The Strongest Materials in the Universe: From Graphene to Nuclear Pasta

A single-atom-thick sheet of carbon — graphene — requires 55 newtons of force to puncture a hole through an area the size of a pencil tip. That translates to an ultimate tensile strength of approximately 130 GPa, roughly 200 times that of structural steel. It is the strongest material ever directly measured in a laboratory. Yet inside neutron stars, pressures so extreme that atomic nuclei can no longer maintain individual identities create a form of nuclear matter that computer simulations suggest is roughly 10 billion times harder to break than steel. Understanding what makes materials strong — and how strength breaks down at extreme scales — is one of the most productive questions in physics and materials science.

What "Strength" Actually Means

Strength is not a single property. Materials scientists distinguish between several distinct measures, and confusing them produces misleading comparisons.

Tensile strength — the maximum stress a material can withstand while being stretched or pulled before breaking. Measured in pascals (Pa), gigapascals (GPa), or megapascals (MPa). This is what determines whether a bridge cable snaps.

Compressive strength — the maximum stress under compression before the material fails. Diamond excels here. Concrete has high compressive strength but low tensile strength — which is why steel rebar is added in construction.

Hardness — resistance to localized surface deformation, scratching, or indentation. Measured on the Mohs scale (1–10) or Vickers Hardness (HV). Diamond is the hardest known natural material (Mohs 10), but "hard" does not mean "strong": a diamond will shatter if struck sharply with a hammer, because it is brittle.

Toughness — the ability to absorb energy before fracturing, which combines strength and ductility. A tough material is difficult to break even if it can be deformed. Spider silk is exceptionally tough by this measure, even though its raw tensile strength is lower than Kevlar.

Specific strength (strength-to-weight ratio) — strength divided by density. This is the measure that matters most for structural applications where weight is important, like aerospace components. Graphene and carbon nanotubes lead here dramatically.

Think of it this way: diamond is like glass — it resists scratching brilliantly but shatters under the right impact. Spider silk is like a fishing net made of the strongest thread you can imagine — it stretches, absorbs energy, and fails gracefully. Nuclear pasta is something else entirely: matter so compressed that the forces holding atomic nuclei together become structural forces on a macroscopic scale.

Source: Callister, W.D. & Rethwisch, D.G. (2020), Materials Science and Engineering: An Introduction, 10th ed., Wiley — standard materials science reference covering tensile strength, hardness, toughness, and compressive strength definitions with comparative data for common materials.

Graphene: The Strongest Measured Material on Earth

Graphene is a two-dimensional allotrope of carbon: a single layer of carbon atoms arranged in a hexagonal lattice, one atom thick (about 0.335 nm). It was first isolated in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester using adhesive tape and a pencil — one of the least technically sophisticated Nobel Prize-winning experiments in history. They received the 2010 Nobel Prize in Physics for it.

The decisive strength measurement came from a 2008 study by Lee et al. in Science, using a technique called nanoindentation. The researchers suspended graphene membranes over tiny holes and pressed an atomic force microscope tip into them at increasing force until they broke. The result: an intrinsic tensile strength of 130 ± 10 GPa, and a Young's modulus (stiffness) of approximately 1 TPa (1,000 GPa). Both values are the highest ever directly measured for any material.

For comparison: high-strength structural steel has a tensile strength of roughly 0.4–2.5 GPa. Graphene is 50–200 times stronger per unit cross-section. Per unit mass, the advantage is even larger: graphene's density is approximately 0.77 mg/m², making it effectively the strongest material per unit weight ever measured.

The limitation: producing graphene in large, defect-free sheets remains technically challenging. Real-world graphene always contains grain boundaries, folds, and vacancies, and these defects dramatically reduce practical strength. Laboratory measurements are of perfect single-crystal graphene membranes. The world has not yet built a graphene structural cable, though researchers are working toward graphene-reinforced composite materials.

Source: Lee, C. et al. (2008), "Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene," Science, Vol. 321 — the foundational measurement of graphene's mechanical properties using atomic force microscope nanoindentation.

Carbon Nanotubes: Theoretical Peaks, Practical Challenges

A carbon nanotube (CNT) is graphene rolled into a cylinder. Single-walled carbon nanotubes (SWCNTs) — tubes a single carbon layer thick, with diameters of 0.4–2 nm — are among the most studied materials in nanoscience. Their theoretical tensile strength, derived from molecular dynamics simulations and the carbon-carbon bond energy, is estimated at 100–200 GPa.

