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Explaining The Flashlight Sessions

Thursday, October 30, 2014 - 06:04 PM

If you listened to our recent Halloween story "Haunted," and you're still skeptical of our skepticism about spirits talking through flashlights, this is for you.

If you have no idea what I'm talking about, go listen to the story here 

After I first heard Dennis’ story, I poked around on the Internet, looking for someone to explain how a flashlight could communicate with the dead. A bit of googling led me to a 21-minute-long video on YouTube that breaks down the particulars of what are known as "flashlight sessions." 

The video was made by a man in Germany named Burkhard Reike. When I called him up, I was greeted with the most incredible sound I have ever heard.

Once out of his cocoon, Burkhard told me this started for him when he was watching the ScyFy show “Ghost Hunters” (I’m assuming you get the gist of the show from the name). Over and over, these ghost hunters would pull out flashlights, ask questions into the air and then - just like in Dennis’ story - the lights would flash on and off.

At first Burkhard thought, eh, they're probably just tapping the table or some sly trick. But then he noticed something: all the different ghost hunters were using the exact same flashlight. The mini-Maglite, two-cell AA, with an incandescent lightbulb. 

So Burkhard bought a couple, brought them home, and took them apart. Now, the thing about these flashlights is that to turn them on or off, all you have to do is screw or unscrew the top of the flashlight. When you do this, two tiny bits of metal come into contact with each other. When they're touching, the electrical circuit is open and the light is on. When they aren't, the circuit is broken and the light is off. Here's an illustration of the inside of the flashlight from Burkhard's video (contact point is on the right-hand side, in yellow):

Burkhard ran through a dozen or so trials and experiments, five weeks worth, and found that this whole trick comes down to one part of the flashlight, the reflector. It's the dome-like mirror that surrounds the light bulb and focuses all that light. And here's how it works: 

When you turn a flashlight on, the bulb generates a bunch of heat and the reflector starts to get really hot. As it gets hotter and hotter, it starts to expand, getting bigger and bigger. Then, if you want to ask some ghosts questions, what you do is you unscrew the top of the light JUST enough so that the light goes off. Now, because the light is off, the reflector starts to cool down and contract until it pushes one tiny piece of metal into contact with the other tiny piece of metal and … BOOM! The light bulb goes on. With the light back on, the reflector gets hot again and starts to expand … and expand … until it pulls the metal pieces apart again. And the light goes off. Then the reflector contracts, and so on. 

Burkhard used a microscope camera and math to figure out that the expansion and contraction of the reflector is basically like turning the head of the flashlight 3 degrees. Cool detail, right?

But, I should say that it gets way more complicated than that - there's oxidization, fritting, molten metal - but the point is, as Burkhard said, "this is by definition something that is normal and not paranormal."

If you want to dive into the deep end, check out his explainer video. He's a good man and thorough. 


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Comments [39]


Ok here's the thing not all flashlights are like the one the experiment was done with so from my point of view you didn't disprove the exsitance of ghost in anyway also science can't prove,disprove,or explain everything in the world. Take Stonehenge for example. No type of science we know or anything has been able to explain that yet.

Mar. 01 2016 11:26 AM
Tyler Durden

Wow, literally can't even. #3spooky5me

Feb. 02 2015 11:35 PM
Niklas Lagergren from Oslo

Mark L:

Did the "psychic" know the name or address beforehand? Were there pictures on the internet? It could've been a warm reading where she simply just looked up info. Alternatively, it could've been a cold reading, where she was going down the guessing route. Guessing that his father might not have had a full head of hair and probably a similar height to the son is not very hard. That was all the information she gave before the son filled in the rest of the gaps for her.

Victor Bradley:

You say that the explanation of how the flashlight trick works doesn't disprove the hypothesis that something supernatural is going on. You're right, it doesn't - to actually disprove this you would have to perform a study with a blind test and all that jazz. The hing is, though, is that it's oddly convenient how they've chosen a method of communication with ghosts which could, demonstrably, just be random nonsense without any ghosts present at all. It's like I would claim to be able to communicate with the dead through the rattling of the wind in the leaves - sure, they're rattling away anyways, but I'm asking yes and no questions so I say there's meaning to it.

