Okay Folks...about Professor Kaku...

[Thurisaz]

...if you don't know who I mean, lookee here.

 

Because even the most rabid propaganda machine can't babble crap 24/7/365 without becoming too blatantly obvious as what it really is, our local German "news" TV stations offer a schedule of 95+ % documentaries. For several months now, Mr Kaku's "Scifi science" show has aired prominently over here. Actually I'm watching another rerun as I'm typing this.

 

And I wonder.

 

Most of what he says makes quite a bit sense, considering that it's clearly labeled as SciFi = not yet possible but might become so in the future. But he's a professor for theoretical physics as I understand it.

 

Such a man should know about conservation of energy right? Or am I missing something here?

 

There's that episode of the show where he plans a way to establish interstellar colonies on other planets, and one idea proposed there is sending a cloud of tiny robot probes to Jupiter, let them orbit it while electrically charged, and wait until the Lorenz force has accelerated them to near-lightspeed before switching off the current and catapuliting them away into space.

 

Umm. I know about the Lorenz force, it's a hard-to-deny fact (unless you're a babblical cretinist or such ). But if I remember correctly this thing is about moving electrical charges being deflected in a magnetic field... not accelerated. If this worked like he says in that show, where would the energy come from exactly?

 

I'm trying to figure out what's wrong in that since I first saw that ep but I keep running into a wall. As he seems to say it (inasmuch as I can understand the English audio behind the German translation he really seems to make that statement) we would fire those probes with a fixed velocity v into Jupiter's magnetosphere, carrying a certain electrical charge e. We also have the constant field strength of Jupiter's magnetosphere m. All constants. Where does the acceleration come from? A miracle™?

 

You sciency folks out there... I know you're here. Is that just a dumb mistake in the show's translation, am I wrong (very possible I guess) or is something else fucked-up here?

[RogueScholar]

I don't follow Doctor Kaku, so I'm not familiar with the show:

 

Have you studied any electromagnetic theory? For example, are you familiar with Maxwells equations and concepts such as dot and cross products? If not, really understanding this concept will be difficult. First, I need to point out that forces cause acceleration. Acceleration is any change in velocity. Therefore change in direction or speed is acceleration. Remember velocity is a vector and has both a magnitude and direction. In calculus terms velocity is the derivative of position with respect to time and acceleration is the second derivative of position with respect to time.

 

When you say something is being "deflected" it is being accelerated. The fundamental formula that deals with this goes as follows:

 

Force on the charged object = charge multiplied by velocity (cross) the magnetic field (F=qV X

 

I've attached a link to a very good introductory video on Lorentz Force:

 

 

Let me know if you have any questions, but I think the issue from your post is that you may not have had an accurate understanding of the concept of acceleration? I'll try to clarify anything else if possible. It's been a while since I took undergrad physics, so I'm probably rusty on many concepts myself.

[mymistake]

Science fiction is fictional science.  They have to change something to get from known reality to fiction.  This change could be an educated guess or it could be something made up.  As time passes occasionally science discovers a real way to get to what we previously imagined as science fiction.  But most science fiction winds up being laughable decades later.

[Fernweh]

I'm going to take a wild ass guess and say the energy is taken from Jupiter's spin in the same way space probes transfer a little bit of planetary orbital velocity when performing a gravity assist slingshot maneuver. 

[RogueScholar]

In the context of Lorentz force, the energy comes from the magnetic field. A magnetic field will have potential energy. Jupiter's magnetic field ultimately comes from electrical current in the planet's core. The electrical current comes from the movement of a very strange type of matter known as metallic Hydrogen. Hydrogen can exist in this state due to the immense pressures experienced in the core.

[Fernweh]

In the context of Lorentz force, the energy comes from the magnetic field. A magnetic field will have potential energy. Jupiter's magnetic field ultimately comes from electrical current in the planet's core. The electrical current comes from the movement of a very strange type of matter known as metallic Hydrogen. Hydrogen can exist in this state due to the immense pressures experienced in the core.

