I would be careful not to confuse correlation with causation here. Most old people have medical conditions. For example, about 75% of older people have high blood pressure [1] so seeing a 75% rate in the virus fatalities should not mean much.
I suspect age and immune function drive mortality, and the other factors are merely along for the ride.
When I studied medicine 15 years ago 130-139 mm Hg was not considered high blood pressure. We were young students and we were toying everyday measuring our blood pressure. Most males had over 130.
"The prevalence of borderline hypertension was calculated by determining the number of persons who had systolic pressures between 140 and 160 mm Hg or who had diastolic pressures between 90 and 95 mm Hg."
This is more inline with what I've been thought in med school in my time.
Due to optical aberration wavelengths outside of visible range don't get focused the same way as visible light. This means that the energy is spread over larger area.
Also, both UV and IR light is absorbed in a different way. UV tends to be absorbed much faster than visible light so that little of it reaches the retina while for IR opposite is true, the eye is more translucent to IR and only a portion of it is absorbed at retina and a lot of it tends to pass through it.
What it means is that, while a source of visible light is very well focused on the retina and absorbed in very small volume of retina cells, UV and IR are spread over larger area and then large part of it is absorbed somewhere else.
Still it doesn't mean IR or UV beams aren't dangerous. It is just that you can't directly compare beams by their power.
The way I understand it the main danger is that, since people may not see the IR or UV beam very well, there might be no involuntary response to close the eye.
Love these kind of analyses on HN (still where you can find them!) where someone will describe how the details matter.
Thank you to all involved.
If anyone can point me to the generalized best studies for safety margins and laser energy, please post links -- it's pretty relevant to a lot of AR designs to use laser projectors, and it is of course relevant to the lidar self driving cars at question.
Actually most pulsed lidar systems use pretty high peak powers, which result in an eye-safe average power only because they are on for a sequence of very short pulses (~1ns). It's pretty unlikely OP is actually experiencing vision problems due to lidars, but it's probably possible for some kind of weird interaction to happen in the eyeball due to the high power pulses. Even so, it's unlikely to be causing an damage, temporary or otherwise. I would hope it doesn't happen to him/her while driving or something, though.
I'm being a bit pedantic - I'm pretty sure the visibility of the wavelength does matter (slightly) for lower power lasers, as visible lasers will allow your eye to react to the laser (by looking away) before serious damage - again only in low power lasers (like laser pointers).
If it's not visible I'm not sure that your eye will react quickly enough to prevent damage.
I'm not one to proselytize since I use a handful of languages every day, but when my Java hat is on, I double click a build target, my software is tested, built, deployed side-by-side with my current production build.
New users are automatically pushed to the new build, and users with existing sessions remain on the previous build. When I undeploy the previous build, the rest of the users start seeing the new build as well.
That's all out of the box with small config tweaks for our environment. It is truly torturous.
Which isn't to say that 1550 nm light is safer -- the mode of destruction is just different, e.g. corneal damage leading to cataracts or surface burns rather than retinal damage.
As I understand it, it’s largely a focusing issue. Close to the visible range, a distant point source gets focused to a point on the retina. At 1550nm, the energy is deposited uniformly on the cornea unless the laser is focused to a tiny spot on the cornea.
edit: I don’t know to what extent this is relevant, but humans can regenerate the corneal epithelium. Think about all the sand you’ve gotten in your eye as a kid, and the fact that it probably didn’t accumulate enough damage to blind you.
Typically you select a class of laser safe for the environment it will be used in -- class 1 is typical of LIDAR systems for this reason which poses no eye damage risk.
The lasers in these things are often not class 1, but the whole system is. Perhaps it's fairer to say that laser classification is not just about the power of the laser, it's about how it's used and under what conditions. Class 1 basically means that it's safe under normal operation. You can look at the certifications for scanning stations (e.g. Faro put theirs online) and they usually get round it by specifying that the system is spinning, so you don't get hit with a laser that often, and that you're standing far enough away that the divergence is large.
If you somehow fixed the laser and stared into it, it would probably hurt.
according to the test report, if the mirror fails, you would hit dangerous levels of energy deposited within 0.2s and they recommend that the laser must be turned off within 100ms to avoid risk of eye damage.
The same way that Spotify doesn't just ham-fistedly show you all your Facebook messages... and other apps don't show you messages intended for Spotify.
Presumably messages are tagged in such a way that the source and/or destination are intended for Spotify. Using that same system, you should be able to specify "Spotify can only read & write Spotify messages."
Didn't downvote, but your premise that people don't understand that there are heating/cooling cycles is not really a thing for anyone even minutely interested in this area of study.
In fact, here's a very detailed page describing those cycles and why it appears we are deviating from the natural order.
Tangential to the topic, but your assumption there is very wrong. Due to the politicization of the topic and the media reporting, which is frequently equally sensationalistic and inaccurate, many people are extremely interested in climate change yet also know practically nothing about it. Some know less than nothing, again thanks to the media. For instance the recent report about the oceans warming even 60% than thought turns out to be wrong. The paper had a fundamental mathematical error that was detected just hours after publication by a skeptical reader. The authors' new method of measuring the warming there remains, yet now their warming figures are no different than what has already been normally reported. [1][2][3] Many media sites have run articles trying to correct their mistaken reporting, but due to the nature of social media the sensational headline gets shared a billion times, the correct indicating it was unjustified gets shared a few dozen times. So you now end up with individual basing their worldview on false facts, which is rather less than productive.
What were the most common pre-existing conditions?
"More than 75% had high blood pressure, about 35% had diabetes and a third suffered from heart disease."
How common are those conditions in the United States?
High Blood Pressure - 1 in 3
Diabetes - 9 in 100
Heart Disease - 1 in 10