We humans are very, very good at seeing patterns in things. This is how we learn and understand the world. Speaking is patterns of sounds, experience is based on recognizing different patterns around us, etc. Recognizing patterns also gives us satisfaction. The problem is that we're so good at recognizing patterns we will see patterns where there are non. You can compare it to how we can see this :) as a smiling face. It doesn't look like a real face at all, yet we have no problem seeing it as a face. Similarly, we can see patterns in a flashlight randomly going off to our questions as something meaningful, especially if we want it to be so.

Plenty of people will say that I need to open my mind up. Hey, everyone is entitled to their opinion, but I don't think I am. I would say, to the contrary, many other people seem to have closed their minds to the possibility of random chance, coincidences and statistical probabilities. We live in a giant world, full of loads of people and an unimaginable amount of events happening constantly that all have a very, very small chance of resulting in huge coincidences that might seem meaningful. It might be strange if the story you described *didn't* happen to anyone considering how often circumstances like that would occur (most often resulting in the person involved getting a face full of metal).

To change perspective just a little, think of all the people who got into accidents and weren't saved. If a benevolent deity was involved in saving the person in your example from getting smashed, why did that deity chose not to intervene in all these millions of other cases? Is it so outlandish to claim that it is just random chance?

For me, at least, that's the explanation that seems to most likely. An open mind is important, but that should go both ways.

Jan. 21 2015 01:10 PM
Sally from Sussex, NJ

Love it! I've purchased 2 of these flashlights. One for me to mess with and one for my sister to use to freak out her husband next April 1st or October 31st. For anyone who is still on the fence about the mysticism of this one, invest 10 bucks on the right flashlight...if nothing else, it's a good little light to have in the car. And you might just have fun showing off your psychic abilities to friends.

Dec. 23 2014 09:52 AM
The J from The Couch

Small correction to offer here- The write up reads: "When they're touching, the electrical circuit is open and the light is on." This should read 'closed', not open. An electrical circuit that is 'off' is disconnected, or 'open'; closing a circuit describes completing the connection described above.

Dec. 14 2014 06:48 AM
chris from MN

Thanks for sorting out the flashlight trick! Now would you explain how divination rods work?

Dec. 11 2014 02:41 PM
Brad from Madison, WI

Although I am a huge sceptic, this explanation of the flashlight seems incorrect.....If the light is on, heats up and then unscrewed a bit till it goes off, then you just created space between the metals and broken the connection. Heat expands things and cool contracts them. So if you turn the light on and it heated up then you break the connection, why would cooling(contracting) allow the metals to meet again? If things are cooling they should be getting further apart, not closer together. This explanation video seems pretty poor. Everyone knows that a loose contact can cause the on and off thing to happen. But his videos are taken over many hours and then sped up. In the the radio lab story the light turning on and off was happing right away as well as on cue to the end of most questions asked. Not saying it was ghosts at all but I dont see this as a good explanation.

Dec. 05 2014 11:49 AM
Bryan from United States

"He's a good man and thorough." I nearly fell out of my chair laughing. Subtle Lebowski references get me every time. Aside from that, this was a nice addition to the original story.

Nov. 17 2014 04:12 PM
Arthur L from SCOTLAND

It was a great Halloween show and was suppse to generate skepticism, even though it is obviously fake. Reporting and telling a tale for a Halloween special is nothing wrong. They always produce outstanding podcasts and were entertaining again. Great job!

Nov. 11 2014 08:43 PM
Nathan from Colorado

Maybe you guys can do a show about confirmation bias. It's pretty evident in the comments section on this article, especially in the closed mindedness of supposedly scientific thinkers.

Nov. 11 2014 06:35 PM
Jim in Texas from Texas

...and every good ghost buster out there watches this video and exclaims "But this doesn't prove that ghosts aren't causing this to happen as well!" It's almost impossible to prove the non-existence of something.

Nov. 11 2014 12:59 PM
Wendy from Chicago

"Radiolab is a show about curiosity. Where sound illuminates ideas, and the boundaries blur between science, philosophy, and human experience."
This episodes fits perfectly with what Radiolab is all about. You covered science -how the flashlights trick really works, philosophy - is there life after death, and the human experience - grief and how we move on. Excellent work!

Nov. 10 2014 12:06 PM
Jill from Texas

I can't believe the hate being spewed by commenters here for RadioLab daring to create a "spooky" episode for Halloween.

