Ask any question you want about Physics

originally posted by: pfishy
a reply to: prevenge

African or European?

WAAAAAAAAAAHHHH!

originally posted by: Arbitrageur
a reply to: prevenge
I don't know and it doesn't sound like a physics question.

(SYRYSLY?)

....

WAAAAAAAAAAHHHH!

a reply to: Arbitrageur

Hi Arbitrageur.. I have one question of which I would like to understand the answer.

How is it possible that the vacuum of space is not sucking our atmosphere away. The vacumm of space is such a powerful force that it is hard to believe earth's gravity is pulling harder than this force.

For as much I can understand it this must be the answer. If so... how would a person start to make a calculation to proof this is indeed the case.

Are there examples in where such huge differences in pressure stays in balance without a hard seperation between the two different pressures. For example...a spraying canister its pressure is "protected" by metal surrounding it. Our atmosphere has nothing "hard" between space and the earth to protect its pressure. You understand what I mean..?

Thx for showing how to calculate this "miracle" ..

Seriously though...

What is.....


...your favorite color....


No seriously...

I'd actually like some semi-concrete opinion on:

How neuro transmitters may react to the presence of dark matter.

Ie: if dark matter is present in the universe...
Then why not here on earth?
And if so, if it were to be in the same area of a human being's body, then would there be any sort of positron (real vague and uneducated here on the details)... sensed by the neurons in the human's nervous system?

If this is of any interest to anyone qualified to explain, then please do so.
Thank you.

...."red."

...."NO, BLUE! ....WAAAAAAAHHHH!"

originally posted by: zatara
How is it possible that the vacuum of space is not sucking our atmosphere away.

Who told you it wasn't? It is, though mostly what we are losing is hydrogen (about 3kg/s) and helium (about 50g per second), and a physicist wouldn't phrase it that way; they refer to "atmospheric escape".

The vacumm of space is such a powerful force that it is hard to believe earth's gravity is pulling harder than this force.

There's a bit of a language barrier between physicists and laypeople in using terms like "force" which to a physicist has a very specific meaning, and using that meaning the vacuum doesn't have any force at all (or if it does, it has a very small force that pushes things apart, which we refer to as dark energy. That force is so small it can be considered negligible for the purposes of atmospheric escape.)

To study atmospheric escape requires expertise in statistical mechanics, fluid mechanics, plasma physics, collision theory, and surface science, according to authors who have described it, and the phrasing of your question makes it fairly clear you don't have such expertise but I can try to give you an analogy. Look at this video of a homemade lottery ball machine:


Notice how the bouncing balls tend to concentrate at the bottom, but some bounce much higher and every once in a while one hits the top? This is a crude model of how the molecules in our atmosphere bounce around and against each other, except all those balls are the same size and in our atmosphere there are different molecules like oxygen, nitrogen, CO2, hydrogen and helium which are not the same size or mass.

What ends up happening is because the hydrogen atoms are the lightest, they are the most likely to end up with the highest velocity. To make an analogy of earth's atmosphere with the lottery balls, take the top off the lottery ball box, so now it's open with no "barrier" just like between Earth's atmosphere and the vacuum.

Notice that every once in a while a ball hits the top of the box, but if you took the top off it would fly out of the box. The ball that flies out of the box is a crude model of atmospheric escape. In our atmosphere it would likely be a hydrogen atom. So if you can figure how most of those balls stay in the box, you have also figured how how the earth keeps most of its atmosphere. After all it's the same force pulling down in both cases...gravity.

Now the reason you think the vacuum has a force is maybe you hold a vacuum cleaner tip next to a piece of fuzz and you see what seems to be a "vacuum force" sucking in the fuzz, right? Well there is no such vacuum force and that's not what really happens. What really happens is the machine creates a "low pressure" area inside it, and the "normal pressure" gas outside the machine will have a tendency to flow toward the low pressure area (all else being equal like gravity etc) and it's actually those normal pressure molecules pushing their way toward the low pressure area that carry the fuzz along with them. So this hopefully explains how the vacuum cleaner works without any "vacuum force".

a reply to: prevenge
In the last second, about 100 trillion neutrinos passed through your body and you probably didn't even notice, neurotransmitters or otherwise, right? In fact neutrinos interact with matter so little that most will pass right through the entire earth without interacting with anything, so that headache you got yesterday afternoon was probably caused by something other than neutrinos.

We don't know exactly what dark matter is but one popular hypothesis is that it's made of "weakly interacting massive particles" aka "WIMPs". So what does "weakly interacting" mean? It means they interact with matter even less than neutrinos do. So if that hypothesis is true and there are many dark matter particles passing through your body, you'd notice them even less than the trillions of neutrinos passing through your body every second, which is to say not at all since you don't notice the neutrinos.

One of the contributors here worked on an experiment to try to detect those WIMPs and I think it's running right now but even if the WIMP hypotheses is true we don't know if they even can be detected; maybe the interaction is too weak, as Eros has explained to us before.

There are also other hypotheses about dark matter but those wouldn't be as relevant to your question. We still don't know what dark matter is, but we have pretty good evidence for its existence.

a reply to: Arbitrageur

Got a question on magnetism, please. Do all magnetic fields have a toroidal/torus structure? Can they come in any other shapes, aside from distorted toroids?

originally posted by: BELIEVERpriest
a reply to: Arbitrageur

Got a question on magnetism, please. Do all magnetic fields have a toroidal/torus structure? Can they come in any other shapes, aside from distorted toroids?

There are two types Toroidal and poloidal depends on rate of spin as to which one you get. But I'm not sure if this is the question your meaning to ask. What is this in reference to??

a reply to: dragonridr

Wouldn't the toroid and poloid have to coexist, like different aspects of a single entity? Basically, do all magnetic fields take on the basic donut shape, even if the donut is distorted?

