sethoflagos

It looks like one or more of the floating varieties of Sargassum. The controlling factor is I understand nutrient supply to the historically low nutrient Sargasso sea. And this was thought to be dominated by mineral dust carried by the trade winds off the Sahara. Most likely recent increasing influx of nutrients may be from ecological changes occurring in the Amazon system and possibly our neck of the woods in sub-saharan West Africa. Coupled as you say with locally significant shifts in surface currents.

You want me to yield to your opinion? It isn't me that's having a problem with established science. I suspect pride is clouding your judgment. Good night.

Only if you want it to be. Once dmB has been exhausted it plays no further part in rocket propulsion. I'm pretty sure I'm free to reset the counter back to zero again. The total amount of exhaust is of no relevance to the OP. So why bother keeping track of it.

Over the time interval dt, mB increases from 0 to dmB. So in context mB = dmB.

Ftotal = dp/dt = mdv/dt + vdm/dt = F1 - F2 = 0 For total system Consider momentum change of body A (rocket +unused fuel) FA = dpA/dt = mAdv/dt + vdmA/dt = F1 - F3 = X (non-zero!) Consider momentum change of body B (exhaust) FB = dpB/dt = d/dt (mB (v-(v-ve)) = d/dt (mB (v - ue)) = dmB(dv/dt - due/dt) + (v - ue)dmB/dt = dmBdv/dt + (v - ue)dmB/dt Since dmB = - dmA FB = - dmAdv/dt - (v - ue)dmA/dt = F4 - F3 - F5 = -X (non-zero!) Add FA and FB Ftotal = FA + FB = dp/dt = mAdv/dt + vdmA/dt - dmAdv/dt - (v - ue)dmA/dt = (mA - dmA)dv/dt + vdmA/dt - vdmA/dt + uedmA/dt = 0 Hence (mA - dmA)dv/dt = - uedmA/dt or F1 + F4 = F5 There's a couple of differences here to your thrust equation. I've used ue instead of ve to show that the exhaust velocity is specific to the comoving inertial reference frame of the rocket whereas v is for any observer. I've also left the dmA term in the left hand expression to emphasize that the thrust equation involves mA rather than m of the overall equation. Mathematically, it's justifiable to delete this dmA as is is overwhelmed by mA. Please take note how I have distinguished different forces with different subscripts. Much of your confusion appears to stem from an expectation that all Fs must be equal. Sometimes they are. Generally they are not.

It's hardly my field, but I'd been led to understand that quantum information behaved rather like entropy. ie that if it is erased from one part of the universe (requiring some form of work) at least as much must be released elsewhere. Perhaps I'm misunderstanding you.

I was thinking more generally than that. More 'every breath we take, every move we make' adds to the quantum information of the universe, albeit in a highly garbled form, but it's there for eternity.

You're absolutely right. There was no call for my response. I've no idea why I wrote it. Can we put it down to a senior moment?

I see you contributing quite frequently on climate change issues. Maybe it's a generalisation, but the impression that I get from your posts is that every little bit that we can do to reverse the current trend counts. No matter how insignificant our personal efforts may seem at the time. I guess I've a tendency to vote with my feet. I may not have much impact at the ballot box, but transferring my economic activity to a different country is probably more significant overall.

I lile these products. As do my wife and children. Why should we answer to you about our personal preferences? None of your business I think.

I watched a Youtube video tonight that pulled together a few lines of thought that I'd been pondering over without linking them together. What really grabbed me was the contrast between the fragility and improbability of complex civilisation with the indestructability of quantum information. Why such a visceral reaction to this? Well I've not taken part in any democratic process for over 25 years on the grounds of too much hassle; I don't live in the country where I could vote; my vote probably wouldn't make much of a difference anyway. And yet those decisions not to act, via the indestructabilty of quantum information, must have measurable consequences stretching out to the end of time. That's one hell of a long time for the butterflies wingflap to perturb the evolution of the universe. I'm seeing the epitaph on my tombstone. Seth 1958 - 2028 Did f*** all to defend his personal values Suddenly I'm drawn a lot closer to a POV often expressed by @Ken Fabian

I'm no expert in this but I'll say it anyway. My understanding is that in SR the spacetime interval between two events is invariant for all inertial reference frames. The minimum spatial separation occurs for the observer who sees the events as simultaneous. All other observers see a greater spatial separation and an increasing temporal separation per s2 = x2 + y2 +z2 - (ct)2 = constant. Local clocks and measuring rods must vary accordingly.

