’ do otmetki na 15 gradusov po Farengeytu vyshe, chem ta, pri kotoroy my zhivem segodnya. Eto byl mir prakticheski bezo l’da, a obychnaya letnyaya temperatura na polyusakh dostigala pochti 70 gradusov po Farengeytu. Glyadya na izotopicheskiye dannyye perioda PETM, uchenyye vidyat, chto i uglerod, i kislorod vedut sebya rovno tak, kak, soglasno nashim ozhidaniyam, oni budut vesti sebya v geologicheskikh sloyakh antropotsena. Yest’ i drugiye sobytiya v istorii Zemli, podobnyye PETM, kotoryye nesut v sebe sledy, pokhozhiye na te, chto ostanutsya ot nashego antropotsena. Syuda vkhodit sobytiye, proizoshedsheye cherez neskol’ko millionov let posle PETM, obrazovavsheye eotsenovyye otlozheniya zagadochnogo proiskhozhdeniya, i masshtabnyye sobytiya v melovom periode, v rezul’tate kotorykh okean ostalsya bez kisloroda na mnogiye tysyacheletiya (ili dazhe dol’she).
Yavlyayetsya li vse eto svidetel’stvom sushchestvovaniya predydushchey negumanoidnoy industrial’noy tsivilizatsii? Pochti navernyaka net. Khotya yest’ svidetel’stva togo, chto PETM byl vyzvan massivnym vybrosom v vozdukh iskopayemogo ugleroda, zdes’ vazhny vremennyye ramki, za kotoryye vse eto proiskhodilo. Izotopnyye vspleski vo vremya PETM sluchalis’ na protyazhenii neskol’kikh soten tysyach let. Antropotsen v istorii Zemli delayet takim osobennym ta skorost’, s kotoroy my vybrasyvayem iskopayemyy uglerod v atmosferu. Sushchestvovali geologicheskiye periody, kogda kontsentratsiya CO2 na Zemle byla takoy zhe vysokoy ili dazhe vyshe, chem segodnya. No nikogda yeshche za mnogo milliardov let istorii nashey planety tak mnogo iskopayemogo ugleroda ne bylo vybrosheno v atmosferu nastol’ko bystro. Poetomu izotopnyye vspleski, kotoryye my vidim v geologicheskikh profilyakh, vozmozhno, nedostatochno rezkiye, chtoby podtverdit’ siluriyskuyu gipotezu.
No zdes’ yest’ odna slozhnost’. Yesli promyshlennaya deyatel’nost’ boleye rannego vida byla kratkovremennoy, vozmozhno, nam budet nelegko yeye uvidet’. Vspleski v PETM glavnym obrazom pokazyvayut nam te vremennyye periody, kogda Zemlya reagirovala na «razdrazhiteli», a vovse ne obyazatel’no na vremennoy period, kogda, sobstvenno, sam etot razdrazhitel’ deystvoval. Takim obrazom, dlya vyyavleni
Максимально допустимое число символов (5000) превышено на 3012:
я по-настоящему краткосрочного события по древним отложениям, могут потребоваться особые инновационные методы обнаружения. Иными словами, если вы конкретно не будете его искать, вы можете его и не увидеть. Понимание этого, возможно, стало самым конкретным выводом нашего исследования. Нечасто пишешь статью, где излагаешь теорию, которую не поддерживаешь. Гэвин и я не верим, что на Земле когда-то в палеоцене жила цивилизация возрастом в 50 миллионов лет. Задаваясь вопросом, можем ли мы «увидеть» следы существования древней индустриальной цивилизации, мы были вынуждены поднять и вопрос родовых воздействий любой цивилизации на планету. Именно это и есть астробиологическая перспектива климатических изменений. Построение цивилизации подразумевает, что вы собираете энергию планеты и заставляете ее выполнять работу (работу по построению цивилизации). В тот момент, когда цивилизация действительно достигает планетарного масштаба, она сама начинает влиять на планетарную систему, которая дала ей жизнь (воздух, воду, горные породы). Это в особенности справедливо для молодых цивилизаций вроде нашей, которые все еще карабкаются по лестнице технологических возможностей. Другими словами, за все надо платить. И хотя некоторые источники энергии будут иметь меньшее воздействие — например, энергия солнца по сравнению с ископаемым горючим — все равно невозможно вырастить глобальную цивилизацию, совсем не оказав влияния на планету. Когда вы осознаете, увидев климатические изменения, что нужно искать какие-то менее агрессивные способы добычи энергии, то начинаете оказывать меньше влияния на планету. Так что, чем более экологически сознательной становится ваша