Experimental measurements have confirmed values up to about 63 GPa for individual single-walled nanotubes (Yu et al., 2000, Physical Review Letters), with significant scatter due to the extreme difficulty of gripping and measuring nano-scale objects. Multi-walled carbon nanotubes (MWCNTs) — multiple concentric graphene cylinders — show lower effective strength because mechanical load transfers poorly between layers, causing them to telescope apart.

The practical problem with carbon nanotubes is the same as with graphene, amplified: defects catastrophically reduce strength, and producing long, aligned, defect-free nanotube fibers at scale has proven extremely difficult. The theoretical nanotube-based space elevator — a cable stretching from Earth's surface to geostationary orbit at 35,786 km — requires a material with specific strength far exceeding steel. Carbon nanotubes theoretically qualify. Practical nanotube fibers currently do not.

Young's modulus — a measure of a material's stiffness, defined as the ratio of stress to strain in the linear elastic region. A material with a high Young's modulus resists deformation under applied force. Graphene and carbon nanotubes approach 1 TPa; steel is around 200 GPa; rubber is around 0.01–0.1 GPa.

Source: Yu, M.F. et al. (2000), "Tensile Loading of Ropes of Single Wall Carbon Nanotubes and Their Mechanical Properties," Physical Review Letters, Vol. 84 — direct experimental measurement of single-walled nanotube tensile strength using atomic force microscope pulling tests.

Spider Silk: Nature's Toughness Champion

Spider dragline silk — the structural silk used for the main frame of webs and for safety lines — has a tensile strength of approximately 1–2 GPa, which is lower than Kevlar's 3–3.6 GPa. By raw tensile strength, Kevlar wins. But tensile strength is not the whole story.

Silk's exceptional property is toughness: the area under a stress-strain curve, representing energy absorbed per unit volume before failure. Spider silk can extend to 30–40% of its length before breaking, while Kevlar stretches only about 3.5%. The combination produces a toughness modulus for spider dragline silk of approximately 150–180 MJ/m³ — greater than Kevlar and comparable to carbon fiber composites.

The biological reason: a web must absorb the kinetic energy of flying insects without shattering. A web that was maximally stiff would be useless — the silk would snap on impact. Instead, silk is tuned to absorb energy through deformation, sacrificing stiffness for durability. Evolution produced a material that is precisely what a web requires: not the hardest, not the stiffest, but the toughest per unit mass.

Spider silk's tensile strength per unit mass exceeds that of high-strength steel by a factor of roughly five. A cable of steel spider silk (if it existed at usable scale) as thick as a pencil would hold a commercial jet. The catch: spiders are territorial and cannot be farmed, and synthetic production of silk proteins with the full mechanical performance of natural silk remains an active and incomplete research challenge.

Source: Gosline, J.M. et al. (1999), "The Mechanical Design of Spider Silks: From Fibroin Sequence to Mechanical Function," Journal of Experimental Biology, Vol. 202 — comprehensive analysis of silk mechanical properties across species, covering strength, extensibility, and toughness.

Diamond: The Hardness Standard

Diamond is the hardest naturally occurring material on Earth, rating 10 on the Mohs scale — meaning nothing in nature scratches it except another diamond. Its hardness arises from its crystal structure: each carbon atom forms four covalent bonds in a tetrahedral arrangement with its neighbors, creating a three-dimensional lattice with no slip planes and enormous resistance to indentation.

Hardness, however, is not the same as strength. Diamond's tensile strength is approximately 1.6 GPa in perfect crystals, but natural diamonds contain inclusions, grain boundaries, and cleavage planes that reduce this substantially. More importantly, diamond is brittle: it fractures along cleavage planes with relatively low force if the impact is precisely oriented. Jewelers split diamonds deliberately using this property.

Diamond's real superiority is in compressive strength and wear resistance. It withstands pressures up to approximately 600 GPa before transforming to another carbon phase — higher than any other known natural mineral. This is why diamond anvil cells — two diamonds pressed together with a sample squeezed between their tips — can recreate pressures comparable to Earth's core and are used to synthesize exotic high-pressure materials.

Synthetic diamonds and boron nitride-based superhard materials have pushed the boundaries further. Wurtzite boron nitride (w-BN) and lonsdaleite (hexagonal diamond, synthesized from meteorite carbon) are theoretically harder than diamond under specific loading geometries, though practical production challenges mean diamond remains the standard reference for hardness.

Source: Blank, V.D. et al. (1998), "High-Pressure Polymerized Phases of C₆₀," Carbon, Vol. 36; and Tian, Y. et al. (2013), "Ultrahard nanotwinned cubic boron nitride," Nature, Vol. 493 — experimental characterization of materials exceeding diamond in specific hardness metrics.

