pavelcherepan

We don't give full solutions here. What's your progress on these questions?

Do you mean it like in a bomb? But with "conventional" fission trigger mechanism you do get hot ionised plasma as a result. Plus you get an added bonus of pressure holding your fusion reactants together long enough to produce a lot of energy.

Well, the concentration of particles in V-A belts is very low so your craft would need to spend a significant amount of time collecting ions. At the same time radiation levels in V-A belts are harmful to delicate electronics on the craft and so you'd want to minimise the exposure as much as possible. There's one contradiction. Also, I'm not sure whether collection of ions in V-A belts is technically feasible or not.

Thanks studiot, it was a really good explanation.

Yeah, that's what I read on many sources. I was just confused by the Acoustic Theory article on wiki, which says that waves do have momentum. But doesn't the jet transfer it's momentum to the wall? I can't see similarities between those. Thanks! Found it on Google books. I'll see what kind of exciting stuff I can find there! Robittybob1, gravitational interaction doesn't matter as that momentum is already conserved. Look at this: Force acting upon a meteor: [latex]F = G \frac{Mm}{R^2}[/latex] , where m is the mass of meteor and M is the mass of the Earth. And by Newton's third law the force acting on Earth will be the same but with an opposite sign. Then meteor will be accelerated by that amount: [latex]a_m = F/m = G \frac{Mm}{R^2} * \frac{1}{m} = \frac{GM}{R^2}[/latex] and similarly Earth will be accelerated by: [latex]a_E = -F/M = -G \frac{Mm}{R^2} * \frac{1}{M} = - \frac{Gm}{R^2}[/latex] Then if we take a small amount of time [latex]\Delta t[/latex] during this period meteor and Earth will change their velocities by: [latex]\Delta v_m = a \Delta t = \frac{GM \Delta t}{R^2} [/latex] and [latex]\Delta v_E = a \Delta t = - \frac{Gm \Delta t}{R^2} [/latex] And, finally, momentum change during this time will be: [latex]\Delta p_m = \Delta v_m *m = \frac{GMm \Delta t}{R^2} [/latex] for meteor, and [latex]\Delta p_E = \Delta v_E *M = - \frac{GMm \Delta t}{R^2} [/latex], which are obviously the same but with opposite sign. As a result there's really no need to consider gravitational influence in momentum conservation calculations.

I have a WWRFD t-shirt. Love that one.

That is part true and good job on noticing, but angular momentum of the planet can change due to Tidal interaction with the passing object.

That's the whole idea of the slingshot effect. An object passing by a more massive object "steals" some of it's momentum to increase/decrease it's own velocity. https://en.wikipedia.org/wiki/Gravity_assist I'm still reading the link you've sent. It was so interesting (the Tunguska part) that I didn't really skip to formulas as I planned but in the mean time I've ran into a bit of an issue. A part of the relationship above was the bit cleverly titled "sound-wave-momentum" but depending on the source I look at some say that sound waves carry no momentum (but have energy and can perform work) and some (for example wiki article on Acoustic Theory) have formulas above what I can comprehend. What I was thinking in the plane is that the sound wave propagates as a cone so if we consider the surface it hits to be completely flat and we know how to express momentum transfer at any point of contact then we can express the momentum transferred to Earth in retrograde direction as [latex]x*sin(\alpha)[/latex] where x is that formula for momentum of sound wave at a point and alpha is measured from horizontal. Than I could take a half of the cone and to get the entire momentum I could integrate that relationship by alpha from 0 to pi/2, since if the surface is flat every point of contact will have a different alpha, and then doubling this entire expression I could get the full momentum of sound wave. I hope I'm making some sense. Would that work? You can guess, calculus is not my strongest field. And further on, since sound waves are created all along the path of the projectile, in order to get the complete momentum from the sound wave all of this above would have to be integrated either by time or distance traveled through atmosphere.

Thanks I'll do that once I get off a plane.

I've given it a bit more thought. [latex]v_p[/latex] should be the vector sum of escaped particles velocities.

So just through sound waves? Thanks, that helps a lot! Ok, so here's the main problem I'm having. So say we have a meteor that impacts atmosphere from prograde direction. At infinity it's velocity is v and then it has an inherent momentum of mv that it has to transfer to Earth. I don't take into consideration acceleration due to gravity interaction with earth, because both bodies will be accelerated proportionally to mass and hence this momentum is already conserved. So it hits atmosphere and burns up. From what I know now the following effects will account for that original momentum: degassing in a preferred direction, mass loss of earth due to increased escape of gases, sound waves, but in fact escaping gases will preferrentially escape in prograde direction and hence will in fact result in thrust on retrograde vector. Then is this relation correct? [latex]mv = m_2*v_e - m_g*v_p + sound-wave-momentum[/latex] Sorry it's ugly, I'm typing from my phone. Here m2*ve is mass of all gas that wouldn't have escaped without the impact times velocity of earth, mg*vp is mass of the gas that's escaped in prograde direction times vp - average velocity of escaped particles.

So what I was wondering about is whether the impact of a meteorite or a meteor into earth's atmosphere will change it's linear momentum apart from potential increase in atmospheric escape? So to put it short, is the impact onto the atmosphere somehow passed onto the solid Earth itself?

Robitty, this is not your discussion so please stop derailing it. You're at a computer, open a new tab in the browser and search for linear momentum. Very easy, nay?

OK, but what about linear momentum? Will it also change because of gravitational interaction or some other mechanism is also possible? I was thinking that if meteor burns in the atmosphere it increases average temperature of said atmosphere and increases the rate at which gases escape. That could also lead to a decrease in linear momentum.

