Controversy Over the Expansion Rate of the Universe: Hubble Tension
Brought to you by Odyssey
Jan 27, 2023 (1 session)
Friday, 6PM- 8PM
Course Description:
This is an evening lecture to highlight the debate centered around the precise value of the expansion rate of the Universe. This controversy is known as Hubble Tension. The fundamental features of the Universe, such as its age and observable size are characterized by an important parameter known as Hubble parameter, H0. In order to understand the past and future evolution of the universe, it is very important to know an accurate value of this parameter. Historically, this value has been measured by observing distant galaxies and calculating how quickly they are receding from observers. Collecting a large amount of such data from Hubble telescope can yield an accurate estimate for H0.
Alternatively, scientists can extract the value of Hubble parameter from the Cosmic Microwave Background (CMB) data. The CMB is the very first light in the early universe produced around 300,000 years after the Big Bang. At that time the universe was cool enough for matter to form, and for light to propagate freely through the universe. CMB data from Planck spacecraft can be used to determine the value of Hubble parameter in the early universe, and then infer the present value of the parameter using Cold Dark Matter Model. Hubble Tension arises because two values of the Hubble parameter obtained by the above two different methods do not coincide. There is a 9% discrepancy between these two values, The Cepheid-Supernovae Distance ladder measures a value (H0= 73.5±1.4 km/s/MPc) in the present-day universe on galaxy receding, and a value (H0= 67.4±0.5 km/s/MPc) inferred from the early Universe using the CMB
Planck data, it is not clear if this discrepancy in values arises due to an inaccurate measurements or if there is a fundamental issue in the model, demanding for new physics to be incorporated in the model. The present talk will discuss various ideas proposed to resolve Hubble Tension.
Johns Hopkins Tuition Remission Policies
Current and retired full-time Johns Hopkins faculty and staff, as well as their spouses or domestic partners, are eligible for tuition remission. Eligibility details can be found here.
After registration, tuition remission eligibility will be confirmed by the Odyssey registrar. If eligibility cannot be confirmed, you will be required to pay full tuition for the course. Under the terms of the University’s remission program, Hopkins employees must withdraw in writing at least five working days before the first class to receive a 100% refund. No partial refunds are given to JHU employees and affiliates. All other participants should review the JHAA Event Cancellation and Refund Policy