Neil9327

Not exactly. Linear motion doesn't require anything to "push against" either — that's not the principle involved in a rocket. It's conservation of momentum' date=' and action/reaction, from Newton's third law.

 

And rotation has its own application of Newton's laws. Absent any torque, angular momentum is conserved. A nonrotating rigid object cannot start spontaneously rotating. A cat, however, is not a rigid object; it does its reorientation without having any angular momentum by twisting different parts of its body having different moments of inertia.

 

The rotation of part of an object, like a satellite, can be achieved by rotating another part in the opposite direction, which conserves angular momentum.[/quote']

 

But the point I'm trying to make is that the cat IS able to turn in mid air to change the direction it is pointing in space. Which is relevant to the original poster's question. Do a google on "drop cat feet angular momentum" for explanations as to how the cat's angular momentum remains at zero while it spins its feet one way and turns its body the other etc.

How can you move in space when there's no matter to push on? Any ideas?

 

And I was also wondering what kind of force or technique can escape a black hole?

 

Thanks' date='

FROGGIE[/quote']

 

It should be noted though that if the type of motion you want to achieve is a rotation (rather than a linear motion) this can be done without anything to push against.

As an example of this, try dropping a cat upside-down from a height. It will right itself and land on its feet using this principle.

 

(no DON't try this yourself. Your cat may be stupid)

I had a discussion with my boss today regarding my gym tee-shirt. He claimed that it was unhygenic to hang it up on a rail under my desk, but I thought it was not. My view is that it is actually less unhygenic to hang a gym shirt up than it is to wear a shirt for a whole day, for the following reasons. I'd be interested in any comments (apart from "get a fresh shirt you lazy so and so")

When you wear a shirt in the office, although you don't sweat much, the small amount of sweat you build up is sufficient to allow anaerobic bacteria to build up under your armpits and create smell-producing chemicals. And it does this for 16 hours during the whole day.

When you go to the Gym however, although you produce much more sweat, it is only for 45 minutes, and there is therefore much less time to grow smell producing (unhygenic) bacteria. Then when you hang it up under the desk it has continued access to oxygen (so the anaerobic bacteria can't survive) and it dries out quickly, so no further bad smells can be produced.

I don't know what you mean by going ninja on my post. But yes I did edit it after posting it for some reason I can't remember. But I didn't see your post, they both arrived at the same time!

Thanks for the double bond clarification. didn't know that.

Does that mean that if you produce perfectly layered graphite that it will be a conductor in one direction, but an insulator in the other?

http://www.scienceforums.net/forums/archive/index.php/t-19680.html

Thanks Google.

Of course we will expect you to put the SFN Science Forums logo onto both the launcher and the egg. We like the advertising

Hmm I think I see what you mean Woelen. Rotation is acceleration. Of course rotation is NOT acceleration if you are at a point location rotating about youself. Maybe that's where my arguement falls down. If you are at a point location you would feel zero centrifugal force so my definition of this as the zero point of rotational angular momentum has no meaning.

I'll have to put my thinking cap on, but for now I'll defer to your greater wisdom on this

Ditto.

I like that exploding transformer. Who says that chemistry is the only source of flashes and bangs.

I think its funny the way the sparks stop suddenly.

Of course all these videos show AC sparks, not DC. But I expect that the visual effects would be essentially the same in a DC scenario?

[[in air, things take on a whole new set of "rules".

air current is the biggest Pain in the a$$ mostly, as the arc tends to rise and break (heat rises) this doesn`t happen in a vacuum.

for a 1mm gap at Low current, 1--> 1.5 KvDC should do it in a sustainable way (providing a still air current is around it).]]

YT: Thanks for the above. I suppose one way round the air current problem is to have a DC power supply that detects in microseconds the breakup of the arc, indeed the start of the breakup of the arc, and increases the voltage produced to either maintain the arc before it breaks, or indeed to force the creation of a new arc across the shortest path between the electrodes.

I suppose this would result in a scenario where the arc is initially created, rises as its hot air rises, reaches a height (several meters?) to a point where a new arc forms directly between the electrodes, causing the first to break.

It starts to make sense now.

What would happen if you placed the electrodes at the top of the room directly below an insulator such that the rising hot air has nowhere to go. Would the arc then take on a semblance of stability? I guess the air would heat up more and more. What happens to the resistivity of air as it gets hotter (into the thousands of degrees)?

I think you didn't mean to say what you did. Let's rephrase your question (Let me know if this is wrong)

"Why is the C-C bond weaker in Graphite than it is in diamond"

Well the answer is that the actual C-C bond is the same strength in both materials, and is as strong as diamond. But in graphite the carbon forms layers and these layers are connected with other layers by only a very weak force, and they can shear apart very easily. Whereas in diamond the carbon atoms are held together in a three-dimentional lattice (christal) structure which is strong in all directions, so no shearing can easily occur

They say that there is absolutely no zero referance frame for location or velocity, which is true. I think that there IS a zero frame for acceleration (this would be the acceleration where no external force is required), and that this is defined by the gravitational field where you are located. Where I am sat it is 9.8 m/s2 straight down. So in a sense the presence of mass, which causes gravity, defines the zero frame.

