Twissa & Hanbra
Hanbury Brown–Twiss Effect Physics
Size guide S–5XL · inches
Twissa and Hanbra stand back to back at their searchlight dishes under Sirius. Their photons like to bunch.
The Physics
Correlating the intensity flickers at two separate detectors measures the coherence of light, and from it the angular size of a star. For thermal light the correlation at zero delay is 2 (bunching), for ideal laser light it is 1, and for single-photon sources it is below 1 (antibunching, a purely quantum effect).
g⁽²⁾(τ) = ⟨I(t) I(t+τ)⟩ / ⟨I⟩²
- g⁽²⁾(τ): normalised intensity correlation (dimensionless)
- I: light intensity (W/m²)
- t: time (s)
- τ: delay between detectors (s)
R. Hanbury Brown and R. Q. Twiss measured Sirius with two searchlight mirrors (Nature, 1956): angular diameter 0.0068″ ± 0.0005″.
Honest caveat: The value 2 is the ideal for a single polarisation of thermal light; it is not what their 1956 electronics measured.
On the shirt
Front: Twissa & Hanbra, the pixel-art character, with the title. Back: the g⁽²⁾ definition, thermal, laser and single-photon values, the Sirius result and the 1956 paper. 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.
| Size | Width | Length | Sleeve |
|---|---|---|---|
| S | 18 | 28 | 15.1 |
| M | 20 | 29 | 16.5 |
| L | 22 | 30 | 18 |
| XL | 24 | 31 | 19.5 |
| 2XL | 26 | 32 | 21 |
| 3XL | 28 | 33 | 22.4 |
| 4XL | 30 | 34 | 23.7 |
| 5XL | 32 | 35 | 25 |
For scale: size M is 20 in (50.80 cm) wide, about 3.143 × 1034 Planck lengths (lP = 1.616255 × 10−35 m). A tape measure is quicker.
Measurements in inches, ±1.5 in tolerance.
ShippingBy destination
Shipping calculated at checkout by destination. Printed to order for you.
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.
Field notes
View all-
Marie Curie’s Discoveries: Radioactivity, Polon...
Marie Curie did not discover radioactivity. Henri Becquerel found the rays in 1896. What she did was turn a strange effect into a science: she showed the rays were an...
Marie Curie’s Discoveries: Radioactivity, Polon...
Marie Curie did not discover radioactivity. Henri Becquerel found the rays in 1896. What she did was turn a strange effect into a science: she showed the rays were an...
-
What Are Neutrinos? The Ghost Particles That Pa...
Neutrinos are the most elusive particles we know of. Thousands of billions stream through your body every second without touching you. Pauli invented them in 1930 to save energy conservation,...
What Are Neutrinos? The Ghost Particles That Pa...
Neutrinos are the most elusive particles we know of. Thousands of billions stream through your body every second without touching you. Pauli invented them in 1930 to save energy conservation,...
-
Hideki Yukawa and the Meson: How a Force’s Rang...
In 1934 Hideki Yukawa asked why the force that holds the nucleus together reaches only about the width of a proton. His answer: a force carried by a particle with...
Hideki Yukawa and the Meson: How a Force’s Rang...
In 1934 Hideki Yukawa asked why the force that holds the nucleus together reaches only about the width of a proton. His answer: a force carried by a particle with...
