This term is a generic concept that has to do with the idea that it just doesn't make sense at a very basic level. No need to get into advanced scientific analysis to figure this out, the "physics" of the thing makes no sense without having to do a single calculation.
For example, compare these two options:
Option 1: Take 10 or 20 bus routes. Each being 5 to 10 miles long. Convert all buses to electric power.
Option 2: Take the same routes. Rip-up 200 miles of sidewalk (yeah, they'll be some overlap, this is just a quick mental exercise). Develop new technology. Install 400 miles of it (you need two directions of travel). Staff for installation, support, etc.
The first passes "physics" in that asking "does it make sense given all we know?" test results in a pretty quick "yes!". The second is such an obscene deviation from what would make sense from almost any perspective that it is surprising anyone would consider discussing it at all.
Take, for example, having 400 miles of active sidewalks. You just replaced a few buses with 400 miles of sidewalk moving most of the time. Why would anyone wait if the sidewalk is right there. Whereas before people would wait a few minutes for a ride now you are going to have dozens of miles of expensive power-consuming active sidewalks moving all the time simply to carry a single person 100 meters to then have them cross the street and get on the next active sidewalk. And, if it snows, now you are carrying tons of snow until you devote a small army of trucks to go clean the snow. I mean, the more you think about the reality of this utopic concept the stupider it sounds.
It'd probably make far more sense to have a small fleet of electric scooters available for rent and use only along a predetermined route. If you get off that route they turn off. So now, you'd have small one or two person clean scooters distributed along a 5 to 10 mile route for anyone to hop on and off as needed. At most you might have to walk a block or two to get one. This isn't an idea that I thought through. I'm just pulling it out of a hat to illustrate that the "physics" of this off-the-cuff concept would make far more sense than ripping-up hundreds of miles of sidewalk to install a monster of a system that makes less than zero sense.
The "does it pass physics" test refers to stuff that just doesn't make sense. Like a miracle, or the earth being 6,000 years old, or buying a supercomputer to do basic math or commuting in a Humvee. In other words, there are things that defy reasonable reality to such an extent that they simply don't make sense.
> if it snows, now you are carrying tons of snow until you devote a small army of trucks to go clean the snow
I don't think you've thought this part through. Not that snow isn't a problem that needs dealing with, but "carrying tons of snow" is not the problem you have. If this works anything like a traditional conveyor belt then while it is running it is dumping all the snow at one end, the same end where it is dumping all the passengers, whereupon you are no longer "carrying" that snow. There could be heating elements or blowers along the way that melt the snow such that it drains off the side, or perhaps the slowing-down-at-the-end step involve grating separation such that snow falls through to some lower level? Something along those lines. I'm not sure what the precise solution for snow-on-a-conveyer-belt is but surely it would make use of the massive running conveyer belt as part of the solution, not rely on a "small army of trucks".
No, I thought it through. I am actually very surprised anyone would even argue in favor of any version of this hair-brained idea.
Do the math on the cost of accelerating and decelerating people + snow and melting of moving the snow. Calculate the cost of the personnel needed to manage that and the cost of the trucks needed to manage equipment, etc.
The entire thing is dumb beyond description.
Let's put it this way. If you had to pay for it yourself you'd take a look at the outrageous immensity of the bill, turn around and say "hey guys, what's wrong with a couple of buses?".
What's wrong with buses includes that they take up a lot of space, have a high energy cost to run, tend to have a relatively low peak throughput, tend to be noisy and polluting, and you often have to wait a long time for the next one.
It's expensive to build these contraptions now but the cost is likely to come down over time. Once built, by energy cost per person they don't compete with "make people walk on a non-moving sidewalk" but do compete pretty well with most of the alternatives. You COULD build them in such a way that the cost of dealing with snow is minimal, it's just a matter of deciding on a suitable strategy and implementing that strategy. The dumbest, simplest strategy would be to add some sort of roof or canopy or shade structure such that snow and rain fall on either side of the conveyer belt. (Like, say, the conveyer belt entrance to Bally's Casino in Las Vegas: https://rlv.zcache.com.au/ballys_las_vegas_conveyor_belt_pos... )
Other options include digging a suitable drainage/collection area that snow can fall into as the belt turns or, yes, melting snow with a heater as it passes a grating. The heater option is only energy expensive while it's snowing but it's still likely cheaper than having guys with trucks clear it. But if the area just plain has too much snow for melting it to be practical you go with the roof option.
We'll agree to disagree. The paper is academic nonsense. Pointing to a paper doesn't mean the thing paper is about makes sense. All it means is that someone wrote a paper about it.
In the real world, to those of us with experience in non-trivial construction projects, such an idea is ridiculous beyond comprehension.
Take a look at the insanity that the California high speed train has become. A train to nowhere that nobody is going to use and will not be high speed and will cost massively more than the sixty billion politicians promised it would cost. And that's a "simple" project compared to tearing-up a city.
But,yeah, cool science fiction.
EDIT: Just thought of adding one thing. This is the same kind of "there's a paper about this" project as flying cars. There are people --and INVESTORS!!!-- who keep throwing time and money at flying cars. They don't make sense. It's a bad, bad, bad idea. Yet here we are, every six months someone wants to build a flying car.
For example, compare these two options:
Option 1: Take 10 or 20 bus routes. Each being 5 to 10 miles long. Convert all buses to electric power.
Option 2: Take the same routes. Rip-up 200 miles of sidewalk (yeah, they'll be some overlap, this is just a quick mental exercise). Develop new technology. Install 400 miles of it (you need two directions of travel). Staff for installation, support, etc.
The first passes "physics" in that asking "does it make sense given all we know?" test results in a pretty quick "yes!". The second is such an obscene deviation from what would make sense from almost any perspective that it is surprising anyone would consider discussing it at all.
Take, for example, having 400 miles of active sidewalks. You just replaced a few buses with 400 miles of sidewalk moving most of the time. Why would anyone wait if the sidewalk is right there. Whereas before people would wait a few minutes for a ride now you are going to have dozens of miles of expensive power-consuming active sidewalks moving all the time simply to carry a single person 100 meters to then have them cross the street and get on the next active sidewalk. And, if it snows, now you are carrying tons of snow until you devote a small army of trucks to go clean the snow. I mean, the more you think about the reality of this utopic concept the stupider it sounds.
It'd probably make far more sense to have a small fleet of electric scooters available for rent and use only along a predetermined route. If you get off that route they turn off. So now, you'd have small one or two person clean scooters distributed along a 5 to 10 mile route for anyone to hop on and off as needed. At most you might have to walk a block or two to get one. This isn't an idea that I thought through. I'm just pulling it out of a hat to illustrate that the "physics" of this off-the-cuff concept would make far more sense than ripping-up hundreds of miles of sidewalk to install a monster of a system that makes less than zero sense.
The "does it pass physics" test refers to stuff that just doesn't make sense. Like a miracle, or the earth being 6,000 years old, or buying a supercomputer to do basic math or commuting in a Humvee. In other words, there are things that defy reasonable reality to such an extent that they simply don't make sense.