The Scale of the Universe

How Big Is Everything? From a Quark to the Cosmic Horizon

31 October 20265 min 40

Plays from YouTube (privacy-enhanced mode).

How far can you zoom out before we run out of things we know? We start at a quark, which as far as anyone can tell has no size at all. Then we climb through atoms, DNA, cells and you, out to the city, Earth, the Solar System, the Milky Way and the cosmic web.

Along the way there are a few things worth saying out loud. Nine-tenths of you, by weight, was made inside stars. The Sun is 109 Earths wide. And the farthest light we can see left just 380,000 years after the Big Bang, and we cannot see past it because the light from beyond has not reached us yet.

The last part of the video goes past our horizon, and it is clearly labelled as speculative. Nobody knows what is out there, so it is guesses from physicists, not facts. Scientists have even searched our sky for signs of a bubble universe. So far, nothing, but they looked.

Numbers to remember

  • 9/10

    of you, by weight, was made inside stars

    You are stardust.

  • 109

    Earths wide is the Sun

    Its light takes eight minutes to reach us.

  • 8 min

    for sunlight to reach Earth

  • ~1 light-day

    from home: how far Voyager 1 has got

    Launched in 1977, it is the farthest thing we have ever sent.

  • 4.2

    light-years to the next star

  • 100,000

    light-years across: the Milky Way

    It has a few hundred billion stars.

  • 380,000

    years after the Big Bang, the oldest light left

    We cannot see past it because that light has not reached us yet.

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Chapters

  1. 0:00 From rooftop to fingertip
  2. 0:20 Quarks, atoms, DNA and you
  3. 1:24 Rooftop, city, Earth
  4. 1:49 The Sun's family
  5. 2:36 Our stellar neighbours
  6. 3:05 The Milky Way
  7. 3:20 Galaxies, groups and superclusters
  8. 3:56 The cosmic web and the oldest light
  9. 4:27 Beyond our horizon? (speculative)
  10. 5:07 Let's go home
  11. 5:17 Stay curious: what's next

Keep exploring

Sources and credits

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