Nov. 09 2014 03:14 PM
Ed Miner from Anchorage, Alaska

The description, written by Radiolab, which links to this episode starts with "There are many ways to communicate with the dead." Radiolab has received grants from the National Science Foundation. The tags for this article are "ghosts, paranormal activity, science, storytelling." What is wrong with this picture? I suggest RL should decide what it wants to be. A storytelling podcast with audio creativity? Great. Return the NSF funding. A science podcast? Start by reading the recent NYTimes article "the unbelievable skepticism of the amazing Randi."

Nov. 09 2014 11:50 AM
Toby from kansas

I can't imagine what it's like to have produced something with so much love and imagination only to see these brain dead hateful comments in return. All the more respect for everyone working at radiolab.

Nov. 07 2014 04:12 PM

Loved this episode and the show in general. RadioLab and This American Life are my favorite radio shows. For all of the cynics out there, eventually we will all die and learn the truth. Try to be kind to each other and tolerant in the meantime.

Nov. 07 2014 11:02 AM
Billy from United States

VERY disappointed in Radiolab for putting out this so called "haunted house" episode. This nonsense has NO place in a science podcast. You should not give these "paranormal" hucksters any more exposure in our culture than they already have. Shame on you!

Nov. 06 2014 05:54 PM
chimcham from United States

I think they could have leaned a little harder on the real explanation, but even the guy who experienced it said he doesn't really think it was ghosts. I just kept thinking what if the "no" light had come on when he asked if they were proud of him? Would have crushed this dude. "Psychics" are the worst but whatever, it was mostly just a silly episode, who cares.

I have been disappointed how this podcast has moved towards just telling stories instead of being more about science and the tackling of major topics from different angles. Translation was a wonderful step back toward what made this show great and I hope that tremd continues. I'm fine with the Shorts being a little more toward the other end of the spectrum.

I'm really only commenting because that Todd from NY and Cincy (thanks for the specifics btw) fella somehow thinks ghosts are a political issue. What?

Nov. 06 2014 04:38 PM
Lauren from Los Angeles

Today we're yellin' and cussin'-out a podcast. Mmm hm...

Nov. 06 2014 12:59 AM
Annie from California

Love the Lebowski reference!!

Nov. 05 2014 02:13 PM
Todd from NY and Cincy

As someone who is disappointed when Radiolab delves into political issues, I will add my 2 cents and say that I didn't mind this story at all.

Actually, I would go so far as to say that it was almost an arch-type radiolab story. After all, Jad is the rationalistic foil to Robert's spiritual musings. This episode balances that perfectly. It left open a few possibilities of the unknown while basically showing that the core event had a rational explanation.

I personally was much more puzzled by the stories of people having feelings about a specific spot (the one by the basement) and the dreams than I was of the ghost hunters, the latter of which, appeared to me to play up every single thing they said.

And the dreams seemed to involve a psychological longing, and even if the event was faked, it seemed quite cathertic, if only temporarily.

As someone who is both a PhD student and who has experienced phenomena that was as of yet unexplained, I rather enjoyed both sides.

Just for a second, suppose this: if there is life after death, I'm pretty confident that the spirits of those who have passed wouldn't be engaged in the kind of behaviors we call hauntings. After all, if there is life after death, then it is we mortals who are in the minority and in the dark much more than those who have passed. I'm just saying. If you don't buy into any spiritual concepts, then this makes no sense, but if you do, then to think that after we die, we're going to hang out and haunt stuff is kind of absurd.

But as far as whether radiolab should have covered it, I think it was a perfect "radiolab way" of enjoying the holiday.

Nov. 04 2014 03:00 PM
Beau from Earth

Bob Dobber-
You might want to listen to the podcast again.

Robert and Jad are FAR from skeptical- if anything, it seems they to want to push Dennis to say he really thought he was talking to his dad and when he says "no" they act disappointed.

As many commenters have pointed out, psychics are predatory con-artists that exploit desperate people.
Dennis is being taken advantage of- this is not a healthy, therapeutic, way of gaining closure.

By treating the story in such an open-ended fashion, Radiolab is enabling these shameless frauds.

