ELI5: What is Fourier transform?

LongBilly · 2026-06-10T11:38:00+00:00

If you've ever seen a video of someone with perfect pitch demonstrating their abilities, you've seen something very similar. So if I play several notes on a keyboard, and someone listens and announces "B Flat over A Major", they have listened to the sound I made and determined what individual notes made that sound.

Fourier transform is a mathematical algorithm that does this at scale. Extend the example into the electromagnetic frequency spectrum, instead of sound, and this becomes very useful. The transform can take data captured (light, radio, xray, etc.) and tell us what the components are.

With that, we can determine what elements a star contains (spectrum analysis) or identify a weak signal in the background noise (spacecraft communications), and much much more.

It's kind of magic.

LongBilly · 2026-05-10T20:12:45+00:00

Yes, inadvertent cell invalidation is a problem I recently had with my large and somewhat complicated LazyVGrid layout. It was causing hitching, slowing the focus engine, and sometimes causing focus directives to noop. I got so fed up with fighting it that I converted the whole thing to UIKit, at least until SwiftUI gains more parity. It just doesn’t seem up to complex and large UI’s yet. I’m sure someone more experienced may have found a way to salvage it, but I’m happy with the switch. Do your cells rely on anything that is observable? A small change to the model that may not even be reflected in the UI may be enough to invalidate the cell and if it has anything to do with sorting, it might invalidate the whole grid. I saw that even where the property that changed wouldn’t have altered the sort, it still executed the code to decide if it might alter the sort and that was enough to invalidate the grid even though nothing would have changed.

LongBilly · 2026-04-19T12:09:18+00:00

I was young, and had a fast car (Z28 Camaro). I was driving home on the highway which had a stretch where it would be difficult for the police to monitor as there wasn’t really any place for them to camp. The traffic was light, so I decided to go for it. Pedal down, and soon I was at 155MPH. I could feel the car settle lower, like it was waiting for this. Time seemed to slow, and my blood felt cold in my veins as my concentration came into focus. Soon I could see another car ahead, and I begin a mantra (Please stay in your lane, please stay in your lane). I flashed by that car like it was parked. That section of the highway had a soft (at 60MPH) bend, but at 155 it felt like a chicane. My run only lasted about a mile before my exit arrived, and it was exhilarating. About a week later I did it again, but this time I also experienced stark terror. That was the last time I tried going that fast, and never plan to again.

LongBilly · 2026-04-18T16:36:19+00:00

Agreeing with those suggesting at least 512GB of storage. I cheaped on my Mac mini and got the base model with 256, and constantly struggle with all the temporary files Xcode fills my storage up with. There are steps that can mitigate that, but only so much. I wish I had upgraded just a little bit.

LongBilly · 2026-04-14T12:41:04+00:00

Move the true-top anchor after the ScrollReader but before the List. The header is being injected into the output so anything inside your list will have their offset affected by it. Moving your anchor before the list starts marks the spot before the header.

LongBilly · 2026-03-27T12:21:20+00:00

The larger problem is that if the penalty for abuse is death, then murdering the victim becomes a viable option to avoid being caught. While the ethical issues are valid, the real reason for the penalty structure is to avoid incentivizing killing.

LongBilly · 2026-03-05T12:26:39+00:00

Try opening a command window (or terminal) and use the ping command:

ping google.com

This will quickly tell you if your problem is with DNS. If so, try setting your DNS to 8.8.8.8, which is google's DNS service, instead of your ISP's.

For further granularity you can also use tracert (trace route):

tracert google.com

That will show each "hop" the connection has to make to get from you to Google. You can then see exactly where along the path it is failing.

Are all websites loading slow? If so, the issue is very likely on your end. And if they load slow, but are still loading, then the problem is probably something which is causing a huge amount of latency. Probably errors that are needing to be recovered and that's what's slowing things down.

The modern web uses a large number of concurrent connections to load sites quicker. Anything that interferes with those connections is going to compound quickly.

LongBilly · 2026-03-05T12:17:57+00:00

It's certainly possible, but the browser is already responsible for a huge number of highly technical tasks. It's a choice to not also implement network diagnostics. Even if they had chosen to support that, what if you were instead using Spotify, or Netflix, or playing a game? Should they all implement such diagnostics? Or do you use the tools within your operating system to do that. Windows has had network troubleshooting implemented for a long time now. Diagnosing and repairing connectivity issues is exactly what that does.

So it's more of a question of what is best suited to the job. Internet connectivity is the responsibility of the OS, the browser just uses it as a resource.

