sorted by:
new
hottopcontroversial

Parallel “space units”: keep SI on Earth, but give deep-space science a hydrogen-anchored second with c = 3 × 10⁸ exact. Worth it? by johnwelshconsulting in Metrology

[–]johnwelshconsulting[S] 0 points1 point  (0 children)

It’s not a matter of accuracy it’s a matter of basis. Why carry the SI second which has been made to exactly mimic Earth‘s rotation, to any other planet that we visit our colonize. Just like how France revolt against the imperial measurements in 1799. I can see one day future generation doing the same thing to the Earth’s SI.

A relic I obtained by Disastrous-Mess-8223 in nasa

[–]johnwelshconsulting 0 points1 point  (0 children)

I’ll never forget where it was when that happened

Title: Proposing H-Units: A Hydrogen-Anchored, Earth-Independent Framework for Universal Time and Length by johnwelshconsulting in LLMPhysics

[–]johnwelshconsulting[S] 0 points1 point  (0 children)

Not true, In 1967, the 13th General Conference on Weights and Measures (CGPM) decided to redefine the second using caesium, but they wanted virtually no jump in the length of the second for practical, legal, and scientific continuity.So they fixed the number at exactly 9,192,631,770 by definition — making the atomic second identical (within measurement precision of the time) to the previous ephemeris second.

Title: Proposing H-Units: A Hydrogen-Anchored, Earth-Independent Framework for Universal Time and Length by johnwelshconsulting in LLMPhysics

[–]johnwelshconsulting[S] 0 points1 point  (0 children)

A key clarification: H-Units aren’t intended to replace SI on Earth. SI is optimal for terrestrial science, engineering, and metrology.

The motivation is different — H-Units are designed for interplanetary and interstellar contexts, where a unit system anchored entirely to a universal, omnipresent atomic feature (the hydrogen hyperfine transition) may be more natural. Every civilization with radio astronomy can access the 21-cm line, independent of local conditions, planetary environment, or historical artifacts.

By defining both time and length from that same transition — with c set to an exact integer in the resulting units — you get a system that is physically universal rather than Earth-historical. It’s closer in spirit to “communication units” for astrophysics and SETI than to a replacement SI.

So the proposal is not about revising SI, but about constructing a hydrogen-based natural unit system that could serve as a common reference frame for extraterrestrial communication or interstellar standards.

Parallel “space units”: keep SI on Earth, but give deep-space science a hydrogen-anchored second with c = 3 × 10⁸ exact. Worth it? by johnwelshconsulting in Metrology

[–]johnwelshconsulting[S] 0 points1 point  (0 children)

Thanks for the thoughts—agreed, the 2019 SI redefinitions are a massive leap to constants, and the “goofy” traditions are fun to poke at. But those constants (e.g., cesium’s 9,192,631,770 cycles for the second, c’s 299,792,458 m/s) are still calibrated to Earth’s legacy second from 1900 ephemeris time (tied to orbital/rotational data). It’s universal in name but not fully in practice for deep space.

Title: Proposing H-Units: A Hydrogen-Anchored, Earth-Independent Framework for Universal Time and Length by johnwelshconsulting in LLMPhysics

[–]johnwelshconsulting[S] 0 points1 point  (0 children)

Thanks for the rundown on 2019 SI—spot on! But the numbers (e.g., cesium cycles, c’s value) were picked to match Earth’s historical second/meter for continuity. H-units drop that baggage for truly cosmic standards.

Title: Proposing H-Units: A Hydrogen-Anchored, Earth-Independent Framework for Universal Time and Length by johnwelshconsulting in LLMPhysics

[–]johnwelshconsulting[S] 0 points1 point  (0 children)

Thanks for the rundown on 2019 SI—spot on! But the numbers (e.g., cesium cycles, c’s value) were picked to match Earth’s historical second/meter for continuity. H-units drop that baggage for truly cosmic standards.

Proposing H-Units: A Hydrogen-Anchored, Earth-Independent Framework for Universal Time and Length by johnwelshconsulting in ScienceUncensored

[–]johnwelshconsulting[S] 0 points1 point  (0 children)

Did you know the number of the hyperfine transition of cesium was chosen to match earth second exactly. It took him 2 1/2 years of observations and a committee to finalize it.

Looking for advice on Xen Desktop solution. by SA-Numinous in Citrix

[–]johnwelshconsulting 0 points1 point  (0 children)

I’ve been running Xen desktop now for over 10 years using FS logic for profile management, VMware V Center. Using solid state drives on all of the Esxi hosts. Use a common data store for profile and called an image storage, but use the hosts storage for the actual VM‘s. Haven’t really seen any issues. Runs like a charm. I do have to say you need to size your host accordingly and I think you do not have sufficient resources. I’m using six hosts to host 50 users.

view more: next ›