First atomic clock wristwatch (2003)
leapsecond.com
leapsecond.com
And pictures: http://www.leapsecond.com/great2005/tour/
It's a cute experiment with the kids, and i'm glad they got away without injury -- but on the other hand i've witnessed first hand what a lead battery that is floating around the cabin can do during a wreck -- and what I witnessed was, sadly, deadly for the driver.
single orientation nylon straps that are strapping heavy square objects against foam cushioned seats and sandwiching the chaos with human meat on both sides. It's a recipe for disaster regardless of what vector the force of the impact comes from -- and that's ignoring the batteries.
Please folks , when you drive a vehicle the heavy stuff gets strapped behind a bulkhead at the front or rear of the car, or atop the car with appropriate and well-tested strapping & mounting equipment.
Don't risk your life for the sake of convenience.
The batteries are behind a seat row, the stuff in the seat is strapped in, the loose stuff is in the pass front foot well per OSHA guidelines (I figure most here worship at that altar). It'll be fine. They're not tracking the minivan.
I know that every time something like this is posted everyone likes to swoop in and talk about how X or Y is unsafe and you need eye protection every time you pick up a screwdriver and fall protection every time you even glance sideways at a step ladder because that's a way to score easy virtue points but it just comes across as tone deaf posturing. They aren't driving the van around like this 40hr a week for an entire career likewise it is not reasonable to expect them to implement a tie down solution that scales to that level.
I’m not sure why you read GP’s comment as virtue signaling. Sure, those examples you gave sound like virtue signaling. I dislike that sort of people probably more than you. Maybe it was his italicized “terrified” comment. I guess you were thinking “Seriously? This terrifies you?”
But GP is talking about something more serious. Maybe read their comment again. He literally said he saw someone die due to a similar situation.
Your OSHA comment sounds like you have a chip on your shoulder about something.
If it helps you process things better or at least put things in a different perspective, how would you feel if someone said they were _terrified_ that the kids weren’t wearing seatbelts? Would your response be slightly different?
That would still be an overreaction but to a lesser extent. Especially if they were talking about how dangerous it would be on a track.
At least I gave you the benefit of the doubt and seriously reflected about both yours and GP’s viewpoints.
I wasn’t talking specifically in this article context. It was a completely made up hypothetical situation yet actually does happen in real life resulting in deaths. According to a quick search when typing in “seatbelt deaths”, Google says in 2017 that ~33% of vehicle deaths in the U.S. were or could have been prevented if seatbelts were worn. That’s tens of thousands of people, _each year_.
What if you saw a drunk driver get into a car headed for the highway? Same response? “Oh, no you’re just exaggerating, he only lives 5 blocks down the street, he’ll be ok”.
You’re complaining about one extreme where people overreact over safety. Yet, you exist at the other extreme, telling people that they’re overreacting just to fit your narrative. Terrible.
EDIT: I see that the most recent comment was from a Dylan. I thought I had been replying to “throwaway”. Are you two the same person? It’s even more funny thinking that someone was so annoyed by someone talking about safety that they had to make a throwaway to complain lmao.
This is just isn't - this stuff will kill you in a 30mph collision. If you saw someone put a baby on the hood and drive around like that would you also say "oh do you expect these people to secure their babies for a one time trip - relax!". Like, it's just not safe. At all.
And the fact that it's a one-off makes it worse, not better - they won't be used to the handling a van this heavy, you will try to come to a stop and discover you're missing a car length - enough to get t-boned by a truck. I don't know why people treat it as some kind of wild and completely improbable incident that just won't ever happen - of course it will! These sort of things happen all the time!
>>not reasonable to expect them to implement a tie down solution that scales to that level
It's unreasonable to not expect them to.
200 pounds of clock in a seat, and 300 pounds of battery with a removed seat. That's on par with simply having two people sit in the middle row.
With 3 expensive clocks, 3 priceless kids, not to mention hot coffee in hand, I accelerated and decelerated modestly. The drive from Bellevue to Paradise Lodge up on Mt Rainier is mostly rural and then follows a long slow winding mountain road to 5000 ft elevation.
Besides, it’s not just the pounds that matter. Would you rather be hit by 200 pounds of hardness/sharpness/person bouncing to-and-fro or not be hit at all during a car crash cause that 200 pounds, whether object or person, was secured?
It reads much easier like this.
But there's a cultural opposition to helmets in many countries, chief among reasons being that "helmets don't look good" and "real cyclists don't need one". If you didn't wear one your whole life, you won't start at 65.
In my 30 years of life, I’ve never read an article, seen a TV show, watched a movie, read a book, heard a conversation, etc where the idea about wearing helmets in cars was even discussed.
I’ve never even heard a comedian joke about it.
Who is opposing this? Are you saying there’s opposition just because it’s a thing that doesn’t exist?
https://colvilleandersen.medium.com/the-case-for-motorist-he...
