The Cosmic Triangle: Revealing the State of the Universe
Neta A. Bahcall,
1*
Jeremiah P. Ostriker,
1
Saul Perlmutter,
2
Paul J. Steinhardt
3
The cosmic triangle is introduced as a way of representing the
past, present, and future status of the universe. Our current location
within the cosmic triangle is determined by the answers to three
questions: How much matter is in the universe? Is the expansion rate
slowing down or speeding up? And, is the universe flat? A review of
recent observations suggests a universe that is lightweight (matter
density about one-third the critical value), is accelerating, and is
flat. The acceleration implies the existence of cosmic dark energy that
overcomes the gravitational self-attraction of matter and causes the
expansion to speed up.
1 Princeton University Observatory, Princeton,
NJ 08544, USA.
2 Institute for Nuclear and Particle
Astrophysics, Ernest Orlando Lawrence Berkeley National Laboratory,
Berkeley, CA 94720, USA.
3 Department of Physics,
Princeton University, Princeton, NJ 08544, USA.
*
To whom correspondence should be addressed. E-mail:
neta{at}astro.princeton.edu
