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Through-Wall Human Pose Estimation Using Radio Signals (mit.edu)
355 points by signa11 9 months ago | hide | past | web | favorite | 169 comments

I've noticed, recently, that literally every major chain store I go into blocks my cell signal. I get full bars outside, perfect LTE, and about 5 ft past the glass doors, I'm suddenly cut off. Specifically, Meijer grocery stores and Home Depot are the worst offenders. Coincidentally they offer free in store WiFi to track me with, so I turn off my wifi radio on both smartphone and smartwatch before walking in the door... Note, this was not the case in the exact same physical stores a couple years ago, and they weren't closed for remodeling in the interim.

Does anyone know if this sort of Faraday cage technology for large buildings is easily available for me to install in my own home? If so, what's it called, what does it cost and where do I get it?

FWIW, if they are intentionally (or unintentionally) blocking your cell signal with an electronic signal (And since you mentioned that they didn't remodel, this is the only way they could feasibly do it), they're breaking a very serious FCC law - https://www.fcc.gov/general/jammer-enforcement.

I know that the FCC is kind of regarded as a joke lately, but this is a law they take pretty seriously as jammers can interfere with E911 calls. It would just take one emergency that 911 couldn't respond to for the FCC to realize what was going on, and no large store is going to take those odds. It's likely something else.

That said, if you really believe that they are blocking cell signals, you should probably file a tipoff, as they could honestly be putting lives at risk (go to https://consumercomplaints.fcc.gov/hc/en-us and click "phone"). As far as I know there's no penalty if you are wrong (as long as you honestly believe there might be an active jammer in the area and you aren't abusing their system somehow), worst case you'll get a call confirming they don't use one.

Yeah, I think it's more what lgats suggested, and simply that they have a naturally impermeable building in the middle. Not even the cabinets, more the metal shelving up to the ceiling and such. I also notice that my current phone does a terrible job of falling back on the much more long distance 3G, so maybe that's part of it.

> Yeah, I think it's more what lgats suggested, and simply that they have a naturally impermeable building in the middle.

That kind of contradicts the OP... since they said that it was only recently that the signal stopped working, and that the building was not being remodeled during that time. So if the building is now impenetrable then something changed. Maybe modern phones just have a horrible time falling back from LTE to 4G/3G.. But if that’s the case then I feel like the OP would have checked for that since he seems to have already been tracking his connection strength over different locations and over time.

I was the OP...

I noticed this recently, but cell towers get upgraded/replaced at intervals unrelated to "nationwide rollout of LTE!" from carriers.

Why you contradict yo self...

A spectrum analyzer or SDR dongle would tip you off really quickly if there’s active jamming, and the FCC doesn’t play games with those types of violations.

I believe you can achieve the same result in your home by adding a sheet metal roof, metal cabinets, and refrigerators along every wall.

It's a rather unfortunate coincidence, isn't it? Certainly it's not their fault that their buildings just happen to be constructed in such a way, and their products arranged such that it blocks signal causing customers to not be able to compare prices and have to use their approved internet connection. /s

I see this in the Targets in my town. I just expect signal to drop to zero.

I would be very surprised if the benefits from blocking signal outweighs the cost of constructing the building to intentionally block signal, and the risk of being sued for it. It's probably just something that happens naturally with those types of buildings.

I have a tin roof, metal front porch and a large metal rear-facing verandah at my house.. This effectively becomes a massive faraday cage as far as my phones concerned. The things that you wish you'd considered in hindsight when choosing construction materials.

My Lowe's and Home Depot both have free Wifi. I use it all the time to use their app or site to find the location of items in store (obv. can't talk to humans).

Target (specifically mentioned by the parent) in my town also offers free WiFi.

Good luck with that. I tried unsuccessfully, to buy an item at both Lowes and Home Depot but nobody was able to determine where in the store the item was even when I pulled the information up on my phone.

