fsh

46 ms·

631.
by fsh 5y ago
Estimating the uncertainty is indeed quite difficult. Stability can be measured by comparing two uncorrelated clocks. This is why standard institutes tend to build them in pairs. Measuring absolute accuracy is a different beast, since two s
632.
by fsh 5y ago
TAI is a weighted average of the clocks. The lower the estimated uncertainty of a clock, the more it contributes to the average. This is given in the second to last column in the first table of Circular T [1]. For example, in the last repor
633.
by fsh 5y ago
The International Atomic Time (TAI) is defined on earth's geoid. The participating institutions correct their clocks for the offset due to the local gravitational redshift. The geoid is fairly stable, but with future optical clocks tim
634.
by fsh 5y ago
The atomic clock on their card performs much worse than the built-in GPS receiver. In normal operation, it serves no real purpose. I guess some bored engineers wanted to have something fun to play with.
635.
by fsh 5y ago
It is usually much simpler to put a GPS receiver in the device and to make use of the dozens of atomic clocks flying over our heads. Or to use NTP over the internet.
636.
by fsh 5y ago
These experimental clocks are generally not used for time keeping. They are room-filling atomic physics experiments, which are not reliable enough for permanent operation. It is better to think of them as frequency standards. This means tha
637.
by fsh 5y ago
A car can measure its speed in kilometers per hour without having to travel for an hour. The choice of units is completely arbitrary and is ultimately a matter of taste. Most people know what a second is, and that a billion years is a reall
638.
The Case Against Manned Spaceflight (1986)(apnews.com)
1 points by fsh 5y ago|0 comments
639.
by fsh 5y ago
The basic reproduction number of COVID-19 in an immunologically naive population is much higher than that of Influenza. Most countries stopped the first COVID wave using non-pharmaceutical interventions that should work against all respirat
640.
by fsh 5y ago
The fine structure constant can be measured in two different ways. One is to measure the g-factor of the electron in a Penning trap. This can be related to the fine structure constant using quantum electrodynamics (QED). The other is to mea
641.
by fsh 5y ago
It is a misconception that things are ill-defined just because they are at a quantum scale. The proton has an electric charge distribution. The definition of the proton size used here is the root mean square charge radius of that charge dis
642.
by fsh 5y ago
The value of the proton charge radius in itself is pretty much irrelevant, otherwise it wouldn't be so hard to measure. As scientists we want to know if our understanding of nature is correct. To test this, we measure the same quantity
643.
by fsh 5y ago
This is not even wrong [1]. [1] https://en.wikipedia.org/wiki/Not_even_wrong
644.
by fsh 5y ago
Angela Merkel's dissertation lists five programs she wrote for various physical chemistry calculations. Two ran on an HP 9810A, two on the east German Robotron EC1055 mainframe, and one on the Soviet BESM6 mainframe. Maybe the listings
645.
by fsh 5y ago
In my experience, modern integrated synthesizer or DDS chips perform not that much worse than old benchtop signal generators. You don't get creature comforts, such as calibrated electronic step attenuators, and may have to calculate th
646.
by fsh 5y ago
I don't see a resolution bandwidth in the plot. How do you judge the noise floor without that?
647.
by fsh 5y ago
Noise figure is a property of receivers, not sources. Signal generators don't have noise figures. The MAX2870 synthesizer chip used in the project has pretty good phase noise specifications. I don't see any broadband noise above t
648.
by fsh 5y ago
I still don't get WETH. What is the purpose of exchanging ETH, which is a token on the Ethereum blockchain, for WETH, which is also a token on the Ethereum blockchain (with the same nominal value)?
649.
by fsh 5y ago
I have never seen a consumer IPv6 router without a restrictive firewall enabled by default. Could you give some examples where this is not the case?
650.
by fsh 5y ago
In the US and Japan the fraction of primary energy supplied by nuclear power is almost negligible (8% [1] and 3% [2]). Even the famously large French nuclear industry only manages 39% [3]. Nuclear power would have to be scaled up by orders
651.
by fsh 5y ago
Or you can go to a harbor and watch ships drop below the horizon.
652.
by fsh 5y ago
All deep UV wavelengths are energetic enough to break chemical bonds and the cross sections have quite non-trivial wavelength dependences. The authors of the article claim that 222 nm has a much shorter absorption length in tissue than 254
653.
by fsh 5y ago
If the light emitted by the LEDs is "really close" to the mercury light, it should be just as carcinogenic. I also seriously doubt that the LEDs are based on silicon since indirect bandgap semiconductors make horribly inefficient
654.
by fsh 5y ago
And now the receiving computer has an unintentional $100M bug bounty on all its software and hardware. For digital money to be actually usable, you need some kind of authority that can revert transactions in case of mistakes or fraud.
655.
by fsh 5y ago
In my experience, fractional scaling in Gnome Wayland works at least as well as on Windows. I use 150% on my 4K 27" monitor and have experienced basically zero problems in the last few months.
656.
by fsh 5y ago
The CSAC is specified for operation at < 120 mW (< 140 mW at warmup) so one could in principle build a novelty watch with it. However, a standard quartz movement with daily sync to GPS would outperform it at a thousand times lower pow
657.
by fsh 5y ago
This is a very bad comparison. Radioactive heating is only significant because the earth is very large. Soil has a very low background activity of a few hundred Bq/kg. High-level nuclear waste has 2 TBq/kg after 100 years.
658.
by fsh 5y ago
From the website of the manufacturer [1] it appears that the co-processor is essentially an analog computer for matrix-vector multiplications. I am quite sceptical about the accuracy and value range of the computations. Even puny single-pre
659.
by fsh 5y ago
"Traditional vaccines" are by no means free of side effects. The smallpox vaccine is a live vaccine and causes much more severe side effects than mRNA COVID-19 vaccines, including myocarditis [1]. This risk was accepted since smal
660.
by fsh 5y ago
I think the methodology of this paper is quite weak and the results do not support the strongly opinionated conclusion the authors draw from them. The first example is a plain text with a few footnotes in a two-column scientific journal lay

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