WWW.ASTRONOMY.COM 23investigate our universe. But so far, these
problems have proven to be remarkably
stubborn and persistent. With the goal of
identifying the individual particles that
make up dark matter, scientists have
designed and built a series of impressive
experiments — yet no such particles
have appeared. Even powerful particle
accelerators like the Large Hadron
Collider have revealed nothing that
moves us closer to resolving any of these
cosmic mysteries. And despite having
measured the expansion history and
large-scale structure of the universe in
ever increasing detail, we have not
gained any substantively greater under-
standing of the nature of dark energy,
the force that seems to be accelerating
the expansion of the cosmos.
It is from this perspective that some
cosmologists have found themselves ask-
ing whether these cosmic mysteries
might be symptoms of something more
significant than a few loose threads.
Perhaps these puzzles are not as unre-
lated as they might seem, but are instead
collectively pointing us toward a very
different picture of our universe and its
earliest moments.What we’ve learned by not
discovering dark matter
Dark matter is likely the most celebrated
problem facing modern cosmologists.
Astronomers have determined that most
of the matter in our universe does not
consist of atoms or any other known
substances, but of something else —
something that does not appreciably
radiate, ref lect, or absorb light.
Despite not knowing much about the
nature of dark matter, cosmologists oftenTOP: This galaxy cluster, nicknamed El Gordo (Spanish for “The Fat One”), ranks as the largest known cluster
in the distant universe. Composed of two individual clusters colliding at more than 1 million mph (1.6 million
km/h), this structure holds a mass equivalent to 3 quadrillion Suns. ESA/HUBBLE & NASA/RELICS
ABOVE: The blue color added to this image maps the distribution of dark matter in the El Gordo galaxy
cluster. Astronomers traced the presence of this shadowy substance by looking at how it distorts the
appearance of more distant objects. NASA/ESA/J. JEE (UNIVERSITY OF CALIFORNIA, RIVERSIDE)