One of the Home Depot's in my area had broken Wifi for multiple months. You could connect, and go through the disclaimer, but nothing was reachable through it. Particularly annoying because the other store, which is about the same distance away, has working Wifi but horrible reception. Since I'm occasionally in each, I had to remember to forget the Home Depot Wifi and add it back in depending on when I wen tto different stores.

Both the Lowe’s and Home Depot by me have the aisle/bay listed on their website. It’s usually super convenient, except for their numbering of end caps. That time it took a couple of tries until I found an employee who knew what was meant.

That's probably it. Perhaps I want some decorative brushed aluminum sheet metal instead of drywall...

Tin foil with a good earthing should do the trick.

Aluminum siding works pretty well!

Don't forget to stack large quantities of tin and aluminum cans about 8 feet high or so.

> and refrigerators along every wall.

Seems like a sound investment!

In terms of passive signal blocking, I wonder if the chickenwire mesh that holds exterior stucco in place could serve as an effective Faraday cage? Or aluminum siding? I'm sure the metal roof and walls of a modular storage building would.

Most businesses use metal studs to support interior walls, though I doubt their ~2 foot spacing would block wifi or cellular RF.

In terms of active cellular jamming, that should be pretty easy to detect -- by standing in an outside doorway where you'd be exposed to inside AND outside signals, and then checking if your cellular bars fade out. That should indicate that you've been exposed to an internal jamming signal, since the external signal should still remain.

It's hard to imagine that the advantage to a corporation of isolating the customer's phone would be worth the risk of FCC prosecution.

> I wonder if the chickenwire mesh that holds exterior stucco in place could serve as an effective Faraday cage?

I can confirm that. I've had a shed in the past where I've used chicken wire to secure insulation and it seems to work well, albeit unintentionally at the time.

Your idea of mesh inside the stucco is way better than my idea of simply wrapping chicken wire all over the outside. Ha.

It should work, as long as it all has electrical continuity and is grounded. I think that's where a lot of normal mesh in stucco or plaster falls short; nobody is going to bother to connect it all up with copper strips or whatever if that's not their explicit goal.

Even if it's not, it should attenuate radio waves somewhat. Just not as a full-coverage Faraday cage.

Steel roof trusses, steel roof material, and racks and racks of steel shelving don't exactly make for an ideal radio signal environment. They aren't blocking signal, you are standing in an un-intentional Faraday cage. It likely has more to do with who your carrier is and what frequency your phone is connecting at. And FWIW, you don't have to be connected to a store's WiFi for them to track you - https://www.fastsensor.us/en/ is only just one of the many companies who don't require your cooperation to track you in-store.

Could it be that they had repeater antennas before, but after the LTE upgrades, they either declined to renew the repeater leases in favor of wifi+tracking or perhaps the carriers didn't want to pay for hosting repeaters?

Or a previously good cell radio nearby was moved, decommissioned, broke down, blocked by something else.

A common cause for this is foil backed insulation. A number of companies install this in the ceiling spaces and outside walls to reduce the energy costs of keeping the store at a comfortable level.

I've noticed this, but my thought is that it is just the natural faraday cage created by having a cement building filled with metal shelves. Combine that with towers transitioning to use LTE over 3G and you get reduced coverage indoors in large buildings.

Although where I live, the introduction of LTE on low bands reclaimed from analog TV has actually dramatically increased indoor coverage

If you could publish evidence of this phenomenon, the public would be very interested.

Anecdotally, I've had the same experience. Been going to Home Depot for a number of years, routinely using the app to locate the aisle I want in the store. Starting less than a year ago my signal becomes almost unusably weak as soon as I walk through the doors. No construction on the store, same store as has been there for a decade, but something changed. Might be a coincidence.

It's somewhat similar, but AT&T (and Apple) have forced my iPhone to always join the "attwifi" public wireless networks (present in Home Depot, airports, etc.).

I can't make my iPhone NOT auto-join it, no matter how many steps, guides, hop-on-one-foot voodoo that I've tried.

The wireless network is terrible at everything except signal strength.

