omenti

the universe has it in for computers

a minipost

Cosmic rays have fascinated me since I was 13 and found a detector with a couple of patient physicists on the summit of Sulphur Mountain in Banff.   That was my first exposure to relativity.  I written a few posts on cosmics, but just say the word if you ever want to get me started on particles that can have the energy of a fastball and require detectors spread over thousands of square kilometers to properly detect.   Smashing into molecules in the upper atmosphere they produce large showers of elementary particles.  These can make it to the ground - or to a memory chip in a computer.  A direct hit on a memory cell can flip a bit from 1 to 0 without damaging the memory.  It's why you don't locate computer animation companies in Albuquerque or Denver.  It's why you use ECC memory in computers that run programs for more than a few hours and why many spacecraft have multiple radiation-hardened computers.   In addition to computer problems they're responsible for a large number of biological mutations.  They're one of many reasons why I think it's nutty to send humans into space beyond near Earth orbit. 

 

It's a very rich topic and this video by Derek Muller is an excellent introduction with historical examples of problems.  They've even interfered with an election. 

low distortion rearview mirrors

 

History Does Not Repeat Itself, But It Rhymes

      -  Mark Twain

Except it wasn't him.  

His clever and prolific writing made people assume he said it even though he never did.  It turns out it first appears around 1970 in a poem by a Canadian artist named Robert Colombo.  When asked if he knew where it was from Colombo couldn't recall other than he might have seen it in a literary section of the New York Times a few years earlier.  In fact it appears with and without attribution several times around the time of Colombo's poem in the early 70s.   That said, a hundred years from now people will still think Twain said it.

 

The process of science is much messier than the simple order kids learn in school.   There are too many dependancies to list.  A few philosophers of science  - notably Karl Popper and Thomas Kuhn - have tried to describe how scientific revolutions and change happens.  The how, where and why of scientific change.  Kuhn and Popper are somewhat at odds.  Kuhn's ideas were popularized and are still taught as how scientific revolutions happen.  It turns out that both of the frameworks are deeply flawed and have fallen from favor with serious students of the history and philosophy of science.  I came to it late, but I'm more a fan of an earlier step - trying to understand some of the history of science. 

 

Unfortunately the history of science is often neglected in scientific training.  Students are told a few selective stories from the great revolutionaries without much context.  Experiments, theories and techniques are described with little background.  The struggle and small steps forward and backward are  missing.  The world seems much too messy when you start doing real science on your own.  (this is probably true in many fields!)

 

One gets bits and pieces of local history from the last generation or two in their subfield.  This can be very powerful. I learned a lot about the development of the atomic bomb as some of the people I studied with were parts of the Manhattan Project.  You need to learn the importance of failure as well as hunches and the need to distrust your own work.  

 

The history of science, like the history of art or music,  is a story of the development of ideas that can be appreciated by non-specialists.   There are some wonderful books out there.  The trigger for this post was one of them:  Einstein's Fridge by Paul Sen.  I know the technical area well, but have big holes in my understanding of how all of this came about.  If you can follow articles in the New York Times science section, you'll learn a lot of what the physics is saying without the math and how it changed the world.  He gives a very simple, but accurate, description of entropy and has the best description of photosynthesis I've seen that doesn't get into biochemistry.  The historical motivations make it come alive.  I'm stealing some of his clear descriptions.

 

Most of this is probably true in many other fields.  About twenty years ago a friend invited me to dinner with Maurice Wilkes - his grand advisor.  Even though Maurice was in his late eighties the discussion went on late into the night and continued on two more occasions. I'm not a computer scientist or engineer, but Maurice is a physicist who happened to invent a good deal of the fundamentals of computing that's still in use.  Hearing him talk about the early history and the connections to our shared background made it all come alive.  The problems computers had to solve as well as the nuts and bolts of designing one - provided a wonderfully rich learning experience.  There was this hint of how the great mind of this humble person worked. A good history book can provide that kind of experience.