So that does open the question about whether suppression of this lifesaving technology has been something intentional on the part of automotive companies and enthusiasts (see: "jaywalking") or if it's the other way, that making road safety issues about only cycling helmets is an attempt to de-legitimize that mode and blame victims.
I’m assuming you’ve never met anyone that died due to a bike. So insensitive.
It's a bad idea to climb a mountain or go sky diving every day, but doing it once doesn't make you a reckless person.
Stop being facetious just to prove your point, please.
Climbing a mountain with good equipment and a buddy is still dangerous.
Being "properly prepared" is only relevant inside a context. You can't look at just preparation when deciding if something is too dangerous. The actual risk numbers are the important thing here.
If I'm driving 100 miles, and I do something sloppy that doubles my risk of dying in a car crash, the actual danger I face is less than the danger of skydiving just once with perfect prep. If it's also a special occasion where I'm going to get a huge amount of enjoyment out of it... the risk seems okay.
Even if we're focused just on car safety, we should be far more upset when someone buys a car without top-tier safety ratings than about some one-off trip like this.
Being able to point at some specific danger, like a battery on the floor, is just bikeshedding. What matters is the risk per day/month/year, and most of that risk is invisible.
2. Do you really think that's an appropriate comment?
that was fun.
HP Cesium line, the man's watch.
But might we suggest that if you do encounter such a scenario within the earth's atmosphere, that you should address that situation immediately? Otherwise there may soon be no circuit court judges available to hear your case.
https://www.hodinkee.com/articles/introducing-the-bathys-ces...
https://www.microsemi.com/product-directory/clocks-frequency...
https://www.mouser.com/ProductDetail/Microchip-Technology/09...
https://www.hodinkee.com/articles/richard-hoptroffs-atomic-w...
You may be thinking of the nasty radioactive isotope Cs-137, which is unnatural and often a byproduct of nuclear tests or accidents.
It's not unlike Carbon or Potassium; Carbon 12 is the safe stuff, the rarer Carbon 14 is radioactive. Potassium 39 is the safe one and rare Potassium 40 is radioactive. Which is why bananas are slightly radioactive:
https://en.wikipedia.org/wiki/Banana_equivalent_dose
You can make a cesium clock radioactive by placing a banana on top of it. See page 1, 36, 37 of:
http://leapsecond.com/ptti2020/2020-PTTI-tvb-Atomic-Timekeep...
One banana is 0.1 µSv [1].
The granite is therefore 0.18 mSv / 0.1 µSv = 1800 bananas.
This is compared to 4 mSv normal yearly background dose [1]. The granite increases background radiation by 0.18 / 4 * 100 = 4.5%. The yearly dose from natural potassium in the body is 0.39 mSv, so I wouldn't worry about the extra 0.18 mSv if I were you.
You're at much greater risk if you live in a house which used reinforced concrete with steel from the Ciudad Juárez accident - after that accident, 109 houses were demolished. [2] [3]
[0] https://www.nature.com/articles/jes200944
[1] https://xkcd.com/radiation/
[2] https://en.wikipedia.org/wiki/List_of_civilian_radiation_acc...
There's nothing unnatural about Cs-137. Fission occurs naturally in U-235.
All in all it's better suited for a nice pocket watch with a 10MHz out connector. Any takers at 15k$+?
I wasn't seriously suggesting it's a practical answer by any means =)
There is also the time-nuts mailing list where hundreds of us share questions and experiences with repairing and running old atomic clocks. The archive is 20 years deep so there's lots of good info on bringing dead cesium and rubidium clocks back to life:
http://leapsecond.com/time-nuts.htm
The one problem is if the old cesium clock you buy has "run out of gas". The quantum mechanics physics experiment encapsulated inside the tube is a one-way street so once the tube runs out of cesium one has to replace it. The typical solution is to buy a few cesium clocks over time on eBay and mix parts until you have one that works well.
The bandwidth of the tube is VERY narrow (on the order of a few hertz, which means you have to be quite close on the frequency of the crystal oscillator before it can lock in.
You also want to be careful when adjusting for the Zeeman frequency to pick the right peak, or you will end up with locked to the wrong transition, and your clock will drift ,although in a very precise amount of drift ;-)
It's fun, once it works. It's easier the second or third time, of course.
Rubidium cell atomic clocks, on the other hand have a vapor cell which is a closed tube, and doesn't get expended. Thus Rubidium clocks have far longer service lives. You can find them surplus on Ebay for less than $200. The stability is slightly less, but still far more accurate than most electronics technicians need to do adjustments and calibrations.
[Update - Far more than you ever thought you wanted to know about atomic clocks] The main difference between an atomic clock and a quartz crystal oscillator is that in a crystal oscillator, you have a continuous signal that is generated from the circuitry and passed through the crystal, and amplified in a feedback loop. A crystal oscillator can be made with a single transistor and a few passive components.