This isn’t something AT&T can force, afaik.

Two things:

1. Go to Settings > WiFi and turn Ask to Join Networks ON.

2. Any time you are auto-connected to a network and don’t want to do that again, go to Settings > WiFi, tap the blue info icon next to the currently active wifi network, and then tap Forget this Network when the details show up.

Ask to Join Networks is usually off by default. That means your phone will always attempt to join any public wifi without asking you first. Apple thinks this is friendlier for people. All known networks, once joined, will forever be auto rejoined in the future unless you turn Ask ON and forget each network you connect to (except those you trust and want to auto-join).

Thank you (for those who don’t know) but I’ve already done that multiple times. I’ve reset network settings. I’ve done crazy voodoo with restarts, airplane mode, etc.

It’s possible that it’s been “fixed” in subsequent iOS updates. I haven’t tried recently.

Do you have a Mac or iPad that it might be pulling the settings off of?

Buy an iPhone, and get a seperate sim card for it. That way the phone is yours. And if you are careful, it shouldn't cost you more than a 1-digit sum, and even that would only be to cover postage when you hunt down a cheap offer.

Having discussed this with a couple of friends off of here, I should add some evidence of the tracking[0]. I agree with lgats sibling comment that this is likely just a function of the construction of the building and not outright illegal jamming.

[0] https://www.walkbase.com/blog/wi-fi-analytics-in-retail-stor...

I haven't noticed it myself. Cell phone still works inside my local home depot.

Back in college the engineering building used metal plates as the outside facade, combined with concrete construction. It had a side effect of getting rid of any cell phone reception as a result, unless you were beside a window. The building was built before 2G cell phone service was a thing, so it wasn't an intentional thing.

I always assumed stores were blocking cell signal (or certainly not doing anything to improve it, like installing LTE repeaters), to prevent you from going on Amazon and finding cheaper alternatives.

"Available for me". Are you assuming we know who you are? What's available for you might be very out of reach to others. Farady cages are not some wallpaper you put on your house.

Go to hardware store (Home Depot would be ok but watch for poor cell reception). Buy 100 rolls of chicken wire and several gross of outdoor cable clips. Tack up all over outside surface of your house.

You could wrap your house in chicken wire and ground it. I think that's about as cheap and easy as it can get. Might make the HOA mad, though.

That's why you avoid you should avoid living in an area with an HOA that's made up of bored retired middle managers.

classic hackernews

In a 5-4 decision in https://en.wikipedia.org/wiki/Kyllo_v._United_States , the SCOTUS determined that police can't use thermal imaging on a house without a search warrant. I wonder what the vote would have been if the justices could have seen videos like this.

This seems nearly identical issue; why would you suspect the vote would differ?

Sometimes I wonder is this could be mitigated by literally covering your walls in aluminum foil. Maybe those "tinfoil hats" are on to something.

Just get aluminum siding, which was very popular before people switched to vinyl.

Having pulled some of it off to switch to vinyl I wish it was still readily available. It's orders of magnitude more durable than vinyl.

FWIW, I don't think the cops were using thermal imaging to detect humans within a house - they were using it to detect abnormally high heat - from high temperature lamps used to grow pot. Originally they'd talk to the power company to see who is drawing irregularly high levels of power, but the growers started using diesel power generators to power their grow lights.

So this MIT method would be OK, since it's not thermal?

It is still radiation of photons. Just different wavelengths (IR vs Radio).

With this paper our last shreds of privacy are being taken away, but they presented the news with nice background music, so there's that.

Guess you shouldn't read about what synthetic aperture radar systems have been able to do for decades... you can actually make a ghetto radar capable of capturing the data used for this demo with about $350 (in 2012) in materials. But don't worry too much. Their limitations section states that "the operating distance of a radio is dependent on its transmission power" so their system only works reliably up to 40 feet, which is true, but the dominating factor is simply distance, because any signal you get back will be attenuated proportional to 1/r^4. Pumping up the transmitted power to compensate takes a lot of energy that quickly gets you into needing operating licenses. Not to mention moving to using different frequencies that can give higher resolution of whatever you're imaging...

