• Pixel-art sticker of Lightyra, personifying Light-Year, with the caption “A Year Of Travel.”

IndexRelativity & CosmosSticker

Lightyra

Light-Year Physics

\[1\,\text{ly} = c \times 1\,\text{yr}\]
$4.99 USD
$4.99 USD
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Meet Lightyra, a beam of light on a year-long trip who wants you to know a light-year is a distance, not a time: how far light travels in one Julian year, about 9.46 × 10¹⁵ m. 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 Lightyra, a beam of light on a year-long trip, who wants you to know a light-year measures distance.

Space is so big that metres stop being useful. Astronomers use the distance light travels in a vacuum in one Julian year of 365.25 days. Since the speed of light is fixed at exactly 299,792,458 m/s, the light-year is fixed too. The name sounds like a time, but it is a length.

The arithmetic: one year is 365.25 × 86,400 = 31,557,600 s. Multiply by c: 299,792,458 × 31,557,600 ≈ 9.46 × 10¹⁵ m, close to ten trillion kilometres.

The nearest star beyond the Sun, Proxima Centauri, is about 4.2 light-years away, so the light we see from it left about four years ago. Sunlight takes roughly eight minutes to reach us. Looking far away is always looking back in time.

Professional astronomers more often use the parsec, which is about 3.26 light-years. And a light-year is not a speed: light covers one light-year per year, every year.

Equations

\[1\,\text{ly} = c \times 1\,\text{yr}\]
SymbolMeaningUnit
\(\text{ly}\) light-year \(\mathrm{m}\)
\(c\) speed of light in vacuum \(\mathrm{m/s}\)
\(\text{yr}\) one Julian year (365.25 days) \(\mathrm{s}\)

Sources

  1. OpenStax Astronomy 2e — Fundamental Units of Distance
  2. NIST CODATA — speed of light in vacuum c
  3. Wikipedia — Light-year

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