Spiral arms: Protoplanetary disk around a young star exhibits spiral structure

Spiral Arms Embrace Young Star
ALMA discovered sweeping spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. This spiral feature was produced by density waves – gravitational perturbations in the disk. Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO)

Astronomers have found a distinct structure involving spiral arms in the reservoir of gas and dust disk surrounding the young star Elias 2-27. While spiral features have been observed on the surfaces of protoplanetary disks, these new observations, from the ALMA observatory in Chile, are the first to reveal that such spirals occur at the disk midplane, the region where planet formation takes place. This is of importance for planet formation: structures such as these could either indicate the presence of a newly formed planet, or else create the necessary conditions for a planet to form. As such, these results are a crucial step towards a better understanding how planetary systems like our Solar system came into being.

An international team led by Laura Pérez, an Alexander von Humboldt Research Fellow from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, also including researchers from the Max Planck Institute for Astronomy (MPIA) in Heidelberg, has obtained the first image of a spiral structure seen in thermal dust emission coming from a protoplanetary disk, the potential birthplace of a new Solar System. Such structures are thought to play a key role in allowing planets to form around young stars. The researchers used the international observatory ALMA to image the disk around the young star Elias 2-27, in the constellation Ophiuchus, at a distance of about 450 light-years from Earth.

Planets are formed in disks of gas and dust around newborn stars. But while this general concept goes way back, astronomers have only recently gained the ability to observe such disks directly. One early example is the discovery of disk silhouettes in front of extended emission in the Orion Nebula by the Hubble Space Telescope in the 1990s, the so-called proplyds. The ability to observe not only each disk as a whole, but also its sub-structure, is more recent still. Gaps in a protoplanetary disks, in the form of concentric rings, were first observed with ALMA in 2014.

These new observations are of particular interest to anyone interested in the formation of planets. Without these structures, planets might not been able to form in the first place! The reason is as follows: In a smooth disk, planets can only grow step by step. Dust particles within the gas of the disk occasionally collide and clump together, and by successive collisions, ever larger particles, grains, and eventually solid bodies form. But as soon as such bodies reach a size of about one meter, drag by the surrounding gas of the disk will make them migrate inwards, towards the star, on a time scale of 1000 years or shorter. The time needed for such bodies to collect sufficient mass by successive collisions, eventually reaching a size where gas drag becomes a negligible influence, is much larger than that.

Spiral arms: Protoplanetary disk around a young star exhibits spiral structure
Infrared image of the Rho Ophiuchi star formation region at a distance of 450 light years (left). The image on the right shows thermal dust emission from the protoplanetary disk surrounding the young star Elias 2-27. Credit: © NASA/Spitzer/JPL-Caltech/WISE-Team (left image), B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO), L. Pérez (MPIfR) (right image).

So how can bodies larger than about a meter form in the first place? Without a good explanation, we could not understand how planetary systems, including our own solar system, came into being in the first place.

There are several possible mechanisms that would allow primordial rocks to grow larger more quickly, until they finally reach a size were mutual gravitational attraction forms them into full-size planets. "The observed spirals in Elias 2-27 are the first direct evidence for the shocks of spiral density waves in a protoplanetary disk", says Laura M. Pérez from MPIfR, the leading author of the paper. "They show that density instabilities are possible within the disk, which can eventually lead to strong disk inhomogeneities and further planet formation." Such instabilities are not confined to the scale of planet formation. In fact, the best-known example are density waves in disk galaxies, which create the spectacular spiral arms of spiral galaxies.