 

 

the fundamentals

mini-post

The Standard Model of Physics dates back to the mid 70s and is far and away the most complete and accurate description of three of the four forces of Nature.  Add General Relativity for gravity you have the basis to  answer fundamental questions like what we're made of and the forces. That's the bedrock of physics.    (the Standard Model with General Relativity tacked on is sometimes called Core Theory)  It's something that almost every physicist wants to see fail as there are hints of something deeper.

It's very elegant physics with beautiful mathematics, but good enough non-technical descriptions aren't easy.  Here's the best short discussion I've seen.  

 

I should note that while physics can describe all of these interactions, there's a problem with calculation.  Our mathematical techniques are often too weak so we have to resort to clever and not so clever approximations.  A lot of physics turns out to be applied mathematics.

 

frozen bubbles

a minipost

 

First a short video

You can make this yourself.  You'll need a chilly day and a cold surface.  I had success as a teenager in Montana with outdoor temperatures ranging from -25°C up to about -10°C.  Colder worked but the effect wasn't as dramatic and warmer just didn't work. Some of you are in areas that are still seeing chilly weather. You could probably do it in a very cold home freezer if you opened it slowly enough that the warm room air didn't mix in very much.  Use a drinking straw to blow bubbles from a soap mixture onto a cold surface.  Then watch in amazement.  Some of the best views I had were at night using a light to illuminate just the area around the bubble.   Children's soap bubble soap works, but I've found better and you might experiment   My favorite recipe created a bit stronger bubble:  

200g water
35g corn syrup
35g dish soap
25g white sugar

Stir and set aside for awhile so the turbulence from stirring settles down.  The corn syrup makes a more robust bubble. The sugar  was based on a hunch that it would create nucleation sites.

 

Here's a piece on some people who looked into the underlying physics.  My basic toy model back then that was sort of on the right track but missed a central insight and lacked the experimental analysis.  Physics gives tools to understand a variety of phenomena.  The underlying physics is very well understood, but much of what happens around us isn't deeply understood as it hasn't been studied or the math is just too difficult.  Sand, for example, is extremely difficult at the fundamental level. 

 

Bubbles have had an important role in physics.  Newton was fascinated by their formation and optical properties.  Faraday (one of the three great scientific minds of the 19^th century and the last physicist who didn't use sophisticated mathematics) used bubbles in a creative measurement that a led him to develop the idea of field theory - something that James Clerk Maxwell (one of the other great 19^th century scientists) used to explain one of the four fundamental forces.  Fields are central to fundamental physics.  They were also part of particle physics experiments for about thirty years in the form of some of the most sophisticated and exotic photographic cameras ever made - including an early test that used beer. 

 

Probably things I should write about down the road, but for now try to freeze some bubbles if you have the opportunity!

 

 

 

getting down to the bedrock

Some areas are built on foundations of fundamental principals that can be built upon.  For example many of the world's religions have a form of the golden rule in their bedrock.  Physics has a few of these cornerstones that are so deep they're considered beautiful and have become guides.  I've been thinking about one of them - complementarity -  a lot recently.  Particularly as it appears outside of physics in many areas probably including some you're used to thinking about.

 

Neils Bohr and Albert Einstein were contemporaries - peers actually.  Both were great sources of quotes.  Einstein's fame is such that it's difficult to figure out exactly what he did say without original sources. Bohr's lack of fame outside of physics makes it easier. Here are a few:

 

“We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.”

“Never express yourself more clearly than you are able to think”

“A physicist is just an atom's way of looking at itself.”

“There are trivial truths and there are great truths. The opposite of a trivial truth is plainly false. The opposite of a great truth is also true.”

 

None were meant to be flippant and the last one is one of the richest quotes I know.  Really deep ideas have meanings that go beyond the surface.   As an example consider this question

 "is light a particle or a wave?"

 It turns out it's both, but sometimes it's most useful to describe it as a wave while other times you treat it as a particle.  It's impossible to apply both descriptions at the same time.   The essence of complementarity is there are different ways of looking at the world and each can have its own language and domain where it's true. 

