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Author Topic: Feedback: Fusion and mass versus weight  (Read 2258 times)

Phillip Nance

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Feedback: Fusion and mass versus weight
« on: 24/03/2014 08:52:50 »
Phillip Nance asked the Naked Scientists:
   
"In your program [sic] broadcast on the ABC's RN at 4am Oz Eastern Daylight Saving Time Sun 16, you suggested that a UK High School Student had achieved cold fusion in a  3,000 [sic] school experiment. I find no evidence that Physics Professors from your Uni are rushing to see how it was done.

Can you ask a Professor to confirm the result. While I can accept that something was detected, the fact that it was 'wanted' to be a Neutron [sic] does not make it so. Good Science demands all other possibilities are refuted, what remains being a not necessarily unambiguous answer - does a Neutron Detector [sic] only detect Neutrons [sic].

Smashing electrons into a target is a common way of producing X Rays, possibly achieved in the Experiment. In other words, the conclusions were extremely poor Scientifically [sic].

Your program [sic] broadcast on Sun 23 talked about measuring weight on a set of spring scales and a balance at least what I could make of it. Provided both are accurate, they will both read the same for the person (or anything)'s weight on Mars, Moon, Earth or in any Gravitational Field [sic] taking Newton's Gravitational Theory. The weight will be different on each body in direct proportion to the local gravitational acceleration neither scale measures mass directly, which seem to be implied by your presenter.

Please, if you're broadcasting Science [sic], get it correct; there's enough out there who want to make it obscure already.
« Last Edit: 24/03/2014 09:01:10 by chris »


 

Offline chris

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Re: Feedback: Fusion and mass versus weight
« Reply #1 on: 24/03/2014 08:55:19 »
Dear Phillip

I'm sorry to read that you felt the necessity to take issue with some of the recent programme content.

Here I have addressed the points you have raised, I hope with sufficient clarity and depth to enable you to follow. Please do come back to me if there is anything that you don't understand in what I have written.

First, the school fusion project: As Jamie Edwards explained in his interview, he constructed a 2000 form of "fusor". This is a well-established means of achieving fusion and has a long history. This reference will tell you a bit more about it: http://en.wikipedia.org/wiki/Fusor. The neutron detector he used is sensitive specifically to neutrons. He was supported in his endeavours by scientists at Manchester University.

A similar approach was adopted by the US teenager Taylor Wilson, also referred to in our piece. This reference shows him demonstrating the technology to Barack Obama (http://en.wikipedia.org/wiki/Taylor_Wilson), and he has also delivered TED talks on his project: http://www.ted.com/talks/taylor_wilson_yup_i_built_a_nuclear_fusion_reactor

It's therefore perfectly plausible that Jamie Edwards succeeded in his approach; his aim, after all, was to be the youngest successful fusioneer, not necessarily break new scientific ground.

Second, you queried the answer supplied to the question about weighing scales.

The subtle point here is that there are two types of scale: one is the "old-fashioned" balance variety, where a counterbalance of known mass is applied against the unknown mass; when the two balance, the applied mass must be equivalent to the unknown, thus the mass of the unknown is directly reported. This means that, regardless of whether you are on Earth or Mars or the moon, which all have different gravitational accelerations because they are different sizes (masses), the acceleration due to gravity on the counterbalancing mass and the unknown mass will be identical and cancel out; hence the balance will still work without any re-calibration in either place.

But the second type of scale is a sprung system, usually with a dial or electronic read-out to report the "weight" applied to it. When you stand on this, the force you apply to the spring, which is a function of your mass (multiplied by the local gravitational acceleration) will vary according to the gravitational acceleration to which you are subject. Since the spring makes the dial turn around and report your "weight", if you are in a lower-gravity regime (like Mars or the moon) then the spring will feel a lower applied force and hence the scale will report a lower weight, which the scale will report as a "weight" in kilograms, which will be wrong because the scale will be calibrated for Earth's gravity (ie assuming about 10N/kg).

And although such a scale will certainly operate on Mars (or wherever), you'd need to recalibrate it for Mars gravity before the reported mass was correct, which was the point being made by Richard Hollingham on the programme.

