LK99

Why did a grey lump of ceramic fool physicists around the world for six weeks in the summer of 2023? Two ordinary effects, happening at the same time, produced both signatures of a superconductor — and neither one was superconductivity. LK-99 is a copper-doped lead apatite, roughly Pb9Cu(PO4)6O. On 22 July 2023, Sukbae Lee, Ji-Hoon Kim and colleagues posted two preprints on arXiv claiming it superconducted at up to 400 K — 127 °C, hotter than boiling water — at ordinary pressure. The claim collapsed within 25 days. But the physics of why it looked so convincing is worth understanding, because the same two traps will be waiting in the next claim. For the full timeline of what happened, see our earlier explainer: What Is LK-99? The Room-Temperature Superconductor Claim, Explained . The Two Tests Every Superconductor Must Pass A material earns the name only by passing both tests in the same sample, at the same temperature. The first test is zero resistance . Below its critical temper...

Have you ever wondered why the name of this blog keeps showing up in searches for a "room-temperature superconductor"? LK-99 is not a superconductor. It is a copper-doped lead compound that a Korean research team claimed in July 2023 could carry electricity with zero resistance at room temperature — and within 25 days, independent labs showed the claim was wrong. This is the full story, the numbers behind the verdict, and where the real search stands in 2026. What LK-99 Is — and What Was Claimed LK-99 is a copper-doped lead oxyapatite, roughly Pb9Cu(PO4)6O. The name comes from the initials of Sukbae Lee and Ji-Hoon Kim, the Korea University researchers who led the work, and 99 for 1999, the year they began studying the material. On 22 July 2023, the team posted two preprints on arXiv claiming LK-99 was "the first room-temperature ambient-pressure superconductor," with a critical temperature up to 400 K — that is 127 °C, hotter than boiling water — at ordinary p...

Have you ever stepped outside on a clear night, looked up, and wondered where to even begin? Tonight is the best night of the month to find out. The Moon is new, the sky is at its darkest, and with no telescope at all you can see about 2,000 stars, four planets, and a galaxy 2.5 million light-years away. This is a timed plan for your first night out: what to look at, in what order, and what each step actually adds. No equipment to buy first — just a clear evening, 20 minutes of patience, and a willingness to look up. What Your Eyes Can See Tonight — the Numbers From a dark site, your unaided eyes can pick out roughly 2,000 to 2,500 stars at once. Across the whole sky there are about 9,000 stars brighter than magnitude 6.5, the usual naked-eye limit. You only ever see half the sky at a time, and haze near the horizon hides more, so the practical count on any given night is around 2,000. That number collapses fast under city lights. The Bortle scale, published in Sky & Telescop...

Is recycling an old EV battery a money-maker or a money pit? It depends on which step you mean. The full recycling chain loses money in Europe today, while one step in the middle — turning packs into black mass — already turns a profit. Two studies published in 2026 put hard numbers on each side of that answer. One found that recycling a battery pack in Europe loses about €1.90 per kilogram. The other found that producing black mass, the powder that comes out of shredding, nets $4.39 to $5.53 per kilogram. Both numbers are correct. They measure different steps — and the gap between them is where the whole business stands or falls. Two numbers that look like a contradiction The €1.90 loss and the $5 profit describe different steps of the same chain. The loss comes from an interim study by HHL Leipzig Graduate School of Management, done for the EU-funded SAFELOOP project and published in May 2026. It followed an NMC811 pack through collection, hazardous-goods transport, disassembly,...

  Your watch says 72 beats per minute on the couch. Halfway through a hard run it says 118 — while a chest strap says 152. Or it shows nothing at all over the tattoo on your wrist. The short answer: at rest, your skin tone barely affects the reading. During hard exercise, the error on darker skin can grow to around 12 beats per minute — and tattoos can block the sensor's light altogether. The cause is physics, not a software bug. And the fix depends on which problem you actually have: a wrong number, a missing reading, or a blocked sensor. We covered the general accuracy problems — motion, fit, and cold hands — in our guide to how accurate your smartwatch really is . This one is about the two factors most guides gloss over: skin tone and tattoos. How the Sensor Works — and Why Green Light Is the Weak Point Every wrist sensor uses the same trick: shine light into your skin and watch how much comes back. The technique is called photoplethysmography, or PPG. A green LED flashes l...

Will a quantum computer replace your laptop — and should you worry about your passwords? The short answer: no, and not yet. A quantum computer is a specialist machine built for a narrow set of problems, and as of late 2026 the most important thing one has done is prove it can correct its own mistakes. Everything else — the record-breaking benchmarks, the encryption warnings, the 2029 roadmaps — needs that context before it means anything. What a Quantum Computer Actually Is A classical computer stores information as bits. A quantum computer stores it as qubits — and the difference is not speed, it is the kind of math the machine can do. Superposition: A qubit can hold a blend of 0 and 1 until it is measured. Ten qubits can describe 1,024 combinations at once — but measuring them still returns one ordinary answer. Entanglement: Qubits can be linked so their outcomes move together in ways classical bits cannot copy. Algorithms use these links to connect parts of a problem. Interferenc...

An electric vehicle battery is not hard to recycle because of one mystery chemical. It is hard to recycle because nearly everything about it works against taking it apart: the pack is glued and welded into a crash-proof shell, it arrives at the recycler still holding a dangerous charge, every manufacturer builds a different pack, the materials inside are blended into a mixture that resists clean separation, and the economics keep flipping as commodity prices move. Europe's battery rules now require lithium recovery to rise from 50% by 2027 to 80% by 2031 — a target that assumes all five problems get solved. Here is what each one actually involves. 1. The pack is built to survive a crash, not to be opened An EV battery pack is a sealed housing — a lower tray plus an upper cover — holding modules, a battery management system, cables, electrical connections, and a cooling system. Every one of those connections was designed for permanent service life, not for disassembly. Researche...