 

You can step back a bit and look at a satellite in orbit.   Physics developed by Newton are good enough to put it there and predicting where it is to good precision, but if you're worried about the accuracy of its clock you need to bring in relativity.  Einstein and Newton offer very different theories that describe orbital motion and how clocks keep time.  Relatively turns out to be richer, but Newton's ideas are good enough for almost everything people normally do - that and I'd hate to describe the motion of a volleyball using special and general relativity.  

 

I won't go into quantum mechanics, but complementarity is at the core how you think about things.  That and like Newton and Einstein's models, there are boundaries where one is more useful than the other.  The trick is knowing both and where the boundary lies.  It's for another discussion, but I think complementarity is a good basis for talking about the concept of free will. 

 

Bohr was so taken with the idea of complementarity that he made it part of his coat of arms with a nod to Eastern religious philosophies and the Order of the Elephant.  (how's that for clickbait?)

 

Light offers another example. Newton used a prism to break whiteish sunlight into a spectrum of colors.  Later Keats objected to the beauty of science claiming Newton unwove the rainbow.  

Do not all charms fly/at the mere touch of cold philosophy?/There was an awful Rainbow once in heaven. 

 In reality something deeper is afoot.

 

 Consider a yellow light on your desk.  The wavelength of the light makes it look yellow, but if you are moving towards at a constant velocity you observe a shorter wavelength.  If you're moving fast enough it looks blue.  Faster still and it's ultraviolet.  If you're moving away the wavelength lengthens and it shifts towards the red.  In fact by selecting your velocity with respect to the light, the wavelength can be anything you want.   In this view of nature the color of light only depends on your velocity relative to it.   It may not seem useful, but it turns out to be one of the most important tools for measuring the size and age of the Universe. 

 

Complementarity appears all over physics and turns out to be a useful way of thinking about new phenomena.   Over time I've come to think of it in areas outside of physics.  The spoken word and a television show can both get across their own versions of something.  Neither is complete and understanding both can lead to a deeper appreciation.  Picasso and Rembrandt had very different portrait styles and both tell us something deep about their subjects in very different ways.  Mix different forms of art - a piece of music might describe the feeling of Winter quite differently from a painting, but both can offer deep if incomplete views of the feeling of the season.   Sports are offer many examples.  Movement in a sport can make statements that added with the emotion of the crowd give a more complete picture.

 

You can't use a flat Earth, geocentric universe, or being able to turn off gravity for an hour tomorrow.  The descriptions have to be valid in some domain  in the first place.  But having two good but very different representations of something in your head at the same time may just lead to a deeper understanding.  Usually you're not thinking about deep truths, but that's fine.  This doesn't come easily, at least not to me, but it's a lot of fun once you get the hang of it. 

 

 

in praise of techs

mini post

1874 saw the opening of the most important inventions of the 19^th century - The Cavendish Laboratory at the University of Cambridge.  Serious science began to take off in the 1850s in universities.  It was mostly applied and work aimed at solving the problems of the day - railroads and telegraph.  Cambridge was late to the game, but their approach was revolutionary.  Apparatus and expertise were concentrated at one location.  Research cultures emerged. Not only was this cost effective, it freed up researchers to explore new classes of problems - not only hypothesis based and applied work, but true exploration.  That turned out to be the fuel of scientific and technological change in the following century. 

 

The model spread and by the 1890s and areas of deep expertise began to appear.  A dramatic example is the race to zero - how experimentalists tried to achieve the lowest possible temperatures.  Three institutions were deep into the game, but success and failure came down to who had the best apparatus and laboratory technicians. The experiments had become so difficult that expert technicians who built, understood and modified the experimental apparatus made all the difference. 

