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EV Safety, Chinese Colliders, Quantum Space-time, and the Origin of Everything
This week’s science bits from SWTG
Marcus Gee-Lim
December 17, 2025
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Electric Cars Now Match Conventional Cars on Pedestrian Safety
Figure: Wadud, Nat Comm 16, 10824 (2025)
A researcher from the University of Leeds in the UK analysed ten years of British road accident data and compared pedestrian casualties per billion miles driven for different vehicle types. Before about 2019, pedestrian casualty rates for electric cars were higher than that of cars with combustion engines. But since around 2020 onwards, the two rates have been statistically indistinguishable, and injury severity is also similar. Hybrid vehicles, however, still show higher pedestrian casualty rates, likely due to heavy use in urban taxi fleets, though injuries tend to be less severe. Overall, the study finds no evidence that the recent large-scale adoption of electric cars has made roads less safe for pedestrians. Paper here. Press release here.
This week’s episode of Science News is about … everything. The universe is full of a seemingly unending number of different things, from subatomic particles to plants and animals to gas giants and supernovae. But where did all of this stuff (for lack of a better word) come from? Let’s take a look.
China Does Not Pursue Plans for Mega Particle Collider
Design plan of the Chinese mega-collider. Credits: IHEP
Particle physicists in China and Europe have similar plans for a next larger particle collider: A circular collider with a circumference of about 100 km that will reach an estimated 100 TeV of collision energy, about 6 times higher than that of the Large Hadron Collider. Chinese researchers handed in design plans for their Circular Electron Positron Collider (CEPC) to be considered for the upcoming 5 year plan, from 2026 to 2030. However, the Chinese government did not select the proposal.
The Chinese government instead favored the Super Tau-Charm Facility, a relatively small (ca 800 m circumference), high-luminosity circular collider. This collider would operate at comparably small collision energies of 2-7 GeV, and is optimized to produce tau particles and charm quarks. It has not yet been approved, but according to Wang Yifang, it is shortlisted.
The CEPC collaboration plans to reapply in 2030. The CERN administration sees the development in a positive light, because it means that Chinese researchers will support CERN’s plans for their Future Circular Collider, whose funding has not yet been secured.
Personally, I think the Chinese government made a smart decision to not waste money on this mega collider. They announced in October that their next 5 year plan for science and technology will focus on research areas with practical applications, such as AI, quantum technology, brain-computer interfaces, biotechnology, and fusion energy.
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Researchers Discover New Link Between Gravity and Quantum Physics
Illustration for the change in particle trajectories caused by quantum fluctuations on cosmological scales. Credit: Oliver Diekmann, TU Wien
A group of physicists from TU Wien have found a connection between the quantum behaviour of space and time and the motion of stars in galaxies that no one has thought about before. Common estimates say that, while quantum fluctuation of space and time do affect the motion of particles, these effects are ridiculously tiny and impossible to measure.
The authors of the new paper point out that when calculating particle trajectories, one needs to take into account that the equations are non-linear in the key quantity that describes space-time (the metric tensor). This means that one has to first calculate the quantum effects and then average over them, and not the other way round (as one could do in a linear theory).
With the so-corrected procedure, they find that in the solar system, the quantum corrections are still ridiculously tiny. But, they say, on scales of galaxies and beyond, there is a surprise. It's that the cosmological constant contributes that can become large. The first author, Ben Koch, says in the press release: “On very large cosmological scales – precisely where major puzzles of general relativity remain unsolved – there is a clear difference between the particle trajectories predicted by the [quantized new equations] and those obtained from unquantized general relativity.”
I am skeptical the difference is as “clear” as the authors seem to think, but it is an interesting connection between quantum physics and cosmology that could prove fruitful. Paper here. Press release here.