цивилизация, тем меньше следов вы оставите для будущих поколений. Вдобавок ко всему, наша работа приоткрыла потенциальную возможность того, что на некоторых планетах, возможно, существуют циклы цивилизаций, основанные на использовании ископаемого топлива, которые создаются и разрушаются. Если цивилизация использует ископаемое топливо, климатические изменения могут привести к тому, что уровень кислорода в океане сильно упадет. Такие низкие уровни кислорода в океане, называемые «океанической аноксией», способствуют созданию условий, при которых образовывается разное ископаемое топливо, в первую очередь нефть и уголь. Таким образом, одна цивилизация, пришедшая к гибели, может подготовить почву для существования новой цивилизации в будущем. Задаваясь вопросом о цивилизациях, затерянных во времени, мы также интересуемся, не могут ли существовать некие универсальные правила, которым подчиняется развитие всех биосфер во всем их разнообразном потенциале, включая возникновение цивилизаций. Даже и без гоняющих на пикапах жителей палеоцена мы только начинаем понимать, как богат, возможно, этот потенциал. Адам Франк (Adam Frank) профессор астрофизики в Рочерстерском университете. Его работы публиковались в «Сайентифик Американ» (Scientific American), «Нью-Йорк Таймз» (The New York Times) и НПР (NPR). Написал книгу «Свет звезд: Чуж
Now that our industrial civilization has become truly global, the collective activity of humanity leaves behind a variety of traces that scientists will be able to discover in the future, in 100 million years. The active use of fertilizers, for example, allows feeding seven billion people, but also this means that the planet’s nitrogen reserves are diverted to food production. Future researchers should see this according to the characteristics of nitrogen deposited in the sedimentary rocks of our era. The same goes for our unquenchable greed for the rare earth elements used in electronic gadgets. Now much more of their atoms are on the surface of the earth than it would have been without us. They can also be found in future sediments. We are also so active in producing and using synthetic steroids that they can be detected in geological layers in 10 million years.
Then all this plastic. Studies have shown that an increasing amount of plastic and polyethylene “marine debris” is deposited on the seabed everywhere from coastal areas to deep-sea depressions and even in the Arctic. Wind, sun and waves grind large objects from this material, and fill the seas with microscopic plastic particles that can settle on the seabed, forming a stable geological layer.
The big question, however, is how long all these traces of the existence of our civilization will remain. During our research, we found that each of them has a chance to form future deposits. Ironically, however, the most promising marker of the existence of mankind as an advanced civilization can be the products of its activities, which most of all threaten it.
When we burn fossil fuels, we release carbon, which was once part of living tissues, back into the atmosphere. One of the three kinds of this ancient carbon, one of the isotopes of this element, is exhausted. The more fossil fuels we burn, the more the balance of these isotopes shifts. Scientists working on the atmosphere call this the Susse effect, and the change in the isotope ratio of carbon due to the burning of fossil fuels is easy to follow during the last century. The temperature rise also leaves isotopic signals. These changes will be obvious to any scholarly future who will analyze the bare layers of the rock of our era. Along with these indicators, anthropocene geological layers can also reflect short jumps in nitrogen concentration, contain plastic nanoparticles and even synthetic steroids. So if all these traces of our civilization remain in the future, maybe the same “signals” in the rock are now just waiting to tell us about the long-gone civilization?
