
But what is the Fourier Transform? A visual introduction.
3Blue1Brown12.6M viewsA visual introduction to the Fourier transform: winding a signal around a circle to find its frequencies.
785,248 videos · Physics, biology, chemistry, astronomy and the mathematics underneath them.

A visual introduction to the Fourier transform: winding a signal around a circle to find its frequencies.

Builds up what a neural network actually is — neurons as numbers, layers, weights and biases — using handwritten-digit recognition as the running example.

Matrices as linear transformations of space — the single idea that makes linear algebra click.

The first chapter of Essence of Calculus: discovering derivatives and integrals from the area of a circle.
11:15Works through the famously hard Putnam problem about the probability that a random tetrahedron in a sphere contains its centre, by first solving the 2D version.

Fourier series from the heat equation to drawing pictures with rotating circles.

What a vector really is, from the physics, computer science and mathematics perspectives.

Bayes' theorem as a geometric picture, with the classic 'Steve the librarian' example.
22:11Visualises the Riemann zeta function as a transformation of the complex plane and explains what analytic continuation actually means.

How a network 'learns': cost functions, the gradient, and stepping downhill in a space with thousands of dimensions.

Gödel's incompleteness, Turing's halting problem and the limits of mathematics.

Gilbert Strang's first lecture of MIT 18.06: the geometry of linear equations.
28:34Explains why light appears to slow down in glass and where the index of refraction comes from, building from driven oscillating charges.

Entropy, the arrow of time and why the Sun is a source of low entropy rather than just energy.

Eigenvectors and eigenvalues, seen as the directions a transformation only stretches.

An intuitive walkthrough of backpropagation — how each training example nudges every weight and bias.
10:04Matrix multiplication as composition of linear transformations, chapter 4 of Essence of Linear Algebra.
21:14Uses the 'medical test paradox' to motivate rewriting Bayes' rule in terms of odds and Bayes factors.
9:59Linear combinations, span and basis vectors, chapter 2 of Essence of Linear Algebra.

The determinant as the factor by which a transformation scales area and volume.

How imaginary numbers arose from solving cubic equations in Renaissance Italy.

MIT 8.04 Quantum Physics I, lecture 1: superposition, introduced through experiments with 'hardness' and 'color'.

Andrew Helwer's Microsoft Research talk teaching quantum computing to programmers with only linear algebra: qubits, gates, and the Deutsch oracle problem.

Lecture 1 of Joe Blitzstein's Harvard Statistics 110: probability and counting.
28:33Terence Tao and Grant Sanderson walk through how humans measured the size of the Earth, Moon, Sun and the distances to stars and galaxies, rung by rung.
23:01Convolution seen three ways: moving averages, polynomial multiplication and probability, ending with FFT-based fast convolution.
31:15What the central limit theorem actually says, its assumptions, and why sums of random variables tend to a bell curve.
34:41Builds the Laplace transform from exponentials and the s-plane, showing what poles mean and how it turns differential equations into algebra.
22:21Starts from a curious spiral pattern in plots of primes and uses it to explain residue classes, Euler's totient and Dirichlet's theorem on primes in arithmetic progressions.
1:23:01MIT 8.04, lecture 19: Identical particles, bosons, fermions and the Pauli principle.

Biochemist Nick Lane explains the Krebs cycle and its central role in metabolism, ageing and cancer.
1:20:12MIT 8.04, lecture 2: The experimental facts that force quantum mechanics: interference, the photoelectric effect and electron diffraction.
1:22:19MIT 8.04, lecture 6: Time evolution of states and stationary states.

Sean Carroll and Jennifer Ouellette discuss the black-hole firewall paradox and the clash between general relativity and quantum mechanics.
1:20:07MIT 8.04, lecture 18: The hydrogen atom and where the simple model falls short.
50:14MIT 18.06, lecture 9: Linear independence, basis and dimension.
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