The two sweeping spiral arms in Elias 2-27 extend more than 10 billion kilometers away from the newborn star, at a larger distance than the location of the Kuiper Belt in our Solar System. "The presence of spiral density waves at these extreme distances may help explain puzzling observations of extrasolar planets at similar far-away locations", Pérez notes, "such planets cannot form in-situ under our standard picture of planet formation." But in regions of increased density, planet formation could proceed much faster, both due to those region's gravity and due to the more confined space, which would make collisions of grains or rocks more probable. In this way, the problem of how to go beyond meter or ten-meter size objects could be solved. On the other hand, planets that have already started forming within a disk can launch spiral waves in the disk as they orbit their host stars. Distinguishing those two roles of spiral and other features – consequences of planet formation, or the cause of it? – will require a deeper understanding of such features, which in turn requires high-resolution images that show details of these structures.

The new observations with ALMA targeted the young star Elias 2-27, a member of a much larger star-forming region known as the ρ-Ophiuchi star-forming complex. Elias 2-27 is estimated to have formed about a million years ago; a very short time, compared to the age of our Sun of five billion years. The star was already known to have a circumstellar disk, but judging by previous observations (at resolutions showing details in the range of 0.6″-1.1″) this appeared to be a featureless, axisymmetric disk. The new ALMA observations with a spatial resolution of 0.24'' were made in the millimeter wave regime, at a wavelength of 1.3 millimeters. They trace the thermal emission from dust grains, which may make up between 1 and 10% (by mass) of protoplanetary disks. In this way, astronomers were able to trace a gigantic spiral pattern at distances between about 100 astronomical units (that is, 100 times the average distance of the Sun from the Earth) and 300 astronomical units away from the central star.

Spiral arms: Protoplanetary disk around a young star exhibits spiral structure
Telescopes of the Atacama Large Millimetre Array (ALMA) directed at the night sky in the Chilean Atacama desert, 5100 m above sea level. © ESO/C. Malin.

"Finally, we see the disks around young stars in all their beauty and diversity – and now this includes seeing spiral structures. These observations will be a great help in understanding the formation of planets", says Thomas Henning, Director at MPIA, and a co-author of the paper.

"Over the past two decades astronomers have found a great variety of exoplanets. To understand that diversity, we need to understand the early stages of planet formation. Detailed images such as those delivered by ALMA provide crucial information about the various mechanisms at work in protoplanetary disks", adds Hendrik Linz, also from MPIA.

The interaction with a planet that has already formed and is now orbiting within the disk, is one plausible explanation for these spiral features. ALMA detected a narrow band in the disk with significantly less dust, but such a small gap is not consistent with the large planet needed to create the observed spiral arms. On the other hand, the disk's own gravity causes instabilities which can trigger the formation of the spiral pattern. Taking into account estimates for the total mass of the disk, and the shape and symmetry of the spiral pattern, the authors consider this possibility as also likely.

"Similar observations with ALMA will become increasingly common, and more and more detailed images showing inhomogeneous structures in disk density become available", concludes Karl Menten, Director at MPIfR and also a co-author of the paper. "Astronomers should increasingly be able to investigate the properties of such features, and to eventually define their role in the planetary formation process."


Explore further

ALMA spots possible formation site of icy giant planet

More information: L. M. Perez et al. Spiral density waves in a young protoplanetary disk, Science (2016). DOI: 10.1126/science.aaf8296
Journal information: Science

Citation: Spiral arms: Protoplanetary disk around a young star exhibits spiral structure (2016, September 29) retrieved 15 October 2019 from https://phys.org/news/2016-09-spiral-arms-embrace-young-star.html
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Sep 29, 2016
We need a Zwicky acolyte to get here real fast to explain to us why the gravitational perturbations of this star 450 LYs away, is caused by DM cosmic fairy dust.

Just look at those Radial Arms made of VM baryonic matter, just like the VM baryonic matter found in Radial Arms of spiral galaxies. If Zwicky were here he would conclude this star is enshrouded in an enveloping halo of cosmic fairy dust.

RNP
Sep 29, 2016
@Benni
NOBODY is claiming that this effect is caused by DM. So, what is your point? Or, more importantly, do you actually have one?

Sep 29, 2016
So, what is your point?
......making "correlations", your new catchphrase. I mean like surprise, surprise.....how is it I was able to predict how fast the Zwicky acolytes would show up? All I need to do is bring up the name Zwicky & who are the first ones to show up?

