Tag: Tech

Exploring Airport Security: How Baggage Scanners Work | September 02 2025, 20:29

The day after tomorrow, I am flying to Amsterdam (and then to Turkey), and I remembered that I had an unanswered question to myself about how baggage scanners work at the airport. Of course, I knew that it was essentially computer tomography, X-rays and all that, but I wanted more details. And below is the response as to why they ask you to take out water, and why sometimes they do not.

It turns out that modern scanners can not only see the shape of objects but also determine what material they are made of. How does a regular scanner work? Dense materials (such as metal) absorb a lot of radiation and appear bright or opaque in images. Less dense materials absorb little radiation and appear dark. Hence laptops, for example, had to be taken out — not because the scanner couldn’t recognize them, but because their dense components (battery, boards) could be used to hide other prohibited items behind them. So, it has long been not just scanners, but computer tomography — in essence, the bag or suitcase is scanned from all sides, then a 3D image is created. It seems like everyone knows this.

But I mentioned that they understand the materials items are made from. How?

It turns out that the scanner uses dual-energy X-ray technology. It scans the object with two beams of rays of different energy levels (high and low). Since materials absorb radiation differently depending on the energy of the ray and their atomic composition, the system analyzes this difference. Based on the absorption ratio of the two beams, the effective atomic number Z — a key characteristic, a kind of “elemental fingerprint” of the substance, is calculated.

The problem is that this “fingerprint” of water (~7.4) and many explosives are almost identical. This is precisely why water was banned. Relying only on this parameter would mean receiving a huge number of false alarms.

Here is where computer tomography (CT) comes into play. The scanner creates an accurate three-dimensional (3D) model of the contents of the bag. From the 3D model, the system obtains the exact volume (V) of each object. Based on data on the absorption of X-rays, its mass (m) is calculated. Then it’s simple: ρ=m/V.

That is, the system does not make a decision based on one parameter. It plots each detected substance on a two-dimensional graph with axes “Z — density.” On this graph, water and explosives, having almost the same atomic number, occupy completely different positions due to different densities.

And that’s precisely why water can sometimes be carried through. Smart machines simply do not mark it as something significant, but still identify it as water. Then procedures follow. If the airport has updated the machines, but not the procedures, they will ask to dispose of the water. But also, not all machines are updated everywhere, and at the same airport, it depends on which line is open at the moment.

The cost of such a scanner is $300-400 thousand.

The scanners for people work differently. They use millimeter waves. They pass through clothing and reflect back from the skin. Water absorbs them significantly, so they penetrate only a couple of millimeters. The system registers the reflected signal and constructs a three-dimensional map of the body surface and objects under the clothing. But it does not show this — instead, it displays a simplified contour of a person and shows on it what ML found unusual. Therefore, by the way, many try to carry various items inside themselves, knowing that such a scanner absolutely cannot see it.

Echoes of Anthrax: The Amerithrax Investigation Unveiled | September 02 2025, 13:33

From the museum of the day before yesterday. Probably, some of you remember the notorious case in 2001: shortly after the 9/11 attacks, the USA experienced a series of bioterror attacks: someone mailed letters containing powder with anthrax spores (Bacillus anthracis). This led to the deaths of 5 people and infected 17, but it could have ended much worse for the entire planet. The investigation, known as “Amerithrax,” was conducted by the FBI in collaboration with other agencies and became one of the most complex in history.

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For those who might not know — the inhalational form of anthrax has a mortality rate of 85–90% without treatment. Symptoms appear after 6 days, by which time dozens will be infected. It can’t be destroyed — spores remain viable for decades in the soil. For example, on the Scottish island of Gruinard, they lingered for nearly 50 years after wartime testing. Only after 50 years had passed and after 280 tons of formaldehyde solution had been sprayed across all 196 hectares of the island, and the most contaminated topsoil around the dispersal site had been removed, did the island become relatively safe. Thus, anthrax could easily be more terrifying than a global nuclear war.

