Next on the walk · 6
The dark is what is.
Almost all of the universe is dark, and that is where the discoveries are.
Two rulers.
Measure the universe’s expansion two careful ways and you get two answers that do not touch. The honest thing is to hold them both.
5 · The walk · the universe
The universe is growing. Galaxies are carried apart as space stretches, and the farther away a galaxy is, the faster it recedes. How fast is set by one number, the expansion rate, and astronomers have two great rulers for reading it.
One ruler starts from the oldest light in the sky, released when the universe was about 380,000 years old, and works forward to today. The Planck satellite’s map of that light gives 67.4 kilometres per second for every 3.3 million light-years of distance, give or take half a unit. The other ruler climbs outward, rung by rung, from stars in our own galaxy to exploding stars in distant ones. Its best reading is 73.0, give or take one.
The two ranges do not touch. Both teams have checked and rechecked for years, and the gap has held. Astronomers call it the Hubble tension. A third team, reading the brightest red giant stars, lands between them. The question is open, and it is one of the most exciting in science: either something subtle is hiding in a ruler, or the universe has something new to teach us.
Three readings of one number
The universe’s expansion rate, in kilometres per second for every 3.3 million light-years
Hold two rulers
When two careful readings disagree, the tempting move is to split the difference and report one tidy number. Astronomers don’t, and neither does our index. Hand our index two rulers and it holds two rulers. Disagreement shows in the colour: a concept softens as the looks at it pull apart, so you see the open question instead of an average that hides it.
Piling up more readings of the same kind doesn’t settle it either. How vivid a concept is depends on how far its looks spread, not on how many there are: on average, ten independent looks of the same kind read no more agreed than two. What moves it is a different kind of look: a new ruler, a new mind.
That is how science gets to the truth: it keeps the disagreement in plain sight until the evidence settles it. Your organisation can work the same way.
For your organisation: when your experts disagree, you see it plainly before anyone averages it away, and the question stays open until the evidence settles it.
Where we’re heading
Open questions kept in plain sight, so the next good measurement lands exactly where it matters.
See the Observer’s IndexWhat stands under this piece
Proved: a theorem in our own maths. Built in: how the index works. From the field: something observed, by scientists or in our own index.
- From the field
- Two careful measurements of the universe’s expansion rate, 67.4 and 73.0, whose ranges do not touch.
- Built in
- When looks disagree, the concept softens, so the disagreement shows.
- Built in
- No reading adds up to one score.
- Proved
- On average, more independent looks of the same kind don’t make a concept more vivid: it reads their spread, not their number.
Read on
Its partner across the centre · 3
Vivid means agreed.
The purest colours are light whose waves keep in step.