 

So in this case the magnetic field is energy that could be harnessed by the Lorentz force that is otherwise "wasted"? A pool pump creates a magnetic field that is converted to mechanical force used to pump water. If no water is running through the pump the magnetic field is still created but wasted since no work is being done?

[Thurisaz]

Rogue granted that I didn't express myself well in the OP. Yes a change in direction of travel is also an acceleration, technically. But I fail to see how this would somehow also speed up the probes instead of just forcing them into a circular motion.

 

(Don't have the time at the moment to check out your video, hope to do so later. Back at school I was one of the physics wizards but that was a looooong time ago and I didn't have to really use those skills for all the years inbetween - so of course they got quite rusty. )

[RogueScholar]

There are a couple of concepts. One is the concept of an electrodynamic tether. Attached is a paper and it covers some of the advanced maths.

 

http://russell.ae.utexas.edu/FinalPublications/ConferencePapers/2013Aug_HiltonHead_AAS-13-899_TethersJupiter.pdf

 

As stated, I do not follow Kaku so I am not entire sure what the exact idea was, but clearly we are still far out from developing any significantly complex propulsion technology that could take humans to the stars.

[skepticalme]

I haven't seen the episode so I don't know exactly what setup he is picturing.  Perhaps he means placing the probes deep inside Jupiters magnetic field with conventional propulsion and then turning on the electric field that propels them outward.  It's sort of the same concept as a rail gun, except in a rail gun you are creating the magnetic field as well with massive amounts of electric current.  The energy would come from Jupiters magnet field (the spin of it's core).  A similar idea has been floated by NASA about using conductive tethers on space stations around Earth.  NASA has done experiments extending a long metalic cable from a spacecraft to a counter weight at a higher orbit and found that a large electric current is produced.  A conductor moving through a magnetic field (Earth's) at a high velocity (orbital velocity) produces an electic current, just like every electic generator.  If you opposed that current with an electric charge produced by a stations solar array, you could produce enough trust that a station could change it's orbit with just electricity. 

[RogueScholar]

 

In the context of Lorentz force, the energy comes from the magnetic field. A magnetic field will have potential energy. Jupiter's magnetic field ultimately comes from electrical current in the planet's core. The electrical current comes from the movement of a very strange type of matter known as metallic Hydrogen. Hydrogen can exist in this state due to the immense pressures experienced in the core.

 

 

So in this case the magnetic field is energy that could be harnessed by the Lorentz force that is otherwise "wasted"? A pool pump creates a magnetic field that is converted to mechanical force used to pump water. If no water is running through the pump the magnetic field is still created but wasted since no work is being done?

Yes, in a sense if I understand your analogy. I'm not quite sure about the pool pump analogy however, but a magnetic field can be thought of as a sort of reservoir of energy that can apply a force to charged particles that interact with said field. It's not intuitive but electricity and magnetism are two faces of the same phenomenon. Whenever you have a current (flow of electrons), a magnetic field is always produced that runs perpendicular to the electric field if that makes sense. This is how planets produce magnetic fields from electric currents within their cores.

[Thurisaz]

As for the setup proposed in that ep, it's made very clear that 1. it's all about the Lorenz force and not some other effect (the name is specifically mentioned several times) 2. the probes are shot into orbit around Jupiter and electrically charged (in theory one might assume that the charge is building up over time but that's neither said nor would we be able to pack that much power into a tiny probe anytime soon) and 3. just the Lorenz force is supposed to keep accelerating the probes on their orbits until finally they approach relativistic speeds and 4. we would then just switch off the electrical field to launch them into deep space.

 

To repeat: The ep explicitly says that with constant magnetic and electric fields the Lorenz force would accelerate the probes but they would stay in orbit.

 

[Voice]

Thurisaz, the Dr. may be referring to a phenomenon that occurs with electricity, something I first learned about when I observed particles of dry organic material take a static charge and literally teleport across a room.  I don't know if or how it would work for LD travel in space, but if it can and does, that would be cool.

