Unraveling the tiny wrinkles in Cosmic Microwave Background Radiation: Determining the past and future evolution of the Universe
J. S. Bagla Harish, Chandra Research Institute
The cosmic microwave background radiation, or CMBR as it is often referred to is radiation received from all directions of the sky, with the characteristic spectrum corresponding to 2.7 degrees Kelvin. CMBR was discovered by Penzias and Wilson in 1965, and the cosmological interpretation was arrived at in the same year by Dicke and Peebles.
We know that the Universe is expanding, and expansion leads to cooling of gases, radiation also shifts to lower energies.he universe must have been very hot at early times. At sufﬁciently early times, it must have been hot enough for matter and radiation to be in equilibrium. CMBR is a relic of this hot phase of the early universe.
If the matter distribution at the time of matter¬radiation decoupling is clumpy then an imprint of these can be seen in the relic radiation. The deviations from homogeneity in the Universe were small at all relevant scales at the time of decoupling, hence the qualiﬁcation as “wrinkles”.
These deviations grow with time due to gravitational instability, and result in formation of a variety of structures: from the very large scale structures in the universe, to microscopic organisms.
Observations of CMBR anisotropies are important achievements for two reasons: First, the ﬂuctuations are so small that it is very difﬁcult to observe CMBR anisotropies. More importantly, observations of CMBR anisotropies put strong constraints on models.
I will discuss these issues, and also the evolutions of small ﬂuctuations in the matter distributions, whose signature we see in the CMBR.
• Wikipedia Article.
• Frequently asked questions about CMBR.
• Nobel Prize 1978: Discovery of CMBR by Penzias and Wilson.
• Nobel prize 2006: Mather & Smoot for discovery conﬁrming cosmic origins, and for discovery of anisotropies in the CMBR.