Please honour Zwicky's genius
.......did he get past 1st semester physics I wonder? Maybe one of those watered down High School versions? I wonder if he passed it?

Sep 30, 2016
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Sep 30, 2016
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Sep 30, 2016
People focus on math today for good reason, but the Copernican revolution was based upon geometry. When the textbook theory for the process for star formation completely resembles the geometry of Birkeland Currents, that is when we will finally start to see people peeing off of this bandwagon. -Chris_Reeve

Only an idiot would think geometry wasn't a type of math.

Sep 30, 2016
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Sep 30, 2016
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Sep 30, 2016
Please honour Zwicky's genius by visiting http://alchetron....15677-W.
No prayers needed, the man was an atheist.
........No honour to an asstrophysicist, someone who like you was never able to figure out that 80-95% of the Universe is NOT MISSING.

Knock it off trying to shove your relative's pseudosciences in the faces of those here who have a far better comprehension of science than you & Zwicky ever had.

Sep 30, 2016
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RNP
Sep 30, 2016
@bschott
.....There is no physical difference between an E-field and a magnetic field or a charge field.


This is SO nonsensical that it is unbelievable that you have posted it. This is schoolroom physics and you obviously have not even TRIED to learn it. I suppose is pointless to ask you tell us how you arrive at this ridiculous conclusion.

Sep 30, 2016
@bschott

.....There is no physical difference between an E-field and a magnetic field or a charge field.


This is SO nonsensical that it is unbelievable that you have posted it. This is schoolroom physics and you obviously have not even TRIED to learn it. I suppose is pointless to ask you tell us how you arrive at this ridiculous conclusion.

I think it has something to do with magical bowls.

Sep 30, 2016
@Phys1

Say "Zwicky was a Great Asstrophysicist and I am just an ignoramissimus."
Do this every morning while looking into a mirror while wishing 80-95% of yourself were MISSING.


Sep 30, 2016
A little courtesy from me
I have never clicked on any link you have ever put up, you're just too zany for me to even bother with any of the rest of your Zany Zwicky family.

Sep 30, 2016
Hi Chris_Reeve, bschott, everyone. :)

Again, a timely reminder: Large astronomical/cosmological features/process are HYBRID phenomena involving Plasmic, Gravitational and Inertial Motion factors/parameters/effects at various stages of a feedback-loop (constructive resonance-destructive reinforcement at/in nodes/streamlines etc. No single factor/parameter-based 'explanation' can ever describe them properly.

I have suggested before that all just step back from your favorite theory/hypothesis, and look at whole reality, not just parts of it which happen to suit (at some stage/juncture of overall extended process/feature) your favorite theory/hypothesis.

PS: My ToE does treat phenomena in its temporally/spatially/evolutionary TOTALITY rather than piecemeal; hence in planetary/galactic disc/spiral arms etc scenarios, it explains ALL the various parameters/factors involved; hence dispelling all the partial-view-based 'arguments, mysteries and unknowns'. :)

Co-operate, guys. :)

Sep 30, 2016
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Sep 30, 2016
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Oct 01, 2016
A star like Elias 2-27, like a galaxy is a concentrated mass of matter that facilitates the creation of new matter/antimatter from virtual particles of the quantum vacuum and becomes the source of ejection or dissipation of matter to surrounding space. Ejection along the minor axis of flat galaxies like the spirals can propel chunks of the galaxy far away in opposite directions. But ejected mass from a compact object like a star or an elliptical galaxy cannot go far but stopped near the mother object and pulled back by gravity in such a way that they form spiral arms: http://redshift.v...2MAL.pdf

This is the exact opposite view of the Big Bang perspective of universal condensation of matter from a diffused state, after an initial one-time creation!

Oct 01, 2016
Chris Reeve
The pseudo science pusher of the day.


