• Terrellion – Terrell–Penrose physics T-shirt
  • Terrellion – Terrell–Penrose physics T-shirt
  • Terrellion – Terrell–Penrose physics T-shirt
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TerrellionTerrell–Penrose Rotation

Terrellion – Terrell–Penrose Rotation Physics T-Shirt

$29.99 USD
$29.99 USD
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Color
White · Black
Size
S–5XL
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Would a fast-moving cube look squashed? Its length really is contracted, but light from its far side leaves earlier to reach your eye at the same moment. The result looks rotated, so you glimpse its back face. James Terrell and Roger Penrose showed this independently in 1959. Terrellion charges past at 0.9c. Pixel-art unisex tee; equation, symbols and sources in the physics panel below.

Color
Size

Size guideS–5XL · inches

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

Measurements in inches, ±1.5 in tolerance.

ShippingFree US

Free US shipping · $10 flat shipping outside the US. 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

Measure a cube flying past at near light speed and it is shorter along its motion: the Lorentz contraction. Photograph it and you see something else.

Light from the far side set off earlier than light from the near side, so the picture mixes moments. James Terrell and Roger Penrose showed in 1959 that the result looks rotated, not squashed; a sphere still has a circular outline.

Terrellion is not crushed. He is turned. Contracted? No. Rotated.

Equations

\[\cos\theta' = \frac{\cos\theta + \beta}{1 + \beta\cos\theta}\]
\[L = \frac{L_0}{\gamma},\qquad \gamma = \frac{1}{\sqrt{1-\beta^{2}}},\quad \beta = \frac{v}{c}\]
SymbolMeaningUnit
\(\theta, \theta'\) direction of a light ray in the object's frame and in the observer's frame \(\mathrm{rad}\)
\(\beta\) speed as a fraction of the speed of light \(\mathrm{–}\)
\(L_0, L\) rest length and Lorentz-contracted length \(\mathrm{m}\)
\(\gamma\) Lorentz factor \(\mathrm{–}\)
\(v\) speed of the object \(\mathrm{m/s}\)

Sources

  1. Terrell (1959) Invisibility of the Lorentz Contraction, Phys. Rev. 116, 1041
  2. Penrose (1959) The apparent shape of a relativistically moving sphere, Proc. Camb. Phil. Soc. 55, 137
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