What stocks do I long, armed with this information :)
Atomic nucleus excited with laser: A breakthrough after decades
101–110 of 229 posts
Re: Atomic nucleus excited with laser: A breakthrough after decades
#102Earlier quoted context omitted.
This actually has significant practical importance, because it is hoped that using this transition of the thorium nucleus it will be possible to build atomic clocks even better than those using transitions in the spectra of ions or neutral atoms, because the energy levels of the nucleus are less sensitive to any external influences. While in the best atomic clocks one must use single ions held in electromagnetic trap…
What could we do with more accurate atomic clocks that we cannot do with current ones?
The article points to a use I wouldn't have thought of.
The deeper you go into a gravitational field, the slower time goes. Therefore comparing clocks in different places gives a way to measure gravity. These clocks could be sufficiently precise to find mineral deposits underground from their gravity signature.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#103Earlier quoted context omitted.
https://apps.dtic.mil/sti/pdfs/AD1012150.pdf Gravitational Detection of Submarines, PM Moser 1989
Look at what paper actually says: flat "not achievable" in the abstract; and the scaling laws on page 4 are third- and fourth- inverse powers of distance (!!!!); and on page 7 they're considering ranges of the same length scale as a submarine itself (few hundreds of meters), and even there it's hopeless. This one's never going to happen. Geologic mass concentrations are an entirely different story: you get a gravitat…
What an excellent retrospectively obvious point!
Re: Atomic nucleus excited with laser: A breakthrough after decades
#104Earlier quoted context omitted.
standard football field size, or empirical average?
I suspect the average football field size across the former British Empire is close to the FIFA standard. Throw in Australian Rules Football fields if you're looking for a maximum, particularly if orginal marn-grook is in the mix.
> suspect the average football field size across the former British Empire is close to the FIFA standard.
The FIFA standard (https://downloads.theifab.com/downloads/laws-of-the-game-202...) leaves a lot of leeway:
“3. Dimensions
The touchline must be longer than the goal line.
• Length (touchline): minimum 90 m (100 yds), maximum 120m (130 yds)
• Length (goal line): minimum 45 m (50 yds), maximum 90m (100 yds)”
So, a field can be almost square at 90m × 89m or approaching thrice as long as wide, at 120m × 45m.
Reason for this is prior art that can be hard to change (if there’s a stadium around your field, and it’s deemed too small, you’d have to demolish it to make the field fit the standard)
Various competitions restrict this, though.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#105Earlier quoted context omitted.
What could we do with more accurate atomic clocks that we cannot do with current ones?
The article points to a use I wouldn't have thought of. The deeper you go into a gravitational field, the slower time goes. Therefore comparing clocks in different places gives a way to measure gravity. These clocks could be sufficiently precise to find mineral deposits underground from their gravity signature.
> These clocks could be sufficiently precise to find mineral deposits underground from their gravity signature.
We've been doing that since the 1960s at least with such things as the LaCoste & Romberg gravimeter (1936).
You can download, see online the "Geoid"
https://americanhistory.si.edu/collections/nmah_865074
https://en.wikipedia.org/wiki/Gravimetry
https://en.wikipedia.org/wiki/Geoid
Magnetic anomalies also highlight inteesting places for minerals, the issue with both magnetic and gravity fields variations lies with determining the "true" depth to target (medium sized shallow target, or massive deep taget?) which is known as an inversion problem.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#106Earlier quoted context omitted.
I suspect the average football field size across the former British Empire is close to the FIFA standard. Throw in Australian Rules Football fields if you're looking for a maximum, particularly if orginal marn-grook is in the mix.
> suspect the average football field size across the former British Empire is close to the FIFA standard. The FIFA standard ( https://downloads.theifab.com/downloads/laws-of-the-game-202... ) leaves a lot of leeway: “3. Dimensions The touchline must be longer than the goal line. • Length (touchline): minimum 90 m (100 yds), maximum 120m (130 yds) • Length (goal line): minimum 45 m (50 yds), maximum 90m (100 yds)” So,…
Interesting .. I hadn't realised there'd be so much give in the FIFA specs!
Thankyou for looking that up.
Re: Atomic nucleus excited with laser: A breakthrough after decades
#107[deleted]
Re: Atomic nucleus excited with laser: A breakthrough after decades
#108Nice to see this happen! When this was attempted with trapped ions, I and my colleagues at GaTech were the first to trap and laser cool Th(232) 3+
https://sites.lsa.umich.edu/kuzmich-lab/wp-content/uploads/s...
Re: Atomic nucleus excited with laser: A breakthrough after decades
#109Earlier quoted context omitted.
Oh that's about 0.0000000014 football fields. More seriously, apparently it takes a photon with a wavelength of 92nm to eject an electron from a hydrogen atom. Maybe this is a reasonable reference/refresher: https://web.archive.org/web/20210413042937/https://www.nagwa...
More to the point >400nm is visible light, this puts 148nm well within the ultraviolet range. Though it's not too far removed from the visible spectrum, wouldn't surprise me if some animals could see it.
148 doesn't feel too far removed from the visible spectrum, but it's in the wrong direction for animals to make use of it. I'm no biologist, but I'd be shocked if there were any animals that had adapted sensitivity to a type of radiation that they are never exposed to in nature. The sun doesn't really emit much UV-C light:
https://en.wikipedia.org/wiki/Solar_irradiance#Absorption_an...
and the light that is emitted is absorbed by the atmosphere:
https://en.wikipedia.org/wiki/Ultraviolet#Solar_ultraviolet
It's useful to be able to see a little UV-A, perhaps, and very useful for predators to see 'heat' into the IR range, but if your eyes were sensitive to 148nm, the world would be pretty dark.
Maybe after a few million years, in the grinding dust in the back of my shop, something will evolve that has a symbiotic relationship to arc welders...
Re: Atomic nucleus excited with laser: A breakthrough after decades
#110Earlier quoted context omitted.
The article points to a use I wouldn't have thought of. The deeper you go into a gravitational field, the slower time goes. Therefore comparing clocks in different places gives a way to measure gravity. These clocks could be sufficiently precise to find mineral deposits underground from their gravity signature.
> These clocks could be sufficiently precise to find mineral deposits underground from their gravity signature. We've been doing that since the 1960s at least with such things as the LaCoste & Romberg gravimeter (1936). You can download, see online the "Geoid" https://americanhistory.si.edu/collections/nmah_865074 https://en.wikipedia.org/wiki/Gravimetry https://en.wikipedia.org/wiki/Geoid Magnetic anomalies also hig…
Yes, but a better clock means more precise measurements, means we can locate smaller masses to higher precision.