• The Silence Beyond Horizon pixel-art physics T-shirt, black tee, front view

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The Silence Beyond

Cosmic Horizon / Observable Limit Physics

\[d_{p}(t_0) = a(t_0)\int_{0}^{t_0}\frac{c\,dt}{a(t)}\]
$29.99 USD
$29.99 USD
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Size guide S–5XL · inches

The edge of sight is farther away than the universe is old, in light-years. The universe is 13.8 billion years old, yet the particle horizon, the edge of the observable universe, lies about 46 billion light-years away, because space kept expanding while the light travelled. The Silence Beyond on a pixel-art unisex tee; equation, symbols and sources in the panel below.

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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

Para hacerse una idea: la talla M mide 20 in (50.80 cm) de ancho, unas 3.143 × 1034 longitudes de Planck (lP = 1.616255 × 10−35 m). Una cinta métrica es más rápida.

Measurements in inches, ±1.5 in tolerance.

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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.

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The physics

The observable universe ends where light emitted at the Big Bang has only just had time to reach us. Space kept expanding while that light was travelling, so the edge is now much farther away in light-years than the age of the universe.

The Silence Beyond walks the edge of everything we have seen so far. It is farther away than the universe is old, in light-years, and that is not a contradiction.

The universe is about 13.8 billion years old, so you might expect the farthest visible things to be 13.8 billion light-years away. They are not. While their light was travelling, space kept expanding, carrying the sources farther off. The formula on this page adds up the distance light could have covered since the beginning, each stretch scaled up by the growth that has happened since. In today's distances the answer is about 46 billion light-years. That boundary is the particle horizon, and the sphere inside it is the observable universe.

Three different edges get confused, and only this one is the edge of sight. The Hubble sphere, where galaxies recede at exactly the speed of light, is much closer, roughly 14 billion light-years. It is not a limit on vision: we already see galaxies that are receding faster than light today. The cosmological event horizon is a third surface, the limit on which events happening now can ever reach us.

Edwin Hubble did not find any of these horizons. In 1929 he showed that galaxies' redshifts grow with distance, the expansion that the horizons depend on. Wolfgang Rindler laid out the distinction between particle and event horizons in 1956.

Nothing beyond the particle horizon is invisible because it is dark. Its light simply has not had time to arrive. The horizon grows every year, and more of the universe comes into view, slowly, from behind the silence.

The Silence Beyond does not hide. They are only early.

Equations

\[d_{p}(t_0) = a(t_0)\int_{0}^{t_0}\frac{c\,dt}{a(t)}\]
SymbolMeaningUnit
\(d_p\) proper distance to the particle horizon \(\mathrm{m}\)
\(t_0\) age of the universe \(\mathrm{s}\)
\(a(t)\) scale factor \(\mathrm{1}\)
\(c\) speed of light \(\mathrm{m/s}\)

Sources

  1. Rindler (1956) Visual Horizons in World Models, MNRAS 116, 662
  2. Encyclopaedia Britannica — Observable universe
  3. PDG 2024 review — Big-Bang cosmology
  4. Hubble (1929) A relation between distance and radial velocity among extra-galactic nebulae, PNAS 15, 168
  5. Davis & Lineweaver (2004) Expanding Confusion: Common Misconceptions of Cosmological Horizons…, PASA 21, 97
  6. Planck Collaboration (2020) Planck 2018 results VI. Cosmological parameters, A&A 641, A6

Source Rindler, W. (1956). Visual Horizons in World Models. Monthly Notices of the Royal Astronomical Society 116, 662–677.doi.org/10.1093/mnras/116.6.662

Field notes

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