It's because of the distance limitation that it will be used for medical purposes mostly, methinks.

Meh, that seems a little sensationalist. Any significant metal would likely throw this in a loop. You could even buy paint with graphite in it to block weak RF signals outright. IIRC most military bases and data centers protect against this sort of leakage.

The potential for open/outdoor spaces is scary though. Radio "CCTVs" that see everyone over a large area.

> Meh, that seems a little sensationalist. Any significant metal would likely throw this in a loop

Maybe even chicken wire in the walls.

They already have your up-to-the-second location and all your private data. All this adds is what pose you're currently making with your body.

Speaking of, I was halfway expecting to see a couple stick figures banging each other behind a wall somewhere in that video. I really think that would have been the frosting on top; they should consider this for the next video when it's time for another round of funding.

The skeletons appear to have very long legs, but no torsos.

I wonder if it was made intentionally that way to make them look less serious.

I also wonder how accurate their estimates are of arm and leg poses, much less their motions. I do believe they can detect the location of a torso. I don't believe they can do the same for forearms, hands, legs, or feet, or their precise motions.

I suspect the articulated pose and motion of their animated stick figures were extrapolated from progressions of articulations of limb poses that were learned from the light-based training videos, and then they were overlaid onto the wifi-based signal of only the moving trunk.

All that animation does look cool, though.

"Attacks only get better".

No, this research documents information you are already leaking, it isn't taking anything away.

What this video (or even the paper) doesn't show is the large antenna arrays that are used to capture the heatmaps. A previous paper called "Capturing the human figure through a wall" [1] shows the type of antenna array used and in this paper they use two such antenna arrays to capture two planes to increase the accuracy.

[1] https://www.semanticscholar.org/paper/Capturing-the-human-fi...

Love it. This is a game mechanic / movie superhero device that's been around a long time, just love the fact that this does it so simply and with so much promise. As sensitivity and the quality of the neural net increases, combined with AR, this is going to make super soldiers out of SWAT teams.

Maybe SWAT can use this to validate that it's actually the right house when serving a no-knock warrant. I'm cynical enough to feel like there's no way this is good for any of their targets, though.

Edit: Kolpa makes a really good point! This seems like a really good counter to SWATting, where the claim is that someone is holding hostages or something -- this could pretty effectively demonstrate that to be false if they see one person in an apartment sitting at a computer.

No possible improvement to a SWAT team is ever good for a target. But I think this will prevent false positives a bit. Knowing the posture and stance of the people inside a room can help with where you aim as you go in.

I'd be more afraid that they'd "fear for their lives" at every broomstick and fishing pole they saw through a wall and would start shooting before they even got to the door.

This. It's quite possible that if it looks like you're holding something, they'll just shoot through the wall before even entering.

> Maybe SWAT can use this to validate that it's actually the right house when serving a no-knock warrant.

How would a stick figure images help a SWAT team validate that they're at the right house?

This could only help them by giving them a clue about where to point their guns once they bust down the door.

For example, if they are expecting to find someone with several hostages, and they only find people lying in bed...

And this is why you build a shipping container house -- free Faraday cage, built right in. Not mention that it's not hard to convert shipping containers to meet California earthquake code, or so I've read.

An earthquake could easily convert such a structure into a casket that 'respects your privacy' with no hope of dialing out for help.

> Not mention that it's not hard to convert shipping containers to meet California earthquake code, or so I've read.

Other than bolting crap down wouldn't that basically consist of making sure it won't tip over?

I hope you're not doing anything illegal, citizen.

Was just thinking that this reminds me of the alien weapon in Perfect Dark: https://youtu.be/8DlVQ6OjRcA?t=6s

Pretty common in games actually:

- Deus Ex: Human Revolution https://www.youtube.com/watch?v=3WoaLJ10ZB8

- GoldenEye: Rogue Agent https://youtu.be/EV8xxZec4j8?t=6m39s

but thermal imaging is already available without AI or WiFi..

