Chapter 2
SETI and Temporal Copernicanism
Amedeo Balbi and Milan M. ´
Cirkovi´ c
Abstract An often used assumption in astrobiology and SETI studies is that the
average condition of the present universe is typical in time, and that many of the
relevant physical quantities can be treated as stationary. The uncritical adoption of
such assumption of ‘temporal Copernicanism’ can lead to wrong conclusions, and
should be treated with extreme care, if not discarded altogether.
2.1 Introduction
Copernicanism has been a guiding principle in the development of astronomy and
cosmology for the past four centuries. The idea is often summarized with the statement that the Earth does not occupy a special place in the universe. More specifically,
the assumption of homogeneity and isotropy has been crucial in the development of
the standard cosmological model, and has rightly gained the status of a ‘cosmological principle’ (henceforth CP). Not only has the large-scale spatial uniformity of the
universe allowed for progress in our understanding of the universe, but it also made
possible to refer our observations to an ‘average’ spatial reference system, and to
assess the typicality of physical quantities with respect to such well-defined average.
In other words, when we consider sufficiently large spatial volumes, we can consider
them as representative of the universe. This is not only important in cosmology, but
also in astrobiology, since it allows us to assume that, although our particular location
is far from average in some respects (its position around a certain kind of star, its
local chemical abundance, and so on), it can still be considered ‘typical’ with respect
A. Balbi (B)
Dipartimento di Fisica, Università di Roma “Tor Vergata”,
Via della Ricerca Scientifica, 00133 Roma, Italy
e-mail: balbia@roma2.infn.it
M. M. ´
Cirkovi´ c
Astronomical Observatory of Belgrade,Volgina 7, 11000 Belgrade, Serbia
Faculty of Philosophy, Future of Humanity Institute, University of Oxford, Suite 8, Littlegate
House, 16/17 St Ebbe’s Street, Oxford OX1 1PT, UK
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
S. Montebugnoli and A. Melis (eds.), The Search for ExtraTerrestrial Intelligence,
Springer Proceedings in Physics 260, https://doi.org/10.1007/978-3-030-63806-1_2
7
SETI and Temporal Copernicanism
Amedeo Balbi and Milan M. ´
Cirkovi´ c
Abstract An often used assumption in astrobiology and SETI studies is that the
average condition of the present universe is typical in time, and that many of the
relevant physical quantities can be treated as stationary. The uncritical adoption of
such assumption of ‘temporal Copernicanism’ can lead to wrong conclusions, and
should be treated with extreme care, if not discarded altogether.
2.1 Introduction
Copernicanism has been a guiding principle in the development of astronomy and
cosmology for the past four centuries. The idea is often summarized with the statement that the Earth does not occupy a special place in the universe. More specifically,
the assumption of homogeneity and isotropy has been crucial in the development of
the standard cosmological model, and has rightly gained the status of a ‘cosmological principle’ (henceforth CP). Not only has the large-scale spatial uniformity of the
universe allowed for progress in our understanding of the universe, but it also made
possible to refer our observations to an ‘average’ spatial reference system, and to
assess the typicality of physical quantities with respect to such well-defined average.
In other words, when we consider sufficiently large spatial volumes, we can consider
them as representative of the universe. This is not only important in cosmology, but
also in astrobiology, since it allows us to assume that, although our particular location
is far from average in some respects (its position around a certain kind of star, its
local chemical abundance, and so on), it can still be considered ‘typical’ with respect
A. Balbi (B)
Dipartimento di Fisica, Università di Roma “Tor Vergata”,
Via della Ricerca Scientifica, 00133 Roma, Italy
e-mail: balbia@roma2.infn.it
M. M. ´
Cirkovi´ c
Astronomical Observatory of Belgrade,Volgina 7, 11000 Belgrade, Serbia
Faculty of Philosophy, Future of Humanity Institute, University of Oxford, Suite 8, Littlegate
House, 16/17 St Ebbe’s Street, Oxford OX1 1PT, UK
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
S. Montebugnoli and A. Melis (eds.), The Search for ExtraTerrestrial Intelligence,
Springer Proceedings in Physics 260, https://doi.org/10.1007/978-3-030-63806-1_2
7