[Thurisaz]

 

Okay...

 

That may possibly be an explanation. Would set my mind at ease for sure - I watched pretty much all the "SciFi Science" eps that have aired here already and aside from this one thing that made me start the thread it all seems pretty decent. If my physics knowledge, based on high-level physics classes back at school in the last century and later "enhanced" by what I read as an interested layman, simply didn't encompass the thing that makes it all logical and plausible... I can finally sleep easily again

 

If you can state some details about what you mean (name of the effect or somesuch) that would be sooo cool

[RogueScholar]

First, I do not think anybody is seriously proposing that using Lorentz forces is a feasible option in the near future. Next, I am still not quite sure what your fundamental objection is. The Lorentz force conjecture surly assumes significant technological advancements would have to occur for this to be a viable option? You seem to be very worried about energy conservation but the concept from a pure "mental masturbation" standpoint does not violate any conservation laws as far as I can see. If you can manage to fire an object with a certain amount of charge into a magnetic field, a force will result, energy transfer will occur and acceleration of the object will occur. Remember, absolutely tiny forces can accelerate objects to great velocities given enough time. In fact, I believe that this has been observed with particles from some of the moons of Jupiter that are ejected from tidal forces but manage to get caught in a torus like structure around Jupiter and are accelerated to great velocities. I believe it's called the Io plasma torus. There are additional, complicated processes occurring in addition to Lorentz forces however.

 

Here is a link to an abstract where it is suggested that it may be possible, assuming great leaps in technology, to use Lorentz forces on satellites. However, you can tell that there is much work that needs to be done and it’s not at all certain that the technology can even be created to support such an idea. http://arxiv.org/abs/0805.3332

 

At the end of the day I think Dr. Kaku was probably just describing a Gedankenexperiment where such concepts could be explored by making multiple assumptions that may or may not ever pan out in real life. In fact, much of the fundamental understanding of Jupiter and its radiation belts and magnetosphere are not well known. However, an advanced probe will reach the planet and extensively study many of the concepts we have discussed in this thread in 2016.

[Thurisaz]

Well my objection (or better... that detail that beats me) is that Lorenz... for all I know... deflects objects but doesn't increase their movement speeds overall. Note that I do retract that part about conservation of energy

 

If something is influenced by Lorenz and brought into a circular motion it circles with a constant speed, or am I wrong there?

 

I'll note though that I should probably check out that link above. At least as far as I can follow it.

[RogueScholar]

Oh man, I think I get what you are asking? Maybe it's really my fault for misinterpreting? I think perhaps what you have been saying is that because Lorentz forces are perpendicular to the motion of a point charge in a uniform magnetic field, no work is really performed on the point charge and it's magnitude of velocity will not change, only it's direction?

 

So, if we model Jupiter as having a uniform magnetic field and a space craft as a point charged particle that moves into the field at a certain velocity, then yes, you have a pretty solid case. I am assuming Kaku probably had a slightly different idea in mind that perhaps involved manipulating the charge on the craft or taking into account how the magnetic field might change? I'm not really up on planetary studies, but like I posited above, I can only assume that Kaku was taking under the assumption that there were new technologies being used to exploit Lorentz forces?

 

Let me know if I'm off base here or if you were thinking something different?

[Thurisaz]

Yup Rogue that's it basically.

 

Of course one might try to pump additional energy into the system (in this case, probably via further charging the probes, unless someone sees a way to talk to ol' buddy Jupiter and make him turn up his field) but I'd think even with tech that's still some time in the future it would be... a challenge... to equip a rather tiny probe with enough energy to make it approach interstellar speed.

 

Other than that, yes it's possible that Kaku originally means something different; it wouldn't be the first time at all that a basically sound English text is translated into crap over here by the "professionals" ("best" example? In some recent docu on evolution the German translation once says that depending on where you draw the line human ancestors have been around for 3 billion, let me repeat, billion years. I'm still about it. I mean, I can understand to a degree that someone might confuse million and billion "in the heat of battle" but in German these are called Million and Milliarde. I see no way to mix those up unless you're seriously hammered). I wish I could get more of the original audio that's still there under the translation. On the other hand, for all I can tell that show is mostly translated very well so that would be a case of very bad luck I guess.

