Sept. 2, 2023, 7:00 a.m. ET
Virginia Gabrielli
By Adam
Frank and Marcelo Gleiser
Dr. Frank
is an astrophysicist at the University of Rochester. Dr. Gleiser is a
theoretical physicist at Dartmouth College.
Not long
after the James Webb Space Telescope began beaming back from outer space
its stunning images of
planets and nebulae last year, astronomers, though dazzled, had to admit that
something was amiss. Eight months later, based in part on what the telescope
has revealed, it’s beginning to look as if we may need to rethink key features
of the origin and development of the universe.
Launched at
the end of 2021 as a joint project of NASA, the European Space Agency and the
Canadian Space Agency, the Webb, a tool with unmatched powers of observation,
is on an exciting mission to look back in time, in effect, at the first stars
and galaxies. But one of the Webb’s first major findings was exciting in an
uncomfortable sense: It discovered the existence of fully formed galaxies far
earlier than should have been possible according to the so-called standard
model of cosmology.
According
to the standard model, which is the basis for essentially all research in the
field, there is a fixed and precise sequence of events that followed the Big
Bang: First, the force of gravity pulled together denser regions in the cooling
cosmic gas, which grew to become stars and black holes; then, the force of
gravity pulled together the stars into galaxies.
The Webb
data, though, revealed that some very large galaxies formed really fast, in too
short a time, at least according to the standard model. This was no minor
discrepancy. The finding is akin to parents and their children appearing in a
story when the grandparents are still children themselves.
It was not,
unfortunately, an isolated incident. There have been other recent occasions in
which the evidence behind science’s basic understanding of the universe has
been found to be alarmingly inconsistent.
Take the
matter of how fast the universe is expanding. This is a foundational fact in
cosmological science — the so-called Hubble constant — yet scientists
have not been able to settle
on a number. There are two main ways to calculate it: One involves measurements
of the early universe (such as the sort that the Webb is providing); the other
involves measurements of nearby stars in the modern universe. Despite decades
of effort, these two methods continue to yield different answers.
At first,
scientists expected this discrepancy to resolve as the data got better. But the
problem has stubbornly persisted even as the data have gotten far more precise.
And now new data from the
Webb have exacerbated the problem. This trend suggests a flaw in the model, not
in the data.
Two serious
issues with the standard model of cosmology would be concerning enough. But the
model has already been patched up numerous times over the past half century to
better conform with the best available data — alterations that may well be
necessary and correct, but which, in light of the problems we are now
confronting, could strike a skeptic as a bit too convenient.
Physicists
and astronomers are starting to get the sense that something may be really
wrong. It’s not just that some of us believe we might have to rethink the
standard model of cosmology; we might also have to change the way we think
about some of the most basic features of our universe — a conceptual revolution
that would have implications far beyond the world of science.
A potent
mix of hard-won data and rarefied abstract mathematical physics, the standard
model of cosmology is rightfully understood as a triumph of human ingenuity. It
has its origins in Edwin Hubble’s discovery in the 1920s
that the universe was expanding — the first piece of evidence for the Big Bang.
Then, in 1964, radio astronomers discovered the so-called Cosmic Microwave Background,
the “fossil” radiation reaching us from shortly after the universe began
expanding. That finding told us that the early universe was a hot, dense soup
of subatomic particles that has been continually cooling and becoming less
dense ever since.
Over the
past 60 years, cosmology has become ever more precise in its ability to account
for the best available data about the universe. But along the way, to gain such
a high degree of precision, astrophysicists have had to postulate the existence
of components of the universe for which we have no direct evidence. The
standard model today holds that “normal” matter — the stuff that makes up
people and planets and everything else we can see — constitutes only about 4 percent of
the universe. The rest is invisible stuff called dark matter and dark energy
(roughly 27 percent and 68 percent).
Cosmic inflation is
an example of yet another exotic adjustment made to the standard model. Devised
in 1981 to resolve paradoxes arising from an older version of the Big Bang, the
theory holds that the early universe expanded exponentially fast for a fraction
of a second after the Big Bang. This theory solves certain problems but creates
others. Notably, according to most versions of the theory, rather than there
being one universe, ours is just one universe in a multiverse — an infinite
number of universes, the others of which may be forever unobservable to us not
just in practice but also in principle.