Nov. 04 2014 07:41 AM
Bob Dobbs from United States

Everyone upset at Radiolab for broadcasting the "garbage" needs to chill out... It was a silly Halloween episode. It didn't claim ghosts were real. It didn't claim the psychics were real. It didn't claim they were really communicating with ghosts. In the end it even said that the person involved with the story didn't really believe he spoke with his dead parents, and how the flashlight trick worked. I don't believe in ghosts at all, yet thought this episode was just fine. It was a little spooky. It's OK.

Seriously, chill out.

Nov. 03 2014 01:54 PM
Ed Miner from Anchorage, Alaska

On their webpage RL states "there are many ways to communicate with the dead. We examine one of them." Does anyone have any recommendations for good science podcasts, perhaps something similar to what Radiolab used to be?

Nov. 03 2014 12:40 PM
Diego from NJ

Easy. They make the exact same flashlights with LED bulbs.
Almost no heat generated here. Do they work too, or the spirits are too picky?

By the way, I loved the episode, and to all the haters I would say that if you don't explore what you don't like, you shouldn't refute it. Radiolab is not giving credibility to this, just posting it in a nice episode, totally appropriate for the season. Good job guys!

Nov. 03 2014 12:03 PM
Wade from Iowa

I thought this was an excellent episode and a little off the norm for Radio Lab. Great for Halloween!

Nov. 03 2014 11:49 AM
Humanosaurus from Osceola, IN.

Wow, apparently some people are really taking this episode quite seriously. I saw it as a simple Halloween ghost story. A bit of a step outside the norm for Radiolab, perhaps, but I never for a minute thought that they were really serious about the whole thing.

Certainly everyone has their own point of view, but I personally saw this as nothing more than a bit of fun on Halloween.

Personally, I'm an atheist and a thinker/skeptic, who just spent the last month acting as a tour guide for a local theatre company's haunted house. No, I don't believe in ghosts. But it was good fun to pretend. Sometimes we all need some fun.

Nov. 03 2014 08:39 AM
Nick from Brooklyn

This was really disappointing.

What's next? An episode giving credence to The Secret or Animal Magnetism? Maybe crystal technology and energy healers.


Nov. 02 2014 06:38 PM
Jair from United States

Victor, I agree with you that the physical explanation does not completely rule out a paranormal explanation, and I don't think very many "true believers" will be persuaded by any number of engineers explaining the mechanics of the flashlight. However, many more casual observers may come away from a demonstration of this trick truly believing they had witnessed an event that defied known scientific laws, and it is important to emphasize that this is not the case. If you think that the perveyors of this trick are sophisticated believers that recognize the scientific explanation and still hold that spirits are at work, why do they use the flashlight trick instead of, say, rolling dice or using other methods that everyone knows are random? These paranormal "investigators" owe a lot of their persuasive power to this simple parlor room magic trick.

Nov. 02 2014 06:27 PM

Great episode. Yes it is important to explore these events if for no other reason than as a sociological exercise. The science zealots, or mystery-phobes in the world can't stand the reality that many people see the world as a place without thorough explanation--and the worst part is that they may be right. We don't have complete explanation now and BOO! we may never. Is it so scary?

Nov. 02 2014 12:52 AM
Father-of-2 from Michigan

Please allow me to put a face on the potential damage this podcast may have caused. I have joint physical custody of my two sons from my previous marriage whom I adore. Their mother believes in the paranormal and is convinced her house is haunted and subsequently had amateur (is there any other kind) ghost séances multiple times to contact the dead. In front of my children... Just a couple weeks ago my younger son told me the following story about my older son. He was sleeping when something in his room fell. He jolted out of bed and ran into his mothers room thinking it was "the ghost". This is the kind of nonsense, dare I say abuse, that my children are subjected to daily at their mothers.Needless to say I have spent a lot of time over the past couple years teaching my sons the importance of rational thinking. But what credibility do I have? Why should they believe me? I am not an expert in any field or have a higher education to point to, I am a mailman. So I bought Richard Dawkins children book "the magic of reality", (amazing, highly recommended) I have showed them YouTube clips of magicians showing how magic is an illusion, and I set their phones to download episodes of radiolab to strengthen their science and understanding of the natural order. They love radiolab. And, we've had great conversations based on past episodes. I don't know if they have heard this episode and I'm not looking forward to having a conversation about it. Radiolab, a source I told them they could use as "truth" gave credence to a spectacularly hurtful lie that continues to damage them. Even with the lame attempt at showing "there may have trickery afoot" flashlight video aid this was not helpful. No. Radiolab, a pillar of science and understanding gave credibility to nonsense at a time when credulity and servility are eroding the moral underpinning of our species. You should show shame. ,

Nov. 01 2014 11:39 PM
David from Austin, TX

From the original story: "We didn't pay these people, they would have no reason to fake this."

