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What Is the Fourier Transform?

quantamagazine.org

121–130 of 214 posts

Re: What Is the Fourier Transform?

#121

> Fourier argued that the distribution of heat through the rod could be written as a sum of simple waves. How do you even begin to think of such things? Some people are wired differently.

I think he was very familiar with differential equations and series expansions and the "wild west" stage of calculus in general. The frontier of cool and interesting mathematics has moved a lot in 200 years.

Re: What Is the Fourier Transform?

#122

> Fourier argued that the distribution of heat through the rod could be written as a sum of simple waves. How do you even begin to think of such things? Some people are wired differently.

I think he was very familiar with differential equations and series expansions and the "wild west" stage of calculus in general. The frontier of cool and interesting mathematics has moved a lot in 200 years.

Also these stories are "storified" over time, the reality is always messier (same with startup founding stories etc..).

A common mistake I see in people reading mathematics (or even computer science papers) is to think the proof set out in the paper is the thought process that lead to the interesting insight. It is almost always an ex post facto formalisation.

Re: What Is the Fourier Transform?

#124
post #74

IANAMathematician, but I've tried to come up with a metaphor which I hope isn't too wrong: 1. You've start with a signal fluctuating going up and down, and it's on a strip of little LEDs labeled from -1 to +1. 2. You mount that strip to a motor, and spin it at a certain rate. After a while the afterimages make a blob-shape. 3. For each rotation rate, measure how much the shape appears off-center. In this way you can…

An interesting mechanical analogy! In this example, the "integration" is done by the eye and perhaps by the LEDs depending on their type. But it's more akin to the Gabor Transform than Fourier, as there is locality in time.

Re: What Is the Fourier Transform?

#125
post #33

If you like Fourier, you're going to love Laplace (or its discrete counterpart, the z transform). This took me down a very fascinating and intricate rabbit hole years ago, and is still one of my favorite hobbies. Application of Fourier, Laplace, and z transforms is (famously) useful in an incredibly wide variety of fields. I mostly use it for signal processing and analog electronics.

When I did EE, didn't have access to any kind of computer algebra system. Have 'fond' memories of taking Laplace transform transfer functions and converting to z-transform form. Expand and then re-group and factor. Used a lot of pencil, eraser and line printer fanfold paper for doing the very basic but very tedious algebra. Youngsters today don't know how lucky.. (ties onion to belt, etc., etc.)

Did you make sproingies from the tear-off side strips of the printer paper, though? That was the best bit. :P

Re: What Is the Fourier Transform?

#126
post #33

If you like Fourier, you're going to love Laplace (or its discrete counterpart, the z transform). This took me down a very fascinating and intricate rabbit hole years ago, and is still one of my favorite hobbies. Application of Fourier, Laplace, and z transforms is (famously) useful in an incredibly wide variety of fields. I mostly use it for signal processing and analog electronics.

When I did EE, didn't have access to any kind of computer algebra system. Have 'fond' memories of taking Laplace transform transfer functions and converting to z-transform form. Expand and then re-group and factor. Used a lot of pencil, eraser and line printer fanfold paper for doing the very basic but very tedious algebra. Youngsters today don't know how lucky.. (ties onion to belt, etc., etc.)

No worries, as a self proclaimed youngster I didn't manage to understand Fourier in 2 days and never bothered again. Also had no other prior knowledge to algebra so maybe that's why I struggled. Never perceived algebra as useful in anything programming related, will continue to do so as most problems are solvable without it. I'll let the degree havers do all that stuff.

Re: What Is the Fourier Transform?

#127
post #33

If you like Fourier, you're going to love Laplace (or its discrete counterpart, the z transform). This took me down a very fascinating and intricate rabbit hole years ago, and is still one of my favorite hobbies. Application of Fourier, Laplace, and z transforms is (famously) useful in an incredibly wide variety of fields. I mostly use it for signal processing and analog electronics.

The so-called "Z transform" for discrete sequences is really just a misnomer for the actual method of generating functions (and formal power-series/Laurent-series). You just write a discrete sequence as a power series in z^(-1).

Re: What Is the Fourier Transform?

#128
This video [1] from a visual effects channel (Captain Disillusion) has an excellent visual illustration of how the Fourier tranform works and how its used in visual effects in his video about blurring and unblurring ("ENHANCE!") images.

1. https://youtu.be/xDLxFGXuPEc?feature=shared

Re: What Is the Fourier Transform?

#130
post #125

Earlier quoted context omitted.

When I did EE, didn't have access to any kind of computer algebra system. Have 'fond' memories of taking Laplace transform transfer functions and converting to z-transform form. Expand and then re-group and factor. Used a lot of pencil, eraser and line printer fanfold paper for doing the very basic but very tedious algebra. Youngsters today don't know how lucky.. (ties onion to belt, etc., etc.)

Did you make sproingies from the tear-off side strips of the printer paper, though? That was the best bit. :P

Of course!
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