The Joy of Why

Quantum gravity is one of the biggest unresolved and challenging problems in physics, as it seeks to reconcile quantum mechanics, which governs the microscopic world, and general relativity, which describes the macroscopic world of gravity and space-time. 

Efforts to understand quantum gravity have been focused almost entirely at the theoretical level, but Monika Schleier-Smith at Stanford University has been exploring a novel experimental approach — trying to create quantum gravity from scratch. Using laser-cooled clouds of atoms, she is testing the idea that gravity might be an emergent phenomenon arising from quantum entanglement.

In this episode of the Joy of Why podcast, Schleier-Smith discusses the thinking behind what she admits is a high-risk, high-reward approach, and how her experiments could provide important insights about entanglement and quantum mechanical systems even if the end goal of simulating quantum gravity is never achieved.

Quantum computing promises unprecedented speed, but in practice, it’s proven remarkably difficult to find important questions that quantum machines can solve faster than classical ones. One of the most notable demonstrations of this came from Ewin Tang who rose to prominence in the field as a teenager. When quantum algorithms had in principle cracked the so-called recommendation problem, Tang designed classical algorithms that could match them.

So began the approach of “dequantizing,” in which computer scientists look at quantum algorithms and try to achieve the same speeds with classical counterparts. To understand the ongoing contest between classical and quantum computing, co-host Janna Levin spoke to Tang on The Joy of Why podcast. The wide-ranging conversation covered what it was like for Tang to challenge the prevailing wisdom at such a young age, the role of failure in scientific progress, and whether quantum computing will ultimately fulfill its grand ambitions.

At first, life on Earth was simple. Cells existed, functioned and reproduced as free-living individuals. But then, something remarkable happened. Some cells joined forces, working together instead of being alone. This transition, known as multicellularity, was a pivotal event in the history of life on Earth. Multicellularity enabled greater biological complexity, which sparked an extraordinary diversity of organisms and structures.

How life evolved from unicellular to multicellular organisms remains a mystery, though evidence indicates that this may have occurred multiple times independently. To understand what could have happened, Will Ratcliff at Georgia Tech has been conducting long-term evolution experiments on yeast in which multicellularity develops and emerges spontaneously.

In this episode of The Joy of Why podcast, Ratcliff discusses what his “snowflake yeast” model could reveal about the origins of multicellularity, the surprising discoveries his team has made, and how he responds to skeptics who question his approach.

How did complex life evolve? Where did space-time come from? Will computers ever understand language like we do? How did geometry create modern physics? These are just a few of the big and bold questions that we’ll be exploring in the latest season of Quanta’s interview podcast, “The Joy of Why,” starting March 20, and released every other Thursday.

As ever, we will be talking to researchers and exploring the latest thinking on great scientific and mathematical questions of our time. But this season sees a new format, with the two of us — mathematician Steven Strogatz and physicist Janna Levin — together in conversation for the first time to offer our own thoughts and questions about each topic.

As a preview, we discuss why we are particularly excited about the new season, and we reveal our favorite standout moments from the previous season.