• Monopola Dirac Monopole pixel-art physics T-shirt, black tee, front view

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Monopola

Dirac's Monopole Physics

\[e\,g = \frac{n\hbar c}{2} \qquad (\text{Gaussian units},\ n = 0, \pm1, \pm2, \dots)\]
$29.99 USD
$29.99 USD
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Size guide S–5XL · inches

Monopola carries a single magnetic pole, field lines bursting out like a sunburst. If she exists anywhere, every charge in the universe has to fall in line.

The Physics

Paul Dirac showed that if even one magnetic monopole exists, quantum mechanics forces all electric charge to come in whole-number steps. That would explain why charge is quantised. The monopole needs a singular line, the Dirac string, which cannot be seen if the condition holds.

e g = n ħ c / 2 (Gaussian units, n = 0, ±1, ±2, …)

  • e: electric charge
  • g: magnetic charge of the monopole
  • n: integer
  • ħ: reduced Planck constant
  • c: speed of light (all in Gaussian units, as printed)

Dirac published it in 1931. B. Cabrera (Stanford) recorded one candidate event on 14 Feb 1982 in 151 days of running; it was never repeated.

Honest caveat: No magnetic monopole has ever been confirmed. The monopole field shown on the back is hypothetical.

On the shirt

Front: Monopola, the pixel-art character, with the title. Back: the Dirac quantisation condition, the hypothetical monopole field, the Cabrera candidate and both papers. Printed on a unisex tee.

Shipping calculated at checkout by destinationMade to order, ships in 2–5 business days

Details

Size & fitS–5XL

Unisex heavy cotton (Gildan 5000), classic fit.

SizeWidthLengthSleeve
S182815.1
M202916.5
L223018
XL243119.5
2XL263221
3XL283322.4
4XL303423.7
5XL323525

參考尺度：M 碼寬 20 in（50.80 cm），約為 3.143 × 1034 個普朗克長度（lP = 1.616255 × 10−35 m）。用捲尺量更快。

Measurements in inches, ±1.5 in tolerance.

ShippingBy destination

Shipping calculated at checkout by destination. Printed to order for you.

Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

I carry a single magnetic pole. My field lines burst straight out, like a sunburst, with nowhere to close. Ordinary magnets always come with a north and a south; I would be the one that doesn't.

In 1931 Paul Dirac showed that if even one of me exists anywhere, quantum mechanics forces every electric charge in the universe to come in whole-number steps: e g = nħc/2 in Gaussian units. My field needs a singular line, the Dirac string, and that condition is exactly what makes the string invisible. It would explain why charge is quantised, though quantised charge does not prove I exist.

On 14 February 1982 Blas Cabrera's superconducting loop at Stanford recorded a single candidate event in 151 days of running. It was never repeated. No magnetic monopole has ever been confirmed, and everything on my back is hypothetical.

Equations

\[e\,g = \frac{n\hbar c}{2} \qquad (\text{Gaussian units},\ n = 0, \pm1, \pm2, \dots)\]
\[\mathbf{B} = \frac{g\,\hat{\mathbf{r}}}{r^{2}}, \qquad \nabla\cdot\mathbf{B} = 4\pi\rho_m \quad (\text{hypothetical})\]
SymbolMeaningUnit
\(e\) electric charge (Gaussian units, statC) \(\mathrm{statC}\)
\(g\) magnetic charge of the monopole (Gaussian units) \(\mathrm{statC}\)
\(n\) integer \(\mathrm{1}\)
\(\hbar\) reduced Planck constant (Gaussian: erg·s) \(\mathrm{erg·s}\)
\(c\) speed of light, 2.997 924 58 × 10¹⁰ cm/s (exact) \(\mathrm{cm/s}\)
\(\mathbf{B}\) magnetic field (Gaussian units) \(\mathrm{G}\)
\(r,\ \hat{\mathbf{r}}\) distance from the monopole and unit vector away from it \(\mathrm{cm}\)
\(\rho_m\) magnetic charge density (hypothetical) \(\mathrm{statC/cm³}\)

Sources

  1. Dirac (1931) Quantised Singularities in the Electromagnetic Field, Proc. R. Soc. Lond. A 133, 60
  2. Cabrera (1982) First Results from a Superconductive Detector for Moving Magnetic Monopoles, Phys. Rev. Lett. 48, 1378
  3. Jackson (1999) Classical Electrodynamics, 3rd ed., Wiley, §6.11

Field notes

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