What We Don't Know Lana Howell

Neutron stars are one of the most extreme astronomical objects in the universe. They are so dense that a single teaspoon, if you were strong enough to collect it, would weigh 4 billion tons. They can spin as fast as 43,000 times per minute, and their magnetic field - for reference, Earth’s magnetic field is around 1 gauss - reaches a trillion gauss. 
The extreme conditions inside neutron stars suggest all kinds of unusual matter might make them up. From neutronium, to nuclear pasta, to soups of strange quarks, neutron stars are a rich source of interesting physics. This episode I will take you on a journey through the star’s layers to the heart of the monster: the core of a neutron star. Here, we will witness the tenets of particle physics break down under the immense pressure, as quarks deconfine and decay. We might see droplets of strange matter fly out and infect the universe. Finally, I’ll touch on the search for experimental evidence to determine which type of matter neutron stars are most likely to keep bubbling away in their cores.

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Very early in our school career, we learn about the states of matter. This table is hard wood - it's solid. This water flows, we can drink it - it’s a liquid. And the air around us, even though we cannot see it, is a gas. But these three states of matter are not the only three. In fact, wikipedia describes around 20 different states of matter. 

One of these is the Bose-Einstein condensate (BEC). In this state, a number of separate atoms or subatomic particles are cooled to near absolute zero, and behave like a single quantum entity. Many become one in the eyes of physics and maths. Since these eyes tend to define our scientific reality, the existence and implications of BECs defy our expectations of how matter should behave. It is another mind-bending quantum phenomenon. Bose-Einstein condensates are interesting to consider from a theoretical perspective, but they also have practical purposes, such as in superconductors and atomic clocks, especially now that they have been created in labs.

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We often use the phrase ‘it’s the end of an era’ to signify some great change in our lives, like leaving school forever. But actual eras are far, far longer than our brains can comprehend, usually lasting several hundred million years, with dramatic, global ecological changes as their finale. Around 541 million years ago, there was such an ending. As the Neoproterozoic era came to a close, so did the Proterozoic eon, and nearly 3.5 billion years of bacterial rule. Suddenly the prokaryotic mats were breaking apart and the slow, soft-bodied organisms that characterised the late Neoproterozoic were dying. Following this mass extinction, the new Cambrian period brought stunning increases in the diversity and complexity of life. These increases are called the Cambrian explosion. But what caused such a striking shift?
This episode I will start with the fundamentals and work our way to the theorised explanations for the Cambrian explosion. I’ll explain how evolution works, summarise the great history of life on Earth, and outline the methods that scientists use to examine this history. Then I’ll draw our attention to the border between Ediacaran and Cambrian periods. We will see what was so significant about the evolutionary changes there, before assessing some of the most plausible reasons why the Cambrian explosion happened, and why it happened then of all times. 

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When particles escape from a black hole via Hawking radiation, they only contain information on the mass, spin and charge of the black hole’s original material. Other information, that is needed to reconstruct the black hole’s past, seems to be lost permanently. This breaks the fundamental principle of unitarity which says that total information must be conserved, creating a paradox. 

This episode, we’ll examine potential solutions to the paradox, with particular focus on AdS/CFT correspondence (ie. the holographic principle) and recent work by Ahmed Almheiri.

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Different areas of physics seem to be incompatible inside black holes. When combining general relativity, thermodynamics and quantum mechanics, you get a paradox, which suggests that our knowledge of these areas is flawed. A solution, whatever it may be, would irreversibly shake up our understanding of the physical world. It may rewrite fundamental laws. It may unveil a new theory of quantum gravity.

In this episode I will unravel what ‘information’ means in physics and how it relates to unitarity. I’ll explain how black holes are formed and their key features, why Hawking radiation was proposed, and how Hawking radiation violates this unitarity. This should reveal what the black hole information paradox is.  Then in the next episode, we’ll examine potential solutions to the paradox.

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What is consciousness? Who experiences it? Why? How?

In this episode, I will first offer a definition of consciousness and consider the aspects that make it up. Then I’ll summarise some of the main questions we can ask about consciousness, drawing a distinction between the philosophical and neuroscientific sides to the problem. I will look over different scientific models of how the brain produces consciousness, as incomplete and flawed as they may be, before finishing with the practical consequences that understanding consciousness would have. 

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