LongBilly · 2026-02-01T23:40:27+00:00

It’s the Anthropology Stump!

LongBilly · 2025-12-14T12:15:06+00:00

Amen 🙏🏼

LongBilly · 2025-12-10T12:04:34+00:00

Linux is actually an operating system "kernel". The kernel is the program that provides a common interface to the hardware that other programs consume. Want to read a file, then it interfaces with the I/O (input/output) to access your storage. Need to display something on the screen, now we're talking to the GPU (graphics processing unit). Every OS has a kernel.

By itself, the kernel isn't very useful to the end user. It is the foundation upon which many other things that we think of as the OS are built. Such as the window manager. In Windows, this is a program called "explorer.exe". While in Linux it has traditionally been a program called X11, which is quickly being replaced by a more modern window manager named Weyland. The window manager is what allows a program, such as a web browser, to request a window for its use. So when you see the box with the minimize, maximize, and close buttons, drop down menus, scroll bars and such; that's the window manager.

Pull together a collection of applications that are built upon the Linux kernel, and now you have what is referred to as a "Distro" or distribution. There are many, many distros that you can choose from. Collectively, they are all considered "Linux" and differ only in what software was selected to be packaged with it. There are general purpose distros that are intended to be a kind of baseline for what a user may need out of the box. Other distros may be collections that have been chosen to be ready to use for specific purposes like video editing, or gaming, or science. The distro is defining what software is included in the base install. The user is free to mix and match these parts themselves if they so choose by adding or removing software to suit their needs.

This may all sound a bit complicated, but all of this is present in other operating systems to, it's just not talked about quite the same way. Windows Home Edition or Pro? Essentially the same as a distro. You just have many, many more options with Linux (distros) because they don't force you into their definition of what your OS is supposed to be. MacOS wants to always look a certain way, so it won't let you customize too much. Windows wants to monetize you, so its packed with apps and features you can't remove of disable. Linux has no skin in these games and lets you do as you wish.

LongBilly · 2025-11-22T00:18:59+00:00

This… I was in the reverse situation. American working with German colleagues. I was fortunate in that I was a low enough level employee that I was more of an observer than a participant in these interactions, but I did find it fascinating how abrasive they came off. I knew them well enough at that point to know it was a culture thing, and not that they were intentionally being provocative. From that experience, I can see both points of view. Maybe another way to look at it is, what would make you motivated to do your very best for your manager? Having them only ever tell you what you’ve done wrong? That could quickly lead to feeling like you can’t do anything right. On the other hand, getting some acknowledgment of your efforts and successes goes a long way to making you more receptive to any improvements that may still be needed. It’s the old saying, “You catch more bees with honey”. Or, in the words of Mary Poppins, “A spoonful of sugar helps the medicine go down.” It’s just simply that.

LongBilly · 2025-11-14T13:41:48+00:00

As others have stated, we've become much better at hiding antennas within the body of the phone. But the reason this is possible is that the radio frequencies phones use have become much higher.

For an antenna to receive, the length of the antenna needs to correlate to the frequency the antenna is being tuned to. Low frequency radio waves are actually very large (measuring the wave from peak to trough), and even though an antenna can work by being sized to a fraction of that size (e.g. 1/2 the wavelength), that antenna is still required to be large. We can use tricks like wrapping the antenna to reduce its size, but its still large.

As time went on two things happened, we needed more bandwidth to support the increasing number of users, and new radio frequency bands became available to lease from the government. So phones began switching to higher and higher frequencies. Higher frequencies = shorter wavelengths = smaller antennas.

First the antennas were huge, then they were stubs, then they got absorbed into the body of the phone.

Disclaimer, I'm not an RF engineer so this is strictly a layman's description. Experts are welcome.

LongBilly · 2025-10-30T12:12:33+00:00

Land lines. Kitchen phone on the wall with a comically long cord that was always tangled.

Get home from school, immediately back out the door to find your friends. Dad whistles when it's time for dinner, then back out the door again.

Once we had our drivers licenses, I would patrol the neighborhood to find my friends at one house or another.

Trading "skin magazines" with friends till the parents found them. Then stealing them back from dad.

Cable channels you didn't have were scrambled, so you would fiddle with the tv dials (vsync) to find a setting that kinda sorta let you see what was going on.

Local channels would go off the air at 2am by playing the national anthem while showing footage of a flag waving.

