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

What about if it was an owl instead of a squirrel. Suppose as you walked around him, he left his body where it was, but turned his head to face you? Would you have circled him?

3n6 a pound

As our positions are in fact static, I, like the photographer, am going home....Oops I am home.

Well, I'm off to bed to dream of chasing squirrels and what I'd like to do to Alex when he turns up again.....*cue the theme from psycho*.

goodnight

Yes I would - I'd have been to his left, front, right and rear therefore I'd have completed a circumnavigation of owl...

Gnomon's dustbin analogy is amusing but false since the squirrel is not inside the tree.



Not so, since our camera-shy squirrel, keeping pace with the photographer, always remains exactly opposite him.

[In reality, the squirrel would not only move around the tree, it would also scuttle upwards; in which case would you still insist that the squirrel was encircled?]

'Not so, since our camera-shy squirrel, keeping pace with the photographer, always remains exactly opposite him.'

But closer to the tree, and so within the circle transcribed by the photographer - so encircled. Even so, at some point during the movement of the photographer, the squirrel will move from being north, to south, to east, to west of him (or vice-versa). It is possible for this to happen even if the squirrel is always opposite him.

I agree that *the path* of the squirrel is encircled...but not the squirrel .

And I'm off to bed too. Buenos noches to all.

My analogy is not false. It is perfectly possible to imagine a very large dustbin around the tree, with both squirrel and tree inside the dustbin.

Elf, if the squirrel stood on a spot and turned as the man walked in a circle around the spot, so that the squirrel was always facing the man, would you say that the man had circled the squirrel?

If not, you are using a different meaning of the word "circle" to me, so there isn't any point in further analogies.

(re my Posting 68)

I forgot to mention another aspect to the rotating bar model. Consider what happens when the point of rotation moves further and further away from the bar (in either direction). The radius of the tree trunk effectively gets larger and larger. At infinity, the tree trunk ceases to be round, and the man and squirrel are moving along parallel straight lines.

Hope this helps (although I somehow doubt it will)

<online2long*

*adds rum to her morning coffee*

nah, make that

"Is it a red squirrel or a grey? If it's a grey, can't we just shoot it, then everyone is happy?" - Skanky

Yes, but he'll have a particularly good reason to hide on the other side of the tree if he knows you're out to kill him


Dustbin analogy - the problem with this is that you assume you don't know what the squirrel is doing. You do. He's keeping opposite you.

Reducing squirrel radius to zero - that's cheating, as it reduces the squirrel's motion to zero, making him into the tree.

'But the photographer encircles where the squirrel is!' - this is more or less the crux of the problem. This argument would work for any situation but the one where the two characters are perfectly out of phase at the same frequency, but in this case we know for a fact that the squirrel is 180 degrees ahead of the photographer. The only way that the photographer can describe the circle around the squirrel in real time is to move at a higher frequency than him - ie go faster. Anything else is a matter of semantics, whereby we are simply allowed to call circling the act of having been around the area in which something lies. What if the squirrel and photographer have the same radius circles? Does the squirrel circle the photographer?


Never mind - the maths proves the viewpoint of the mathematician, while there is little explanation required and not much in the way of proof needed for the opposing viewpoint... Sound familiar, anyone?

Gnomon, It's time I praised you for your patience, as I can see why you feel you've had the argument won from the start.

But lets get real . The man is on the ground, and the squirrel is on the tree - *not on the ground*. It doesn't take a naturalist to know that a squirrel, when startled, will climb as it circles (as mentioned in post 84). With our furry friend 2-3 metres above the height of the man, do you still claim to be right? If so, is the man circling the stars too?

In any event, there will be no photograph.

Taking into consideration the viewpoints expressed in the thread...

... do you think the Entry presents both sides properly?

To be honest Alex, no.

The view that the man encircles the squirrel because he encircles his path is clear, and is the one which is generally accepted here. I'm still not clear on your alternative.

I just read it again, and I wasn't sure if you were saying something like "he doesn't encircle the squirrel because he doesn't act in a circular orbit around it".

The phase is a red herring in my opinion, as they can have the same phase in some of the scenarios I listed. Granted, to have the same phase either the man must materialise inside the tree (on the same side as the squirrel) or the tree needs to have a negative radius, but they're all real numbers in the end.

Any better now?

(That is, have I included both the views properly? I don't want any of this 'I don't believe it, so don't include it' crap. That's for the evolution vs. religion entries only, thankyou very much )

Quite right too!

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I'm not happy with this, as the squirrel is attached to the tree trunk. If you fix the coordinates of the man and the squirrel, then the tree is fixed too. Their whole frame of reference spins around, though.

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I don't think you should link to the PR discussion!!! Your argument should stand up on its own.

Icy

I haven't time to look at the Entry at the moment, but you certainly can't link to the Peer Review discussion.

I've got rid of the PR thread link and have put in some text from the thread

As for the tree spinning round - imagine the whole thing is sitting on top of a record player spinning at the same speed but in the opposite direction to the squirrel. The two characters now stay still from the point of view of someone standing nearby, but the tree spins at the same speed as the record player. This way of thinking is used to explain the precessing of nuclei in MRI, as the whole thing is spinning but we want to look at what's happening minus the spinning motion.

OK, I think we're slowly homing in on the point of the squirrel problem.

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The "no mathematical basis and no real proof" bit concerns me here. It must be pretty straightforward to prove that the man's locus contains the squirrel's locus mathematically. I think you need a bit more precision here, to describe what it is that you say cannot be proven mathematically with this model.

I have other comments, but I'll hang on to them for the moment.

Ah. I didn't mean it quite like that - I've changed it now