However what about rotation? I would define this as the rotational angular velocity where no force is required to hold youself together - ie zero centrifugal force (although I know this is a misnomer).

So what defines what this is? It does seem by coincidence to be the same as the rotation of the rest of the universe. (Indeed as an aside how would we know whether the universe is rotating?)

To help answer this question I must ask another:

If you have a small satellite in orbit around the earth once every 90 minutes, it will be in the zero acceleration state as I have defined above - it is weightless. However for it to also be in a zero rotation state, where it feels no centrifugal force, what must be its rotation? Is it a) pointing to a single point in space (such as the sun) or b) always pointing to the earth's horizon as it ploughs it way round the earth.

I think it is a) in which case the earth's gravity has had no influence on the zero rotating reference.

(What do gyroscopes do in orbit? Do they always point to the sun?)

http://en.wikipedia.org/wiki/Hydrino

talks about it.

It is a bit waffley though, and does not really come to any conclusions (damming or otherwise).

In my experience these types of things are junk. Remember cold fusion.

Electrical sparks through air are always viewed as transient, or at very least caused by alternating current.

Is it possible to have a continuous direct current spark?

If so, what is the lowest voltage that would be required to produce one, and then to maintain one, assuming the following parameters:

1cm air gap between electrodes

standard air pressure

standard air temperature in the surroundings

no external wind

What current would be produced by this, and what temperature in the spark gap. How bright would the spark be?

If the spark is maintained, presumably the air on the spark track would turn to plasma? If so would its electrical resistance reduce, so requiring much less voltage to maintain the same current.

It's 12hrs 34mins 56sec twice a day every day!

Yes good point. So we'll look forward to: 12hrs 34mins 56sec on the 7th August (or 8th July) 2090 to use up all the digits.

But I expect I'll be well dead by then...

OK I think that its time to make the inevitable silly comment on the thread title:

"Life on earth is boring"

Then try watching the living planet, the private life of plants, or any other David Attenborough show. Or better still go out into your garden and try repainting a butterfly.

ha ha

On a serious note, SIX: You say you want more. But you don't define what that might be?

PLZ HELP

if any of you hu read this thread go to cambridge could you plaz mail me with some information on the neurobiology courses and prices

 

e-mail:pedro.v.matos@hotmail.com

 

 

thanks

As an ex-cambridge inmate - er student, I can confirm that you do have to be a complete loony to contemplate going to study there, but that this helps with your application. Or if you are not, you certainly will be once you've been there for three years.

The worst thing about it is that it turns you from an articulate urbane gentleman into a scruffy hunchback who spends his evenings on the internet.

Sour grapes? No Never hehe

(Fitzwilliam, 1988)

A very nice site - I think you have a good computing brain too.

 

If youre ambitious you could expand on it by adding check boxes to each element. Users would then tick' date=' say, copper, sulphur, and oxygen and it would list all compounds made from them (copper sulphate in this case)[/quote']

 

I work as a SQL database developer and this could be done quite easily. The key is to get a list of all chemical compounds you are interested in (OK excluding the organics because there are literally millions of these) and add them to a SQL table. Then run a script that for each element goes through this list and sees whether it has this element in it (do a simple text parse for this check) and add an entry to a second table with each element id.

This will mean there will be three entries for copper sulphate for the three elements.

 

Then run a query each time to find all entries in those tables with a common compound id (name) where the three elements are present.

 

Of course the main question is whether anyone would actually use this feature. I've spent time in the past creating a web service that nobody found useful

 

But if people think it might be of use then I would be happy to give it a shot...

A very nice site - I think you have a good computing brain too.

If youre ambitious you could expand on it by adding check boxes to each element. Users would then tick, say, copper, sulphur, and oxygen and it would list all compounds made from them (copper sulphate in this case)

I think this is a fake, for the following reasons.

What they appear to be saying is that this HHO is the same as water but releases energy when it "burns" (producing water as the products of this reaction). This implies that the HHO has a higher energy state than H2O. I don't see how this is possible, because H can only bind to one thing - another H (Hydrogen gas) or O. So I can't see anything other than water or H2O2 (hydrogen peroxide) as a possible chemical here. And no higher energy state.

Secondly if the reaction is a "burning" without the need for external oxygen it would not burn it would detonate (like TNT which also does not need oxygen). The chemical reaction of this process would track back down the pipe of the guy's blow torch and "ignite" the entire contents of his HHO in the gas bottle. And he would be sent to meet his maker no doubt.

The reason this does not happen with ordinary gas torches is that there is a requirement for oxygen to burn the gas, and this is lacking inside the gas bottle.

Indeed to prove a point, if you put a match to it, TNT will burn with a smokey flame in a reaction with oxygen without detonating, because the temperature/pressure required for oxygen combustion is much lower than that required for detonation.

