Digest

This episode of Dear Hank and John features a conversation with astrophysicist Dr. Katie Mack about the universe, including its expansion, the nature of time, and the possibility of human travel to Mars. Dr. Mack explains that the universe is expanding, but not by creating new matter, rather by increasing the space between existing objects. She also discusses how cosmologists measure time by observing the redshift of light from distant galaxies, which is related to the size of the universe when the light was emitted. The episode also touches on the concept of dark energy, which is thought to be responsible for the accelerating expansion of the universe. The conversation then shifts to the possibility of human travel to Mars, with Dr. Mack expressing her willingness to go, even on a one-way trip. The episode concludes with a discussion of the news from Mars and AFC Wimbledon, including the signing of a new player for the team and the announcement of NASA's involvement in the ExoMars Rosalind Franklin Rover mission.

Outlines

00:00:00

Policy Genius Ad

This Chapter is an advertisement for Policy Genius, a marketplace that helps people find and buy insurance. The ad highlights the benefits of using Policy Genius, such as finding life insurance policies starting at $292 per year for one million dollars of coverage and same-day approval.

00:01:00

Introduction and Guest Introduction

This Chapter introduces the podcast Dear Hank and John, hosted by brothers Hank and John Green, and their guest, astrophysicist Dr. Katie Mack. They discuss the podcast's format and the topics they will cover, including the universe, Mars, and AFC Wimbledon.

00:01:23

The Big Bang and the Universe's Expansion

This Chapter delves into a listener's question about the universe's expansion and whether new matter is created as it expands. Dr. Mack explains that the prevailing theory is that the universe is expanding by increasing the space between existing objects, not by creating new matter. She also discusses the steady state universe theory, which proposed that new matter was constantly being created to maintain a constant density in the universe.

00:41:23

The Nature of Solids and Empty Space

This Chapter explores a listener's question about how atoms, which are mostly empty space, can support our weight. Dr. Mack explains that the solidity of objects is due to electrostatic repulsion between the electrons in atoms, which prevents them from passing through each other. She also discusses the concept of neutrinos, which are tiny particles that can pass through the Earth without interacting with its atoms due to their lack of electric charge.

00:47:20

AFC Wimbledon News

This Chapter focuses on the news from AFC Wimbledon, a football club that holds a special place in John Green's heart. John shares the exciting news that the club has signed a new player, Maddie Stevens, who is a retired professional boxer. He also discusses the club's recent relegation and the upcoming season.

00:49:41

Mars News and the ExoMars Rosalind Franklin Rover Mission

This Chapter covers the news from Mars, including the announcement of NASA's involvement in the ExoMars Rosalind Franklin Rover mission. The mission, originally scheduled for 2022, has been delayed to 2028 due to the termination of the partnership with Roscosmos. NASA will now provide support for the mission, including radioisotope heating units and a US commercial launch provider.

Keywords

Q&A

• What is the prevailing theory about the expansion of the universe?

  The prevailing theory is that the universe is expanding by increasing the space between existing objects, not by creating new matter. This means that the amount of matter in the universe remains constant, but the density of matter decreases as the universe expands.

• How do cosmologists measure time?

  Cosmologists measure time by observing the redshift of light from distant galaxies. Redshift is caused by the expansion of the universe, which stretches the wavelengths of light as it travels through space. The amount of redshift is directly proportional to the distance of the object, and therefore, the time it took for the light to reach us. By measuring the redshift, cosmologists can determine how long ago the light was emitted and therefore, how long ago the galaxy was in that state.

• What is dark energy and what is its role in the universe?

  Dark energy is a hypothetical form of energy that is thought to be responsible for the accelerating expansion of the universe. It is a mysterious force that is thought to make up about 68% of the total energy density of the universe. The nature of dark energy is still unknown, but it is thought to be a property of space itself. As the universe expands, the amount of dark energy increases, leading to an acceleration of the expansion.

• Why do things feel solid even though atoms are mostly empty space?

  The solidity of objects is due to electrostatic repulsion between the electrons in atoms. When two objects come into contact, the electrons in their atoms repel each other, preventing the atoms from passing through each other. This repulsion is what gives objects their solidity.

• What are neutrinos and why can they pass through the Earth without interacting with its atoms?

  Neutrinos are tiny particles that have no electric charge. Because they have no electric charge, they do not interact with the electromagnetic force, which is the force that governs the interactions between atoms. This means that neutrinos can pass through matter, including the Earth, without interacting with its atoms.

• What is the escape velocity of Earth and what does it mean?

  The escape velocity of Earth is about 11.2 kilometers per second. This means that an object must be traveling at least 11.2 kilometers per second to escape Earth's gravity and travel into space. The escape velocity of a planet or other celestial body depends on its mass and radius. The more massive and denser a body is, the higher its escape velocity will be.

• What is the ExoMars Rosalind Franklin Rover Mission and what is its goal?

  The ExoMars Rosalind Franklin Rover Mission is a joint mission between the European Space Agency (ESA) and NASA to search for signs of past or present life on Mars. The mission will involve sending a rover to Mars to explore the surface and collect samples. The rover is named after Rosalind Franklin, a British chemist and X-ray crystallographer who played a key role in the discovery of the structure of DNA. The mission is scheduled to launch in 2028.

• What are some of the challenges of sending humans to Mars?

  Sending humans to Mars is a very challenging endeavor. Some of the challenges include the long travel time, the harsh environment on Mars, the need for life support systems, and the psychological effects of long-duration spaceflight. These challenges are still being addressed by scientists and engineers, and it is unclear when humans will be able to travel to Mars and live there for extended periods.

• What is the sleep band and how does it relate to the global population?

  The sleep band is a period of time during which most people on Earth are asleep. Because of the time zones and the distribution of population across the globe, there is a time each day when a large percentage of the global population is asleep. This is particularly true when the sleep band passes over Asia and India, where a large portion of the world's population resides.

Show Notes