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Physics, Astronomy & Cosmology / Re: What makes a magnet a magnet?

« on: 30/09/2016 03:01:17 »

Most magnetism has to do with the "spin" of subatomic particles. The effects of electron spin are vastly stronger than the effects of nuclear spin, so we will ignore that for the moment (though nuclear spin is essential for the performance of MRI and NMR instruments).

Electrons can either be "spin up" or "spin down." This has nothing to do with up and down, and could just as easily be left and right, or blue and red, but by convention they are up and down. Materials in which there are exactly as many spin up electrons as spin down electrons are called "diamagnetic," and are very weakly repelled by magnetic fields. Materials that have an imbalance in the number of spin up and spin down electrons are called "paramagnetic," have a net magnetic moment, and can interact with magnetic fields in much more interesting ways. Now things get tricky... there are several different ways that paramagnetic materials can be, depending on how the electrons interact with each other: ferromagnetic, ferrimagnetic and antiferromagnetic are the most common types, but there are other more exotic types of magnetism, especially when one starts considering rare earth elements, for which electrons can also have significant angular momentum about the nucleus, but I digress... Typical permanent magnets are ferromagnetic, which essentially means that all of the electrons align in such a way that the magnet has poles (this is a significant oversimplification, but perhaps a good starting point).

There are also electromagnets, which don't rely on the spin of electrons, but rather on the overall macroscopic motion of electrons.

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Physics, Astronomy & Cosmology / Re: What would be the transit time to Mars with unlimited power?

« on: 29/09/2016 08:40:14 »

I suppose you could have learned manners at school.

Physics and chemistry makyth Man. And I'll give you full marks for a good question.

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Physics, Astronomy & Cosmology / Re: What would be the transit time to Mars with unlimited power?

« on: 28/09/2016 18:04:06 »

s = 0.5 a t^2 where s = distance, a = acceleration and t = time (you did that at school, surely?)

Minimum transit distance is probably 10^11 meters. Put a = 20 m/s^2 (a bit more than 2g) then t^2 = 10^10 so t = 10^5 seconds, just over a day.

You don't need to be sarcastic.

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Chemistry / Re: How much steel can a kilogram of fluoroantimonic acid burn through?

« on: 27/09/2016 23:00:35 »

Thanks for the very informative answer! It does, however, leave me with one followup question. Would it be possible using any acid to dissolve a circular (Or cubic, it's not really important) hole 5 centimeters deep with  a diameter of 1 centimeter using any combination of acids or electrical currents in under 10 minutes? It's only 5 cm2, however it is 5 centimeters deep and from what I've found many acids tend to act rather slowly. For simplicity's sake assume there are no limitations on the electrical current or amount of acid we could apply.

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Chemistry / Re: How much steel can a kilogram of fluoroantimonic acid burn through?

« on: 27/09/2016 05:19:25 »

Fluoroantimonic acid has the chemical formula HSbF₆, and a molar mass of 236.76 g/mol. It is a very strong acid, in that it is capable of protonating almost anything, but that doesn't necessarily mean that it is the best at dissolving (eating through) materials.

I don't think that metals like steel are soluble in HSbF₆, and protonating steel won't change its solubility, so really the question at hand is one about the chemical reactions:

HSbF₆ --> H⁺ + SbF₆^–
and
Fe + 2 H⁺ --> Fe⁺⁺ + H₂

These reactions indicate the dissociation of the acid into free protons (hydronium ions) and hexafluoroantimonate ions, and the reaction of protons with metallic iron (steel), resulting in soluble ferrous ions and hydrogen gas.

Based on this stoichiometry, it would take 2 moles of  acid to react with one mole of iron (molar mass of 56 g/mol). One kg of the acid contains just over 4 moles (1000/236.76 = 4.22 moles), so this would eat away 2.11 moles of iron, or roughly 120 grams.

In contrast, one kg of sulfuric acid, which is H₂SO₄, could consume roughly 560 grams of iron. Sulfuric acid is no where near as "strong" based on dissociation constant, but it has a much higher concentration of reactive protons per unit mass.

i hope this helps!

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Physics, Astronomy & Cosmology / Re: Is black a colour?

« on: 20/09/2016 15:02:54 »

Martin asked the Naked Scientists:
   Hi. Is black really a colour ? Or just the absence of light ? (visable light)
What do you think?

As stated above black is not a color but the absence of all light, i.e. the absence of color. White is a bit harder to say if it's a color. White light is a composed of a spectrum of other colors. That said, when a car dealer asks me what color I want my new car to be I'll always say "black."

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Just Chat! / Re: What is Trump's opinion about chemtrails?

« on: 23/07/2016 18:53:12 »

We havebeen injecting coal fly ash into the atmosphere for about 6000 years, in ever-increasing quantities. During that time the life expectancy of homo sapiens has tripled. So it can't be doing more harm than good.