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So, returning to the subject. Initially, suspicions fell on various individuals, including Iraq or Al-Qaeda, but no evidence was found.

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The key breakthrough was scientific examination. Scientists analyzed the anthrax strain from the letters — it was the Ames strain used in American laboratories. Using microbial forensics (genetic analysis), they identified unique mutations in the spores that narrowed the source down to flask RMR-1029 in the USAMRIID (United States Army Medical Research Institute of Infectious Diseases) laboratory at Fort Detrick, Maryland.

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In other words, every living being has names and genealogy from birth, it’s just a matter of willingness to dig into the genealogy. Apparently, controlled substances have their own registry office, so to speak.

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Bruce Ivins, a microbiologist who worked there, was the custodian of this flask and had direct access (although more than 100 others did as well).

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Later, investigators gathered circumstantial evidence. Ivins had been working late at the lab just before the mailings in September and October 2001, which was inconsistent with his usual schedule. He could not convincingly explain these hours. Moreover, in early September 2001, he was vaccinated against anthrax, which seemed suspicious. The FBI also accused him of attempting to mislead the investigation: he allegedly provided false anthrax samples to divert suspicion and attempted to frame colleagues. In 2001, Ivins sent an email to colleagues offering the Ames strain for analysis, which might have been an attempt to cover his tracks.

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Behavioral signs also played a role. Ivins suffered from depression and suicidal thoughts, especially after another suspect (Steven Hatfill) was cleared in 2008. In June 2008, he was hospitalized in a psychiatric clinic, where during therapy, he made statements that the FBI interpreted as “denials without denial” — for example, that he “had no heart for killing” and did not remember participating in the attacks.

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By 2008, the investigation had narrowed down to Ivins. When he learned that charges were being prepared against him, on July 29, 2008, he took a lethal dose of Tylenol (acetaminophen). Formal charges were never brought. In 2010, the FBI officially closed the case, declaring Ivins the sole perpetrator.

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However, the conclusions remain controversial: the US National Academy of Sciences noted in 2011 that the genetic examination was not convincing enough for a definitive conclusion, and some microbiologists, victims’ families, and politicians demanded further investigation. As of now, no new discoveries have been made, and the case is considered closed.

Cracking Codes: Interactive Adventures at the Spy Museum | September 01 2025, 18:15

In the spy museum yesterday, one of the devastatingly informative terminals, where you had to crack the code, allowed you to hack into it too

The Ingenious Spy Device Gifted in Friendship: Unveiling The Thing | September 01 2025, 01:03

Today in the museum I saw The Thing in person – simply a brilliant espionage device. In 1945, a group of Soviet schoolchildren presented a large wooden Great Seal of the United States to the U.S. Ambassador in Moscow, Averell Harriman, as a “gesture of friendship”. The seal was beautifully hand-carved and hung in the ambassador’s office for a whole 7 years. And it leaked secrets!

No batteries involved! It was all very clever, especially for 1945.

Essentially, it was a passive radio relay or “parasitic resonator”. Inside the wooden seal was a small metal cylinder with a membrane and an antenna-rod.

Soviet operators directed a specific frequency radio wave (about 330 MHz) into the ambassador’s office.

Inside the device was a cavity resonator, tuned to the same frequency. It “responded” to the radio signal and began to retransmit it back.

On one side of the cylinder was a thin flexible membrane. It vibrated from the sound in the room (voices, footsteps).

The vibrations of the membrane altered the capacity and resonance parameters of the device, slightly shifting the reflected radio signal by frequency and phase. This was the modulation of speech onto the external signal.

Outside the building (like in a KGB car nearby), the retransmitted signal was received and the sound modulation was extracted – effectively capturing the overheard conversation.

Why was this almost impossible to detect? The device had no battery and emitted nothing by itself. It “came to life” only when irradiated with an external radio signal. In standard radio monitoring checks, it remained “dead”. Essentially, it was akin to an ancestor of the RFID tag – a passive device that operates only on external request.