Yep, along with all the mythology inspired posters from EU!
Birkeland currents would be easily seen in the protoplanetary disks, or anywhere else for that matter, due to their emissions. Peratt's galaxy model fails precisely because of the lack of that, amongst many other things. Until the EU geniuses (n < 1) figure out why they aren't seeing such emissions, then their models remain dead. I suspect even Peratt realises that by now.
http://dealingwithcreationisminastronomy.blogspot.co.uk/2009/06/scott-rebuttal-ii-peratt-galaxy-model.html

Oct 01, 2016
@jd
Inspired by my example, Zwicky, I agree !
........you should keep your family members out of the fields of science, like you, they aren't any good at it. Yeah, Zwicky, renowned for interrupting lectures of real scientists with his foul mouthed epithets of profanity because they dare come up against the likes of Einstein in disagreements with his dark & tired fantasies about the cosmos.

Oct 01, 2016
Hi Chris_Reeve. :)

Thanks, mate. Returned. :)

Re the plasma forces/behavior/features processes and evolutions, I think my many years of posts here/elsewhere, and most recently my discussion with Da Scneib re plamoids, flux tubes/flows etc in Sun) will show I am more informed than most on the subject matter (in whole context, not just plasma context).

Which is why I've often reminded everyone that gravity, once established, is "always on"; whereas electro-magnetic forces may transiently locally neutralize, and give gravity the edge in determining further evolution of a particular region of plasma activity/feature.

That is what happens at sun's surface every day of the week; otherwise plasma instabilities would have exploded the sun almost immediately it formed a plasma body/process.

That's why I've been trying to get all here to consider fully the whole phenomena; and its temporal/spatial evolutionary possibilities including ALL the forces at ALL evolutionary stages. :)

Oct 01, 2016
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Oct 01, 2016
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Oct 01, 2016
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Oct 01, 2016
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Oct 01, 2016
Hi Chris_Reeve. :)
To be clear, there is a consensus on this. While there are indeed people who go overboard with electromagnetism in cosmology,...

....During those events -- ......-- gravity has very little importance.

...scale.
Thanks for that acknowledgement of certain overzealous types making claims not supported by the whole reality/forces-set involved (as I described earlier); and for your clarification re current research acknowledging gravity's role.

Re 'scaling' aspect. It appears you/they still missing a subtle but crucial point re Gravity: It TOO 'scales', and CUMULATIVELY.

So even in large plasma structures/features/processes/regions, the EM forces acting over certain distances can be OVERWHELMED LOCALLY where gravitational force is most dominant at some critical-mass/gravity LOCALLY CUMULATIVE FORCE 'scales' (recall my sun's surface example).

Anyhow, it's good to see more reasonable, objective researchers/observers on the scene nowadays. Cheers! :)

Oct 01, 2016
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Oct 01, 2016
Hi Chris_Reeve. :)
Re 'scaling' aspect. It appears you/they still missing a subtle but crucial point re Gravity: It TOO 'scales', and CUMULATIVELY.
It dominates locally. That's important. But, I would not -- personally -- agree that gravity can transmit over interstellar distances....There has to be a medium which is extending it -- like dark matter.
Don't misunderstand me, mate; I have always acknowledged the plasma forces/phenomena, but in the WHOLE context (as I described earlier).

The further point I make is that gravity IS dominant on some regions/scales/directions.

As for gravity's presence/influence over extended regions/scales, I long predicted that MUCH MORE (previously 'dark' but still) ORDINARY (not 'exotic') matter distributions/forms/quantities would BE found.

It is being found NOW. :)

So forget 'exotic' DM etc distractions. There's ample Ordinary Matter out there to help explain HYBRID gravitational/plasmic/inertial-motion phenomena seen. :)

Oct 01, 2016
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Oct 01, 2016
reflect upon the acceptance of Einstein's ideas.


Which of Einstein's ideas are you referring to? And what do you mean by "acceptance"? I'm presuming you're referring to his thesis of General Relativity?

