Superlumen, the Phase-Velocity Courier Mug
Phase velocity can exceed c in dispersive media while the signal (front) velocity does not; no information travels faster than light.
The joke: Fast-talking speakers whose slides move fast but convey nothing. The slogan on the mug reads PHASE VELOCITY ABOVE c. NO INFORMATION SENT.
Source: L. Brillouin, Wave Propagation and Group Velocity (Academic Press, 1960).
Shipping calculated at checkout by destinationMade to order, ships in ~10 days
Details
Size & material11oz · 15oz
Black glossy ceramic mug with a C-handle. Lead- and BPA-free.
- 11oz: 0.33 l
- 15oz: 0.44 l
CareDishwasher & microwave safe
Dishwasher safe (top rack) or hand wash. Microwave safe.
ShippingBy destination
Shipping calculated at checkout by destination.
Made to order: about 10 days of production and handling before it ships.
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.
The physics
Equations
| Symbol | Meaning | Unit |
|---|---|---|
| \(v_p\) | phase velocity | \(\mathrm{m/s}\) |
| \(v_g\) | group velocity | \(\mathrm{m/s}\) |
| \(\omega\) | angular frequency | \(\mathrm{rad/s}\) |
| \(k\) | wavenumber | \(\mathrm{m^{-1}}\) |
| \(c\) | speed of light | \(\mathrm{m/s}\) |
| \(n\) | refractive index | — |
Sources
- L. Brillouin, Wave Propagation and Group Velocity (Academic Press, 1960)
Field notes
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