By Andrew Chaikin
Editor, Space & Science
(Teacher and Professional Lecturer)
Guru dan Dosen Profesional
Department of Physics, Faculty of Sciences and Mathematics
Indonesia University of Education and Follower Open Course Ware at MIT-Harvard University, M.A., U.S.A.
History of Dark Energy
The cosmological constant was first proposed by Einstein as a mechanism to obtain a stable solution of the gravitational field equation that would lead to a static universe, effectively using dark energy to balance gravity. Not only was the mechanism an inelegant example of fine-tuning, it was soon realized that Einstein's static universe would actually be unstable because local inhomogeneities would ultimately lead to either the runaway expansion or contraction of the universe.
The equilibrium is unstable: if the universe expands slightly, then the expansion releases vacuum energy, which causes yet more expansion. Likewise, a universe which contracts slightly will continue contracting. These sorts of disturbances are inevitable, due to the uneven distribution of matter throughout the universe. More importantly, observations made by Edwin Hubble showed that the universe appears to be expanding and not static at all. Einstein famously referred to his failure to predict the idea of a dynamic universe, in contrast to a static universe, as his greatest blunder. Following this realization, the cosmological constant was largely ignored as a historical curiosity.
By that time, the missing mass problem of big bang nucleosynthesis and large scale structure was established, and some cosmologists had started to theorize that there was an additional component to our universe.
The first direct evidence for dark energy came from supernova observations of accelerated expansion, in Riess et al. and later confirmed in Perlmutter et al...This resulted in the Lambda-CDM model, which as of 2006 is consistent with a series of increasingly rigorous cosmological observations, the latest being the 2005 Supernova Legacy Survey.
First results from the SNLS reveal that the average behavior (i.e., equation of state) of dark energy behaves like Einstein's cosmological constant to a precision of 10%.
Recent results from the Hubble Space Telescope Higher-Z Team indicate that dark energy has been present for at least 9 billion years and during the period preceding cosmic acceleration.
- ^ P. J. E. Peebles and Bharat Ratra (2003). "The cosmological constant and dark energy" (subscription required). Reviews of Modern Physics 75: 559–606. doi:10.1103/RevModPhys.75.559. http://www.arxiv.org/abs/astro-ph/0207347.
- ^ a b Hinshaw, Gary F. (April 30th, 2008). "WMAP Cosmological Parameters Model: lcdm+sz+lens Data: wmap5". NASA. http://lambda.gsfc.nasa.gov/product/map/current/params/lcdm_sz_lens_wmap5.cfm. Retrieved 2009-05-24.
- ^ Sean Carroll (2001). "The cosmological constant". Living Reviews in Relativity 4: 1. doi:10.1038/nphys815-. http://relativity.livingreviews.org/Articles/lrr-2001-1/index.html. Retrieved 2006-09-28.
- ^ L.Baum and P.H. Frampton (2007). "Turnaround in Cyclic Cosmology" (subscription required). Physical Review Letters 98: 071301. doi:10.1103/PhysRevLett.98.071301. http://www.arxiv.org/abs/hep-th/0610213.
- ^ a b Adam G. Riess et al. (Supernova Search Team) (1998). "Observational evidence from supernovae for an accelerating universe and a cosmological constant" (subscription required). Astronomical J. 116: 1009–38. doi:10.1086/300499. http://www.arxiv.org/abs/astro-ph/9805201.
- ^ a b S. Perlmutter et al. (The Supernova Cosmology Project) (1999). "Measurements of Omega and Lambda from 42 high redshift supernovae" (subscription required). Astrophysical J. 517: 565–86. doi:10.1086/307221. http://www.arxiv.org/abs/astro-ph/9812133.
- ^ a b D. N. Spergel et al. (WMAP collaboration) (March 2006). Wilkinson Microwave Anisotropy Probe (WMAP) three year results: implications for cosmology. http://lambda.gsfc.nasa.gov/product/map/current/map_bibliography.cfm.
- ^ Kowalski, Marek; Rubin, David (October 27th, 2008). "Improved Cosmological Constraints from New, Old and Combined Supernova Datasets". The Astrophysical Journal (Chicago, Illinois: University of Chicago Press) 686: 749-778. doi:10.1086/589937. arΧiv:0804.4142v1.