56 million years ago, the Earth experienced the Paleocene-Eocene Thermal Maximum (PETM). During PETM, the average temperature on the planet rose to 15 degrees Fahrenheit higher than the one at which we live today. It was a world practically without ice, and the usual summer temperature at the poles reached almost 70 degrees Fahrenheit. Looking at the isotopic data of the PETM period, scientists see that both carbon and oxygen behave exactly as we would expect them to behave in the geological strata of the anthropocene. There are other events in the history of the Earth, like PETM, which carry traces similar to those that remain from our anthropocene. This includes an event that occurred a few million years after PETM, which formed Eocene deposits of mysterious origin, and large-scale events in the Cretaceous period, as a result of which the ocean remained without oxygen for many millennia (or even longer).
Is all this evidence of the existence of a previous non-humanoid industrial civilization? Almost certainly not. Although there is evidence that PETM was caused by a massive release of fossil carbon into the air, the timeframe for which all this occurred is important here. Isotopic bursts during PETM have occurred for several hundred thousand years. Anthropocene in the history of the Earth makes such a special speed with which we throw fossil carbon into the atmosphere. There were geological periods when the concentration of CO2 on Earth was as high or even higher than today. But never before in the many billions of years of the history of our planet so much fossil carbon has been thrown into the atmosphere so quickly. Therefore, isotopic bursts, which we see in geological profiles, may not be sharp enough to confirm the Silurian hypothesis.
But there is one difficulty here. If the industrial activity of the earlier species was short-lived, perhaps it will not be easy for us to see it. The outbursts in PETM mainly show us those time periods when the Earth reacted to “stimuli”, and not necessarily for a time period when, in fact, the stimulus itself acted. Thus, to identify a truly short-term event in ancient sediments, special innovative detection methods may be required. In other words, if you do not specifically look for it, you can not see it. Understanding this may have become the most concrete conclusion of our study.
It is not often that you write an article where you state a theory that you do not support. Gavin and I do not believe that on Earth once in the Paleocene lived a civilization 50 million years old. Asking whether we can “see” the traces of the existence of an ancient industrial civilization, we were forced to raise the issue of generic influences of any civilization on the planet. This is precisely the astrobiological perspective of climate change. Building a civilization means that you collect the energy of the planet and make it perform work (work to build a civilization). At a time when civilization really reaches a planetary scale, it itself begins to influence the planetary system that gave it life (air, water, rocks). This is especially true for young civilizations like ours, who are still climbing the ladder of technological opportunities. In other words, you have to pay for everything. And although some energy sources will have less impact – for example, the energy of the sun compared to fossil fuels – it is still impossible to grow a global civilization without having any influence on the planet.
When you realize that when you see climate change, that you need to look for some less aggressive ways of extracting energy, then you begin to exert less influence on the planet. So, the more environmentally conscious your civilization becomes, the less traces you leave for future generations.
In addition, our work has revealed the potential possibility that on some planets, there may be cycles of civilizations based on the use of fossil fuels that are created and destroyed. If a civilization uses fossil fuels, climatic changes can lead to a drop in the oxygen level in the ocean. Such low levels of oxygen in the ocean, called “oceanic anoxia,” contribute to the creation of conditions under which different fossil fuels are formed, primarily oil and coal. Thus, one civilization that has come to ruin, can pave the way for the existence of a new civilization in the future.
Asking about the question of civilizations lost in time, we are also interested in whether there can be some universal rules that govern the development of all biospheres in all their diverse potential, including the emergence of civilizations. Even without the Paleocene inhabitants driving pickup trucks, we are just beginning to understand how rich this potential may be.
Adam Frank is Professor of Astrophysics at the University of Rochester. His works were published in Scientific American, The New York Times and NPR. He wrote the book “The Light of the Stars: Other Worlds and the Fate of the Earth” (Light of the Stars: Alien Worlds and the Fate of the Earth).
