Modern Cosmology, an Amuse-Gueule

TL;DR

This paper provides a broad, accessible overview of modern cosmology, covering evidence for the big bang, the universe's composition, its history, current challenges like the Hubble tension, and future prospects.

Contribution

It offers a nontechnical, comprehensive summary of key cosmological concepts, evidence, and open questions for a general audience.

Findings

Evidence for the big bang is well established.

The universe's composition includes visible matter, dark matter, and dark energy.

Current challenges include the Hubble tension.

Abstract

This essay is a nontechnical primer for a broader audience, in which I paint a broad-brush picture of modern cosmology. I begin by reviewing the evidence for the big bang, including the expansion of our Universe, the cosmic microwave background, and the primordial abundances of the light elements. Next, I discuss how these and other cosmological observations can be well explained by means of the concordance model of cosmology, putting a particular emphasis on the composition of the cosmic energy budget in terms of visible matter, dark matter, and dark energy. This sets the stage for a short overview of the history of the Universe from the earliest moments of its existence all the way to the accelerated expansion at late times and beyond. Finally, I summarize the current status of the field, including the challenges it is currently facing such as the Hubble tension, and conclude with an outlook onto the bright future that awaits us in the coming years and decades. The text is complemented by an extensive bibliography serving as a guide for readers who wish to delve deeper.