You might want to take a look at Big Clive's video about the radar motion detectors in Chinese E27 socket LED bulbs [0], which have become cheaper even back in mid-2016 than good old PIR motion detectors. The latter are basically a castrated Flir-style camera, the former closer to this.

[0]: https://www.youtube.com/watch?v=FgdXRLjYkc4

Not through walls. Radio penetrates a lot more than heat.

Thermal doesn't work through/around walls.

It’s pretty amazing that they only trained it to create pose estimation from radio signals, and that its ability to see through walls is only a byproduct of them not blocking RF.

Given how much information is out there that we can’t sense I wonder if this area will be a main source of AI advancements. Another example of something like this is using videos of plants that vibrate slightly with sound waves to recreate the original sound.

Use ultra-wideband radio pulses, an array of a few thousand 3D printed UWB antennas and a phased-array scanning beam. You'll get a machine you could fit in the back of a truck that can scan a city block in real-time to mm precision. Sweet dreams, citizen.

Potentially not that simple, as there are fundamental limits on the information capacity of a MIMO system, based on the surface area of the volume occupied by the antenna array (in wavelengths squared). The capacity limits apply whether you use the array for communications or radar, as both are governed by Information Theory.

Not to say that it can't be done, but the maths exists to definitively prove whether it can be, so no need for speculation and tinfoil. My gut feeling is that you could scan a small volume from afar, but not a whole block. No, I haven't done the maths.

Yeah this is why you'd use UWB -- the capacity is insane. Also the raw information theory calculation makes sense only if you have zero prior information about the sample you're reconstructing. But 'people in buildings' is a pretty strong prior. And it's not like you have to do any extra work, just put a simulated raw signal through a neural net and regress to groundtruth data.

But let's do the math, I'm curious!

So Dark Knight style imagery, all from 1 truck?

What's the range?

Depends on UWB bandwidth+power, how good your processing is + how many antennas you have... You could also get way better with a fleet of trucks spaced over a large area, or a city-sized swarm of drones, or satellites...

The paper [1] doesn't show the antennas, but the text seems to indicate the antennas are quite large, as large as the area being observed. Plus, you have to have two perpendicular axes of antenna, so you have to be behind two walls, or one wall and a floor or ceiling. That's a big setup.

It might be useful if you wanted to count people in a crowd going in and out through a big opening, like a subway station or mall.

[1] http://openaccess.thecvf.com/content_cvpr_2018/papers/Zhao_T...

I'll repeat it again.

- Machines that see through walls are coming

- Microscopic drones are coming

- Mind-reading machines are coming

- Private key cryptography will become obsolete

Fighting for privacy is backward. It's unsustainable. We must work toward a post-privacy world. The sooner we do it, the smoother the transition will be.

Describing the exact same inevitable phenomena as "The Age of Transparency" is probably going to elicit a better response from most people. "Post Privacy" is negatively charged and makes it sound like more of a net loss as opposed to progress.

But they're the same thing. You can't get rid of the negative consequences just by using a different term.

I'm scared. What is a post-privacy world?

A world where you don't have to lie and keep secrets.

A world where people freely share knowledge and resources.

That sounds like a Mark Zuckerberg quote.

freedom is slavery

ignorance is strength

Smelly air is "coming", so prepare for it by eating lots of onions? Nah.

> I've heard quite a lot of people that talk about post-privacy, and they talk about it in terms of feeling like, you know, it's too late, we're done for, there's just no possibility for privacy left anymore and we just have to get used to it. And this is a pretty fascinating thing, because it seems to me that you never hear a feminist say that we're post-consent because there is rape. And why is that? The reason is that it's bullshit.