But most interestingly, the inventor was Leon Theremin, the same person behind the musical instrument “thereminvox” (played with hands in the air).

His biography reads like a novel. In the early 1920s, Theremin went to the U.S., patented his thereminvox instrument, and collaborated with RCA; his New York studio was visited by Charlie Chaplin, Albert Einstein, Gershwin, and other notable personalities. It is written that he visited the USSR – Already in 1926, he demonstrated television at the Kremlin.

At that time, televisions with screens the size of a matchbox were being created, but his television had a huge screen (1.5 x 1.5 m) and a resolution of 100 lines. In 1927, the scientist demonstrated his installation to Soviet military leaders K.E. Voroshilov, I.V. Tukhachevsky, and S.M. Budyonny:

state minds watched in horror as Stalin walked through the Kremlin courtyard on the screen.

This sight so frightened them that the invention was immediately classified and quietly buried in the archives, and television was soon invented by the Americans.

Eventually, in 1938, he secretly returned to the USSR, but was soon arrested as a “non-returnee” and sent to the camps, but his talent was still used in the so-called “sharashka” – on projects together with Sergei Korolev, including the development of radio-controlled apparatuses and listening systems, including the aforementioned “Great Seal bug”.

Inside Apple AirPods: Design, Battery, and Antenna Secrets Revealed | August 23 2025, 01:52

Very interesting video about how Apple Airpods headphones work (in the comments). You can read about it, or you can just like this post and go check out the original video in the comments. It has pictures!

Battery. 6 hours of operation, but the capacity is only 2% of the iPhone battery capacity. “Dead zones” in the battery, which lead to reduced operating time, can occur due to sudden temperature changes or even just dropping the headphones on the floor. There is a very dense “layered cake” made from a couple dozen layers of anode-cathode. Batteries of fake AirPods or cheap analogs are much worse. Physics: Poor packaging means less active material and fewer lithium ions moving with each cycle => reduced energy density and increased internal resistance => more energy is lost as heat => battery wears out faster.

Antenna. It is located in the stem because the human head significantly dampens the signal. But there is little space in the stem. Metal strip antenna, size 2 mm by 10 microns(!). That’s thinner than human hair. At such size, it cannot maintain shape on its own. In other consumer electronics, antennas can be etched on the printed circuit board, but this limits them to two dimensions. For the AirPod stem, there isn’t enough space. Therefore, Apple uses a clever solution. They embedded the antenna in the surface of a molded plastic cylindrical part. There, clever conductive plastic is used, with added metal. A laser engraves the exact shape of the antenna in the form of small channels with a rough surface. Then, this groove is subjected to electroplating, first with copper, then covered with gold to protect against corrosion. As a result, a durable conductive track is formed, which matches the 3D geometry of the molded part, which would be impossible to create using traditional machining methods. The plastic not only structurally supports the antenna. Other components are attached to it, such as the cable wrapping around the stem to connect the antenna to the Bluetooth chip, the pressure sensor in the stem.

Microphone. In AirPods, not electret microphones, but MEMS: a microelectronic” version of the condenser type. Well, actually, this is not only Apple – any modern TWS headphones, unless they are the cheapest ones. That is to say, modern microphones are made using the same technology as types – photolithography, layer by layer, only in this case it’s a mechanical device, with calculated cavities and flexible layers. Separately interesting is how they make the cavities – they make holes through which etching solution penetrates inside and dissolves the sacrificial layers of silicon dioxide.

Because of such microscopic size, there are several microphones. But why more than one microphone is needed? At the bottom of the AirPods, you will see a small mesh that allows air to enter the second microphone. When you talk, your voice reaches both microphones, but not at the same time. With a difference of only a few millimeters, the chip can detect a delay of six microseconds between when your voice reaches each microphone. This is enough to determine where the sound is coming from and focus on it. Since it precisely knows the distance the microphones are from one another, the chip can compare each signal and amplify your voice during calls.

The third microphone is for noise cancellation. It is located right in front of the speaker, inside your ear.

