[HN Gopher] Scientists shine a laser through a human head
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Scientists shine a laser through a human head
Author : sohkamyung
Score : 93 points
Date : 2025-08-04 13:07 UTC (9 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| milliams wrote:
| Original paper at https://doi.org/10.1117/1.NPh.12.2.025014
| luguenth wrote:
| Wearing a tin foil hat is getting real world applications
| amelius wrote:
| But how do you stop the neutrinos?
| thrance wrote:
| Just make your tinfoil hat a few light-years thick.
| davidmurdoch wrote:
| You could also wear a black hole as a helmet!
| adolph wrote:
| The authors suggest black foamboard with cloth and a
| laser safety curtain is sufficient. Better safe than
| sorry though. To prevent light from
| reaching the detector from sources other than light
| transmitted through the head, the experiment was
| performed in a light-tight enclosure that
| surrounded the head. The enclosure was built using black
| foamboard and covered with two layers of black cloth and
| a laser safety curtain.
|
| https://doi.org/10.1117/1.NPh.12.2.025014
| lawlessone wrote:
| Not for neutrinos it isn't
| HelloUsername wrote:
| The title made me think of Anatoli Bugorski, a Soviet scientist
| who in 1978 survived a high-energy proton beam from a particle
| accelerator passing through his head.
|
| https://en.wikipedia.org/wiki/Anatoli_Bugorski
| brenainn wrote:
| Me too! Amazing that he's still alive.
| FirmwareBurner wrote:
| Yes but ...
|
| _" In 1996, Bugorski applied unsuccessfully for disability
| status to receive free epilepsy medication. Bugorski showed
| interest in making himself available for study to Western
| researchers but could not afford to leave Protvino."_
|
| This is just sad all around through and through.
| genocidicbunny wrote:
| Interestingly, one of the things studied at the institute where
| this happened is proton therapy.
| shadowgovt wrote:
| There's a lot of pieces of the physics of that story I don't
| quite understand. The main one is that (IIUC) one of the
| reasons the damage wasn't as bad as it could have been is that
| at the relativistic speeds the protons were travelling at, his
| head was _extremely_ space-dilated, so they were basically
| blasting through tissue paper. But I would expect that tissue
| paper to have all the mass of a human head dilated into a thin
| disc, so the density would be far, far higher... Is density not
| a factor in proton-beam interactions with the material its
| interacting with (or is it more "it is, but total distance is
| a much larger factor")?
| whatshisface wrote:
| The fact that cross sections become smaller at high
| velocities is very intuitive: force applies its kick over
| time, and there is a lot of distance between the parts of an
| atom. If a particle is going fast enough it whizzes by
| without pushing on the other atoms for very long.
| shadowgovt wrote:
| Yes, thank you, _this_ was the intuition I was missing!
|
| Protons almost never collide directly with a nucleus
| because most of an atom is empty space; a proton beam
| disrupts the matter it's passing through mostly by
| electrostatic effect, and that's a function of position
| _and_ time!
| cma wrote:
| Thinner makes it get through faster if it doesn't collide. If
| it is a charged particle dwell time is important as it
| usually doesn't collide unless its charge interacts with
| other charged particles enough to slow itself down giving it
| more time to interact with charged particles. This is how I
| understand ion beam deposition in silicon to work at least,
| it goes to a predictable depth and if the silicon is thinner
| than that it goes on through most of the time.
|
| Thinner and denser then makes it interact more per unit time
| but any induced charge imbalances have closer neighboring
| material to rebalance charge shifts with, maybe you have a
| better chance of getting through the same number of particles
| over a shorter distance than at higher distance.
|
| You definitely have a better chance faster than slower. its
| when it slows to a critical speed its non-collision charge
| based interactions build.
| 1970-01-01 wrote:
| The 2nd photo is named exactly as it looks; This isn't a parody?
|
| https://spectrum.ieee.org/media-library/a-3d-illustration-sh...
| hagbard_c wrote:
| Looks like they used the ALT attribute as file name, maybe by
| feeding the image to a model which spit out this description. I
| do not see this as a sign of a hoax.
| purerandomness wrote:
| It's just SEO.
|
| It's very common to have a CMS feeding images to an LLM that
| extracts the contents and gives image files a meaningful file
| name and alt tag.
| brulard wrote:
| It's the prompt they used to generate this image
| echelon wrote:
| There have to be ways of getting high space and time resolution
| signal capable of reconstructing people's exact thoughts,
| memories, and senses.
