The Rest Is Science – "What We Said To Aliens" (Nov 27, 2025)
Hosts: Professor Hannah Fry & Michael Stevens
Theme: Humanity’s attempts to communicate with extraterrestrial life, focusing on the Arecibo message—how we constructed it, what it says about us, and what happens when we try to listen back. Plus, a listener mailbag on diamonds and the most impactful recent scientific discoveries.
Episode Overview
In this episode, Hannah Fry and Michael Stevens dive into the fascinating story of the Arecibo message—humanity's 1974 radio broadcast aimed at communicating with extraterrestrials. They explore the technical and philosophical intricacies of the message itself, reflect on why we haven’t heard anything back, and answer listener questions about diamonds and major scientific discoveries of the last 25 years. The conversation blends humor, skepticism, and wonder, reflecting on both the limitations and grand hopes of human scientific efforts to reach beyond our planet.
Key Discussion Points & Insights
1. The Arecibo Message: What Did We Try to Say?
[03:13–18:36]
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Setting the Scene: Michael Stevens introduces the Arecibo message, a binary-encoded broadcast sent from Puerto Rico in 1974, aimed at the M13 star cluster 25,000 light years away. He shows off posters of the message and walks through its composition.
"The messages are still not even close to where we shot them at, even though they're traveling at light speed." – Michael [03:39]
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The Mathematical Trick: The message’s 1,679 bits are a product of two prime numbers (23 and 73), meant as a clue for arranging the data as a grid.
"That is two prime numbers multiplied together." – Hannah [05:01]
"We gave the message ... as a bunch of bits to a whole bunch of groups of mathematicians, college students. And we just told them, crack the code, figure out what this is. ... None of them were able to figure it out." – Michael [05:40]
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Decoding Nightmares: You must recognize the semi-prime nature, arrange it as a 23x73 grid, interpret binary numbers with unusual “bullet point” indicators, and read numbers written bottom-to-top.
"Even if you have the same counting system, the same concept of prime numbers ... you still also then have to decode this weird extra pattern..." – Hannah [09:03]
"It's almost hilarious how hard it is to decode this purple shape." – Michael [09:34]
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The Message Content:
- Binary numbers (top): 1–10 for context
- Chemical elements: H, C, N, O, P (for life’s building blocks)
- Nucleotides: DNA details
- A double helix: (inaccurately represented)
- Human figure: Height encoded as “an average man”, number of humans (incorrect at the time and now)
- Solar System: With all nine planets (including Pluto)
- Arecibo Telescope: Visual + specifications
"There is something very cool about this ... a picture of what humans look like. So the aliens can go, wow, that's what their bodies are ..." – Michael [11:50]
"You've got incorrect information about the number of molecules in human body, incorrect population data, incorrect solar system information. And a telescope that doesn't exist." – Hannah [18:09]
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Comedic Critique:
- Both hosts lampoon the complexity and "pixelated junk" aesthetics.
- The message will never reach its intended target as those stars will have moved.
"It's this great wonder and awe and then this absolutely, completely rubbish image." – Hannah [15:17]
"We are essentially broadcasting this nonsense message that is impossible to decode even when you decode it properly. It's just a pile of pixelated junk to nothing." – Hannah [16:33]
"This is not for aliens. This is for us. ... an exercise in how do we describe ourselves at the most basic level..." – Michael [17:42]
2. Why Haven’t We Heard Back? (The Fermi Paradox)
[18:39–25:09]
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Listening for Aliens: Michael shares his experience lending computer power to SETI@Home rather than mining Bitcoin (a "choice" with humorous financial consequences).
"I found none." – Michael [19:28]
"You could have been a squillionaire." – Hannah [19:39]
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The Fermi Paradox & Explanations:
- The “Great Filter”: Intelligent life destroys itself before it can establish communication.
- The universe is too vast; signals rarely overlap in time and space.
- We may be deliberately avoided (“zoo hypothesis”) or not advanced enough to join a cosmic community.
- The sheer statistical unlikelihood vs. the enormity of possibility.