I hope that this explanation of these points is clear and helpful. In case not, this page on Wikipedia might help you to understand: http://en.wikipedia.org/wiki/Mass_versus_weight

Thank you for listening to the programmes and for your feedback,

Chris Smith, Managing Editor


 

Offline syhprum

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Re: Feedback: Fusion and mass versus weight
« Reply #2 on: 24/03/2014 11:12:07 »
I entered into discussion with "Bored Chemist" about this program and had to acknowledge that my interpretation of what constituted a fusion device was rather too limited there is no doubt that the Neutron generating devices that the two school groups developed were fusion devices although the 30Kv source of energy can by no means considered "cold" having an equivalent temperature of 340MK if in fact the broadcast referred to cold fusion.
« Last Edit: 24/03/2014 13:44:26 by syhprum »
 

Offline Pmb

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Re: Feedback: Fusion and mass versus weight
« Reply #3 on: 26/03/2014 08:52:32 »
Quote from: chris
Dear Phillip

I'm sorry to read that you felt the necessity to take issue with some of the recent programme content.
He questioned the accuracy of the claiml, not the content. And a good scientist should questions remarable claims such as believed it was.
 

Offline yor_on

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Re: Feedback: Fusion and mass versus weight
« Reply #4 on: 26/03/2014 17:08:13 »
Chris, I'm not sure I follow your argument about different types of scales there? If you mean that the spring system is calibrated against a (pre)known figure whereas the balance variety (older scales) always is a result of balances equalizing out I agree, both types defined against a commonly agreed upon value, as grams and kg nowadays. But I would expect both to present you a lesser weight on the moon, compared to measuring ones weight while on Earth?
=

Rethinking it, you might mean the really old type of scales, as a plank placed on a pivot, my weight getting balanced by a equivalent counterweight? Then I can see how you mean.

I was thinking of the old scales you could see some decades ago in hospitals etc. They used counterweights too :)
« Last Edit: 26/03/2014 17:16:27 by yor_on »
 

Offline evan_au

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Re: Feedback: Fusion and mass versus weight
« Reply #5 on: 26/03/2014 21:04:30 »
The show was talking about a balance scale as seen on traditional "Justice" statues: http://en.wikipedia.org/wiki/Weighing_scale#Balance

The balance scale does not actually weigh anything - it merely tells you if the two weights in the pans are equal (or, in the case of unequal balance arms, that the weights are in a certain ratio). When you see that the scale is balanced, you look to see what weight is in the other pan.

If you were on Mars, how would you know that the weights in the other pan are correct? Maybe they were:
  • Weights made and calibrated on Earth (expensive to launch into space)
  • Created in a balance from weights made on Earth
  • Or they were measured in a spring scale, and corrected by manually dividing by the local value of "g"
  • A modern electronic spring scale designed to be carried into space could well incorporate an accelerometer or "gravity meter" (these are now very cheap, being included in all smartphones), which then divides the measured weight by the local "g" to provide Earth-equivalent readings. (Do not attempt to use in zero-g: dividing by zero does not produce a useful result!)
  • You could use the definition of the metric system - one cm3 of pure water at a specific temperature and pressure has a mass of 1 gram.
  • Attempts are being made to create an independent measure of mass (not needing access to standard weights on Earth) by creating a perfectly spherical ball of silicon (isotopically pure), and then "counting" the atoms. This is proving difficult to create on Earth - I expect it will be a considerable time before it can be reproduced on Mars!
 

Offline yor_on

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Re: Feedback: Fusion and mass versus weight
« Reply #6 on: 26/03/2014 21:36:23 »
Yes Evan  :) "the balance scale does not actually weigh anything - it merely tells you if the two weights in the pans are equal". That was why I reread it, as I first thought we was discussing weight, not mass. A weight usually follows a 'weighting' standard of some sort, a mass on the other hand doesn't need to be described in stones, kg etc.
 

Offline chris

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Re: Feedback: Fusion and mass versus weight
« Reply #7 on: 27/03/2014 21:10:43 »
Quote from: chris
Dear Phillip

I'm sorry to read that you felt the necessity to take issue with some of the recent programme content.
He questioned the accuracy of the claiml, not the content. And a good scientist should questions remarable claims such as believed it was.

The op suggested that the answer about weight and mass was incorrect, which is not the case; the programme content is correct.
 

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Re: Feedback: Fusion and mass versus weight
« Reply #7 on: 27/03/2014 21:10:43 »

 

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