 

The public often sees science as the quirky theorist standing at her slate board and, chalk in hand and on her shirt and pants,  having deep thoughts. In fact most of it is very careful labor that can consume a small army of people for years to get a result that something didn't exist (that's as important as finding something!)  The Nobels celebrate the principal scientists and praise is warranted, but it often misses the supporting staff. (I think the Nobels have their place as they tend to focus on the frontier rather than hypothesis driven work.  I wish they were more inclusive, but another story)

 

Here's a short video on a tech at EGO-Virgo - the gravity wave observatory near Pisa, Italy.  Three such instruments exist with a forth coming online in Japan soon and a fifth under construction in India.  Able to measure distortions more than ten thousand times smaller than the diameter of a proton, these are far and away the most precise instruments ever built.  The technicians responsible for various bits and running them made it all possible.  I've worked with people like this - they're among the greatest craftsmen and women in the world.

yet another confusing word

These days we're hearing and talking about a future that is suddenly very difficult to predict.  Uncertainty is frequently invoked.  I know what it's supposed to mean, but the scientific context is very different.  It's one of those words - theory, hypothesis, work, energy, power, model, significant, natural, ...  - with a very specific scientific meaning at odds with their popular meaning.  (science communication is hard)

 

Who knows what's going to happen? frequency comes to mind,  while uncertainty is well defined in the context of science.  It's the quantification of how tightly we can constrain what we don't know.  That's a very powerful concerpt.  Being the simplest of the sciences, physics has the most rigid requirements.  In order for a discovery to be accepted by particle physicists uncertainty that it could be something else has to be lower than one part in three point five million - the five standard deviation level.  People living in this world spend much of their time thinking about what could go wrong and devising other measurements to disprove their original hypothesis.   We speak in terms of confidence levels.  

 

Henry Cavendish was one of the first to work at understanding and minimizing uncertainty when he weighed the Earth to determine the gravitational constant.  Even today the measurement is difficult as gravity is incredibly weak as forces go.  Without going into details,  Cavendish built an exquisitely sensitive  torsion balance that measured the attraction between small lead spheres and a much larger lead sphere.  His early measurements made sense, but was it just gravity?  Perhaps there was a bit of a magnetic effect .. he rebuilt the experiment with a large magnetic ball replacing the lead ball.  This wasn't to rule out magnetism as much as to set a quantitative limit on how large the effect was.  Then he turned to thermal effects heating and cooling different parts of the experiment.   He was left with his best measurement and the level of confidence that he had removed all other controllable effects (including human error).    

 

The game becomes trying to make a more precise measurement and perhaps seeing something new in the process - some measurable effect that can't be explained conventionally.  A good deal of science advances in this way.

 

Here's a cute introduction to uncertainty that I almost really like - the bear in the moonlight - almost as it doesn't touch on fundamental uncertainty.

 

There's another deep form of uncertainty - you've probably heard of Heisenberg's uncertainty principle and Schrödinger's poor cat.  Broadly stated Heisenberg showed that it was impossible to perfectly know both the position and momentum of anything.  He called it ungenauigkeit (inexactness) or unbestimmtheit (undeterminedness). Niels Bohr called it unsicherheit (unsureness).  Even today German physicists (like their Prime Minister, Angela Merkel) will call it unschärfe (fuzziness).  All of these terms are more descriptive of the physics than uncertainty.  The use of uncertainty suggests to some there is an exact value and we just can't measure it.  Instead there is just a probability distribution.  It is indeed fuzzy - at a microscopic level all of the atoms that make us up are fuzzy - it's just our world is mostly too large to notice.

 

In some parts of my life I try to avoid what is usually thought of as uncertainty, but when you want to really understand something diving in and reducing your uncertainty and increasing your level of confidence is a powerful tool. 

 

beyond 3d

Ask a physicist, biologist or chemist what got them interested in science and chances are they'll talk about a dramatic single moment - some refer to it as a calling.  I've written about mine on Sulphur Mountain in Banff.  Two young physicists took the time to try and explain their cosmic ray telescope.  Much of it was beyond me but the idea that something from outside our solar system slammed into the upper atmosphere and created a shower of other particles stuck.  And that these wouldn't live long enough to make it from the upper atmosphere to their telescope unless time was different for them.  I had no idea how that worked, but the fact that they could show that universal time - a master clock for the universe - didn't exist ate at me for nearly two years.  I didn't know it but I was about to become a physics student.