There is
nothing inherently fishy about these features of the standard model. Scientists
often discover good indirect evidence for things that we cannot see, such as
the hyperdense singularities inside
a black hole. But in the wake of the Webb’s confounding data about galaxy
formation, and the worsening problem with
the Hubble constant, you can’t be blamed for starting to wonder if the model is
out of joint.
A familiar
narrative about how science works is often trotted out at this point to assuage
anxieties. It goes like this: Researchers think they have a successful theory,
but new data show it is flawed. Courageously rolling up their sleeves, the
scientists go back to their blackboards and come up with new ideas that allow
them to improve their theory by better matching the evidence.
It’s a story
of both humility and triumph, and we scientists love to tell it. And it may be
what happens in this case, too. Perhaps the solution to the problems the Webb
is forcing us to confront will require only that cosmologists come up with a
new “dark” something or other that will allow our picture of the universe to
continue to match the best cosmological data.
There is,
however, another possibility. We may be at a point where we need a radical
departure from the standard model, one that may even require us to change how
we think of the elemental components of the universe, possibly even the nature
of space and time.
Cosmology
is not like other sciences. It’s not like studying mice in a maze or watching
chemicals boil in a beaker in a lab. The universe is everything there is;
there’s only one and we can’t look at it from the outside. You can’t put it in
a box on a table and run controlled experiments on it. Because it is
all-encompassing, cosmology forces scientists to tackle questions about the
very environment in which science operates: the nature of time, the nature of
space, the nature of lawlike regularity, the role of the observers doing the
observations.
These
rarefied issues don’t come up in most “regular” science (though one encounters
similarly shadowy issues in the science of consciousness and in quantum
physics). Working so close to the boundary between science and philosophy,
cosmologists are continually haunted by the ghosts of basic assumptions hiding
unseen in the tools we use — such as the assumption that scientific laws don’t
change over time.
But that’s
precisely the sort of assumption we might have to start questioning in order to
figure out what’s wrong with the standard model. One possibility, raised by the
physicist Lee Smolin and the philosopher Roberto Mangabeira Unger, is that
the laws of physics can evolve and
change over time. Different laws might even compete for effectiveness. An even
more radical possibility, discussed by the physicist John Wheeler, is that every
act of observation influences the
future and even the past history of the universe. (Dr. Wheeler, working to
understand the paradoxes of quantum mechanics, conceived of a “participatory universe”
in which every act of observation was in some sense a new act of creation.)
It is not
obvious, to say the least, how such revolutionary reconsiderations of our
science might help us better understand the cosmological data that is
flummoxing us. (Part of the difficulty is that the data themselves are shaped
by the theoretical assumptions of those who collect them.) It would necessarily
be a leap of faith to step back and rethink such fundamentals about our
science.
But a
revolution may end up being the best path to progress. That has certainly been
the case in the past with scientific breakthroughs like Copernicus’s
heliocentrism, Darwin’s theory of evolution and Einstein’s relativity. All
three of those theories also ended up having enormous cultural influence —
threatening our sense of our special place in the cosmos, challenging our
intuition that we were fundamentally different than other animals, upending our
faith in common sense ideas about the flow of time. Any scientific revolution
of the sort we’re imagining would presumably have comparable reverberations in
our understanding of ourselves.
The
philosopher Robert Crease has written that philosophy is what’s
required when doing more science may not answer a scientific question. It’s not
clear yet if that’s what’s needed to overcome the crisis in cosmology. But if
more tweaks and adjustments don’t do the trick, we may need not just a new
story of the universe but also a new way to tell stories about it.
Adam Frank (@AdamFrank4)
is a professor of astrophysics at the University of Rochester and the author of
the forthcoming book “The Little Book of Aliens.” Marcelo Gleiser (@MGleiser)
is a professor of physics and astronomy at Dartmouth College and the author of
“The Dawn of a Mindful Universe: A Manifesto for Humanity’s Future.”
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