Episode 39: Chinese Invasion Alarm

Air Date: October 19, 2005

The ancient Chinese were able to detect an invading army tunneling beneath the ground by using a drum submerged in a shaft.


Kari was able to hear Jamie and Tory’s digging in an underground mine shaft in two of the three tests. She actually detected them better by listening to the drum compared to Grant’s use of modern geophone equipment.

The "five-second rule" is valid when it comes to food dropped on the floor.


This myth yielded a varied number of results, but in the definitive test where the only variable was time the myth was definitively busted. There was no real difference in the amount of bacteria collected from 2 seconds exposure as there was from 6 seconds exposure.

The toilet seat is the cleanest place in your house.


Adam tested this myth just out of curiosity and when the results were compared to the bacteria samples from the "five-second rule" tests, the toilet seat actually proved cleaner than all other surfaces tested.

A dog’s mouth is cleaner than a human’s.

partly confirmed

The sample collected from Adam’s mouth had much more bacterial growth than the sample collected from Lulu the dog. Jamie suggested, however, that the bacteria from the dog may be more potent.


  1. Ninja says:

    I believe that the dog’s mouth myth is hard to test. I’m pretty certain that a dog has different types of bacteria than a human’s mouth, thus not being able to compare “cleanliness.”

  2. Ray says:

    Yeah, kissing dogs isn’t my thing. I mean the people who do that normally have other germs anyway, or other STD’s. It is interesting with all of the technology that we try to remove germs from areas that are actually created to deal with these things.

    • christopher says:

      really. thats not true at all. and if tou believe it for any reason without difinitive proof then you might as well believe you can catch aids by hugging

  3. Keith says:

    Human bites to human limbs lead to greater infection rates than dog bites to human limbs. So it seems that a dogs mouth is cleaner than the human mouth.

    • mimi says:

      no thats not true a dog has ABOUT the same amount of germs a human does but the grems only affect the dog thatg why we dont get sick if a dog bits us rather than a humman

      • Stephen says:

        Agreed, we got more or less the same amount of bacteria of a dogs, but the bateria is different.

        I learnt this around new years, my hand was bitten by a stray dog who went beserk with all the fireworks going on. We to hospital and got treated straight away, had my shots for infection and rabies.

        Doctor said it could be have been worse if I got bitten by another person. Thats when he told me he treated a man’s hand who had been bitten by a woman he tried to rape. The rapists hand swelled to nearly 3 times the size of his other unbitten hand!
        OUCH! (but serves him right, hoped he went to jail!)

  4. Robin says:

    About the Chinese Invasion Alarm… in the myth it is stated that an army was tunneling beneath the ground. In the MB test there were only two people tunneling. Wouldn’t the army, with more people tunneling at the same time, put off more vibration and cause the drum to emit more and louder sound? It’s been a while since I have seen that episode, but that question has been nagging at me ever since I watched that episode. I’m just thinking that maybe Adam and Jamie should try that myth again with as many people tunneling that they can get.

    • PFC Ridgley says:

      hey, im focusing on this project with my sgt. i would really love more info on this tunneling detection if anyone can find some.

  5. dude6935 says:

    I don’t understand why the myth is “Plausible”. The experiment was a success… What more can they do to prove it than that??? It’s not about the history; it’s about the science in historical context.

  6. Muzzy says:

    Plausible because this method would work if they were tunneling in just the right spot, but a tunneling force could come from so many directions it’s not confirmed that this would be successful enough to have been the best method. That’s what I think anyways.

  7. Hornet says:

    I agree with Ninja on the dog’s mouth myth. Dogs have different bacteria on their mouths than humans, and they have very different imune sytems than humans. (I mean, it’s not every day you see a person getting into a cat litter box or an animal carcas the way a dog would) And on Keith’s note, another reason alot of human bites lead to greater infections than dog bites is because humans carry alot of diseases that dogs don’t, such as AIDS, herpes and other defilements that can be carried be people.
    By the way, sorry for the long comment.XI

  8. Shaun says:

    Remember kids an amry of 10,000 tunneling will probably make more noise than an army of 2 MB’s. Thats why its plausable. Its like that whole thing with two people talking and 2000 people talking. Alot more sound, alot more vibration.

  9. alexia says:

    Im doing a science fair project on who’s mouth is cleaner a dog or a human.your research has been alot of help.Im a sixth grader.

  10. Vanessa says:

    I totaly belive that dogs mouths are cleaner than humans! (It depends though on what they eat)
    Go mythbusters!