 

Somehow I found two correspondence mentors who taught me a little physics and more math.  Two years after Sulphur Mountain I finally understood why time ran more slowly for those speeding muons than for me.  That and what E =mc² really meant and how Einstein figured it out.  Einstein figuring it out was extraordinary, but more extraordinary is Special Relativity is simple and clear - beautiful - even if the results seem odd.  A high school student could read his paper and follow everything with just basic algebra and trigonometry.  

 

There are more than a few explanations in print and online.  To really learn it you need to puzzle it out for yourself with pencil and paper guided by a good textbook and problems.  Instead I'll talk about how he came to that flash of insight. 

 

Around the age of sixteen Einstein had been kicked out of the German school system.  He moved to Switzerland and spent a year at a school that put a premium on visualization and individualism.  There he learned about electromagnetism - light was just oscillating electric and magnetic fields that traveled at the speed of light. He found himself wondering what it would be like to run alongside a beam of light. Could he visualize what these fields looked like?

 

Maxwell's equations said that electromagnetic radiation - light - travels at 300,000,000 meters per second in a vacuum.   If he was going that fast the fields would vanish.  That didn't work.  Since Galileo physics was built on the idea of relativity.  The laws of physics didn't depend on how fast you are traveling.  All you can measure is the velocity of one object relative to another.  He had run directly into a wall.

 

For a decade Einstein kept at the problem.  Finally he went with a crazy idea (to be fair he tried a few crazy ideas).  What if the speed of light was the same for all observers no matter how fast they were moving? If you were on a train traveling at 80% the speed of light and pointed a flashlight forward, you'd measure the speed of light from the flashlight as 300,000,000 meters per second, as would a stationary observer watching from the ground as your train sped past.

 

The way out of this paradox was the person on the train and the observer on the ground experienced time differently.  Two events can happen simultaneously for one observer and at different times for another and both could be right.  Understanding exactly how that works requires learning about special relativity and you can't avoid the math and some sketches.    

 

Einstein offered the following gedankenexperiment (thought experiment):  An observer near a train track watches a speeding train go by.  Exactly as the midpoint of the train goes by two bolts of lighting strike the train - one at the front, the other at the back.   The distance from each strike to her is exactly the same and she says the lightning strikes were simultaneous. 

 

A passenger is sitting at the train's exact midpoint.   Because the train is moving the light from the pulse at the back has to travel a bit further than the pulse from the front. He says the strike at the front of the train came first.  They weren't simultaneous.  The key is it's simultaneity that's relative.  Once you understand that the algebra is simple.  The construction you are left with is space and time are intimately connected in a four dimensioned coordinate system called spacetime.  Spacetime doesn't change, but objects in the 3d world we perceive and time have different measurements for observers who are moving relative to each other.

 

I remember the amazing feeling when it came together in my mind.  It was early June around sunrise.  I got on my ten speed and rode as fast as I could.

 

 

 

 

lessons

Recently Om wrote an excellent piece on Derek Jeter’s career and some lessons one might draw from it. Even if you don’t like baseball, it’s worth reading.

 

Consistency, finding opportunity, leading by example .. and the ultimate goal.

 

One of my heroes is Ray Davis. I got to know him when I was a grad student and postdoc at Brookhaven National Laboratories. He was an experimental physical chemist who was doing some interesting solar physics. He was also of those people who mentored those more junior by example. I sailed with him on his homemade sailboat and joined him on numerous nature walks around the BNL installation as he photographed almost everything. He’d show up on Mondays with bandages from whatever home repair he had attempted. 

 

It’s worth reading a personal statement he made in 2002

 

also check out how people recognized him at the bottom. I’m sure he didn’t put that in himself. He was exceptionally humble.

