# A watched kettle doesn't boil

1. May 11, 2005

### Bigtex005

I read of an experiment in which people actually timed how long it took water to boil, if it was watched and not watched. The results were that indeed watched water boiled faster. Now at first this blew my mind because I can't believe no one had tried it before, or maybe they have it was just the first time the people in the article had done it, who knows. Anyway, if this is true, are quantum effects at work here, or is this post just stupid? Please be kind if the latter is the case.

2. May 11, 2005

### wangyi

Are there any other reasons that caused the different length of time? I can't believe the result unless it is rigorously and repeatly tested.

3. May 11, 2005

### JamesU

I agree, if it is repeated many times, THEN it is believable

4. May 12, 2005

### inha

5. May 12, 2005

### Edgardo

6. May 12, 2005

### El Hombre Invisible

This depends on temperature. At normal temperatures reached by a household kettle, neither a watched nor unwatched kettle boils.

7. May 12, 2005

### HallsofIvy

Staff Emeritus
Of course, if the "watched" pot doesn't have a lid on it (so you can watch it) and the "unwatched" pot does, then of course, the "watched" pot will take longer!

8. May 12, 2005

### vanesch

Staff Emeritus
Hehe, I was about to post the same observation

cheers,
Patrick.

9. May 12, 2005

### DaveC426913

I think you're missing the point here.

An unwatched pot cannot have its boiling vs. not boiling time determined - the pot is unobserved. That means unobserved, unlistened to, un-everything-that-tells-you-what-it's-doing. And that includes listening for the whistle. There is no such thing as "passive" observation. If there is some form of information transfer (heat, light, sound) that is exiting the pot, such that we might see/hear/feel it and thus determine what it is doing, then the boiling/not boiling state collapses.

As with quantum mechanics, as soon as you observe, you alter the experiment.

10. May 12, 2005

### ZapperZ

Staff Emeritus
You need to be careful in using that phrase because in the classical limit, you do not "alter" an experiment upon observation. And unless I missed something, what has been described is not a quantum mechanics experiment. If it is this easy to observe quantum effects, QM would not be this mysterious.

We also need to keep in mind that when question like this, and at this LEVEL, is being asked, the word "observation" has a rather pedestrian meaning. Most people associate it with 'seeing' with their own eyes. I suggest that the OP here is indicating an observation by the participants in actively looking and waiting for the water to boil, and considers doing this automatically or remotely without anyone looking as something different. Unless he/she explains further, we'll never know exactly if this is true.

[Note: people who say "I read somewhere..." or "I heard somewhere..." should REALLY put some effort into giving an exact citation on the source. If you can't, there's no way for us to double check if what you read is right, or if you simply misinterpret what was said!]

It is imperative that we present our answers within the frame of understanding of the person who pose the question. We have seen how quacks can really run with things because they read about things that have specific meaning with the context of physics, but with their lack of understanding, have completely different picture to them.

Zz.

11. May 12, 2005

### Bigtex005

Ok, I cannot give reference to this experiment, I tried to find it again but couldn't. It was found just by surfing around. Next time I post I will give references. 2 things though, first I typed the result of that experiment incorrectly, the watched pot boiled slower not faster. Second thing is that the experiment said they basically just set the water up to boil, and then tried a couple of different things, left the kitchen, stayed in the kitchen but turned around, etc... The results were something like 20 seconds difference between the boiling time of a watched and unwatched kettle. Anyway, thx for being kind when answering my stupid post By the way, I am pretty sure that this experiment wasn't in a scientific journal. I think it was some college student's class website or something to that effect. Better questions to come I promise, thx for the replies.

12. May 12, 2005

### LURCH

Dave brings up a point I was going to speak to. The time at which the kettle boils is merely a recorded time at which the observer became aware it was boiling. If you watch a kettle, you know the instant it begins boiling. If you check it every two minutes, you might write down a time that's up to two minutes later than boiling actually began or, if your observation is very "lucky", you might record time that is spot-on. You will not, however, record a time that is two minutes early (to compensate for the ones that were two minutes late), and so your observations will statistically tend toward later boiling times.

13. May 12, 2005

### DaveC426913

No, "..in the frame of where it was asked...."

It was posted in the Quantum Physics forum. The poster is looking for an answer of the thought experiment type, framed in quantum physics logic (a la Schrodinger's Cat).

14. May 12, 2005

### ZapperZ

Staff Emeritus
But do you think you have left a reasonably accurate description of this apparent "water boiling at different rates" thing by ending it with "As with quantum mechanics, as soon as you observe, you alter the experiment."? If I am ignorant of what QM is, I would jump to the conclusion that classical, macroscopic events such as boiling rate of water is depending on whether I physically look at it or not, or if I measure it. This would violate all classical mechanics EVEN in its realm of validity, because you have removed one of its basic tenets where the "observer" plays no role.

If this is what you are implying, then we need to first and foremost establish that water boiling in a kettle is a quantum event and show that it cannot be described accurately with classical thermodynamics.

Zz.

15. May 12, 2005

### gonzo

Sounds like something from the JIR to me.