• Pixel-art sticker of Chirpa, personifying Gravitational Waves, with the caption “Space Rings Like A Bell.”

IndexRelativity & CosmosSticker

Chirpa

Gravitational Waves Physics

\[h = \frac{\Delta L}{L}\]
$4.99 USD
$4.99 USD
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Meet Chirpa, who rings space like a bell: two black holes spiralling together shake spacetime, sending out waves whose frequency and strength rise to a chirp at merger. LIGO made the first direct detection on 14 September 2015, and the art draws the chirp and ringdown in code. Pixel-art kiss-cut sticker in 2, 3, 4 and 6 inches; equation, symbols and sources in the physics panel below.

Size
Surface

Flat $6 shipping worldwideMade to order, ships in 2–5 business days

Details

Size3″ × 3″

3″ × 3″ kiss-cut sticker.

Shipping

Flat $6 shipping on every order, worldwide, whatever's in it.

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

Meet Chirpa, a ripple in spacetime itself, sent out when two black holes spiral together.

General relativity predicts that accelerating masses send out gravitational waves, ripples in spacetime travelling at the speed of light. A passing wave stretches distances in one direction and squeezes them in the other. Its strength is measured by the strain h = ΔL/L: the fractional change in a length L.

As two black holes orbit closer, the waves grow stronger and higher in pitch, up to a final 'chirp' at merger. LIGO made the first direct detection on 14 September 2015 (GW150914), from black holes about 1.3 billion light-years away. The peak strain was about 10⁻²¹, so LIGO's 4 kilometre arms changed length by only a few thousandths of a proton's width.

Rainer Weiss, Barry Barish and Kip Thorne received the 2017 Nobel Prize in Physics for this detection. Gravitational-wave astronomy now detects mergers of black holes and neutron stars regularly.

Detection needs extremely sensitive interferometers, and ordinary objects make waves far too weak to measure.

Equations

\[h = \frac{\Delta L}{L}\]
SymbolMeaningUnit
\(h\) gravitational-wave strain —
\(\Delta L\) change in a length \(\mathrm{m}\)
\(L\) the length \(\mathrm{m}\)

Sources

  1. OpenStax Astronomy 2e — Gravitational Wave Astronomy
  2. OpenStax University Physics Vol. 1 — Einstein's Theory of Gravity
  3. NobelPrize.org — The Nobel Prize in Physics 2017
  4. Wikipedia — Gravitational wave

Field notes

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    Stephen Hawking: What Did He Predict, and What ...

    Hawking’s 1974 prediction that black holes radiate is central theoretical physics — and still unobserved in astrophysical black holes. Analogue experiments are not detections. The information paradox is open. Penrose’s...

  • Pixel-art illustration for this Pixelated Physics post: two pixel crowds: fermion characters each standing alone in their own boxes, and boson characters happily piling together into one box

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    What Is the Spin–Statistics Theorem?

    The spin–statistics theorem ties a particle’s spin to the symmetry of its quantum state. Integer spin → bosons (symmetric); half-integer spin → fermions (antisymmetric). Fierz (1939) and Pauli (1940) made...

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    How Does a Foucault Pendulum Prove Earth Rotates?

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