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The Environment / Re: What criteria would be required to refute man-made climate change?

« on: 06/06/2016 00:21:28 »

One way to refute man made climate change is to explain how the magic trick works. If you went to a magic show and the audience saw someone levitate, it will be hard to convince people it did not happen, unless you can show how the trick works.

There are several aspects to the man made climate change magic trick. One aspect is connected to hyped fear. For example, when an airliner crashes (beyond terrorism), there will be a lot of media hype and endless expert analysis. After listening to this for several days, many people begin to assume all air travel is at risk. Politicians will cater to the fear insisting something needs to be done, industry wide. The induced fear and hype, reinforce by the actions of leadership, will cloud judgment. This fear is the house lights being dimmed for the magic trick. All the doom and gloom predictions, connected to man made global warming, that never panned out was the house lights dimming. It did not matter if this happened or not, the goal was the fear. Those who got the fear bug, will not care if the bogeyman did not show, since he is out there.

Another aspect of the magic trick is connected to semantics. When they say this is the warmest summer on record, science only has good weather data for about 150 years, tops, even though the earth is 6 billion years old. Yet the term, on record, is often interpreted by the fearful, to mean the entire life of the earth. Nobody who performs this magic trick will ever clarify this.

This distraction blends into the next aspect of the illusion. We generate more weather data, today, than any time in history of weather data collection. More data makes it look like more is happening. From a satellite, you can see weather in remote areas where data was never collected. This counts as manmade change, since nothing there could be substantiated, to prove otherwise.

If we needed to look at the weather from 200 years ago, there is little if any direct data to use. Even if this was the worse in 500 years, it is still not the worse on record, since officials records are 150 years old. Due too the scarcity of the hard direction data, one may need to rely on indirect data, like tree rings to give us a clue of what happened. This can tell us the annual averages, but you can't see day to day like we record today. The result is there is more climate change today, based on a hard data.

Here is an experiment we can do in schools. This is the magic trick. We will have a group of students observe and record, with their cell phone cameras, any bird or squirrel they see, during one month of time. When all the data is compiled, we will tell them there are more birds and squirrels in that area, now, that in any anytime in history.

Technically, the students will have recorded more hard data than any skeptic can produce, for any other time in history, for that area. The claim of more birds and squirrels, although unsubstantiated and probably not true, will be hard to disprove, especially since anyone who denies my claim, will not be able to provide as much hard evidence as the students. We then make fun of the skeptics so they don't spoil the trick.

To help my claim along, I will use fear to dim the house lights. I tell them that bird and squirrel droppings can cause disease. This is the distraction needed to get others to fixate on birds and droppings so thy start to observe and see more than they ever noticed before. The fear will require something be done, with the school now making a big deal about cleaning the sidewalks. This will reinforce the fear, due to remediation being employed.
 

.

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The Environment / Re: What criteria would be required to refute man-made climate change?

« on: 05/06/2016 09:19:02 »

To Bored Chemist,

It would be really nice to know what it would take in your case.

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Chemistry / A Chemicals Point Of View !

« on: 17/12/2009 11:59:55 »

Pentacene: The first picture of a molecule's anatomy. Made bij an Atomic Force Microscope with a CO molecule at the tip.

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Question of the Week / Re: QotW - 07.12.09 - Power Source for Magnets?

« on: 06/12/2007 13:51:10 »

We put this question to Alastair Rae, University of Birmingham:

At this time of year, many of us decorate our fridges by attaching magnets carrying pictures of Christmas puddings, holly, Father Christmas, snowmen and so on. One advantage of these magnets is that they are easily removed and replaced when Christmas is over. Brian Starkey asks, ‘how can they stay on the fridges when there is no obvious power source?’

[img float=right]http://www.thenakedscientists.com/HTML/uploads/RTEmagicC_Magnet0873.png.png[/img]The first point to note is that we don’t need any energy to stand still! A stationary car with its engine turned off doesn’t use any petrol!  Power is required only when the engine starts turning and the car starts moving.  What we have in the case of a fridge magnet is a magnetic force pulling the magnet against the iron door; this then leads to a frictional force that stops the magnet sliding down under gravity, but once the magnet is in place, no energy or power is consumed keeping it there.  It’s not very different in principle to sticking the magnet onto the fridge using glue.

When Brian pushes the two like poles of a magnet together, he has to apply a force and use energy.  If they are then allowed to move apart, this energy is released and converted into motion.  However, if he holds them together without letting them move, no more power is needed.  It’s perhaps easier to understand this if we think of the magnets being supported by a rigid frame instead of by a person. Why then do Brian’s arms grow tired if he is not doing any work?  This is all to do with biology and the complex way our muscles work: chemical energy has to be burned to keep them stiff and able to exert pressure.  But magnets are not like that: they exert a force pushing each other apart and do not consume any power as long as they don’t move.