|
| Non-invasively. No "below threshold of detection". Beyond
| anything our scientists say is possible.
|
| We're just not advanced enough as a species to do it yet.
|
| We need to keep pushing these boundaries.
| short_sells_poo wrote:
| This would likely require completely new forms of physics and
| interacting with matter I'm afraid. It simultaneously requires
| extremely high resolution and high penetration (we need to see
| deep into the brain). You'll need to be able to measure the
| state of neurons and connections - probably down to the quantum
| level - and do this real time, and then record the data that
| you collected.
|
| I suppose you could flood the brain with nano-machines which
| would latch onto all the bits and pieces and collect the data?
| But where would they store it? How would we get them all back
| out again?
|
| I don't think it's possible to do this with our current
| understanding of physics. This is not a question of needing
| better technology, but needing a whole new universe with
| different physics altogether.
|
| I'm not even sure what is more far fetched, this or
| superluminal travel. I'm actually leaning towards the former :D
| throwaway173738 wrote:
| At least there's a theoretical path forward to super-luminal
| travel beyond hand-waving. Just find some exotic negative
| energy density matter.
| orbisvicis wrote:
| Imagine n^3 EMF-generating cubes surrounded by 6n^2 EMF-
| detecting cubes. Starting from an initial given state, is
| there any n for which over time the state of any given EMF-
| generating cube cannot be deduced?
|
| Then consider a further constrained version in which the EMF-
| generating cubes may only generate EMF in response to
| external inputs, i.e. as in the game of life.
| hollerith wrote:
| >The group measured the times that millions of photons took to
| travel from a 1.2-watt laser emitting 800-nanometer wavelength
| light into one side of the head to a detector on the other side.
|
| Sunlight contains copious amounts of 800-nm light, so this is
| probably completely non-hazardous.
| ben_w wrote:
| While it's almost certainly safe or it wouldn't have passed the
| ethics committee, what you say is an insufficiently detailed
| description of setup to determine if it's fine or not.
|
| 1.2 watts over your entire head is fine.
|
| 1.2 watts in a 800nm-diameter cylindrical path is "for some
| reason we decided to make the outer few millimetres of your
| skin explode, but we had to be in contact with your skin to
| manage that because that power density of laser would have
| ionised the air before it reached you".
| astrobe_ wrote:
| What can one actually do with a 1 Watt laser? That's a good
| question to ask to an AI: "A 1-watt laser can be used for
| various applications, such as cutting materials, engraving,
| and even lighting cigarettes. However, it poses significant
| risks, including the potential to cause instant and permanent
| eye injuries, so safety precautions are essential".
|
| So it looks like it packs some... Power. But I guess the
| frequency of the light makes all the difference, or maybe
| exposure duration?
| cogman10 wrote:
| Energy is what your looking for.
|
| Static electricity discharges at around 400 to 600W. Yet
| it's for an extremely brief amount of time. Sub millisecond
| usually) so the actual energy transferred is minimal.
|
| It takes around 1Wh to heat a liter of water 1 degree just
| to put things in perspective.
| codedokode wrote:
| The laser concentrates the power in a small spot that's
| why it is more dangerous. Consider what 1W would do to 1
| mm3 of water.
| addaon wrote:
| > That's a good question to ask to an AI
|
| What makes you say that? By what metric?
| imchillyb wrote:
| Not OP, but...
|
| Asking Google about one watt lasers inevitably produces
| junk that does not address the question at all.
|
| Sifting and sorting through that junk is tiresome.
|
| AI provides a succinct answer with as much depth is
| requested and can further clarify or expound on the
| original findings.
|
| What's not to like about such interactions? And,
| furthermore, how is the AI interaction in this case not
| objectively 'better' than a Google search?
| addaon wrote:
| > What's not to like about such interactions?
|
| The at-best-coincidental correlation with accuracy and
| truth.
| ben_w wrote:
| While I agree (despite generally liking AI, I agree),
| this has been a shared similarity with web search results
| for some years already.
| astrobe_ wrote:
| I think at least it is good at answering questions that
| have been asked before, in some way or another. But the
| real question is, why didn't I also ask my follow up
| question to it, instead of trying to talk with humans? I
| think I prefer to learn from real people with hands-on
| experience, and maybe hear amazing or amusing stories in
| the process.