I'm sorry, but what an idiot.

Nov. 01 2014 07:26 PM

Another question: Why 3 flashlights when only 2 are actually needed? Perhaps a third reply is sometimes used (like "try again" or "I don't know) - but I doubt it. I suspect that the key is in randomness. Note that they don't say, "Turning on the flashlight next to the bowl will mean yes, the one furthest from the bowl will mean no, and the one in the middle will mean [whatever]." Instead, they designate the first light that goes on as "yes." Perhaps this tends to be the flashlight that's most sensitive; here I just mean that the most sensitive flashlight turns on more frequently. That would be useful if you want to have a "yes" answer first, and you'd be pretty sure that a different light - "no" - would turn on after your second question. For then on out, you'd ask a few more "yes" questions than "no" questions.

The third flashlight could legitimately be used just to make sure that at least two flashlights work, but it could also be there just to create confusion. One would like to know more about how the flashlights are distributed - does it make confusion more likely?

I do not know whether this actually works or not, but, as I think Carl Sagan used to say, "extraordinary claims require extraordinary evidence." To me, the most parsimonious explanation is that the people who led the "seance" were sincere and not out to scam anyone. The human drive to perceive patterns, intention, and meaning, adequately explain (to me) how the random flickering of flashlights impressed the participants as actual two-way communication.

Nov. 01 2014 05:19 PM
Lance from Hawaii

You should be ashamed for putting out this piece of crap. Promoting sharlatins who pray on people who have lost love ones is a new low. Thank you for dumbing down our country even more. I am writing your sponsors, The National Science Foundation and The Alfred P. Sloan Foundation and recommend that the spend their money on "The Skeptics Guide to the Universe" podcast instead of the garbage you put out this week. I can not tell you how disappointed I am in both of you. You have lost all of your credibility. What's next, Bigfoot, UFO's? How sad.

Nov. 01 2014 03:27 PM
Victor Bradley from Harlem, New York.

The flashlight revelation really doesn't make a difference. It is in the nature of "miracles" that they have a material i.e. "rational" mechanism. If I'm walking down fifth avenue, and I bend down to pick up a quarter thus avoiding a large chunk of swinging metal on a rope (don't ask why that's there) which would have surely brained me had I not bent down; there's a perfectly rational explanation other than "God did it." The presence of the quarter can be explained by some college kid with hole-ly pockets who'd just gotten change for laundry, among a panoply of other random circumstances. Proving that clairvoyant pixies didn't scurry out of a gutter and put the magic quarter in position, then make it invisible to everyone but me, doesn't disprove supernatural theories. There is no satisfactory explanation for why that quarter fell in the exact location as to save my life, just as there is no explanation for why the expanding metal in the flashlight contrasted at such points as would make it seem that one was communicating with the dead (assuming there's not willful self delusion, and an unconscious self-timing concurrent with the flickers of the bulb). Believers in miracles almost never claim that the laws of nature are fully suspended, merely that intelligent powers are able to tweak the randomness which inheres to events occurring within them.

Oct. 31 2014 09:30 PM
Burkhard Reike from Germany

Hi Matthew!

Sorry about that sound :)) just my armchair in need of oil...

Thank you, I enjoyed our talk!

Cheers and Happy Halloween,

Oct. 31 2014 04:53 PM
george peterson from United States

Mark, she knew his dad was dead. It's not much of a guess to say "I saw a man," then when he asked her if the man had his build, it was very easy to say yes and seem that much more knowledgeable.

Oct. 31 2014 02:42 PM
Mark L

So was the psychic guessing his dad's appearance just a lucky guess? Perhaps something she does to try and make the other person connect the dots?

Oct. 31 2014 12:44 PM
Steve-O from Mpls

Your comments are spot on, and why folks spend mental and fiscal resources on such bunk. And why some folks become skeptic zealots, actively working to debunk frauds -- perhaps to deny that part of them that would like it all to be possible.

Oct. 31 2014 10:47 AM

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