If possible, could you provide a visual representation of a poloid vs a torus?

a reply to: BELIEVERpriest
I'm not quite sure what you're after here, but yes if you set your compass so that magnetic north points to your left in a poloidal (poloidal, north *pole*, get it?) direction, then you can walk east in a toroidal direction with respect to Earth's magnetic field. That's how they are related.

One exception to a dipole magnetic field could be a monopole if such a thing exists. While no true magnetic monopole has been found, monopole-like phenomena have been created in labs and with a monopole the field lines are radial rather than toroidal. While magnetic monopoles have been hypothesized, none has ever been found and they may not exist.

Interesting field line shapes can be made by combining magnets, like quadrupole with two north and two south poles. You can find many interesting shapes of combined magnetic fields here.

a reply to: Arbitrageur

Basically, I was involved in a debate over fractals, magnetism, and basic field theory. I submitted that the torus was the universally natural shape of all naturally occurring magnetic fields, and I was abruptly told that I was wrong without any sort of explanation. Hence my question: Do all magnetic fields naturally take the shape of a toroid?

Thanks for your reply. It helps.

Im not sure about monopoles, they might be entangled at a distance with a counterpart to form a dipole.

originally posted by: BELIEVERpriest
Hence my question: Do all magnetic fields naturally take the shape of a toroid?

That depends on context and how you define magnetic field. Take for example the moon, which doesn't have a dipole magnetic field like the Earth does through even the toroid of the Earth's magnetic field is distorted by solar wind. Since the moon's magnetic field is not a dipole it can't be said to have a toroidal configuration but somewhat like the images link I posted showing the effects of combining magnetic fields, I suspect the moon's overall magnetic field is composed of smaller fragmented areas which would tend to be dipole and thus toroidal. For example one idea is that an impact can create a magnetic field antipodal to the impact site, so you might have had a toroidal field around that site, except you might not because of other antipodal sites have their own field, so the magnetic structure of the moon gets a little messy.

On a much smaller scale than the moon, you have the crystalline structure of magnets that similarly have different magnetic domains which can each be said to have their own magnetic field and they don't necessarily all align so this microstructure might also challenge the toroidal claim on the relevant scales.

Magnetic Domain

Microcrystalline grains within a piece of NdFeB (the alloy used in neodymium magnets) with magnetic domains made visible with a Kerr microscope. The domains are the light and dark stripes visible within each grain.

If you map the magnetic fields at the scale of this photograph they will be messy and have more resemblance to that photograph than to a torus, but at some distance from this magnet will be a magnetic field which is the combination of all these, with a toroidal shape.

a reply to: Arbitrageur

So basically, the chaotic multipolar MFs of the moon are probably the result of densely populated misaligned dipolar MFs (on a smaller scale). If it weren't for the chaotic interference of misaligned MFs, they would probably have toroidal structures?

Let me know if I got that right, and thanks again for all of your input.

It's probably a stupid question, it's Saturday and late where I am. What I'd like to know is,

Can it be considered quantum tunneling at work when light moves through glass? Just wondering because it's a particle and a solid barrier.

a reply to: BELIEVERpriest
I think that's the general idea though it may be overstated slightly. Let's look at what the source says:

Formation of magnetic anomalies antipodal to lunar impact basins

Significant crustal magnetization anomalies antipodal to lunar impact basins are therefore expected, consistent with orbital mapping results. Weaker magnetization observed peripheral to the Imbrium basin may also be explained by shock effects together with compressed ambient fields in a surface boundary layer. Although other processes such as cometary impacts and a former core dynamo may have contributed significantly to the observed paleomagnetism, meteoroid impact plasmas appear capable of explaining a major part of the large-scale magnetization detected thus far from lunar orbit.

I'm not exactly sure what they mean by "compressed ambient fields in a surface boundary layer" and if that field would map as a toroid, but I think the rest would be fairly consistent with such a description. I don't think the moon's magnetic field is fully understood and this might only explain parts of it.

originally posted by: Peeple
It's probably a stupid question, it's Saturday and late where I am. What I'd like to know is,

Can it be considered quantum tunneling at work when light moves through glass? Just wondering because it's a particle and a solid barrier.

No quantum tunneling isn't needed for that but it is needed for the sun to work, so we literally wouldn't be here without quantum tunneling.

a reply to: Arbitrageur

BTW, are you a physicist or a scientist of some kind?

originally posted by: BELIEVERpriest
a reply to: Arbitrageur

BTW, are you a physicist or a scientist of some kind?

Yes, this is a relevant question, so that we may frame our questions properly.

a reply to: BELIEVERpriest
I double-majored in physics and engineering but I ended up being more of an executive than a scientist. I've had scientists on my staff.

a reply to: Arbitrageur

Very good. I'll keep this thread in mind for future questions. Thanks so much.

a reply to: BELIEVERpriest

Its an excellent thread. The guys in it are tip top with their knowledge of most things physics wise.

Arbi. Is a class act and really knowledgeable.

Eros is a man you should pay attention to when he speaks

and mbkennel is the real deal you can even google his papers. Just dont blame me for any math induced headaches if you read his stuff.

If youre extra extra lucky bedlam might comment. Hes about as knowledgeable as one can become on both the topics of physics and engineering.

Youve found an excellent resource in this thread and i recommend bookmarking it. I always learn something here every time i drop in for a read.

a reply to: Arbitrageur

What do you think of Green, renewable, recycling energies?

What do you think of coal, and nuclear?

Non gas powered cars?

What do you think of man made climate change claims?