Of course it does require some guts to be the person who goes to light it

On a related point, does anyone know of a reaction where hydrogen and carbon dioxide can be combined (with a catalyst, heat, and/or pressure) to produce a simple hydrocarbon?

The combo Mg/HCl has a higher energy content than the combo Mg(2+)/H2/Cl(-). The energy is in the Mg-metal. The idea behind this is not different from the idea behind burning of combustible materials' date=' only the amount of heat involved is a little bit less.

 

Any chemical reaction involves heat. A reaction, which produces heat is called exothermic and a reaction which takes heat is called endothermic. An endothermic reaction usually does not occur spontaneously, one has to put effort in it. The products of such a reaction have a higher energy content than the initial materials.[/quote']

 

Woelen: Apologies if you've been asked this before, but what chemical reaction is taking place in the container in your avatar picture? It looks both quite cool and quite spooky at the same time.

Hello Gutz,

Thanks for posting here.

Are you are concerned about the pills because you are worried they are unnatural, or because you are experiencing side effects from them (mental straight jacket)?

Also could you let us know what mental illness you have been diagnosed with, and how severe, because this would make a big difference to what you should do.

Generally speaking, the correct approach is to do things like exercise if you suffer from mild depression (you've found this works for you) but only take medication if the depression is more severe. If you suffer side effects you should try other drugs to find one that does not cause you significant side effects (there are MANY different types of drugs to try).

With depression and other conditions such as Schizoprenia or bipolar (manic depression) I think the best approach is to only take drugs if other types of treatment fail, and the illness is significantly affecting your daily life.

Although drugs are "unnatural" many things in life today are unnatural. The newer types of Antidepressant (SSRI) often work very well with few side effects, and have vastly enhanced the quality of lives of millions of people.

If you are already taking drugs and are considering stopping taking them, then your doctor will be prepared to take you off them if he/she thinks that you can cope without them. Ask them. So Yes it IS possible for many people to live with their disorders without drugs. Its your choice.

However make sure you stop taking the pills gradually under the supervision of your doctor - don't just stop taking them.

Just because you're on a drug with a funny name that you haven't heard of doesn't mean that there aren't millions of others taking it and getting great benefits from it.

Have you been to http://www.depressionforums.com

This site has hundreds of people to ask about every question under the sun.

Hope this helps

A thought just occurred: In the UK, and I expect also in the US, many streetlights are an orange/yellow which means low pressure sodium lamps. Some others are whiter yellow which are high pressure sodium lamps.

Now if I purchased one of these off ebay (the bulb, not the whole lamppost) and cracked it open with a chissel, would that reveal any metallic sodium?

If you go to www.unitednuclear.com[/url'], they actually sell sodium metal pieces so if you truly want some sodium you can purchase it through them.

Cool! that's quite something. Unfortunately after entering my order for the Na and K with some magnetic liquid an a small amount of truck bomb mix (ammonium nitrate) (sorry Oklahomians was that in bad taste?) I found that they won't ship outside of the US to the UK

Back to the electrolysis. Or maybe I can risk putting some in my hold baggage when I next return from a holiday in Florida...

When I was a spotty teenager 20 years ago I was impressed by the experiment at school where a piece of Sodium metal was placed on water, and it caught fire with the released hydrogen, and danced around.

I thought that I would like to make some of my own and that the best material to use for the required electrolysis was sodium hydroxide (caustic soda) which I bought from a hardware store. With the aid of a camping gas stove I was able to melt it in a metal tray (it melts at 300 degrees centigrade or thereabouts), and attach the electrodes of a low voltage DC power supply to start the process. However even at the low voltage it still drew too much current and burned out the fuses.

I'm thinking of trying again as I've found the tin of caustic soda in the garage, and have the following questions:

1. What voltage is actually required? (I think it was running at 3 volts when I last tried it).

2. A high current is clearly required here. What is the best way to get a low voltage DC high current? Can a unit be purchased from a shop, or can I make my own from purchased diodes etc.

3. Would the sodium produced stick to the electrode, or float to the top of the NaOH? If so would it catch fire?

4. At 100 amps, how long would it take to produce a gram of sodium?

Industrially they use mercury to produce it. I have a small bottle of mercury. I might try using it, but it is very toxic and would produce fumes with the heat.

FYI I tried to buy some from Aldrich Chemicals but they said no. And that was before the days of global terrorism.

I was thinking of the scenario where you have a DC current running through a coil which is one side of a transformer. A static magnetic field runs round the ferrous core of the transformer, and if my memory serves me right this has a specific number of joules of energy associated with it. This energy can be seen when the DC current is shut off - the field causes a current to flow in the other side of the coil (assuming its ends are connected across a resistor) supplying voltage and current (this principle being used when AC current sends a continuous power across).

I'm remembering a little more now: A coil has an inductance L, and the energy carried in the field is half L i squared (where i is the current).

Hmmm I wonder whether I've answered my own question here. If i is constant then the kinetic energy of the electrons will be constant, but you can add materials into the coil to change the inductance without changing the coil itself.

soap