theSIGNAL SCIENCE
30 October 2026
"The most incomprehensible thing about the universe is that it is comprehensible."
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Science

Is the Universe a Pencil Balanced on Its Tip?

Mathematicians at UC Davis say the standard model of cosmic expansion is dangerously unstable, and dark energy may be unnecessary.

Picture a pencil standing perfectly on its sharpened tip. Is that a solution to the laws of physics? Strangely, yes. Every force cancels out.

Gravity pulls down, the table pushes up, and nothing tips the balance. Yet nobody has ever seen a pencil stay that way for long. That image sits at the heart of a provocative new paper in Proceedings of the Royal Society A. Its authors, at the University of California, Davis, argue that cosmology has been building on a pencil.

Blake Temple, a distinguished professor emeritus of mathematics and the study's corresponding author, says the Friedmann spacetimes, the foundation of conventional models of cosmic expansion, are unstable at both small and large scales. He calls the standard solution exceptionally unstable. Why should that matter? In physics, an unstable solution is usually considered unphysical.

Photo: Ryan Hutton / Unsplash
A pencil balanced on its tip: a perfect solution to the equations, yet impossible to sustain.
Discuss
  • Why might scientists treat an unstable mathematical solution as unlikely to describe anything we could actually observe in nature?
  • Temple compares the standard model to a balanced pencil. How well does this analogy explain instability to non-specialists?
  • Should a mathematical argument alone be enough to challenge a model, or must observations from telescopes decide the matter?
Science

Is Your Diet Soda Quietly Costing Memory?

One can of diet soda. That is roughly 191 milligrams of aspartame, the daily dose of the heaviest sweetener consumers among 12,772 Brazilian adults followed for eight years. Their memory and thinking skills declined faster than those of people who ate the least, especially among people with diabetes. Researchers at the University of São Paulo stress this is only an association, not proof.…
  • If sweeteners only correlate with memory decline, should people still avoid them?
∞
Unstable solutions in physics and science are considered not physical, and you'll never observe them in nature.
Blake Temple, distinguished professor emeritus of mathematics, UC Davis
Science

Unrolling a Power Plant in Orbit

Imagine carrying a rolled-up carpet outside a building moving at 28,000 kilometres per hour. That was the job for NASA's Anil Menon and Canada's Joshua Kutryk during their spacewalk. They installed a roll-out solar array on the International Space Station. Why unroll panels instead of unfolding them? Rolled arrays are lighter and fit into a cargo capsule more easily.…
  • If solar upgrades keep the aging station running, who decides when it retires?
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theSIGNAL IN THE LAB
1VOCABULARY
provocativeunstable
unphysicaltopplingseductive
cautiousassociation
2GRAMMAR FOCUS
Mixed conditionals — past condition with present result
Use 'if + past perfect' for an unreal past condition and 'would/could/might + base verb' for its result in the present. Example: 'If I had studied physics, I would understand this paper now.'
had · hadn't · would · wouldn't · could · been · might
  1. If the Friedmann solution been stable, cosmologists would not be questioning the foundations of their models today.
  2. If the pencil had been disturbed by even the faintest breath of air, it be lying on the table now rather than standing on its tip.
  3. If the Davis researchers studied the Einstein-Euler equations years ago, we might already have a clearer picture of cosmic expansion now.
  4. If Einstein's equations had always been understood this way, scientists need a mysterious dark energy to explain the acceleration today.
  5. If the Brazilian volunteers had avoided artificial sweeteners for eight years, their memory be declining so quickly now.
  6. If the researchers in São Paulo had not followed 12,772 adults, we have any evidence about the link between aspartame and memory today.
3COLLOCATIONS
Match the verb on the left with the noun phrase it best collocates with on the right.
  1. to challenge
  2. to reach
  3. to send
  4. to follow
  5. to install
4CRITICAL THINKING
Two of these stories rely on analogies, a pencil on its tip and a carpet being unrolled, to make complex ideas accessible, while the diet soda story relies on a single striking figure. Which of these techniques is most likely to leave readers with an accurate understanding, and which carries the greatest risk of oversimplification? Consider who benefits when science is packaged in a memorable image.
5CREATIVE · HEADLINES
Write a headline for the top story in each of the following styles. One line each, no explanation:
  • TABLOID NEWSPAPER
  • LUXURY MAGAZINE
  • ACTIVIST BLOG
6WRITING
Imagine you are a science journalist who has just interviewed one of the researchers mentioned in these stories. Write a short paragraph (80-100 words) describing the single question you would most want to ask them and the answer you hope to hear.
7DEGREES OF EXTREMITY
Complete each ladder from mild to strong.
  • unusual→→
  • doubtful→→
  • worrying→→
  • appealing→→
  • tricky→→
  • careful→→
8SPEAKING
  1. Which would you trust more: an elegant theory or messy observations? Why?
  2. Have you ever changed a daily habit because of one scientific study?
  3. Would you rather have a rolled-up solution or a folded one? Defend your choice.
  4. What everyday object makes the best metaphor for a hidden weakness?