  11. John says:

    I would say that the Chinese Invasion alarm should be considered confirmed not plausible. In this episode, it was stated that no evidence was found that it was ever used. It was actually used in 1552 by István Dobó commanding a small contingent of men, women and children in Eger Hungary to defend the Eger castle against the invading Turkish army of 40,000+. This is considered by many as the greatest military victory in Hungarian history. A few years ago I toured the fortess museum in Eger and have seen the equipment still installed in its original place in the castle. The guide explained that the large drums placed into the numerous nooks along the passageways under the castle were used to listen for invaders tunneling from the outside. The guide also indicated that Istvan had brought in a specialist to upgrade the defenses of the fortress prior to the seige. This individual had come from another country (Germany or Prussia I believe) and the fortifications he put in place(including the alarm system) were state of the art at the time (1500s).

  12. adrianqx says:

    its not the number bacteria that counts its the type.plus a dog licks its arse all day that cant be good

    • MSpears says:

      Ever tasted wet dog food? It’s no wonder the dog licks their arse, he’s trying to get the taste of the dog food out of his mouth.

  13. Craig says:

    Love the site! The 5 second rule episode has me wondering. Jamie and Adam pressed the samples onto the floor for the timescales stated, they didn’t just let them fall and pick them back up again, which is in my view a fairer scenario. Ergo, the results would be different from reality. Thoughts?

    • JR says:

      Just found this site – hence the late reply! We’ve always had the 5 second rule in our house – as showing a fairly hardy/commonsense approach to life. Also we are a pretty healthy family who rarely visit the doctor. I agree with Craig, that a quickly picked up piece of food would not have come into contact with so much bacteria. However – I’m not sure I would follow the 5 second rule out of the house – say on a street or in a high footfall area… I do think it comes to common sense. An interesting aside – my daughter is part of a large study based in Bristol, UK, which has shown that younger children in the house actually benefit from having older siblings – especially boys – who are outside grubbing about (in germs)!

  14. Katrac says:

    my friend and i are also doing an experiment on which household pet has a cleaner mouth. we’re comparing them to humans and this site has been tons of help. :) thanx a million

  15. earthmover says:

    To those pet owners who let their dogs lick their face!!! REMEMBER they also lick their arse and everything else at the rear. Lovely if your partner then wants to kiss you too.

    • Calen says:

      We do tons of dirty things, including handling money, which has been touched by who knows how many people with diseases and bad hygeine. If you compare that to dog saliva, regardless of what they’ve done, I think you’re pretty safe. As for the ‘ew’ factor, if we knew all the things that were in the stuff we eat and use, like guano, or bat poo, in women’s makeup, I’m pretty sure remnants of dog poo would be low on the list.
      Doggy licks have the benefit of making the dog and owner happy, I’ll take my chances :p

  16. Katie says:

    I am doing a science experiment on Whose mouth is cleaner, a dog’s or a human’s and My results are that the human’s mouth is cleaner than a dog’s. The amount of bacteria is close in comparison, but the dog’s mouths were still dirtier. I am confused!! :/

    • Genaya says:

      I am doing the same project and i got the same results and it is because it depends on how well you take care of your mouth and your pets mouth.

  17. nw says:

    human mouths are less clean the bacteria if introduced to an open wound is more deadly than a culture from a dogs mouth

  18. toxichild311 says:

    for the dog’s mouth is cleaner thing, how come they didnt just test a couple more dogs?????

  19. raymond says:

    Yeah, I’ve seen dog’s eat some nasty stuff before and then walk away like it was nothing. But, we humans can go to a doctor or take some medicine to help us and our body’s system’s out if we get sick.

  20. Cole says:

    I’m a 5 grader doing the test is a dogs mouth cleaner than a humans is their a gel for it or not

  21. Mart says:

    They should have asked a vet about the dog mouth things, any good vet could have told them that yes, a dog mouth is cleaner then a human because dogs have anti-bacteria in their saliva. Thats also why they lick their wounds, it prevent infection.

    • Gra says:

      Maybe YOU should have asked a vet-

      Although ‘all’ saliva has some small amounts of anti-bacterial compounds, ‘all’ mouths have bacteria in them. considering bacteria levels vary all the time in mouths, dogs can definitely have more bacteria in their mouths than humans, it all depends.

      Some of the disease causing bacteria/viruses people have got from dogs licking their wounds are: Pasteurella, Capnocytophaga canimorsus, streptococcus, rabies, tetanus, staphylococcus!

      …btw, My wife is a vet, we have 4 dogs and they can lick my face anytime they like, but I’ll keep them away from open wounds!

  22. Whoa says:

    I’m surprised they didn’t do a control test – i.e., listening for the digging sound *without* the drum.

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