FAST BREAKING PAPERS

Why do you think your paper is highly cited?

The paper provides an overview of the current state of cosmology and is of significant interest to both astronomers interested in the emergence of galaxies and large-scale structure and particle physicists interested in the early universe. These are two large and active communities and this paper has become a standard reference for describing the composition of the universe and the now "standard cosmology."

Because the paper is a product of the Wilkinson Microwave Anisotropy Probe science team, I believe that the community views the derived parameters as reliable. This paper builds on other papers by the WMAP team that describe the experiment, the detector, the analysis method, and the basic results.

Does it describe a new discovery, methodology, or synthesis of knowledge?

The paper reports new results from the Wilkinson Microwave Anisotropy Probe and synthesizes the WMAP results with other cosmological data.

Would you summarize the significance of your paper in layman’s terms?

We show that a simple cosmological model, a flat universe filled with atoms, dark matter, and dark energy and seeded by scale-invariant primordial fluctuations, fits not only WMAP’s observations of fluctuations in the microwave background, but also a host of cosmological observations.

With six basic parameters (the age of the universe, the density of matter, the density of atoms, the amplitude of the initial fluctuations, their scale dependence and the epoch of the formation of the first stars), we fit WMAP’s precision measurements of the power spectrum, observations of galaxy clustering, galaxy lensing, supernova observations, and many other astronomical measurements.

This model is in some ways very simple and elegant: high school geometry describes the large-scale shape of the universe and the statistical properties of the primordial fluctuations seem to be described by only two numbers. In other ways, it is very bizarre: atoms make up only 4% of the universe. The next 23% is in the form of dark matter, most likely sub-atomic particles that couple extremely weakly to ordinary matter and radiation. Most of the remaining 73% is in the form of dark energy, energy associated with empty space.

How did you become involved in this research, and were there any problems along the way?

When Chuck Bennett, the WMAP Principal Investigator, and Lyman Page, the Princeton experimental lead, were putting together the WMAP team, they invited me to join as the "house theorist." This was my first deep involvement with a major experiment; it has been an exciting adventure.

As in any big projects, there were many challenges. For the three-year analysis, we were able to report the first detection of large-scale correlations in polarization. The level of this signal was very low, a few hundred nono-kelvin, far below our design requirements. We had to understand the instrument very well to be able to report this measurement. The polarization detection was essential for our ability to constrain cosmological parameters.

Where do you see your research leading in the future?

The WMAP experiment is continuing to operate. We hope to report results from the five-year analysis later this year and results from the eight-year analysis in either 2010 or 2011.

We are also now operating a new ground-based experiment, the Atacama Cosmology Telescope (ACT), in the Chilean Atacama desert. This experiment has a higher resolution than WMAP along with higher sensitivity. We are now getting our first results and should be able to report new measurements soon.

Do you foresee any social or political implications for your research?

At a superficial level, no. The study of the early universe is far removed from daily political battles.

At a deeper level, I believe that the recognition that simple physical models fit the observed universe have had and will continue to have profound implications. Copernicus, Galileo, and Newton have radically altered our world view by showing that the same laws apply in terrestrial experiments and in space, while showing that a simple physical model (Newton’s laws) describe the dynamics of our solar system. Our work has been a contribution towards establishing a simple model that appears to explain the dynamics of the visible universe.

David N. Spergel
Department of Astrophysical Sciences
Princeton Center for Theoretical Physics
Institute for the Physics and Mathematics of the Universe (IPMU)
Princeton University
Princeton, NJ, USA

RELATED>
• David N. Spergel in past features; 1 | 2 | 3.
• Charles Bennett in past features; 1 | 2 | 3.
• Edward L. Wright in past features; 1 | 2.
• Licia Verde in a past feature
• SCI-BYTES (archived) as the Hot Paper in Physics (First-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations...".

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