The microphones consume about 130 mA, which would quickly drain the battery if they were always active. That’s why they are only turned on when you make a call or use noise cancellation. But AirPods are always waiting for a Siri request. How is this possible without constantly active microphones? Here’s a clever solution. Inside the part that is in your ear, there is a small sensor—an accelerometer. It’s the same type of sensor used in phones to determine orientation. But here it serves a different purpose. Instead of measuring orientation, it senses vibration. When you talk, your voice moves through your jawbone. And this vibration is detected by the accelerometer. This low-power consumption signal is enough to wake up the system and activate the microphones when it senses you want to activate Siri. Imagine that, eh?

The sound in AirPods is tuned not “by ear,” but based on a scientific model of the “ideal sound” (Harman curve), which describes the combination of frequencies most people find most pleasing. For this, there is a complicated system of calculated vents and meshes — to control the air flow, which prevents the occurrence of unpleasant “humming” or sharp sounds inside the ear canal. The larger the cells — more air passes through, smaller — less. Such is the mesh, visible as black things on the white earphone—I thought it was for beauty. No, this is exactly that mesh. But at the same time, some kind of moisture protection must be made, and here the mesh is porous. It is claimed that there is some sort of nano-coating that repels water.

Bluetooth. Why it is so immune to interference. Turns out, it uses frequency-hopping spread spectrum technology (Frequency Hopping). Bluetooth devices quickly switch between different channels many times a second and adapt accordingly.

Uncovering Hidden Hotel Fees: A New York City Experience | August 21 2025, 14:33

Lived in New York on Manhattan for a couple of days recently. The hotel cost 370 USD per day (see photo). Out of which 284 USD is the cost for one day, and the remaining 86 USD are taxes + a mysterious Facility Fee of 35 USD (per day).

From the hotel’s website: “What is a Facility Fee? It’s a hotel service charge! $35 plus tax per day per room provides our guests access to all amenities at Freehand NY, including high-speed WiFi, complimentary 3x filtered water, 24-hour fitness center access, SMART TV connection, priority access to programs and events, and rooftop priority — Broken Shaker!”

Needless to say, these 35 USD were of course not included in the reservation system. It’s not practical to visit every hotel’s website to check for fees before pressing the book button. And yes, the confirmation does state FACILITY FEE TO BE PAID ON ARRIVAL, you can always read and cancel. But for the future, it’s always better to check.

Scam Alert: The Bond Ring Energy Hoax Following My Oura Ring Purchase | August 20 2025, 20:01

I had just bought the Oura Ring 4 when Facebook started running scam ads about the first ring that saps your energy for its own survival. My precious!..

Exploring AI Search Agent: Revolutionizing Automated Browsing and Task Completion | August 19 2025, 01:21

In addition to the main product for search testing, I am developing an AI Search Agent in my leisure time. You only need to provide it with two pieces of information: a website to visit and a goal (described in a short paragraph). In other words, this thing is smart enough to function without any setup – just the site and the goal, and then it’s on its own.

How it works: This virtual agent generates search queries on its own, refines them based on the results obtained (for example, simplifies them), and analyzes how well they match the intended purpose. If suitable results are found, the agent can add items to the cart and place an order — if this is configured in the settings.

I’ve already written about this recently – today is just a slightly nicer demo. It will be even nicer as it is still being pulled from the middle of development, but you can already see how the page is analyzed, and there are initial results that can be used.

The agent can be used for several purposes. Firstly, it’s an excellent way to create ground truth—a set of queries with perfect results. These data can then be used for search testing without involving often slow and expensive large language models (LLM). Secondly, it helps to test the search functions before deploying them to users. Thirdly, the agent generates realistic usage data needed for training recommendation models that require authentic interactions.

The colorful rectangles in the video are the language of interaction of the agent with AI (or LLM). To understand where to click, the system annotates the page and sends a structured description of the page to AI—often along with a screenshot—so it can analyze everything and make a decision about the next action.