So let's say we have a meteor that's burned up in the upper atmosphere like they normally would. Does that meteor change the overall momentum of the Earth, regardless of how small the change may be? On one hand I'm tempted to think that all the energy goes into heat and viscous deformation of the atmosphere, but on the other hand if we had billions of those burning up every second , this should cause some drag and change momentum of the planet. In that case what would be the mechanism of it?

Yes, there should be, but these are not major players. When you try to model something you first take major contributors and then fine-tune the model with minor ones. Instead, what you're trying to do is to understand gas migration using only the minor contributors without even trying to understand the main cause. This is a wrong way to look at a problem and you're not going to get any meaningful result this way.

That's what Mordred really said:

I'd phrase it differently: "In this thread Robittybob1 has gone mad and decided that DDE has major effects on dust clearing" You can try and prove that methodology and simulations are incorrect or find some actual recorded scientific fact that doesn't fit in the model. Below are links to research papers for Nice and Nice 2 models so you can have a look and see if you can disprove the theory. http://www.nature.com/nature/journal/v435/n7041/full/nature03676.html http://iopscience.iop.org/article/10.1088/0004-6256/142/5/152/pdf

Wild guesses. Prove that it could've happened. As I said before it really doesn't matter what you believe and what you don't. Prove it. Also an interesting point is that Jupiter most likely was the first planet to form to completion. Models show that formation of Jupiter could have taken just up to 1 million years while terrestrial planets took tens of million years to accrete. http://www.sciencedirect.com/science/article/pii/0019103588901339 http://www.nature.com/nature/journal/v402/n6759/abs/402269a0.html Again, what you believe is irrelevant. If you have skills and knowledge to disprove Nice/Nice II models, give it a shot. No. It's not the reason they are thought to have migrated. By the time of migration Jupiter and Saturn are thought to have fully formed. It was well after protoplanetary disk was mostly cleared. Nice model shows that such a migration can explain Late Heavy Bombardment, formation of Kuiper belt and Oort clod. Citation needed to show that clearing of dust is an unresolved mystery.

I agree with an addendum: It is this light that can't penetrate the dust disk as viewed by an external observer and only in visible part of spectrum.

All of your objections will make up for just around 1 order of magnitude. In my calculation I've jammed all the dust into a volume thousands of times smaller than the actual volume where material was distributed so in reality it will still be very tiny concentration, much lower that what I've shown with the simple calculation. No it doesn't. Again it talks about protoplanetary disks viewed from outside. And it's true, they are not transparent in visible light at least, more so in infra-red.

As always your scientific discussion manners are impeccable (sarcasm intended). This is not the basis of my knowledge. The basis of my knowledge is my Uni education and further reading of multiple papers and books on the topic. The link I gave you shows how complex modelling of dust migration is and should probably give you an idea that you attempting to come up with the solution of your own is very unlikely given your rudimentary understanding of processes involved (not that I'm claiming to have perfect understanding either). As you've been told before, you should try and tackle small problems one at a time. Once you have a good understanding of those you can try and move on to bigger questions. It won't help if you continuously start meaningless discussions and then don't learn anything from them, and then will the same poor understanding in the next discussion. EDIT: Another back of the hand calculation. All the mass in solar system other than Sun itself is about 1/600th of Sun's mass or 2*1030/600 = 3*1027 kg approximately. Now we assume this mass is all in dust particles with density ~2 g/cm3. And also to not bother with distribution through SS we'll jam all these particles within 1 AU from the Sun and 0.5 AU above and below ecliptic. We'll take particles to be ~1mm in size on average. 4/3*pi*(0.001)3*2000 = 8*10-6 kg per particle, hence 3*1027/8*10-6 = 4*1032 particles approximately. Total volume pi*r2*h = 1*1034 m3 And then particle density would be ~10-2 particles/m3. One particle per 100 cubic meters! So even in this absolutely unrealistic scenario your idea doesn't stand to scrutiny.

You don't seem to read stuff at all. I'm not planning to spoon feed you. You know, "Give Robittybob a fish link and you'll make him happy for one day, teach him how to use search engines and he'll be happy forever". What do you mean by that (below)? There's been plenty of studies, just like the one I quoted.

I've already included the reference, but I'll repost for your convenience. Or if this one is too complicated, go on Google Scholar and search by keywords "dust & protosolar cloud" and ye shall find. http://adsabs.harvard.edu/full/1984ApJ...287..371M That's nonsensical.

That's not it. This is from outside perspective. Look at this simple back-of-the-hand calculation. Say we have a protostellar cloud ~200 AU in radius and we're looking at it from outside. 200 AU is ~3*1013 m. Hence non-transparency of protostellar clouds when viewed from outside only implies that that particle/dust density is somewhere above 10-13 particles/m3. That way most of photons travelling 200 AU is highly likely to hit a particle a get scattered or absorbed. In reality specifically dust density as modelled for proto-solar system is around 10-8-10-15 particles/m3 so it's mostly empty space (I'll add paper reference once I get home). With that kind of thinking you probably also believe that a scene form Star Wars where Han Solo showed "incredible skill" navigating through asteroid belt is realistic. True dat. Robbity, I suggest you have a look at this paper for example and understand the depth of knowledge required to model dust transportation in protosolar cloud. I'm totally lost in all these giant formulas, but who knows, they might make sense to you. http://adsabs.harvard.edu/full/1984ApJ...287..371M