h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I like the entry, but don't know how it got through Peer Review with its most glaring error!

[Now, what this means in terms of the Zeroth Law is that, if two objects are placed in thermal equilibrium (for example, two pieces of metal touching) and a third object is brought up to touch the second, the third object will reach equilibrium with the second and will automatically be in equilibrium with the first.]

This should have to be reworded!! If the third object is brought up to touch the second, it will indeed reach equillibrium with the second but make the second LOSE equillibrium with the FIRST!

They would have to ALL be touching to reach a common equillibrium.

Or, two objects NOT at equillibrium with the first could move to equillibrium with each other and, coincidentally, be in equillibrium with the first as well.

One needs to visualize the heat transfer as a process, in steps.

1. Objects A and B in contact and in temperature equilibrium. (Presumably with the environmental ambient.)

2. Object C brought into contact with object B, a process of heat transfer begins.

3. A gradient of temperature develops from A to C.

4. After a measure of time passes the heat transfer levels off with objects A, B and C all at the same temperature, in equilibrium, presuming a uniform environmental ambient.

5. The objects tend to radiate heat over time, but if heat capacity for the three objects and their heat transfer rates are the same, then they remain in temperature equilibrium.

One of the keys to the process is time. If one merely dips a thermometer into a medium quickly and withdraws it, this doesn't provide a reliable measurement of the temperature. Instead, one has to allow time for the thermometer to come into equilibrium with the medium. An alternative way of measuring temperature is on a basis of thermal radiations coming from whatever one is measuring.

Nothing takes place instantaneously.

Well, thanks; but I wasn't saying that the process doesn't work. I was saying that the wording was far less than clear. In fact, the way it is worded is plain and simply wrong!.

That was the impression I got. The phenomenology is very complex. Reminds me of another conundrum of the character, the prospect of synchronous starts of identical experiments in time. Generally conceded to be impossible however closely one may approximate.

I'm happy to report that my concerns are being addressed. This is what I eventually suggested:

In every sense, any number of objects can be brought into contact and eventually reach SOME level of equillibrium; but I no longer believe that this was the intent of the entry or the example.

I believe that it was trying to communicate the transitive nature of thermal energy, that same as is done in math by the transitive definition:
If A = B
and B = C
then A = C

Written in this form, the example would read:
If object A is in equillibrium with object B
and object B is in equillibrium with object C
then object A is in equillibrium with object C

The example of objects moving to equillibrium creates the NEW equillibrium instead of describing objects that are already in equillibrium, and would read:
If the temperature of object A and object B each reaches an average temperature over time
and object C is introduced.
then, over time, the three will reach a new average temperature.

I don't think that this was the meaning of the entry at all.

In keeping with the theme of the entry, perhaps it should read more like:
'Now, what this means in terms of the Zeroth Law is that, if two objects are in thermal equilibrium, and a third object is in thermal equilibrium with one of the two objects, then the third object is also in thermal equilibrium with the other object.'

yep.

Gnomon writes that he will make the fix.