> We can't have a post-privacy world until we're post-privilege. So when we cave in our autonomy, then we can sort of say, "well, okay, we don't need privacy anymore, in fact we don't have privacy anymore, and I'm okay with that." Realistically though people are not comfortable with that. Because, if you only look at it from a position of privilege, like, say, white man on a stage, then yeah, maybe post-privacy works out okay for those people. But if you have ever not been, or if you are currently not, a white man with a passport from one of the five good nations in the world, it might not really work out well for you, and in fact it might be designed specifically such that it will continue to not work out well for you, because the structures themselves produce these inequalities.

> So when you hear someone talk about post-privacy, I think it's really important to engage them about their own privilege in the system and what it is they are actually arguing for.

-- Jacob Appelbaum

Wi-fi has been researched for this capability since at least 2015: https://www.youtube.com/watch?v=fGZzNZnYIHo

It’s a new paper from the same group.

In 2015, the tracker person was just shown as an amorphous blob on the screen. In the recent paper, they display a stick figure modelling the movements of the person’s limbs.

Do the people that write these papers ever release their source code or trained model? I'm curious about both other researchers reproducing as well as being able to download something and play with it.

They’re using custom hardware to make this work.

This isn’t always clear from the press release. For example, they mention that the technology works at “WiFi frequencies.” That’s true, but they’re sending a radar signal using two huge antennas, not a Wi-Fi router.

Am I correct in assuming they are using a Walabot sensor as mentioned in footnote 2?


EDIT: I see from section 3 that they created their own FMCW antenna array that is somehow similar to a Walabot.

May I ask what's FMCW? Of course I can straightaway google but I would like to hear an intuitive explaination.

Through-Wall Human HeadShot Estimation Using Radio Signals...

I wonder how similar it is to the tech used in this paper on gesture recognition through walls: http://wisee.cs.washington.edu [2013]

They are quite different. Wisee uses a single reciever and uses doppler shift to identify the gestures whereas this "through wall" system uses an array of transmitters and receivers that identify reflections from a position in space.

In layman's terms this system is more like a conventional camera but working in the radio spectrum whereas Wisee is like a microphone that can pick up changes in frequencies around it.

Finally, a legit purpose for my tinfoil hat!

I know you're joking, but that's an interesting idea... I wonder how would the system "see" your head then? Unless it is trained on people wearing tinfoil hats (and aluminium suits) it might produce interesting results.

Adding a tinfoil hat would make you reflect more which the system would pick up even easier.

Probably true - but it wasn't trained on such dataset, so I'm curious how robust it is.


You clearly didn't read the manual.

Just like people running open WiFi access points getting upset about anyone reading their packets. They don't think about what they can't see.

A building that doesn't block radio and IR (and others) is essentially transparent. Putting an emitter like a WiFi point inside is like turning on a light.

What we need is more attention put to building better walls.

maybe so... but only external walls right and even then dont you want wifi in the back yard?

Does it matter if our WiFi points are always on?

Presence detection can easily toggle WiFi on and off based on if people are present.

The defense applications for this are tantalizing. However, given the staggering amount of room clearing that's been taking place in US military operations for the past 15 or so years, I'd be shocked if there wasn't already an existing capability to detect bad guys through walls in a CQB environment.

>I'd be shocked if there wasn't already an existing capability to detect bad guys through walls in a CQB environment.

Existing and exist in a state you can deploy are two totally different things that often happen many years apart. Usually something exists as an impractical wish list item for a long time before some other development pushes it into the realm of being practical to use.

Yeah, it's just that western special operations kick in so many doors on a daily basis that one would think such tech would be fast-tracked.

May I ask what's CQB?

Close Quarters Battle

Awesome. I was playing Batman Arkham City yesterday and this is "Detective Mode" in the real life!

Yeah, I wonder what they are going to use this technology for. "Helping earthquake victims" probably


I bet some RF absorbing material or something that reflects RF at weird angles would probably break it. Or an active RF transmitter.

Build an electronic warfare device that makes it look like hundreds of people are inside, all pointing guns outwards.