"There’s been enough time ... given all of that, though. Why is the sky so silent?" – Michael [23:28]
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Personal Theories & Humor:
- Hannah jokes the Arecibo message may have repelled intelligent life.
- Michael suggests we might be among the first intelligent beings in the universe.
"They saw that message coming for us and they were like, these guys are just absolutely bonkers. Let's stay the hell away." – Hannah [24:06]
"I think we are the ancients. I think we are the first or among the very first intelligent conscious creatures in the universe." – Michael [24:55]
3. Listener Mailbag
Q1: Can an Expert Tell the Difference Between a Natural and Lab-Made Diamond? Do They Have Different Value?
[28:21–31:07]
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Physical Characteristics:
- Lab diamonds tend to have higher clarity (fewer inclusions) than natural diamonds.
- Natural diamonds reflect geological history (e.g., nitrogen inclusions causing fluorescence).
"When diamonds exist in reality ... they are effectively a record of the atmospheric conditions under which they formed." – Hannah [29:49]
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Market Value:
- Lab-grown diamonds are cheaper to produce; inclusions can be introduced but are expensive to remove.
"This whole thing costs like 10 bucks to make." – Michael [31:02]
Q2: Which Scientific Discovery of the Last 25 Years Will Be Most Impactful?
[31:32–36:19]
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Michael’s Pick: Fusion Power
- Would eliminate energy constraints, revolutionize society, allow major advances (e.g., water desalination, carbon removal).
"If we had fusion here on Earth, we would have brought the sun to us." – Michael [33:25]
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Hannah’s Pick: CRISPR Gene Editing
- CRISPR technology allows for precise DNA editing, promising treatments for genetic diseases like sickle cell anemia.
"With the advent of CRISPR, we have been able to essentially create a, a one shot treatment ... you can edit the genes ... so they never have to suffer from ... that disease again." – Hannah [35:49]
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Philosophical Impact & Banter:
- Michael: “With fusion, we become the sun, but with CRISPR, we become the mother.” [36:19]
- Reflections on Oppenheimer and scientific legacy.
Notable Quotes & Memorable Moments
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On the complexity of the Arecibo message:
- "A for effort, F for execution." – Hannah [15:17]
- "You’re welcome, aliens." – Michael [18:36]
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On the Fermi Paradox:
- "Do they mismanage the way they get energy from, say, their own stars?" – Michael [24:06]
- "I think I've got a new theory which is that they're out there. They saw that message ... and they were like, these guys are just absolutely bonkers." – Hannah [24:06]
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On Diamonds:
- "Lab grown diamonds are basically way more perfect and therefore, I think, boring." – Hannah [29:49]
- "[Diamonds] cost like 10 bucks to make." – Michael [31:02]
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On Fusion and CRISPR:
- "If we had fusion here on Earth, we would have brought the sun to us." – Michael [33:25]
- "With CRISPR, we have been able to ... create a one shot treatment [for sickle cell anemia]." – Hannah [35:49]
- "With fusion, we become the sun, but with CRISPR, we become the mother." – Michael [36:19]
Timestamps for Key Segments
- Arecibo Message Intro & Decoding: [03:13–18:36]
- SETI & The Fermi Paradox: [18:39–25:09]
- Mailbag: Diamonds: [28:21–31:07]
- Mailbag: Fusion & CRISPR: [31:32–36:19]
Tone and Style
The hosts maintain a playful, witty rapport, mixing detailed scientific explanations with self-deprecating humor about humanity’s attempts to communicate or find aliens. Their approach is both skeptical and awestruck—a reminder of both the grandeur of scientific endeavor and its frequent, relatable flaws.
Summary Takeaway
This episode offers a vivid, accessible, and funny deep-dive into the strange, often absurd story of how we’ve tried to represent humanity to hypothetical extraterrestrials, why those efforts probably aren’t working, and what this says about science and our place in the universe. Insightful tangents on diamonds and genome editing underscore science’s power to shape—or misrepresent—reality.