LK99

  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...

Your EV battery will probably outlast your ownership of the car. Geotab's 2026 analysis of 22,700 electric vehicles across 21 models found that batteries lose about 2.3% of their capacity per year — which projects to 81.6% of original capacity after eight years, and roughly 13 years before a pack reaches the 70% threshold most warranties use. The failure people fear, a battery that suddenly dies, is rare. What actually happens is slow, predictable fade. What 22,700 real cars show Geotab has tracked EV battery health using vehicle telematics since 2020, and each round of the study has grown larger. The headline numbers, from Geotab's own battery-health report : Average loss: 2.3% of capacity per year. At that rate the average pack holds 81.6% of its original capacity after eight years (Geotab's own projection), and reaches the 70% warranty threshold after about 13 years. The rate got better, then rose again. Geotab's 2020 study found 2.3% a year; by 2023, an 11...

Microplastics have been detected in human blood, lungs, placentas, and brains. Yet no study has proven that they cause a specific disease in people. The strongest human evidence to date is a single observational study that found plastic in artery plaque linked to roughly 4.5 times the risk of heart attack, stroke, or death over about three years — an association, not proof of cause. Everything else is detection plus a newly proposed mechanism. Here is what each landmark finding actually measured, in numbers. The heart finding: plastic in artery plaque, risk up 4.5-fold In March 2024, researchers in Italy reported in the New England Journal of Medicine that microplastics and nanoplastics were present in the fatty plaque surgically removed from patients' carotid arteries. Of 304 patients enrolled, 257 completed an average of about 34 months of follow-up. Polyethylene was detected in the plaque of 58.4 percent of them (150 patients, at a mean level of 21.7 micrograms per milligra...

Your smartwatch is a good heart-rate monitor, a passable sleep tracker, and a poor calorie estimator — and it does one medical screening job surprisingly well That is the short version of what validation studies say about the numbers on your wrist. The longer version matters more, because every reading comes with fine print: how it was measured, under what conditions, and how much confidence it deserves. Researchers have now put the big brands through lab-grade testing — against chest-strap ECGs, hospital polysomnography, and metabolic carts — and the pattern is consistent. Here is the sensor-by-sensor breakdown. Heart rate: the measurement wearables do best Most watches read your pulse with photoplethysmography (PPG): green LEDs shine into your skin, and a sensor tracks how the reflected light changes as blood pulses through. It is an indirect measurement, which is why conditions matter so much. In a Stanford study of 60 volunteers wearing seven devices, six of the seven measured...

When your electric car's battery can no longer push the car down the road, it does not go to a landfill. It enters a defined chain: back through the automaker's service network, then either into a second life as stationary energy storage or straight into a recycling plant, where modern processes claim to recover more than 95 percent of critical minerals like lithium, nickel, cobalt and copper. And the rules around that chain are tightening — in September 2026 the European Commission confirmed that its battery recycling targets remain in force, with the first mandatory compliance reporting due in 2027. If you own an EV or are considering one, the short version is this: you will almost certainly never have to find a recycler yourself. The industry is building the return journey into the car's life — and the October 2026 expansion of the Rivian–Redwood Materials partnership shows exactly how that journey works in practice. Your battery dies slowly, not all at once An EV ...