The understanding of the physical origin of the acceleration of our universe is a big puzzle for both cosmology and theoretical physics. I will first briefly review the evidence for the acceleration of the expansion of the universe, focusing on the assumptions that lead to this conclusion. I will then describe a general classification of the models that could explain this acceleration and explain why it calls for better tests of general relativity on astrophysical and cosmological scales. I will review some of the possible tests and then discuss what constraints can be set from cosmology on a general class of theories including general relativity, namely scalar-tensor
theories.

I will present an overview of the broad program to determine the nature of dark matter that involves investigations in astronomy, astrophysics, cosmology and particle physics. My research concentrates on testing the hypothesis that weakly-interacting massive particles (WIMPS) constitute the dark matter. This hypothesis is testable through direct detection of nuclear recoils at low energy resulting from elastic scattering of WIMPs with nuclei. It is also testable by observing WIMP annihilation products, such as GeV-scale gamma-rays and/or neutrinos, as well as antiparticles in the near-Earth environment. Accelerator facilities, principally the Large Hadron Collider in Switzerland, will probe the TeV energy scale that should be associated with a WIMP solution to the dark matter question. The interplay between these three areas is the subject of my talk, with emphasis given to the direct detection of dark matter via athermal phonon mediated detectors of the CDMS (Cryogenic Dark Matter Search) collaboration and the use of scintillation in liquid Argon and liquid Neon with the DEAP&CLEAN collaboration.

Approximately half the light ever produced from stars and the formation of supermassive black holes has been absorbed and re-emitted by dust. This light traces the formation of structure in a cold dark matter dominated universe, but has until recently been hidden due to technological limitations. I will discuss how I have been studying the galaxies producing this light by using new instrumentation to detect them and find their redshifts, and will discuss future plans for the study of mass assembly at high redshift.