Oct 01, 2016
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Oct 01, 2016
Einstein thought like most everybody else that the challenge he faced was how to construct a universe with only empty space and matter.
.......below is quoted what Einstein wrote in GR:

Part III: Considerations on the Universe as a Whole
Albert Einstein 97

"If we are to have in the universe an average density of matter which differs from zero, however small may be that difference, then the universe cannot be quasi-Euclidean. On the contrary, the results of calculation indicate that if matter be distributed uniformly, the universe would necessarily be spherical (or elliptical). Since in reality the detailed distribution of matter is not uniform, the real universe will deviate in individual parts from the spherical, i.e. the universe will be quasi-spherical. But it will be necessarily finite. In fact, the theory supplies us with a simple connection between the space-expanse of the universe and the average density of matter in it."

Did you have this in mind?


Oct 02, 2016
The matter can behave in ways that are not gravitational.
Yup, and in the context of astrophysics it's normally referred to as "magnetohydrodynamics" (MHD) and additional kinematics.

In the light of his limited palette, Relativity.
Your palette seems to be missing both Earnshaw's theorem and common sense.

The observation of stable gravitationally bound large-scale structure (everywhere in the sky we look, between now and over 13 billion years ago) is strong evidence that electromagnetism is not (and could not be) responsible for the observed long-term stability, and that it necessarily plays a minor role in the formation of the structure (because the structure forms despite induced electromagnetic instabilities [that is, despite MHD, etc.].

Oct 02, 2016

They're transient phenomenona. Sub in the word 'lightning' and reconsider your demand.

In the laboratory, there are three states to plasmas: dark, glow and arc. It should be apparent that electrodynamic phenomena can occur without any emissions. A Birkeland current can happen, and there will be no photon record ... no diff than the cable powering your computer does not glow.


Bollocks! Dark mode is just an antiquated term for emissions that aren't seen in visible light. They are as detectable as any other bloody mode in different wavelengths!
See here: http://dealingwithcreationisminastronomy.blogspot.co.uk/2010/07/electric-universe-everything-i-needed.html
Failing that, ask a plasma astrophysicist. There must be tonnes of them lurking around the crank science sites you frequent.

RNP
Oct 03, 2016
@bschott
Yes, of course, both electric and magnetic fields effect charged particles. However, they are completely different types of field, creating completely different responses from charged particles. You only need to look at a school textbook (or Wikipedia if you prefer) to see this. The rest of your addled diatribe is again so nonsensical as to defy belief. Anybody with ANY grounding in physics will recognize it as such. I am therefore not going to bother dignifying it with a response..

RNP
Oct 03, 2016
@bschott
Here, I have found a textbook for you:

http://www.school...dex.html

Now, explain how you can say they are the same.

RNP
Oct 03, 2016
@bscott
Your posts continue to make no sense because you have not read or understood the textbook I sent you. I will therefore make only one more comment:

When you ask "...........tell us what force is at work in a E-field" you unequivocally demonstrate your lack of understanding. The force at work in an "E-field" is obviously the electrostatic force (sometimes referred to as the electric or electrical force). Now, go and read the textbook.

Bye Bye

RNP
Oct 03, 2016
@bschott
Obviously, the textbook I sent was too advanced. Try:

http://www.physic...eld.html

and

http://www.physic...eld.html

Maybe they can help.

Oct 03, 2016
To children who believe in self aligning currents generating self confining fields despite all experimental and observational evidence that this is not physically possible, magnetism must seem like magic indeed.

C'mon schott, you know why they're magical. No need to obfuscate as if this is new. I've asked before and gotten no answer, here it goes again.
How do the bowls become magnetized w/o electricity? It's been claimed by your idol that this magnetism is "inherent" to the matter, yet these magical bowls aren't inherently magnetic? What gives?
BTW, where is the magnet in these images which clearly shows, observationally, that the matter is self confined?

https://www.googl...;bih=652

When the ball is touched, is it the finger which is magnetized? Is the glass the magnet? Where are these magnets?

