IndexGolven, chaos & materieTee
Celtrix
The Rattleback Physics
Size guide S–5XL · inches
Spin Celtrix the wrong way and she wobbles, rattles, and spins back the other way.
The Physics
A rattleback is a boat-shaped top whose mass axes are slightly twisted relative to its curved base (δ ≠ 0). Friction at the contact point couples wobbling to spinning, so in the unfavoured direction spin turns into rocking and then back into spin the other way. Angular momentum is not violated: the friction force at the contact exerts the torque.
dL/dt = r_c × F_c
- L: angular momentum (kg·m²/s)
- t: time (s)
- r_c: position of the contact point from the centre of mass (m)
- F_c: contact force from the table (N)
- δ: misalignment angle (rad)
G. T. Walker analysed it in 1896.
Honest caveat: Some celts reverse more than once; not every rattleback reverses in only one direction.
On the shirt
Front: Celtrix, the pixel-art character, with the title. Back: the torque equation, the misalignment angle, the friction explanation and Walker's 1896 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 |
Ter vergelijking: maat M is 20 in (50.80 cm) breed, ongeveer 3.143 × 1034 Plancklengtes (lP = 1.616255 × 10−35 m). Een meetlint is sneller.
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
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