It’s an irregularly shaped body so there’s not one single radius. Mean radius is always going to be an approximation (even for Earth); the mean radius of the Moon is 1,737.4 km.
But it's still an approximation, not an estimate, right? (The fact that you can list the mean radius with sub-decimal precision suggests as much.)
To me, an estimate suggests that there's error bars; an approximation suggests that there's variance that we can quantify (or at least we're very confident about our error bars).
Sorry, missed a "large". It would sound pretty strange to me to claim that the distance between New York and London is "an estimated x kilometers" (with single-kilometer precision), even though there is tectonic movement etc.
It’s a little misleadingly worded. Looking at the original press release[1] and an earlier announcement[2] I think they mean that they have prototype versions of this panel with 29.5% efficiency, the first production version they’re talking about here isn’t at that level yet.
Thank you! That makes total sense, if they have one that's that much more effective then that's very impressive. Fingers crossed they can get that into production soon.
If the existing procedures aren’t ensuring a safe workplace, the procedures aren’t adequate. Job site safety can add time, and it’s the company’s responsibility to ensure that there is no incentive for a worker to be able to speed up the job by skipping a step.
I’ve worked in places where the safety procedures were clearly perfunctory (drove a forklift in a warehouse for several years, among other jobs) and if I had insisted on following the actual safety procedures I would’ve gotten endless grief from other employees for slowing them down. This is a management failure.
They’re starting to roll out trash containers in the city, should have been done years ago. There’s a bunch of interconnected factors: all residential buildings in NYC get municipal trash pickup (most other cities require private trash service for large apartment buildings), Manhattan doesn’t have many alleys so trash has to go out front, on-street parking blocks larger curbside bins and using exclusively wheeled cans would crowd the sidewalks. They finally decided to remove some parking spaces to allow for large curbside bins.
You know what crowds the sidewalks worse than wheel bins? Having that same volume of trash bagged and leaking all over the place sustaining local rat populations. Honestly everything you mentioned as a potential con sounds like an improvement to the existing state of affairs.
Ok that's clever. I suspect if would be difficult in many places to find enough pavement slots without re-routing a lot of cables and pipes. And yet, the Dutch must have introduced this solution relatively recently - I guess they already run all their cables and pipes below the road, not the pavement? I know that while in my street the gas, water, and drains run under the road, the electricity supply is under the pavement.
> “The existing two-day period to settle trades exposes investors and the industry to unnecessary risk and is ripe for change,” Robinhood CEO Vlad Tenev said in a February 2021 release. “There is no reason why the greatest financial system the world has ever seen cannot settle trades in real time.”
There’s important context missing at the end of the article. It came up at the time, but it’s a little ironic (given how much of their business relies on customers trading on margin) that Robinhood was advocating for real-time settlement, since that would dramatically limit the ability of entities to trade on margin. Delayed settlement of T+1 (or even T+1/2) allows brokers to net out trades at the end of the settlement period, rather than needing everything to be pre-funded. It’s not a technical problem that we’re not going to T+0, it’s a policy decision.
I think you’re correct, this recent press release from the cited source (Carers Trust) says it’s 1 million total caregivers under 18, of whom 50,000 spend 50 hours/week caring for others.
My understanding that this is to enable things like a lunar GPS system, which requires the satellites themselves to have precise clocks that are synchronized with each other.
> They also mention the dependence of the SI units on the unit of time, which really suggests the writer has no idea how measurement precision is achieved.
Say more? I thought an accurate clock would be necessary to derive a reference meter and kilogram measurement.
> which requires the satellites themselves to have precise clocks that are synchronized with each other.
Yes, the satellites themselves need to keep track of their GR-induced drift relative to the other satellites. But we don’t typically describe this as needing a new timekeeping system (or new timezone, or whatever) for each satellite. We just say the GPS system makes corrections for GR, which it does. And in any case, this takes place on the satellites, not the lunar surface, which is what is mentioned in the announcement.
> I thought an accurate clock would be necessary to derive a reference meter and kilogram measurement.
So first, the fundamental SI definitions are almost never used in the field to make measurements. For the vast majority of field experiments, the measuring equipment is calibrated back at a lab using a reference system, which itself was calibrated using a chain of multiple intermediaries that eventually trace back to the fundamental SI definition. But the equipment necessary to connect to the fundamental definitions are extremely expensive and delicate, which is why it’s only done occasionally and in a few labs specialized for the purpose.
Second, even if you were measuring absolute lengths in the field with the distance light traveled in 10^X ticks of a cesium atomic clock or whatever (as opposed to the much more mundane task of measuring relative length changes with interferometry), it would all work perfectly fine if you did it within a local region of uniform gravitational field. The only reason you need to worry about the difference in clock speeds is if you are comparing event timing being done in different places where the clocks are running differently (as happens with GPS, or something like the LISA gravitational wave experiment, but which is otherwise quite unusual).
Like, don’t get me wrong, I can sort of imagine that NASA is actually planning such experiments. But then they should be mentioned in an announcement like this.
Automated cutting is used for less valuable stones, or when you need to have multiple stones of the exact same size and shape. Hand cutting is used when you want to maximize the yield, so you use the raw stone to guide the final size and shape.
Thanks, that makes sense, when you say 'you use the raw stone to guide the final size and shape' does that mean you might look for things like imperfections in the stone and try to remove those
Yes, finding a shape that excludes incursions is a big part of it. In the video he shows how he uses refractive fluids on the rough surface to make it less opaque so he can spot such inclusions more easily.
Like if the raw stone is elongated you probably don’t want to cut it into a square finished gem, something like an oval cut would have less waste. And instead of trying to decide on an exact size in advance (like, exactly 1 ct), the final gem is whatever it is when the cutting is finished, so if it’s a smidge over you don’t shave it down.
Because you’re dead my with natural objects of varying size, shape, defect, etc. this isn’t taking a 4x4 piece of sheet metal and punching the same shape out of it 100 times.
