Radiolab: “DIY Universe”

Date: March 26, 2009
Hosts: Jad Abumrad, Robert Krulwich
Guest: Brian Greene, Physicist (Columbia University)

Main Theme

This episode of Radiolab explores the astonishing idea that humans could, in theory, create their own universe. Through engaging conversation with physicist Brian Greene, the hosts investigate the science—and the mind-bending speculation—behind the concept of universe-creation, venturing through topics like inflation theory, black holes, repulsive gravity, and the philosophical consequences of such a feat.

Key Discussion Points and Insights

1. What Does “Universe” Mean, Really?

• The hosts clarify that for most people, “the universe” means everything that exists—so by definition, there should be just one.
• Physicist Brian Greene introduces the “multiverse” concept:

  “The idea that there might be many universes has surprisingly cropped up in a variety of different contexts in physics…. [The Big Bang] is an event that happens over and over and over again in distant and far flung regions of our universe. Other universes sprout out, have their own new Big Bangs, giving rise to a kind of cosmic bubble bath.” (Brian Greene, 01:36)

2. The Multiverse and Modern Physics

• Greene lays out the development of these ideas:

  • The inflationary theory was developed in the 1980s.
  • The concept of “many universes” emerged from this work.
  • No one has “explored” another universe—it’s a conclusion from theoretical work, not direct observation:

    “We are confined to our bubble and we really can't get out and explore the other bubbles… it is a mental exercise, but a powerful one.” (Brian Greene, 03:06)

• Greene highlights the need to move beyond human intuition when considering bizarre physical phenomena:

  “The history of physics…the last century has taught us to strenuously challenge our perceptions…. I don't think it's a good guide to use our senses and our intuition to determine what we think is right or wrong, we really have to follow the laws of physics and see where they take us.” (Brian Greene, 03:36)

3. Engineering a “DIY Universe”

• The hosts ask whether humans could actually build a universe as a DIY project.

• Brian Greene explains that physicists haven’t ruled it out; in fact, there are hypothetical scenarios in which it might be possible:

  “People have studied this and nobody's really been able to say that it's impossible.” (Brian Greene, 05:19)

• The underlying mechanism requires understanding a strange feature of gravity:

  • Gravity is not just attractive; under special circumstances, it can be repulsive and push things apart.

  “Gravity can actually be not only attractive… it can also be repulsive. It can push things apart.” (Brian Greene, 06:08)

• This “repulsive gravity” is thought to be what drives the expansion of our universe and would play a key role in creating a new universe.

4. The “Seed” of a Universe

• To start a universe, you’d need to make something “very, very small.”

  “The seed has to be very, very small…. The seed of our universe, we believe from our calculations and our observations, was roughly 10 to the minus 26, 10 to the minus 27 centimeters across, weighed, you know, a few pounds. About 10 pounds.” (Brian Greene, 09:07 and 09:22)

• Surprisingly, even 10 pounds of the right “stuff”—with the right properties—might be enough to seed a universe, because the repulsive side of gravity injects enormous energy into expanding space.

5. Black Holes and Universe Creation

• The conversation turns to black holes as the likely form of the initial “seed.”

  “The seed should come in the form of what he described as a black hole.” (Robert Krulwich, 10:19)

• Contrary to popular belief, black holes can be tiny:

  “There's nothing that you could give me that I couldn't turn into a black hole by squeezing it sufficiently small.” (Brian Greene, 11:26)

• Natural processes—like high-energy particle collisions—can create tiny black holes, and such phenomena might even be produced at the Large Hadron Collider.

6. The Trigger and Safety of Universe Creation

• Creating a universe requires not just a “seed” black hole but also a trigger for setting off the expansion—though the specifics are highly technical.
• The hosts and Greene discuss whether creating a universe would be dangerous:

  “Instead, this universe that you create would, in essence, create its own space…. It would be off on its own, if you will, creating a new bubble universe. That would be a universe in its own right.” (Brian Greene, 13:04)

7. Could We Visit Our Creation?

• If you could make your own universe, “you would never, ever, ever be able to come back to visit anyone or anything you ever have known.” (Robert Krulwich, 14:41)
• Greene speculates that, despite the dangers, the curiosity might prove irresistible:

  “If you could actually do this…. I think I might have a little trouble resisting this possibility.” (Brian Greene, 15:02)

8. Why Bother With “Speculation on Speculation”?

• Greene closes by acknowledging just how speculative the idea is, but stresses its value:

  “I do consider this speculation on speculation…. [But] it's more to push the laws of physics to their breaking point, because that's often where we learn new things about how the world works.” (Brian Greene, 16:07)

Notable Quotes & Memorable Moments

• On the Multiverse:

  “We have learned that the atom is made up of particles that can be both wave like or particle like... None of those things feel right according to our intuition. But I assure you, the experiments that have been done... have confirmed each of those crazy ideas over and over again.” (Brian Greene, 03:36)

• On Making a Universe in a Kitchen:

  “So I can have you see an expanding universe that is born in my kitchen, and I don't have to worry about my dishes.” (Robert Krulwich, 08:21)

• On the Motivation to Try:

  “If you could actually do this... I think I might have a little trouble resisting this possibility.” (Brian Greene, 15:02)

Important Segment Timestamps

• The multiverse concept introduced: 01:36
• Why intuition is a bad guide: 03:36
• Is it possible to create a universe?: 05:19
• Repulsive gravity explained: 06:08
• Universe “seed” size and weight: 09:07–09:22
• Black holes as universe seeds: 10:19–11:26
• Natural tiny black holes & the LHC: 11:36
• Would a DIY universe expand and destroy us?: 13:04
• Could you visit the new universe?: 14:03–14:48
• Why speculate?: 16:07

Tone and Language

The episode balances playful curiosity (banter between Jad and Robert) with awe and humility at the scale of the universe. Brian Greene brings clarity, accessibility, and a sense of infectious wonder, making esoteric ideas approachable to a curious general audience.

Summary

“DIY Universe” is a mind-expanding deep-dive into whether people could theoretically craft new universes. Physics, philosophy, and imagination all intermingle as the hosts and Brian Greene explore how our universe might be just one bubble amid an endless multiverse, how gravity could power new realms, and how the pursuit of such far-out possibilities, though speculative, pushes the boundaries of human understanding. This episode leaves listeners with more questions than answers—and a potent sense of cosmic possibility.