The Rest Is Science – "How To Drink Lava"
Hosts: Professor Hannah Fry & Michael Stevens (Vsauce)
Date: November 25, 2025
Episode Overview
In this vibrant and surprising episode, Professor Hannah Fry and Michael Stevens dive deep into one of the internet’s strangest questions: How to drink lava? Along the way, they explore what water really is, whether it qualifies as "wet," how water's properties shape life and culture, why water is both everywhere and incredibly rare, and how everything we consume is partially—if not mostly—lava in disguise. Expect a lively journey through chemistry, geology, paleontology, evolutionary biology, and even linguistics, filled with the hosts’ characteristic wit and curiosity.
Key Discussion Points and Insights
The "Is Water Wet?" Debate
[03:01-04:00]
- Michael opens with the classic internet question: Is water wet?
- Michael: "One molecule of water? Dry. Once there's more, it's soaking wet."
- Wetness, they conclude, is about water adhering (via intermolecular forces) to something—sometimes even itself!
- Hannah: "We should say first about why this is a memed question...water itself makes things wet, but is the water itself wet?"
What’s In the Water We Drink?
[04:40-11:31]
- Even "pure" drinks are mostly water—Michael notes Diet Coke is about 99% water, while regular Coke is 90%.
- Tap water is likened to "a rock smoothie" (Hannah, 06:13) because it contains minerals like calcium, magnesium, and sodium.
- Different mineral contents ("hardness" or "softness" of water) drastically impact things like tea and beer.
- Michael: "There's a theory that New York's Catskills water is what creates for them their unique, special, one of a kind pizza doughs and bagels." (06:33)
- Replicating local water chemically is used to mass-produce beer and even to solve cases in forensic science and paleontology.
Water as a Geological Time Capsule
[07:43-09:21]
- Water’s mineral content can be traced through human hair, whale ear bones, and even fossils—tracking an organism’s movements or even migration patterns through history.
- Hannah: "You can find a body...take a hair sample and work out what water they were drinking when alive...You can do this with whales as well." (07:43-08:54)
Is Water Actually Lava?
[11:31-13:21]
- Michael makes the bold claim: "A glass of water is actually just a glass of lava."
- Water ice is technically a mineral; melted ice is "molten rock."
- Michael: "Ice is a mineral...So melted ice is molten rock: lava. So water is lava." (11:51)
- Hannah: "They also move the same way...the fluid dynamics of lava is the same as water at that stage." (13:00)
Water’s Remarkable Rarity
[16:11-18:34]
- Of all Earth’s water, only 2.5% is fresh; of that, only 1.2% is surface fresh water accessible to humans and animals.
- Michael: "What we think of as fresh water...in lakes, rivers—that is 0.0072% of all the water on earth." (18:26)
The Power and Mystery of Fridges
[19:43-20:37]
- Fridges are celebrated as miraculous devices that, in just 100–150 years, revolutionized food and drink: “You could have lived...would never have experienced a cold drink.” (Hannah, 20:28)
Earth’s Water Origin Story
[20:37-23:46]
- Most Earth water is “alien,” having arrived via icy comets in the early solar system.
- Over half the water on Earth is older than the Sun itself!
- Michael: "More than half of the water on Earth is older than the Sun." (21:20)
- Discussion of "heavy water" (with deuterium or tritium): traces in nature, dangerous in quantity.
Drinking Too Much or Too Pure Water
[24:28–28:52]
- Drinking pure water is dangerous because it strips minerals from your body—just like drinking too much mineral water can cause “water poisoning” or "hyponatremia."
- Michael: "If you drink too much water, even water that does have minerals in it, you get confused." (25:25)
- Drinking 6 liters in 3 hours has caused fatalities; for rats, even 40g at once can be fatal.
Recycling Water: Singapore & Space
[28:52–29:57]
- Innovative water recycling in Singapore: sewage is purified and distilled before being reintegrated into systems—often too pure to drink, so it’s sold to semiconductor factories instead.
- The ISS (International Space Station) uses a similar recycling setup: “Yesterday’s coffee is today’s cough coffee.”
Perspective on Earth’s Water Supply
[30:10–31:56]
- If Earth were shrunk to classroom globe size (30cm), all its water would equal less than a tablespoon.
- Michael: "A giant that could hold our Earth...would be like, 'Oh, it's soaking wet.' It’d be like a tiny bit sleepy. Brush it off. Yeah. Oh, it's got a little dew on it." (31:08)
Evolution: We’re Just Water Balloons
[32:28–33:59]
- All life’s evolution is a story of carrying water onto land:
- Hannah: "We didn't leave the water behind us. All we did was we just turned ourselves into water balloons." (32:28)
- Weight loss overnight is mostly due to evaporation.
Non-Watery Liquids and Everything is Lava
[34:07–35:20]
- Hosts contemplate what other liquids besides water are common at room temperature. Mercury and bromine: toxic. Oils: contain some water.
- Nearly everything drinkable is at least a little bit water—meaning "everything is either olive oil or dinosaur pee." (35:10)
Etymology: Solutions, Losing, and Dissolving
[35:23-36:40]
- Root of “lose” and “solution”: both about dissolving, disappearing, or being lost in water.
- Michael: “To be a loser is the same as to be dissolved…dissolving to be lost in water.” (35:47)
- Hannah: “If it wasn’t for losers, we wouldn’t be here. We need dissolved solids in water.” (36:40)
Notable Quotes & Memorable Moments
- Michael (03:17): “One molecule of water? Dry. Once there’s more, it’s soaking wet.”
- Hannah (06:13): “Tap water is just... like a rock smoothie.”
- Michael (11:51): “A glass of water is actually just a glass of lava.”
- Michael (18:26): “[Fresh water in lakes and rivers is] 0.0072% of all the water on earth.”
- Hannah (20:28): “It’s wild to me that... most of the planet would never have experienced a cold drink.”
- Michael (21:20): “More than half of the water on Earth is older than the Sun.”
- Hannah (32:28): “We didn't leave the water behind us. All we did was turn ourselves into water balloons...”
- Michael (35:47): “To be a loser is the same as to be dissolved...dissolving to be lost in water.”
Timestamps for Important Segments
- 03:01 – Is water wet? (Defining wetness)
- 04:40 – How watery are drinks? (Cola, Diet Cola, alcohol)
- 06:13 – Tap water as a "rock smoothie" (mineral content, food science implications)
- 07:43 – Tracing water’s origin via forensics and whale migration
- 11:31 – Ice as a mineral; water as "lava"
- 16:11 – Global water distribution and scarcity
- 18:26 – Fresh, accessible water: just a fraction of a percent
- 19:43 – Celebration of fridges and cold drinks
- 21:20 – Earth’s ancient, cosmic water
- 24:28 – Dangers of drinking pure or excessive water
- 28:52 – Water recycling in Singapore and in space
- 30:10 – If Earth were a globe, how much water would be visible?
- 32:28 – Evolutionary perspective: humans as “water balloons”
- 35:23 – Linguistics: solution, losing, and dissolving
Conclusion
Hannah Fry and Michael Stevens transform water from a mundane backdrop to a cosmic, evolutionary, and linguistic wonder—a “loser” (in the best way!) at the heart of every living thing and nearly every drink. Along the way, they break down common misconceptions, drop surprising statistics, and reveal the hidden, geological, and even alien nature of what we gulp down daily. The episode is a lively celebration of science, questioning, and the joy of looking closer at the things that seem most familiar.