Oct 03, 2016
Obviously, the textbook I sent was too advanced. Try:
@RNP
you're talking about a person who stated that the only way to know anything about martian soil is to bring it back to earth (as if there were some special need to have Earth atmosphere and gravity to use a GCMS or other analytical devices)...

you should try finding links that are geared towards gradeschoolers to make your point
(good luck - he ignored those in the past as well...)

you can't teach a fanatical acolyte about reality - however, your posts DO have some great links and references to by all means, keep up the posts @RNP, because a lot of others will appreciate the reference material and education (the real thing - not the delusional regurgitation of some crackpot idea like bschitt and benji, et al)

THANKS

RNP
Oct 03, 2016
@Captain Stumpy
Thank YOU. It is good to hear a kind word when you seem to be surrounded by howling Banshees.

Oct 03, 2016
@Captain Stumpy
Thank YOU. It is good to hear a kind word when you seem to be surrounded by howling Banshees.

@RNP
you're very welcome

I can relate

just remember: for every howling Banshee there are at least ten lurkurr's that read your links because they prefer evidence over stupidity & rhetoric from delusional cult members

problem is that they hate the pseudoscience but they don't want to get involved in a flame war with an idiot (see Mark Twains quote about that one)

the whole pseudoscience bullsh*t thing from idiots like bschitt and the eu cult is the reasons schools around here put Phys.org on the no-go list and locked them out of the servers

i appreciate the links as well
PEACE

Oct 03, 2016
@bschitthead
and will say again after reading the 2 links you provided, nomenclature aside
gotta sound off on this one: the "nomenclature" is required for clear concise communication in science. it is the reason it is utilised. it is also the same when dealing with plasma physics be it a discussion of astrophysics or engineering

this is the reason anyone with even a cursory education will ignore your bullschitt - you can't randomly change the lexicon just because you believe it should be different: there must be an evidenciary based logical methodical reason for said change

and you've not been able to actually provide a reason for your "interpretations" of the nomenclature to be correct over the assigned definitions per the standardized lexicon

for more demonstrations on why you can't arbitrarily change the lexicon for personal gratification see JVK and his pseudoscience/creationism


Oct 03, 2016
@bschitthead cont'd
Volunteer to be part of an army that kills people over resources or made up excuses lately?
you looking for mercenaries for some random terrorist attack because you can't get recognition for your pseudoscience crap?
sorry - i actually have standards. and fighting for a delusional crackpot aint something i can justify doing
Do you have any comments about magnetism
why?
you ignore empirical evidence... hell, you completely ignored a science textbook because you simply believe it all to be wrong

no evidence, no experimentation, and no proof... just your belief

plus, i actually have added relevant argument to why you should be treated as a delusional nutbag

what more can someone ask for?

you're the one demonstrating pseudoscience and how to be a crackpot with arbitrary redefinition as well as belief over evidence - not to mention lack of reputable science or source material

LOL

thanks for helping me

PS - thanks for the validation

Oct 03, 2016
One more reply to the absolute king of the idiots:
My claim is
@bschitthead
1- what you've given is called, technically, a false claim. you've not been able to demonstrate why anyone should accept your "claim" as anything other than ranting banshee cult rhetoric. see also: http://www.auburn...ion.html

2- if ya can't at least learn the basics from his link to talk intelligibly about the topic, then why are you here? to spread your misinformation? or to seek like-minded cult members to pad your account?

3- reality and science are about evidence and repeatable validated information from reputable sources (not just random sources). it's not about what you believe to be true, it's about what can be proven to be true. kinda like courtrooms

It's been fun throwing eggs at the idiot parade, i' know where to find ya'll after my next trip to the grocery store

Oct 03, 2016
Hi RNP, bschott (and cantdrive, Phys1, CapS). :)

The E-M field is ONE field, not two; and

The E force and the M force are TWO 'distinct manifestations' of the ACTION of the ONE E-M field upon any 'test particle' affected.

