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In physics or engineering education, a Fermi problem, Fermi quiz, Fermi question, Fermi estimate, or order estimation is an estimation problem designed to teach dimensional analysis or approximation, and such a problem is usually a back-of-the-envelope calculation. The estimation technique is named after physicist Enrico Fermi as he was known for his ability to make good approximate calculations with little or no actual data. Fermi problems typically involve making justified guesses about quantities and their variance or lower and upper bounds.
== Historical background ==
An example is Enrico Fermi...
21 hours ago, by Emilio Pisanty
Chicago Pile-1 (CP-1) was the world's first nuclear reactor. On 2 December 1942, the first human-made self-sustaining nuclear chain reaction was initiated in CP-1, during an experiment led by Enrico Fermi. The secret development of the reactor was the first major technical achievement of the Manhattan Project, the Allied effort to create atomic bombs during World War II. Although the project's civilian and military leaders had misgivings about the possibility of a disastrous runaway reaction, they trusted Fermi's calculations and decided due to time pressure to carry out the experiment in a densely...
Pages 24-25 of my textbook, Optics by Hecht, says the following:
Using the above definitions we can write a number of equivalent expressions for the traveling harmonic wave:
$$\psi = A\sin k(x \mp vt)$$
$$\psi = A\sin 2 \pi \left(\dfrac{x}{\lambda} \mp \dfrac{t}{\tau} \right)$$
$$\psi =...
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When I saw that thing I did not understand how that shape is formed. To be ideal, take a vertical smooth plane. Now aim at wall with the thin water tube. Then the outer layer forms a parabolic shape with stagnation point as focus of it. I found it by tracing that shape.
How could you explain thi...
The Pauli effect is a term referring to the supposed tendency of technical equipment to encounter critical failure in the presence of certain people. The term was coined after mysterious anecdotal stories involving Austrian theoretical physicist Wolfgang Pauli, describing numerous instances in which demonstrations involving equipment suffered technical problems only when he was present.
The Pauli effect is not related with the Pauli exclusion principle, which is a bona fide physical phenomenon named after Pauli. However the Pauli effect was humorously tagged as a second Pauli exclusion principle...
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In general relativity, the hole argument is an apparent paradox that much troubled Albert Einstein while developing his famous field equations.
Some philosophers of physics take the argument to raise a problem for manifold substantialism, a doctrine that the manifold of events in spacetime is a "substance" which exists independently of the metric field defined on it or the matter within it. Other philosophers and physicists disagree with this interpretation, and view the argument as a confusion about gauge invariance and gauge fixing instead.
== Einstein's hole argument ==
In a usual field equation...
In mathematics, particularly in differential topology, there are two Whitney embedding theorems, named after Hassler Whitney:
The strong Whitney embedding theorem states that any smooth real m-dimensional manifold (required also to be Hausdorff and second-countable) can be smoothly embedded in the real 2m-space (R2m), if m > 0. This is the best linear bound on the smallest-dimensional Euclidean space that all m-dimensional manifolds embed in, as the real projective spaces of dimension m cannot be embedded into real (2m − 1)-space if m is a power of two (as can be seen from a characteristic class...
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