Make all walls a Faraday cage / concrete. If you can’t get cell or radio reception inside, you probably aren’t leaking anything either.

anything metal in the way. I'm sure the image would be a lot less clear if the wall had metal studs instead of wood.

Carry something metallic, so the neural network no longer classifies your reflection as human?

I guess now we know how that beginning scene in altered carbon could work

There are no legitimate uses of this technique. It only applies if you lack the consent of the target. If have that, there are many easier and better ways to monitor them.

A personal home security system could make better use of this instead of motion sensors in each room.

As mentioned elsewhere, detecting earthquake victims maybe, a terrorist or hostage situation where the targets definitely aren't giving consent, military situations and covert surveillance for law enforcement and counter espionage all spring to mind as legitimate and useful applications.

SWAT team dealing with a hostage situation in a closed room

It can also be used to monitor a baby's respiration

We need multiple home robots to fake our presence now!

Amazing what a bit of military funding can achieve.

Wow great work! I'm stunned. Not really by the pose-recognition, that's just a bonus.

Does it only detect moving bodies?

Depends on the training data and the room config. The system sees a difference in an empty vs occupied room, movement doesn’t seem to be strictly necessary. The heat map video looks more like radio spectrum signatures, which might even be working on still frames - which would imply that movement isn’t necessary at all. It would help the AI, though. Easier to classify moving bodies, the speed and gait is a signal.

I would like to get more research of this sort.

Would someone kindly point me towards it?


I built and extended this for a college project years ago: https://ocw.mit.edu/resources/res-ll-003-build-a-small-radar...

It's not a bad place to start. And cheap if you want to build your own too (some third party even sells the "cantennas" so you don't have to fiddle with tuning that part (which is kind of infeasible without a network analyzer anyway)).

Thanks Jach

A good place to start would be the paper's references.

I went to the website and casually looked down. There was a "see also" section. Browsed through those and remembered Prof Dina Katabi demonstrating this concept before Prez Obama in the White House, few years ago.

Will go through references too :)

I come at this entirely from the ML side, not the hardware one, so that stuff is a mystery to me :-)

We could be using this technology to see tumors and other pathologies through patients’ skin. Instead we’re using it to give soldiers and spies x-ray vision.

No we can't use this radio signals to see tumors, because science is not magic and wishful thinking will not solve the technical problems. Let's try to name a few:

The radio signals are absorbed by wet salty meatbags, so you can find them using radio signals, but you can't see thru them. If you raise the power to compensate the absorption, you will cook the meatbags, like a microwave oven.

If you were lucky to get a signal at the other end, the radio signal can distinguish between meat-bone-air-water, but not between tissues like meat and tumors that have a somewhat similar composition. A tomography use contrast to try to distinguish them. A magnetic resonance is better, but it use a huge magnet (and in some cases it use contrast too).

And also, the radio frequency that they are using has a wavelength of an inch approximately. So roughly it can resolve things that are an inch long, so it must be a big tumor to be visible. Perhaps you can try with a higher frequency that has a smaller wavelength.

And if I understand correctly, this device needs a lot of calibration, so you need version of the part of the body without the tumor and a version with tumors of different sizes and positions to calibrate the device and then try to use it in the real subject.

Why can't it be both? Science and technology advance in often unexpected directions and for new purposes all the time. Satellites in orbit came from ICBM research, GPS from military location tracking, the tiny electronics in your phone are the grandchildren of at least one miniature spy device.

MIT's new anti-fapping radar!

Almost like The Eraser (1996), just add squad railgun rifles and X-ray-like targeting.

we have nothing to hide now!

Look at the list of names on this paper. We better fix our immigration system for high skill individuals.

Devil's advocate: "let's fund PhDs with respectable salaries instead of green cards."

We are talking about MIT. Their acceptance rate is around 6%. I am sure they get plenty of applications from the smartest American undergrads. Assuming that they choose the best and the brightest, it makes sense that they would have students from all over the world. Americans don't have a monopoly on intelligence.

You are both correct.