I've just done it. According to your earlier definition: A more interesting question would be to ask "How was the exhaust decelerated from v to v - ve?" One for another day perhaps.

Yes, mdv/dt = -vdm/dt is indeed the overall force balance. So let's separate rocket from exhaust components. Consider an observer travelling with a constant velocity v He sees the rocket of mass m gain a velocity dv. He sees a small amount of mass dm ejected at a velocity of ve in the opposite direction No nett motion of the total becomes mdv = -vedm Hence we recover your thrust equation mdv/dt = -vedm/dt It really isn't rocket science ..... er 🤨

Someone gives you $5. Someone takes $5 off you. You are left with $0. Someone gives you $5. Someone takes $5 off you. You are left with $0. Neither did I mention that integration of the equation yieds the Tsiolkovsky rocket equation. The OP didn't ask for it. But you can mug up on it at https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

So? What is omitted that is pertinent to your OP?

dp/dt gives you BOTH sides of the equation dp/dt = d(mv)/dt = mdv/dt + vdm/dt =0 Hence: mdv/dt = -vdm/dt

edit: deleted

I'm inclined to see even this as a false dichotomy. I like Aristotle's ancient maxim: 'Nature operates in the shortest way possible'. It keeps coming back in various guises: the various statements and restatements of Occam's Razor; Principles of Parsimony and Least Action; even the simple symmetries underpinning the Standard Model. In context, it is indifferent to any concept of supernatural being. Why should a principle that frames much of your core opinions be framed in terms of something you've rejected? Do we label modern chemists as 'antiphlogistonists'? At some stages in our development, explanations involving supernatural beings were the simplest and therefore the best explanations going. But we have better explanantions available to us now and are able to discard some of the more elaborate beliefs of our ancestors. So like @Genady I find the term 'atheist' unhelpful though I stopped believing in fairies nearly 60 years ago. I feel the term is maintained in the interests of those who wish to keep an outdated concept centrestage. Time to move on.

I see scattering as a perfectly elastic exchange of momentum with no energy exchange. ie. the scattering body changes direction without a nett change in speed and no heat transfer. Ditto the photon so there is no change in frequency and no spectroscopic impact (other than directional). Photon absorption processes are quite different though since there is a transfer of energy into the absorber and unless the photon is reemitted very quickly, the increase in internal energy must have a thermal impact. So yes, I agree with @swansont on this point. Yes indeed. if the photon is energetic enough to start shunting electrons into different orbitals then the physical nature of the particle starts changing. But most of the gases I've worked with don't absorb in the optical range so it's not something I've ever had to worry about.

I enjoyed that little read. Thanks! I'd actually guessed Jack Vance from your storyline. It had a bit of an Eyes of the Overworld feel to it.

Bear in mind that there is a dynamic equilibrium between translational, rotational and vibrational components. Compression for example is a direct input of translational kinetic energy, but it it gets partitioned equally between all the degrees of freedom as part of the equilibriation process. If you look at purely the translational modes, the monatomic gases always behave elastically, but other gases only appear elastic on average.

Point understood. A waveguide that can fit into a pea restricts the emitter to W-band or higher. Such wavelengths do not penetrate more than skin deep. Not much use for defrosting purposes.

Without stating it directly, you are making enquiries about an em band that is used primarily for military applications (see https://en.wikipedia.org/wiki/W_band) I reported the thread because I am uncomfortable discussing this technology in detail given the current world situation.

Can I please ask that members not post to this thread until the mods have addressed the report I've raised to it. Thanks in advance for your cooperation.