from a Question on Physics.SE

Q: Is it possible to walk in a friction-less world?

A: If there is no friction you can still move by conservation of momentum. take some stuff with you that you don't need. throw it away opposite the direction you want to go!

I read the answer as (bold text added by myself as my interpretation):

If there is no friction you cannot walk, but you can still move by conservation of momentum. take some stuff with you that you don't need. throw it away opposite the direction you want to go!

from the text above, is it the meaning the author wanted to convey?

  • 1
    The author's answer does not fit the question. Moving is not the same as walking. To me, it is not clear that walking is impossible from just the question and given answer. It is clear to me that walking is impossible from my knowledge of physics, but that isn't addressed by the author's answer. Your addition to the answer is what should have been there in the first place, but isn't directly implied. – Michael Dorgan Jul 16 '15 at 21:05
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    @Michael Dorgan: My first thought is that OP's cited answerer simply hasn't bothered to explicitly say No, you can't "walk" without friction because he assumes this should be obvious to anyone capable of imagining a frictionless environment. So he moves straight on to addressing what he supposes the querent is really interested in knowing - How could you move about in a frictionless environment? – FumbleFingers Reinstate Monica Jul 16 '15 at 22:40
  • The implication comes when they say "can still". If they were not implicitly answering in the negative to begin with, there would be no need at all for that word and using it would make no real sense. – Nathan Tuggy Jul 17 '15 at 3:31

Yes your interpretation is correct, although I would say "If there is no friction, you can't move in any way that relies on friction, like walking. You could still move by methods that use conservation of momentum, however. For example..."




Is it implied in this answer that the OP cannot walk?

Your question is a bit unclear. At first I thought you wanted to know, as your question title asks, can the OP actually walk or not, in real life...

Anyway, it appears you want to know if your interpretation (which you repeat in your question here at ELL) of this answer is correct, namely can we restate this answer in the way you want or in the way you suggest and still unfailingly preserve the meaning that the author of this answer wanted to convey...

And the answer to your question, is NO. You are reading something into the answer which may or may not be intended by the author of the answer. It is really a case in which you need to ask the author. Nothing in his or her use of English makes your interpretation necessary, let alone correct. One could say that this author considers "walk" to be included in the category of "move." You would have to ask the author, as his/her language does not say what you want it to, or at least how you have read it.


The answer can be interpreted to mean:

A: if there is no friction you can still move (a category of action that includes walking) by...


{Then there is the side issue of what do you mean in your question by OP, since the OP is usually the OP at the top of the page, not the "OP" of the answer that you have modified or interpreted. At any rate, when we use OP we should use it in such a way that it is not confusing.}

  • "Walk" by itself is never used, by any fluent speaker of English in any context I am aware of, to mean "just generally move around in a way that doesn't actually necessarily involve one's legs directly moving along a surface". When you walk, you are not floating, or swimming, or driving, or flying, or cycling, or riding. That's not a matter of interpretation or individual variation. – Nathan Tuggy Jul 17 '15 at 3:28

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