Thorium monoxide
In The Demon Job he's the Professor: a two-atom molecule fired down a vacuum pipe to test whether the electron cares which way time runs.
Thorium monoxide plays The Professor in The Demon Job
A detective made of water, a client who was the first molecule there ever was, and a demon who says he can sort for nothing.
Watch from 14:09, where The Professor first appears → or from the start
Booking photographs
The suspect, from its real atomic coordinates. Drag to turn it. Height chart in nanometers, ruled every 0.02 nm. Thorium drawn dark, oxygen light. A marble is about fifty million times wider.
Rap sheet
- Testifying: its slow, cold beam showed the electron has no measurable electric dipole moment.
- Amplifying: gives its electron an internal field of about 80 billion volts per centimeter.
- Keeping a low magnetic profile: stray fields barely move it.
- Showing up in crowds: about 100 billion to a puff, in one quantum state.
- Being outdone, about twofold, by a hafnium fluoride ion in a trap.
- Answers to
- ThO. Formally, thorium(II) oxide.
- Height
- About 0.5 nm, padding and all. Nuclei 0.184 nm apart.
- Weight
- 0.41 zeptograms
- Known for
- Showing the electron is round, to within 1.1×10−29 e·cm.
- Habits
- Gives its electron about 80 billion volts per centimeter.
- Marks
- A tiny magnetic moment. Stray fields barely move it.
- Rival
- Hafnium fluoride ion, which beat its bound about twofold.
- Last seen
- Between electric-field plates in Cambridge, Massachusetts, at about 200 m/s.
- M.O.
- A laser blasts a ceramic of thorium dioxide inside a cell of frigid gas, fifty times a second; the molecules stream out at about 200 m/s between electric-field plates, where lasers read how their electrons' spins precess.
- Associates
- the electron, the real witness; the hafnium fluoride ion, the rival; the few particle decays where time-reversal violation has been seen
- Priors
- First bound from ThO in 2014 (below 8.7 × 10⁻²⁹ e·cm); improved in 2018 to 1.1 × 10⁻²⁹.
of them per puff of the beam, in one quantum state, give or take.
You’ve never seen one.
“The electron's round. The arrow isn't in the laws; it's in how things started.” — Keltar, on the case
Case notes: what the witness can and can't say
Loschmidt's objection (1876): reverse every velocity and the molecules retrace their paths, so entropy falls. Boltzmann answered with statistics, and that answer needs a low-entropy past. An electron electric dipole moment would be odd under time reversal (and parity). ACME's ThO beam found none, to |d_e| < 1.1 × 10⁻²⁹ e·cm at 90% confidence (2018). The molecule's internal field, about 78 GV/cm, is some billion times the field applied in the lab. A trapped HfF⁺ experiment has since set 4.1 × 10⁻³⁰. The Standard Model's own prediction is about 10⁻³⁸.
Time-reversal violation does exist, in some weak decays (first reported in kaons in 1998, and seen in B mesons in 2012, with large asymmetries). It is not what makes eggs unscramble one way only: the evolution stays information-preserving. The mainstream account puts the thermodynamic arrow in the universe's low-entropy start, which David Albert named the Past Hypothesis.
Sources
- ACME Collaboration 2018, Nature 562:355-360, doi:10.1038/s41586-018-0599-8
- Roussy T. S. et al. 2023, Science 381:46-50
- Safronova M. S. et al. 2018, Rev. Mod. Phys. 90:025008
- Carroll S. M. 2008, arXiv:0811.3772; Callender C., 'Thermodynamic Asymmetry in Time', Stanford Encyclopedia of Philosophy
- Loschmidt J. 1876, Sitzungsber. Akad. Wiss. Wien 73(II):128
The interrogation room
Keltar is an AI character. He sticks to the file; the conversation is saved and Kent, the CEO, can read it.
The poster on the street
This is the photocopied wanted poster for Thorium monoxide, No. 123 of the exotic forty. They were made for noticeboards around Boston, Cambridge and the rest of the east coast.
Found one? Scan its QR code with your phone. If you're a signed-in player, the sighting goes on your record with +1 XP.
Not a player yet? Join the Epic Quest: the real role-playing game of Molecular Reality, a nanopore lab, with the CEO as gamemaster.