Many Americans choose not to go into academia (at every level) because the other options are much more lucrative. It is true that many of America's best minds do not pursue a PhD in large part because of the paltry stipend.

It is also absolutely true that the one top CS PhD program I know of does not compromise in admissions and does not suffer from a lack of highly qualified applicants.

> Americans don't have a monopoly on intelligence.

I think it's possible to agree with this point while still believing that American CS Ph.D. programs -- especially those outside the top N -- are not as attractive to domestic applicants as they probably should be.

>Americans don't have a monopoly on intelligence.

Sadly, we seem to be quite deficient in that department compared to other first world countries...

How does that solve the problem of attracting talent?

It solves the problem of attracting American talent, not talent in general.

Immigrants get "paid" more than citizens to do a PhD in the U.S. because there's a green card "stapled" to each degree, which is of no value to citizens but of significant value to immigrants.

I called the argument "Devil's Advocate" because it is more than a little thankless to complain about someone working hard to obtain a privilege you were born into. It still hurts to have your dream job undercut by someone else, though.

>It still hurts to have your dream job undercut by someone else, though.

What an absolutely atrocious way to think of your fellow man...

If someone else is getting the job you want instead of you, they worked harder for it than you did. If you want your dream job, you need to be prepared to compete for it, regardless of what color skin the competition happens to have.

I declare support for a cause dramatically against my own interest but mention that it "still hurts" to do so (on account, you know, of it being against my interest) and you call my feeling an atrocity? It's not enough to merely do the right thing, I must also revel in the pain it causes me?

That's sick, it's an atrocious way to think of your fellow man, and it's the very attitude that put Donald Trump in office.

> If you want your dream job, you need to be prepared to compete...

Your post history suggests you are an American. Unless you are an American PhD student, you are almost certainly benefiting immensely from much stronger protectionism at this very moment, so take your self-righteousness, and stuff it.

> If someone else is getting the job you want instead of you, they worked harder for it than you did.

No, that's not a valid generalization. They may have worked less hard and been more talented. They may have worked less hard, been less talented, but had the good fortune to have better social connections. They may have worked less hard, been less talented, but benefit from non-germane status-based discrimination. Or, well, lots of other possibilities.

I see this sentiment quite often on hackernews. Despite having more than enough, we are just bitter than we don't have more and it's blinding us from enjoying what we have. Immigrants are just the scapegoats.

Could you point at the part where I blamed immigrants? I knew when I posted that the HN crowd would likely hallucinate that I had done so no matter what precautions I took, but I want you to poke at that hallucination and watch your hand go through it.

I want you to understand that your mind created this mirage in order to protect you from the cognitive dissonance of telling someone to enjoy ruin at the hands of competition while simultaneously enjoying stringent protections from the very same kind of competition.

Why do you believe any of those names are not American?

They're all American in some measure as they are all living in the US at MIT. But they are clearly immigrants or the descendants of immigrants.

Look, I get the point you're trying to make, and I know you're not trying to be racist or xenophobic, but implying that having a foreign-sounding name make you less than entirely American is a really bad look.

Literally everyone credited in this paper could have been born and raised in the USA with birthright citizenship. I know that, realistically, that's not the case, but jumping to assumptions about individuals based on how ethnic their names sound is a form for casual racism that has absolutely no place in academia.

More importantly, if non-citizens are so much more likely to get admitted to MIT than citizens, it's not the immigration system we should be worried about. We should be worried about our education system that fails to produce highly-educated and motivated adults that qualify for admittance into MIT.

I also need to call you out for even bringing "descendants of immigrants" into this conversation. The children of immigrants have a name in this country: American citizens. We ought not judge people for the national origins of their parents, we should judge them for their academic and professional merits.

Thank you for taking the time to write this.

I mean... in 2016 1.2% of Americans were "American Indian", so outside of that small group everyone is "clearly immigrants or the descendants of immigrants".

It's pretty bad form to look at names and assume that someone isn't an American.

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