 

His statement doesn’t go into the controversy and drama of the Homestake Gold Mine experiment. By 1960 physicists had a good idea how fusion took place in the Sun. It’s a somewhat complicated multistep process and different from how manmade fusion machines or bombs work. Some of the energy is released in the form of neutrinos. You may have head about neutrinos. They have a very small mass and barely interact with matter. A standard comment is more than half the neutrinos that strike a piece of lead a light year thick will travel though as if it didn’t exist. But the Sun was making a lot of electron neutrinos and a few will interact. In the late 60s Ray decided to count them and nail down what was going on in the Sun’s core.

 

He was exceptionally careful. Every month he was able to count about three dozen argon37 atoms They started out as chlorine37 but were turned into argon37 when an electron neutrino struck them. Ray spent years making sure hhis results were accurate. His numbers were very consistent… and about a third of what everyone knew was required for the Sun to shine like we see it. It seemed eithre Ray was wrong or the solar models were wrong. Ray persisted. People were in awe of how careful he was. The solar models were also holding up in other tests.

 

It turned out new physics was afoot. Ray was only sensitive to one type of neutrino - the electron neutrino - the type the Sun had to generate. What they found, when another observatory was built that detected another type was neutrinos oscillated from one type to another as they sped along. It was as if your Ford changed into a Chevy and then a Toyota regularly. You owned a “car” that was an admixture of these different brands. Startling new physics. Ray had peered into the core of the Sun with a tank of chlorine about a mile underground in South Dakota and by not giving up when the numbers seemed wrong, found Nature was answering with a new question

 

Ray was sprinkled with Swedish holy water in 2002 for his work.

 

It is remarkable that his institution - BNL - gave him that level of freedom. It’s also remarkable how he stuck with it and impressed all of us with the beauty of his work.

 

lessons…

connecting the titanic, sputnik and dealing with forgetfulness

1955, Fred Whipple had just been appointed to head the Smithsonian Astrophysical Observatory in Cambridge.  The International Geophysical Year was less than two years away and he wanted to involve citizen scientists as much as possible.  Whipple was one of the few who realized a satellite was likely and set about creating a web of radio operators to monitor and relay transmissions from satellites along with groups of amateur astronomers who could optically track their orbits.  Operation Moonwatch was formed and by Sputnik's launch over 200 teams were in place. 

 

Tracking a satellite was done with a clock and a low power telescopes that could read azimuth and declination.  The National Bureau of Standards time signal broadcast on WWV in Fort Collins, Colorado used as the reference clock and most people into amateur astronomy had a shortwave radio. Readings from stations separated by hundreds of miles were sent by amateur radio operators to a computer at MIT that gave the project a bit of its precious time.  More clusters of readings would come in from around the world and a model of the satellite's orbit generated an ephemerides - predictions of where it would be. Later specialized cameras were developed by Bell Labs to automatically generate satellite ephemerides as well as tracking ICBM tests, but Moonwatch was a success and lit the imagination of a few people.  

 

In physics it's common to turn a problem on its head to gain a bit of insight.  Operation Moonwatch used known positions on earth and an accurate clock to measure a position in orbit.  What if you put synchronized clocks in space and measured how long it took radio signals to reach a position on earth?  With enough satellites with synchronized clocks you could triangulate a position anywhere on the Earth's surface.  The technical details were difficult details, but the basic idea was simple.  

 

It turns out accurate navigation is very difficult and expensive and a limiting factor in fighting the cold war.  It was so difficult that as technology progressed ARPA decided to push ahead with a satellite based global positioning system - the inverse of Operation Moonwatch.  It was a bargain for what it gave to the military.  Finally a good enough signal was made available to civilians and navigation changed.¹ 

 

GPS doesn't work everywhere.  It would be nice to track things indoors and at a lower cost. Bluetooth and WiFi are currently used -  usually measuring signal strength from several transmitting beacons and triangulate a position.  Sometimes it's just proximity to a single beacon - a lighthouse model.   The approaches aren't very accurate - three to ten meters is common.  Good enough to track your phone as you move around, say, in a mall or subway, but doing better would be nice.

