Twinne & Twynne
The Twin Paradox Physics
Size guide S–5XL · inches
Twinne stays home. Twynne flies out at 0.8c and back. They meet again 20 years later for one of them and 12 for the other.
The Physics
Each clock records the proper time along its own path through spacetime. The traveller's path is shorter in proper time, so at 0.8c a 20-year round trip on Earth lasts 12 years for the traveller. The gap comes from the geometry of the two paths, not from acceleration itself.
τ = ∫ √(1 − v²/c²) dt
- τ: proper time on the clock (s)
- v: clock speed (m/s)
- c: speed of light (m/s)
- t: Earth-frame time (s)
Einstein predicted the clock effect in 1905, and Paul Langevin recast it as a human traveller in 1911.
On the shirt
Front: Twinne & Twynne, the pixel-art character, with the title. Back: the proper-time integral, the 0.8c worked example, the geometry note and the 1905 and 1911 sources. 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-
Feynman Diagrams Explained: What the Little Squ...
A Feynman diagram is not a photo of particles bouncing around. Each little drawing stands for one term in a calculation of how likely a process is. Here is how...
Feynman Diagrams Explained: What the Little Squ...
A Feynman diagram is not a photo of particles bouncing around. Each little drawing stands for one term in a calculation of how likely a process is. Here is how...
-
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,...