| pier25 wrote:
| Yeah but to be pedantic 800nm is the wavelength of the light
| of the laser :)
| ben_w wrote:
| Which is why I chose that spot size :P
|
| Technically it is possible to focus on things a bit smaller
| than a wavelength, but not by much and some of the options
| don't even work far from the lens itself.
|
| https://en.wikipedia.org/wiki/Diffraction-
| limited_system#The...
| cadr wrote:
| Warning: do not look at laser with remaining eye.
| Onavo wrote:
| Did they figure out the dark hair issue? It's been a major
| problem for fNIR systems.
| stronglikedan wrote:
| Could they just shave an area, like they do for procedures?
| (and whenever I have to get an EKG because my chest hair is
| apparently adhesive resistant)
| bbor wrote:
| This is a very interesting experiment, and props to the team
| involved! Exploring the frontiers of the possible is almost
| always worthwhile.
|
| That said, in my humble (amateur!) opinion the framing from IEEE
| leaves a little to be desired, for one simple reason: _they don
| 't mention that most of what we're looking for is in the cortex
| (outer layer) of the brain, anyway!_+ And it kind of has to be,
| AFAIK... Namely;
|
| fNIRS[1] is one of the four main brain imaging technologies (that
| I know of?): EEG, fMRI, fNIRS, and ultrasound. Like fMRI (&
| ultrasound?), fNIRS measures the oxygenation levels of different
| parts of the brain, which has been shown to be a close analogue
| for brain activity (more activity => more respiration, just like
| muscles). In this context, it's not enough to simply receive the
| signal you sent through -- you want to infer which emitter the
| signal came from so that you can infer the oxygenation levels of
| the regions it passed through/reflected-off-of.
|
| All of that is a very amateur, high-level overview, but hopefully
| it clearly supports my underlying point/question: _how could you
| possibly make this work with a cross-head emitter-detector
| setup??_ It seems impossible to disentangle more than one emitter
| 's signals, and I'm not sure how you'd map oxygenation levels
| without more than one. The diagram in the article seems to
| support this confusion, given how chaotic it is.
|
| Then again, fNIRS and EEG both already rely on some serious
| statistical wizardy to turn 16-128 1D time series into a 3D model
| of activity, so perhaps I'm underestimating our tools! For
| example, the addition of frequency modulation to the fNIRS setup
| is an ongoing area of frontier research, which seems _insanely_
| complex to me.
|
| P.S. In case any of the hackers here haven't heard yet: BCI
| (Brain-Computer interaction) is _blowing up_ right now thanks to
| the unreasonable efficacy of LLMs for decoding brain
| activity[2][3][4], and it 's a very hackable field! There's a
| healthy open-source community for both fNIRS[5] and EEG[6], and I
| can personally highly recommend the ~$1000 Unicorn EEG system[7]
| for hackers.
|
| [1] https://en.wikipedia.org/wiki/Functional_near-
| infrared_spect...
|
| [2] https://www.nature.com/articles/s42003-025-07731-7
|
| [3] https://arxiv.org/abs/2309.14030v2
|
| [4] https://arxiv.org/pdf/2401.03851
|
| [5] https://openfnirs.org/2024/01/01/continuous-wave-
| spectroscop...
|
| [6] https://openbci.com/
|
| [7] https://www.gtec.at/product-configurator/unicorn-brain-
| inter...
|
| +: As a human, you're not even a brain piloting a skeleton --
| you're a 3mm wrap around the basic mammalian brain!
| https://en.wikipedia.org/wiki/Cerebral_cortex
| derbOac wrote:
| > That said, in my humble (amateur!) opinion the framing from
| IEEE leaves a little to be desired, for one simple reason: they
| don't mention that most of what we're looking for is in the
| cortex (outer layer) of the brain, anyway!+ And it kind of has
| to be, AFAIK...
|
| I have friends who do research in this area pretty heavily and
| my impression is the same, that it's pretty limited to the
| outer layers of brain, and not super high in resolution.
|
| There are advantages but they are more practical than anything
| else. Of course, practical can be critical but there a large
| percent of applications where it would have little utility. But
| hopefully things will improve.
| shadowgovt wrote:
| The next time someone asks me about quantum light effects, I'm
| going to try to remember this story.
|
| "The quantum nature of light is why it's possible to shine a
| bright light through a human head without setting that head on
| fire... As long as it's the right color."
| pixelpoet wrote:
| These Cornell box path tracers are getting out of hand
| jstummbillig wrote:
| That's a good headline
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