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It is a common belief that cacti absorb radiation; consequently, a lot of people put potted cacti by their computer as a safety means.

Do cacti actually absorb radiation? Even if so, will a small cactus (or several of them) by one's computer make any difference?

Some sources to prove this is a popular belief:

Sam I Am
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Armen Tsirunyan
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    A simpler answer would be "no harmful radiation is emitted by a computer." If it were, someone would have noticed and made it a regulated device and it is not. In the USA, there are FCC govt regulations limiting the amount of radio waves emitted by a computer or any other consumer devices, for interference purposes. The common manufacturing practice of enclosing the computer in a metal case that is then grounded limits this radio interference. – Paul Mar 11 '12 at 08:31
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    Also see this nice [xkcd visualization of radiation sources](http://xkcd.com/radiation/) – David LeBauer Mar 13 '12 at 16:21
  • @David: Nice one – Armen Tsirunyan Mar 13 '12 at 16:54
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    (Tongue firmly in cheek.) Well a screen does emit radiation in visible wavelengths. So one way to use a cactus for this purpose is to plant the cactus (a large one, that completely obscures the screen from view, maybe a full grown saguaro) immediately in front of the screen. Since this effectively prevents all use of the computer, the user will just power it down. No more radiation emitted by the screen. –  Apr 07 '12 at 09:09
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    @woodchips Of course the same goes for any other "harmful" radiation. Radiation travels in straight lines, so the only way this could work (and it doesn't, nor is there any need for it) is to surround the PC and monitor with cacti... – hdhondt Sep 11 '12 at 00:08

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The 'cactus absorb radiation' meme is very widespread, but seems very short on detailed analysis. So let's start with some basic facts.

  1. None of the articles are explicit about what radiation they are talking about. However the only significant radiation emitted by computer monitors is electromagnetic radiation, which is all around us all the time, and in general one of the least harmful kinds. Studies have shown again and again that radiation emitted from monitors is not a health problem.
  2. Almost everything blocks electromagnetic radiation to some extent. Water and living tissue are good at it. Cacti do, but so do other plants; metal; plastic; clothes and water. Some of these are much better absorbers than plant tissue. There appears to be no evidence that cacti are better than other plants, for a given plant size. However thicker barriers absorb more than thinner; so cacti, being unusually thick plants, are probably slightly better than other plants (but worse than many other things). However even if this is true it is irrelevant because...
  3. Electromagnetic radiation travels only in straight lines. So any kind of radiation shield works only if it is sitting between you and the source of radiation. So even if it were good at absorbing radiation, for a cactus to be effective as a radiation shield it has to be large enough to fill the space between you and the monitor, an approach which would obviously make the monitor unusable. Having a small cactus sitting beside the monitor will do nothing.

In short: this is a complete fabrication, supported by a few misleading half-truths.

The only way a cactus will shield you from radiation is if you have a giant one between you and your monitor. Even then its effectiveness is doubtful.

DJClayworth
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  • A search for ("nuclear cross section" "plant tissue" cactii) doesn't turn up much. http://www.google.com/search?num=20&hl=en&safe=off&client=firefox-a&hs=Oq3&rls=org.mozilla%3Aen-US%3Aofficial&q=%22nuclear+cross+section%22+%22plant+tissue%22+cactii&oq=%22nuclear+cross+section%22+%22plant+tissue%22+cactii&aq=f&aqi=&aql=&gs_sm=3&gs_upl=14222l15462l0l16189l4l4l0l0l0l0l105l393l2.2l4l0 If cacti are good at absorbing radiation, I'd expect someone would have made a measurement to back up the claim. –  Feb 27 '12 at 15:57
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    Succulents may have more water retained than other plants. That would be good at stopping alpha particles... (and that's where I peter out, because the idea is ridiculous.) – Oddthinking Feb 28 '12 at 16:54
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    "Almost everything absorbs electromagnetic radiation to some extent.". You can remove the "almost". Everything will absorb some type of electromagnetic radiation. That is why, for instance, we see colors. – nico Feb 29 '12 at 20:39
  • @DJClayworth apparently CRT's *do* emit x-rays, a type of ionizing radiation), even though, according to the [EPA](http://www.epa.gov/radtown/tv-computer.html), "most TV sets and computer screens have not been found to give off any measurable level of radiation." – David LeBauer Mar 13 '12 at 16:23
  • @David X-rays are a form of electromagnetic radiation. Do you have a source backing up the claim that CRTs emit them in quantities coming anywhere near being a health issue? (Not forgetting that CRTs are now a very small fraction of computer monitors). – DJClayworth Mar 13 '12 at 16:40
  • @DJClayworth Although they are EM, X-rays apparently produce ionizing radiation (although they are EM). My point was only to make a small technical correction to your post - that CRTs produce X-rays and X-rays are known to produce ionizing radiation, even if in trivial amounts (the EPA document gives standards which control the amount released by CRTs). – David LeBauer Mar 13 '12 at 18:14
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    @DJClayworth references: from the same reference ([EPA](http://www.epa.gov/radtown/tv-computer.html)): "Like microwaves, radio waves and visible light, the x-rays produced by an x-ray machine are a form of electromagnetic radiation. Unlike microwaves, radio waves, and visible light, x-rays are a form of ionizing radiation,". I have no reference (nor did I claim) that this is a health issue. – David LeBauer Mar 13 '12 at 18:15
  • "Electromagnetic radiation travels only in straight lines." That's not true. It will diffract around objects that are smaller than the wavelength. – endolith Apr 07 '12 at 18:55
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    Find me a cactus smaller than a wavelength of light and I will modify the answer. – DJClayworth Apr 09 '12 at 22:56
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    Another very important issue is that the visible light, the wanted product of computer monitors **IS** by itself **EM radiation**. Computer screens are omitting EM radiation because that is what there are used for! – SIMEL Apr 14 '12 at 13:55
  • A simple, and maybe the best, method for anyone to test it themselves, would be to get an earthed multimeter and measure their body voltage (relative to the earth, due to this difference being an indicator of EMR near where the tester is), an RF meter to measure the ambient EMR levels within the relevant EM ranges, and a gauss meter to read the computer's EMR levels that way also - and see if having the cactus anywhere near the vicinity reduces levels of all those three common EMR readings, or not. In a well-controlled experiment I can't see why you couldn't trust the results. –  Jul 14 '14 at 05:55