Cosmic Structure - The Research
The Universe has structure on many scales. In the largest of scales, we see that the Universe is not random: galaxies are not haphazardly strewn around willy nilly. Rather, they form a tight, interconnected "cosmic web". To study the formation of this web, KIPAC scientists use experiments like Planck, BICEP2, POLAR, and Quiet II to study the Early Universe in an effort to understand the "seeds" that led to creation of the cosmic web we see today.
Our understanding of these initial conditions --- the state of the early universe --- is then used to perform state of the art numerical simulations, which KIPAC scientist use to determine how the tiny lumps in the early universe growth through gravity, creating the web-like structures that we see today. By combining these numerical simulations with observations of cosmic structure in the largest scales --- for instance using galaxy clusters, or experiments like the DES, LSST, and WFIRST --- KIPAC scientists can study both dark matter and dark energy; too little dark matter, or too much dark energy, and gravity would not be able to form the structures we see today. Conversely, too much dark matter, or too little dark energy, and the Universe would look much more structured (clumpy) than what we see today.
KIPAC scientists do not stop there, however. While we continue to explore how the cosmic web formed, there are equally pressing questions that we need to understand on smaller scales to understand how the Universe looks today. When and how did the first stars form? What was their impact on the cosmos? How do galaxies form, and how do they populate the gravity-generated cosmic web (http://kipac.stanford.edu/kipac/research/galaxy_formation)? Are most galaxies today forming stars, or is the most vigorous epoch of star formation behind us? From developing state of the art numerical simulations, to using observational tools like gravitational lensing to better understand the connection between galaxies and dark matter, KIPAC scientists aim to understand the Universe as a whole, from the largest structures in the cosmic web, to the structure of individual galaxies, and the interplay between them.