In an atomic clock, there is a stabilized quartz oscillator, which actually keeps time, but it is then steered up or down in frequency slightly by using a harmonic of that frequency, along with a very slight amount of frequency modulation, to inject into a cavity containing the atom of interest.
In Cesium (Caesium outside the US) beam clocks, the physics package is all packed inside a large vacuum tube. Inside the tube is an oven with microscopic holes in the top containing cesium metal, the oven is heated to about 200 degrees. A small stream of individual atoms exit. Those atoms pass through a magnetic field which diverts them according to spin. The atoms then drift through a microwave chamber where there is a 9.129 Ghz signal imparted. If the frequency of the signal exactly matches the natural resonance frequency of the cesium atom, its spin will flip.
On the other side of the drift chamber, a second magnet selects only those atoms which have flipped state, all other atoms are diverted and trapped. Then the atoms encounter a hot wire with high voltage where they are ionized, them passed through another magnetic field which is a mass spectrometer, this serves to filter out impurities and contaminant that are present in the tube. There is a fine slit that allows entrance only to the cesium beams (now regardless of their spin), and they imping upon a plate in a photomultiplier.
The net result of all this physics is that if you have exactly the correct frequency, there is a DC current of a microampere or so output, too high or too low, and the output drops quickly. The line width is on the order of a few hertz.
To sample against this, the quartz oscillator is multiplied in frequency the appropriate amount using multipliers and phase locked loops, and combined with a very small amount of frequency modulation at 137 hertz.
The DC output of the tube varies with the modulation... if it increases with increasing frequency, the reference clock is too slow... if it is out of phase, the reference clock is too fast, and if you get a 274 hz second harmonic, you are right on frequency.
They take about 10-20 minutes to warm up and lock.
There are some adjustments, and it is possible to have them locked on the wrong frequency if you aren't careful.
Cesium clocks, used, are on the order of $5000
--
Rubidium clocks are easier to use... they are also quartz oscillators probing with FM signals, but instead of a stream of atoms, there is a lamp with one isotope of rubidium which is then passed through a chamber with microwaves and the other isotope of rubidium... if the frequency is just right, the light transmission dips by 1%, and this is used to lock the oscillator.
Rubidium standards are about 10 times less stable, but have far longer service lives, and can be had used for about $200.
This was one of the atomic clocks I used for the time dilation / relativity experiment linked at the bottom of the page.
http://www.leapsecond.com/great2016a/
And in 2018 I was asked to be part of a "time travel" episode on a History channel show. We used Palomar Mountain in California:
http://www.leapsecond.com/great2018a/
Each experiment was a little different; different combination of clocks, different audience, different mountain, different elevations, different latitude, etc.
Of all the clocks you own, what's your favourite and why?
[1] https://www.mouser.com/new/microchip/microchip-macsa5x-atomi...
Actually, a three letter agency did ask me what was going on: NPS, the National Park Service! But they kindly allowed us to park in front of the Lodge for the weekend. The advice I was given by old timers was to refer to the electronics simply as accurate clocks instead of atomic clocks or cesium clocks because many people false trigger on words like cesium or atomic. You'll notice that the official name on the front panel of a 5071A is "Primary Frequency Standard".
What's the cheapest clock you can purchase (used or new) where you can still do a similar experiment (i.e. that's accurate enough to measure dilatation over a day/week/month period of time)?
Are they a restricted item because of the radio-isotope?
Just take your time. Some of us look for months and even years before we find one worth the eBay risk.
There is one fact to consider. I have heard that the 5071A clock is still ITAR classified. It's not because of "atomic" or "cesium", but because the internal design is so advanced that the US decided it was essentially like a military weapon.
If in doubt look for vintage models like 5060, 5061, 5062, or 4050, 4060, 4065 instead of the still current model 5071.
For the valley-mountain gravitational time dilation experiments that I've done I use 5071A cesium clocks. Even though 25+ years old, no commercial clock works better for this portable application. That is to say, rubidium clocks and older model cesium clocks are not quite good enough to detect these tiny relativistic effects with confidence.
Others here have mentioned prices. Surplus rubidium atomic clocks can be found for as low as $100 on eBay. Surplus cesium clocks range from $1k to $10k, depending on model and condition. Factory new 5071A are close to $100k so no one I knows is crazy enough to do that. If you are very patient and lucky on eBay you will find 5071A for as low at $2k to $5k once every couple of years.
Out of curiosity, do the output formats of the different models differ? With output format I mean the way that the (current) time is represented.
Not being familiar with atomic clocks, my hope and expectation is that the output is something different than a single large integer (compare unix timestamp). :)
Cellular base stations used to have rubidium sources disciplined to GPS as a reference frequency for synthesis. AIUI, put the expensive, precise part in the base station, have the cheap handset lock onto that. Free accuracy. Not sure if they still do it that way. That's where all the cheap used rubidium sources on eBay come from.