# The Crisis in Cosmology

- Kiara Jacob, FYBSc

Cosmology is a branch of astronomy that deals with the origin, nature, evolution, and the ultimate fate of the Universe. It also involves studying exotic concepts like dark energy, dark matter, string theory, inflation theory, the concept of a multiverse, etc. Cosmology essentially covers the entire lifespan of the Universe. One of the most interesting facts about our universe is that it is expanding at an increasing rate. Cosmologists studying the expansion, and by extension the origins of the universe, were naturally led to ask the question: How old is our Universe? The answer to this question, however, isn’t quite as simple as one might expect.

Hubble’s constant Ho, named after astronomer Edwin Hubble, expresses the rate at which the universe is expanding (Hubble, 1929). Knowing this rate of expansion helps cosmologists to then determine the age of the universe. The “crisis” in cosmology has arisen because the values for this constant, obtained from cosmologists best methods, are not in agreement (Di Valentino et al., 2019). In fact, the discrepancy between the values means there could be a difference in the age of the universe of about a billion years!