Strength Comparison: Earth-Based Materials

Material	Tensile Strength (GPa)	Toughness (MJ/m³)	Hardness (Mohs)	Notes
Graphene	130	Very high	N/A (2D)	Lab measurement, perfect crystal
Carbon nanotube (SWCNT)	63–200 (theory)	High	N/A	Experimental up to ~63 GPa
Diamond	~1.6 (crystal)	Low (brittle)	10	Highest compressive strength
Spider silk (dragline)	1–2	150–180	~1	Highest toughness per mass
Kevlar 49	3.6	~50	~3	Synthetic fiber, armor applications
Carbon fiber (T1000)	6.4	Moderate	~5	Aerospace composite standard
High-strength steel	0.4–2.5	Moderate	~6.5	Structural engineering reference
Titanium alloy (Ti-6Al-4V)	1.1	High	~5	Aerospace alloys

Source: CRC Handbook of Chemistry and Physics (2023), 104th ed. — standard reference for material mechanical properties; manufacturer data sheets for Kevlar (DuPont) and T1000 carbon fiber (Toray Industries).

Nuclear Pasta: The Strongest Known Material in the Universe

Now leave Earth behind. Inside a supernova. About 20 km wide but containing more mass than the Sun.">neutron star — the remnant of a massive star's core after a supernova, compressed to roughly 10–12 km (6–7.5 mi) in diameter containing 1.4–2 solar masses — the density reaches 10¹⁷ kg/m³ at the core. A teaspoon of this material would weigh approximately one billion tons on Earth's surface.

In the outer crust of a neutron star, densities are extreme but still below nuclear saturation density (roughly 2.3 × 10¹⁷ kg/m³). In this intermediate zone, nuclei cannot maintain their familiar spherical shapes. Competing forces — the strong nuclear force (attracting nucleons to each other) and the Coulomb electromagnetic force (repelling protons from each other) — are roughly balanced. The result is a series of exotic nuclear structures called nuclear pasta, named for the shapes they form: gnocchi (spherical nuclear clusters), spaghetti (cylindrical tubes of nuclear matter), lasagna (flat nuclear sheets), bucatini (cylindrical voids), and Swiss cheese (spherical voids in nuclear matter).

Nuclear pasta — exotic phases of nuclear matter occurring in the inner crust of neutron stars, where nucleons form non-spherical geometric structures due to the balance between nuclear and electromagnetic forces. The phases are named by analogy to pasta shapes.

A 2018 study by Caplan et al. (Physical Review Letters, Vol. 121) used large-scale molecular dynamics simulations to calculate the breaking strain and elastic properties of nuclear pasta. The result: nuclear pasta requires a breaking strain of approximately 0.1 — meaning it can be strained by 10% before breaking, which is far higher than typical crystalline materials. More significantly, the yield stress (the force per unit area required to cause plastic deformation) is of order 10²⁶ Pa — roughly 10 billion times the force required to break steel.

The physical reason: in nuclear pasta, the relevant forces are the same nuclear forces that hold atomic nuclei together — the residual strong force. In ordinary materials, the forces are electromagnetic (chemical bonds between electrons). The strong force is approximately 100 times stronger per nucleon than electromagnetism over the relevant length scales. Nuclear pasta harnesses this directly as a bulk material property.

Source: Caplan, M.E. et al. (2018), "Elasticity of Nuclear Pasta," Physical Review Letters, Vol. 121 — molecular dynamics calculation of nuclear pasta's elastic and breaking properties, establishing it as the strongest known material in the universe.

Why Nuclear Pasta Cannot Exist on Earth

Nuclear pasta requires the extreme gravitational pressure of a neutron star to exist. At neutron star core densities, gravity provides confinement that keeps the nuclear matter from expanding and decaying into ordinary matter. Remove that pressure, and nuclear pasta instantly and catastrophically decays: the nuclear matter expands, the nucleons rearrange into ordinary protons and neutrons, and the pasta structure simply ceases to exist.

This is the same reason that a neutron star, if somehow transported to Earth's vicinity, would not just sit there as an exotic material — it would be gravitationally catastrophic. The physics that makes nuclear pasta the universe's strongest material is inseparable from the physics that makes it inaccessible and unreplicable.

The nearest neutron star to Earth is PSR J0437-4715, approximately 156 parsecs (509 light-years) away. Its nuclear pasta remains firmly out of reach. For now, graphene is the strongest material that humans can actually make and test in the lab — and that is extraordinary enough.

For more on the extreme physics of neutron stars and the objects that carry nuclear pasta in their crusts, see What Is a Neutron Star and What Is a Magnetar.

