Are we alone in the universe—or just early to the party? We’ll explore the math, models, and megastructures that might answer how many alien civilizations are out there, and why the night sky remains so quiet.

Watch my exclusive video Fishbowl Starships - Water As Shielding - https://nebula.tv/videos/isaacarthur-fishbowl-starships-water-as-shielding

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SFIA Discord Server: https://discord.gg/53GAShE

Credits:

How Many Alien Civilizations Are There?

Episode 723; June 8, 2025

Written, Produced & Narrated by: Isaac Arthur

Editor: Ludwig Luska

Graphics: Ken York YD Visual

Select imagery/video supplied by Getty Images

Music Courtesy of Epidemic Sound http://epidemicsound.com/creator

Phase Shift, "Forest Night"

Chris Zabriskie, "Unfoldment, Revealment" & "A New Day in a New Sector"

Koalips, "Kvazar"

Stellardrone, "Red Giant" & "Billions and Billions"

See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.

Are we alone in the universe—or just early to the party? We’ll explore the math, models, and megastructures that might answer how many alien civilizations are out there, and why the night sky remains so quiet.

Watch my exclusive video Fishbowl Starships - Water As Shielding - https://nebula.tv/videos/isaacarthur-fishbowl-starships-water-as-shielding

Get Nebula using my link for 40% off an annual subscription: https://go.nebula.tv/isaacarthur

Get a Lifetime Membership to Nebula for only $300: https://go.nebula.tv/lifetime?ref=isaacarthur

Use the link gift.nebula.tv/isaacarthur to give a year of Nebula to a friend for just $30.

Visit our Website: http://www.isaacarthur.net

Join Nebula: https://go.nebula.tv/isaacarthur

Support us on Patreon: https://www.patreon.com/IsaacArthur

Support us on Subscribestar: https://www.subscribestar.com/isaac-arthur

Facebook Group: https://www.facebook.com/groups/1583992725237264/

Reddit: https://www.reddit.com/r/IsaacArthur/

Twitter: https://twitter.com/Isaac_A_Arthur on Twitter and RT our future content.

SFIA Discord Server: https://discord.gg/53GAShE

Credits:

How Many Alien Civilizations Are There?

Episode 723; June 8, 2025

Written, Produced & Narrated by: Isaac Arthur

Editor: Ludwig Luska

Graphics: Ken York YD Visual

Select imagery/video supplied by Getty Images

Music Courtesy of Epidemic Sound http://epidemicsound.com/creator

Phase Shift, "Forest Night"

Chris Zabriskie, "Unfoldment, Revealment" & "A New Day in a New Sector"

Koalips, "Kvazar"

Stellardrone, "Red Giant" & "Billions and Billions"

See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.

A new industrial revolution is coming—not on Earth, but above it. This episode delves into how orbital shipyards will produce everything from shuttles to megastructures, changing how we explore and inhabit space.

Watch my exclusive video Fishbowl Starships - Water As Shielding - https://nebula.tv/videos/isaacarthur-fishbowl-starships-water-as-shielding

Get Nebula using my link for 40% off an annual subscription: https://go.nebula.tv/isaacarthur

Get a Lifetime Membership to Nebula for only $300: https://go.nebula.tv/lifetime?ref=isaacarthur

Use the link gift.nebula.tv/isaacarthur to give a year of Nebula to a friend for just $30.

Visit our Website: http://www.isaacarthur.net

Join Nebula: https://go.nebula.tv/isaacarthur

Support us on Patreon: https://www.patreon.com/IsaacArthur

Support us on Subscribestar: https://www.subscribestar.com/isaac-arthur

Facebook Group: https://www.facebook.com/groups/1583992725237264/

Reddit: https://www.reddit.com/r/IsaacArthur/

Twitter: https://twitter.com/Isaac_A_Arthur on Twitter and RT our future content.

SFIA Discord Server: https://discord.gg/53GAShE

Credits:

Orbital Shipyards: Building Fleets in Space

Episode 722; June 5, 2025; Nebula Exclusive

Written, Produced, & Narrated by: Isaac Arthur

Graphics:

Anthrofuturism

Bryan Versteeg

Fishy Tree

Jeremy Jozwik

Melanovis

Sergio Botero

SpaceResourcesCGI

Udo Schroeter

Select imagery/video supplied by Getty Images

Music Courtesy of Epidemic Sound http://epidemicsound.com/creator

Phase Shift, "Forest Night"

Kai Engel, "Endless Story of Sun and Moon"

Chris Zabriskie, "Unfoldment, Revealment", "A New Day in a New Sector", "Oxygen Garden"

Stellardrone, "Red Giant", "Billions and Billions"

Chapters

0:00 Intro

0:15 Why Build in Orbit?

1:29 The Gravity Well Problem

3:22 Material Sourcing – The Importance of ISRU

5:44 Early Orbital Shipyards – Existing & Near-Future Projects

6:37 Lessons from Space Stations & Prototypes

8:22 Port George & Linus Scrapyard – Revisiting Fictional Shipyards

13:08 Infrastructure & Logistics of Orbital Shipyards

23:39 Constructing Different Types of Ships

31:58 Challenges of Large-Scale Shipbuilding

34:10 Maintenance, Repairs, and Refits – Sustaining a Spacefaring Fleet

39:25 Salvage and Recycling

40:37 The Future of Orbital Shipyards – Expanding Beyond Earth

43:03 The Rise of Megastructure Shipyards

44:29 Privatization and the Spacefaring Economy

46:12 Shipyards as Strategic Military and Political Assets

47:54 The Role of AI, Automation, and Post-Human Workforces

See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.