 

And sorry that I didn't get this clear to you sooner... you know, they don't exactly tell us English physics terms at school and I rarely talk that much science anywhere so it's sometimes hard for me to find the correct words

[RogueScholar]

No problem at all. I'd love to see the show and find out what was stated. I do know it's not uncommon for scientists to give out sound bites that are easier for the lay public. Unfortunately, much of the important context is missing.

[Voice]

One thing I've learned writing science fiction is to never underestimate the rate of acceleration of technological progress.  We've been on a slow grade upward for most of the million (or billion as some may have interpreted) years we've been here, until recently when we started upward on the chart and are approaching (at the rate of doubling every 18 months) an asymptotic spike within the next 30 to 50 years.

[pantheory]

Thurisaz quote: ........we would fire those probes with a fixed velocity v into Jupiter's magnetosphere, carrying a certain electrical charge e. We also have the constant field strength of Jupiter's magnetosphere m. All constants. Where does the acceleration come from? A miracle™?......

 

 

 

Dr. Kaku is an interesting fellow. He is a theoretical physicist, theorist, and science fiction writer. I think he is best known for his promotions of string theory. I find most of his ideas and theoretical promotions interesting but unrealistic, like most versions of string theory, in my opinion. I am unfamiliar with his sci-fi proposals.

 

As to the subject question by Thurisaz in his quote shown in this posting, the visible atmosphere of Jupiter rotates on its axis very rapidly about once every 10 hours. The innermost liquid or possibly liquid-solid planet might rotate even faster. The atmosphere (possibly most of the planet's mass) is full of hydrogen, helium, and free electrons. The atmosphere has different strata that rotate and interact with each other at varying relative velocities. The vast quantities of electrons in motion create magnetic influences that extent far beyond the physical planet which is called its magnetosphere. Any incoming particles such as protons and electrons given off be the sun during solar activity can either be deflected or absorbed by these magnetic influences. The transfer of energy from atomic particles and atoms in the atmosphere and its  momentum, to resultant magnetic influences of the atmosphere, would provide most of the energy needed to accelerate charged particles, or ionized atoms/ molecules. The other major source of energy would be Jupiter's large gravitational field/influences.

[Bhim]

I'm going to take a wild ass guess and say the energy is taken from Jupiter's spin in the same way space probes transfer a little bit of planetary orbital velocity when performing a gravity assist slingshot maneuver. 

 

Actually that's not a bad analogy.  It seems the fundamental confusion here is as to how a transverse force can do work on a body.  It can't, of course.  But if you push a block up an incline, the normal force from the incline is always perpendicular to the motion of a block, yet it's a component of this force that pushes the block against gravity.  Here, the energy is coming from the person doing the pushing, but the transverse force facilitates the energy transfer.  In all cases where a magnetic field does work, the energy can be traced to another source.

 

Having said that, I remember in my first year of grad school I asked my E&M professor how this works in the case of picking up objects with permanent magnets...and we couldn't work out a solution.

[Jedah]

I've gotten over the fact that anything you see on television is always going to have some degree of fluffbunnyism. At the end of the day, Michio Kaku is an entertainer first and scientist second. He may not even believe some of the things he is saying and the network just decided to add stuff in because they believe it would sound interesting to the general public. The biggest issue I see is with how TV science documentaries cover the "singularity". The reality is we don't really know for sure what will happen after that singularity is reached, but for sake of entertainment these shows love to speculate AI suddenly shifting us to utopia. While such a thing is possible, they talk about it like it's fact.

[Thurisaz]

Hehe yeah the entire "make it sound cool to a semi-/unscientific audience" thing doesn't exactly make things easier for those who try to understand how it's meant to work...