Source: Özel, F. & Freire, P. (2016), "Masses, Radii, and the Equation of State of Neutron Stars," Annual Review of Astronomy and Astrophysics, Vol. 54 — comprehensive review of neutron star physics including crust structure, pasta phases, and equation of state constraints.

The Takeaway

Strength is not a single property, and the title of "strongest material" depends entirely on which measure you apply. Graphene leads in tensile strength and specific strength at the lab scale. Carbon nanotubes are theoretically stronger but practically limited. Diamond wins on hardness and compression. Spider silk wins on toughness per unit mass. And nuclear pasta — inaccessible, exotic, existing only under neutron star gravity — requires forces on the order of 10 billion times those needed to break steel.

The physical principle underlying each record is the same: strength comes from the forces that hold matter together at the relevant scale. Chemical bonds dominate for earthly materials. The strong nuclear force dominates for nuclear pasta. Understanding where one regime ends and the other begins is one of the active frontiers of condensed matter physics, nuclear physics, and materials engineering.

Frequently Asked Questions

Q: If graphene is so strong, why don't we use it to build bridges and cars?
A: The laboratory measurements of 130 GPa are for defect-free, single-crystal graphene membranes measured at the nanometer scale. At larger scales, graphene sheets always contain grain boundaries and defects that reduce strength dramatically. Additionally, integrating graphene into structural composites — where it can reinforce a matrix material — is still an active manufacturing challenge. Graphene-enhanced composite materials are already used in some high-performance applications (sporting goods, aerospace components), but bulk graphene structures remain a future prospect.

Q: Is diamond actually the hardest material, or have harder things been discovered?
A: Natural diamond holds the Mohs 10 position, but synthetic materials have exceeded it under specific conditions. Wurtzite boron nitride and lonsdaleite (hexagonal diamond) are theoretically harder than cubic diamond under certain loading orientations. More practically, aggregated diamond nanorods (ADNRs) have been measured as harder than natural diamond. However, these are laboratory synthesized materials, not minerals, and diamond remains the standard practical reference for hardness.

Q: Why is spider silk so much tougher than Kevlar even though Kevlar has higher tensile strength?
A: Toughness measures total energy absorbed before breaking — the area under the stress-strain curve. Kevlar has higher peak tensile strength (~3.6 GPa vs. ~1.5 GPa for spider silk) but stretches only about 3.5% before failure. Spider silk stretches 30–40% before breaking. That enormous extension at moderate stress allows the silk to absorb far more energy overall, giving it a toughness modulus of ~160 MJ/m³ versus ~50 MJ/m³ for Kevlar. For stopping a bullet (rapid energy absorption), a material that can deform significantly is better than one that is very stiff and snaps.

Q: How do we know nuclear pasta exists if we cannot observe it directly?
A: Nuclear pasta is inferred from neutron star observations and theoretical nuclear physics, then modeled using large-scale molecular dynamics simulations that treat nucleons explicitly. Evidence supporting its existence includes: the cooling rates of neutron stars (which depend on thermal conductivity in the crust), pulsar glitch behavior (sudden spinup events interpreted as interaction between superfluid layers and the crust), and gravitational wave signals from neutron star mergers. The pasta structures predicted by simulations are consistent with these observational constraints.

Q: What is the strongest artificial material humans have made so far?
A: In terms of directly measured tensile strength, individual single-walled carbon nanotubes at approximately 63 GPa hold the record. For practical bulk materials, ultra-high molecular weight polyethylene (UHMWPE) fibers like Dyneema achieve specific strengths exceeding steel, and carbon fiber composites reach about 3.5–6.4 GPa in fiber form. For hardness, synthetic aggregated diamond nanorods exceed natural diamond. No human-made material approaches the theoretical limits of graphene or carbon nanotubes because manufacturing defects remain the central limitation.

Q: Could we ever manufacture something as strong as nuclear pasta?
A: Not through any foreseeable technology. Nuclear pasta's strength derives from nuclear forces operating at densities requiring neutron star gravity for confinement. Recreating those conditions on Earth would require a neutron star. Hypothetically, extremely dense quark-gluon matter (as studied in particle accelerators) operates at higher energy densities than nuclear pasta, but is even more inaccessible as a structural material. The question is better understood as: "What is the theoretical upper bound on material strength?" The answer, as far as current physics knows, is set by the strong nuclear force — which nuclear pasta accesses.

---

Read next:

• The Most Extreme Organisms: Extremophiles
• The Biggest Explosions in History
• What Is a Neutron Star