 

This is where the Titanic comes in..

 

On April 15, 1912 the Titanic struck an iceberg.  Frantic radio signals went out, but there was confusion among rescue vessels and people on land trying to coordinate the rescue effort.  Sometimes it takes a disaster to create order and an effort to regulate radio frequencies began soon after. Transmitters were assigned narrow swaths of the electromagnetic spectrum that were large enough to effectively communicate with receivers that could tune to those frequencies. Regulations changed as larger chunks of this resource were needed - AM radio required more than Morse Code, FM radio even more and television much more. Government would parcel out these increasingly scarce resources, but power was also regulated and it was possible to give much larger chunks to low power short range communications - WiFi and Bluetooth are examples.  Most of radio engineering tried to pack as much information into as little spectrum as possible and to build transmitters and receivers that could be accurately tuned to specific frequency ranges  If you waited for some technology to catch up there was another way (actually several, but I'll only mention one) way to do radio.

 

You may have heard about ultrawideband (UWB).  In the mid 2000s it was supposed to be a good way to send large amounts of information over short distances.  Cheaper and higher bandwidth than the WiFi of the day. Often existing technologies are improved with scale and an embedded base making it difficult for new players.  Sophisticated coding technologies and enormous penetration (WiFi has greater penetration than smartphones) cemented WiFi as the prime high bandwidth low range wireless connection.  In a few years UWB went from redundant to lagging. Many thought it was dead, but it had a few advantages in some use cases.   

 

Here's how it works.  Rather than sending out a precisely tuned narrow band frequency, UWB sends out narrow (in time) digital pulses that "splash" over a very wide frequency range.  The signals are usually only one or two billionths of a second long and aren't sent that often - a hundred thousand to ten million a second are common rates. The frequency range is so wide that usually at least some of it can pass through objects that block signals like GPS and WiFi.  It's also so weak that narrowband communication can't detect it.²

 

 Imagine scattering a few UWB transmitters around where you know their location with some accuracy.  Now start transmitting synchronized pulses.  A receiver notices the time of arrival of each signal and, using the fact that light travels about 30 centimeters in a billionth of a second, can triangulate it's own position.  Accuracy is about ten centimeters - about four inches.

 

A use case I'm familiar with is finding the locations of players in a beach volleyball game.  In international FIVB games a very small (less than a half ounce) UWB device goes in the back of each player's  shirt or sports bra.  Their positions are tracked within ten centimeters about a hundred times a second and accelerometers and a compass send out rotation and orientation information on the UWB signal that the announcers, coaches and sports science people use.  Four transmitters are used and all four players are easily tracked.

 

It would also be useful for augmented reality and Apple has included an UWB chip in every iPhone 11 - the greatest deployment of the technology so far.  For now it's being used for data transfer, but wait a bit.  Someone could also make very cheap ($10 or less) postage stamp devices that might be powered by available light that could be location tags.  Put them on your keys, glasses, remote control .. anything you tend to lose track of.  We went through trying to manage dementia with my mother.  I would have paid a lot for this capability.  And thousands of other uses from amateur sports to tracking boxes accurately in warehouses.

 

There are probably some bad things that can be done with it.  We need to be thinking these things through, but our track record isn't exactly good. 

__________

¹ It also gives a very good frequency standard and a timing signal.  Without this our mobile phone system, high frequency trading and a host of other core technologies we depend on would break.  This is an issue as GPS is vulnerable to attack and we've done almost nothing on backup technologies. 

² The FCC defines it as taking up at least 500 MHz of spectrum somewhere from 3.1 to 10.6 GHz.  Power is under -41.3 dBm/MHz .. or 75 nanowatts.  Since it only deposits a tiny bit of power in any narrowband frequency, it's just below the noise floor of a narrowband receiver.  Fortunately it's straightforward to build a receiver that can detect the signal.