= 27d567bc2d48d9f40e9ccc20ea370b15)
PhilGoetz comments on The Correct Contrarian Cluster - Less Wrong
You are viewing a comment permalink. View the original post to see all comments and the full post content.
= 783df68a0f980790206b9ea87794c5b6)
Loading…= b715d02e85f7b3b4ae65ca3d3e450868)
Subscribe to RSS Feed
Powered by Reddit
= f037147d6e6c911a85753b9abdedda8d)
You are viewing a comment permalink. View the original post to see all comments and the full post content.
Comments (228)
I just watched the video. It's a trick, though probably not intentional. The windsock is mounted directly behind the propeller. So when the vehicle moves and the propeller turns, it blows the windsock backwards, and this is the "proof" that the vehicle is travelling faster than the wind.
ADDED: Folks. Think about it. The sock blowing backward is supposed to show that the vehicle is moving faster than the wind. It doesn't show that; the sock would blow backwards as long as the speed of the vehicle plus the speed of air impelled from the propeller is greater than the speed of the wind. There is no evidence in the video that the vehicle is travelling faster than the wind.
Downvoting this comment is not a vote saying that travelling downwind faster than the wind is possible. This comment does not dispute that. Downvoting this comment is disagreeing with the math and claiming that watching a sock blown backwards by a propeller demonstrates movement faster than the wind.
Did you read the "Solution" post that Vladimir linked to? What about it was unconvincing? (If it's any comfort, that guy ate enough crow for the both of you ;).)
I read the solution. I don't need to think too deeply about his long, complicated explanation that begins with a detailed and erroneous description of the gears, because I have a short, simple explanation of how the illusion is generated in the video, and a short, simple explanation of why such a device would violate conservation laws, which I gave below.
It wouldn't have convinced me, if I thought the thing didn't work — it never mentions rolling resistance!
What do you mean by that term? The post does say this:
(Emphasis added.)
Okay, it does there, but I refer to this part:
This seems to equivocate between wind/propellor force and net force.
Don't trust socks? Try this one with shoestrings instead.
I'll have to think about that.
think think think
It appears to demonstrate the same thing, convincingly.
The sock shows only that at the point where the sock is mounted the air is going backwards relative to the vehicle. What are the implications of that? Where is the energy required to do this coming from? As the vehicle approached the wind speed what would happen to the sock?
From the wind. Which is travelling faster than the vehicle. Except in the immediate vicinity of the propeller.
If the vehicle moved exactly at the speed of the wind, with the propeller moving, the air would appear dead still before taking into account the movement of the propeller, and so the sock would be blown strongly out behind the vehicle, making it look as if the vehicle were moving much faster than the wind.
So the parts of the vehicle that are travelling slower than the wind receive energy from the wind but not the propeller? If I took off the propeller would the vehicle go faster or slower?
The point is that the propeller blows the sock backwards, regardless of whether the vehicle is moving faster than the wind; and this is shown as proof that it's travelling faster than the wind.
It is a very good feature of the video (from rationality test standpoint) that this piece of evidence is compromised: you are handed a conspiracy theory right away, and so when rationalization kicks in, you know what to point to.