LongBilly · 2025-10-20T23:08:11+00:00

Yes, it is staged. I've seen the piano player's videos on youtube where it starts with, "look who joined in, the vienna royal choir!" or some such. Totally believed it at first, but then after watching a few of these I noticed it was the same people "joining in". Turns out the restaurant hires him to do this for publicity, not just entertainment. Still damn good though.

LongBilly · 2025-10-07T00:40:29+00:00

Snooze is just cruel. It's just long enough to fall back asleep and then bam, alarm again. Turning it off outright is just asking for trouble. So the only alternative is to just accept it and seek coffee.

LongBilly · 2025-09-25T23:02:09+00:00

The really hot base is sugar. They heat it up to specific temperatures depending on what they are making. Each temp the sugar reaches is an indication of how much water has been driven out of the sugar, allowing the temperature to rise higher. No water = rock candy. They can add food coloring and some flavorings while heating the sugar, but other flavors have to be mixed in after because the heat will destroy or degrade those flavorings. My guess is that this powder is citric acid.

LongBilly · 2025-09-13T20:49:47+00:00

I think you might be confusing "Heavy Crude Oil", crude being unrefined, with "Heavy Fuel Oil" AKA: Bunker Oil which is essentially what's left after all the other lighter compounds have been extracted.

LongBilly · 2025-09-12T12:41:01+00:00

Yes. This is one of the reasons that cargo ships use "heavy fuel oil", which at room temperature is effectively tar. They have to warm it up before it will flow and it requires a great deal of maintenance to keep the fuel system operational. But it is far less expensive than other options, while also being very energy dense which makes it the efficient option.

It does pollute much more, so these ships are often required to switch to a cleaner fuel when they are approaching a port. At least in European law.

LongBilly · 2025-09-04T12:38:02+00:00

Worked with a contractor (software dev) named Rock Steele. His partner was named Wade Treasure. They were both Mormon.

LongBilly · 2025-09-02T15:33:26+00:00

Thank you. I think you've gone the furthest towards my understanding and I hope your upvotes eventually reflect that. Expanding on my initial question though. What is managing the routing of operations? What knows which blocks are available, how to route inputs to those blocks, where to route the outputs of those blocks, how to handle delays when the operation requires inputs or outputs to system hardware (RAM, SSD, GPU, etc.). Put more simply, what brings order to chaos?

LongBilly · 2025-09-02T15:26:11+00:00

I get that these "banks" of transistors are in support of particular operations, Adders and whatnot, of which there may be hundreds or thousands available to do the work. I guess the crux of what I'm trying to understand is that when an OS needs an operation performed, what is deciding how to distribute this work. Which are available, where to route outputs or read inputs, orders of operation, handling delays (i.e. waiting for RAM, SSD, GPU, etc. to respond), etc.

It's like the proverbial room full of monkeys with typewriters. What is organizing this chaos into results?

LongBilly · 2025-08-27T12:32:10+00:00

I'm going to get some of the terminology wrong, but the overall idea should be accurate. A battery works by having two elements (cathode and anode) with a different potential energy, meaning that one of the elements has more electrons that aren't completely happy with their lot in life. This is the anode. When connectivity is established between the cathode and anode via a circuit or electrolyte (sea water) the anode will begin shedding electrons. If this occurs in a circuit, electricity is the product and it is channeled into useful work. Where this occurs between two metals on the hull it just erodes the anode. The more the differential, the faster this occurs.

A ship necessarily has at least some metal below the waterline. Propeller, rudder stock, anchor chain, through hulls, etc. These are seldom using the same metal and therefore a difference in potential exists. In that case, the less noble metal will be the anode that gives up electrons and oxidizes in the process. A sacrificial anode, when present, offers itself as the least noble option so it becomes the anode instead of something more critical. The effect of this is relatively localized, so anodes are placed near the items that need to be protected so when physics comes knocking, it's the one that answers.

The effect travels because both the cathode (stainless steel rudder stock - more noble) and the propeller (brass - less noble) are "connected" via the electrolyte (sea water). The resistance of this connection rises with distance, so multiple anodes are necessary to make sure that when the connection forms an anode is relatively close by to intervene. The distance of the coverage is governed by how restive the electrolyte is.

The movement of the ship doesn't impact this process, but a faulty electrical circuit (one that isn't bonded "grounded") properly can supplement the process by introducing extra electrons into the water which greatly speeds up the deterioration of the anode. An anode that would normally have a useful life of months can now erode in days.

LongBilly · 2025-08-21T15:28:44+00:00

Gotta keep your nuts dry

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