The commonest cause of confusion is the graphing CONVENTION depicting "LINES OF FORCE" of the separate E and M 'forces manifestations' over a 'closed loop region' where a test particle may be forced to move around a certain path Which may differ depending on whether the E or the M force is the dominant action on that particle.

NOTE WELL: The 'depicted' E and M "LINES OF FORCE" are NOT REAL; they merely illustrate where action VALUES of the E or M 'forces' are in equilibrium along an AXIS of action/motion; which is why test particles are caused to orbit/spiral such equilibrium axis 'lines'.

Since those 'lines of LEAST ACTION' are DIFFERENT PATTERN for E and M, some unwary students may think that E-M field is 'two separate fields'. No!

Carry on. :)

Oct 03, 2016
Do you have any comments about magnetism
.....he hasn't gotten that far with his online courses at MIT yet.

2- if ya can't at least learn the basics from his link to talk intelligibly about the topic, then why are you here?
........."basics"? The only "basics" you know is your foul mouthed name calling & other cyberbully "basics" that have abolutely nothing to do with science.

3- reality and science are about evidence and repeatable validated information from reputable sources
....for example just like you. Unceasingly going on & on about the same stuff post after post calling people names & only Copying links to Physical Science material way beyond your educational comprehension. The only discussions you ever engage with others are personal issues never involving science.

Hey, how's that MIT online course coming along? Gotten into any Differential Equations yet? There we go, the math challenge will get you going off half cocked again as usual.

Oct 03, 2016
Utter rubbish, bschott.
Where do you get this laughable nonsense, on insane.org?
Can't you be right for once?


Uh. oh. it's another one of the zany Zwicky family descendants off on another one of Grandpa Fritz' s tirades.

Oct 04, 2016
The roach is never far.
.......barbarina

Oct 04, 2016
Of course,all of your skin surface has either a positive or negative potential across it, this is well documented.

So our skin has an electric potential, or at least the matter that makes up the skin. Silly magnets don't stick to me without super glue though.
Well, all stable particles carry a + or - charge and react to each other without contact...
All electric charges can react without contact.
There is a reason it is called electromagnetism, they are inseparable. There are limited conditions where an E-field can exist without a magnetic field and vice versa. The claim magnetism is primary is silly.

RNP
Oct 04, 2016
@RealityCheck
.....some unwary students may think that E-M field is 'two separate fields'. No!


I strongly suggest that you go and study Maxwells's equations that describe electromagneitc fields before you start trying to give advise to students. The 4 equations give the source equations and interrelationships between the TWO fields, electric and magnetic.
Your continued insistence that they are one field is patently incorrect and is likely to cause students of get things WRONG.

RNP
Oct 04, 2016
@Phys
Yes. And energy and momentum are components of the the momentum-energy 4-Vector, but this does not make the the same. So, isn't this a little misleading?

RNP
Oct 04, 2016
@Phys1
Of course, I understand the physics, but are you saying that your interpretation of the tensor representation is that there is only one force? Remember, that was the claim that I objected to.

RNP
Oct 04, 2016
@Phys1
OK. Let me express my concerns by asking one last question: The metric tensor contains both temporal and spacial components, but time and space are clearly not the same. So, what does "same" mean in your interpretation?


Oct 04, 2016
Hi RNP. :)
The E-M field is ONE field, not two; and

The E force and the M force are TWO 'distinct manifestations' of the ACTION of the ONE E-M field upon any 'test particle' affected.
...
Since those 'lines of LEAST ACTION' are DIFFERENT PATTERN for E and M, some unwary students may think that E-M field is 'two separate fields'. No!
I strongly suggest that you go and study Maxwells's equations that describe electromagneitc fields before you start trying to give advise to students. The 4 equations give the source equations and interrelationships between the TWO fields, electric and magnetic.
Your continued insistence that they are one field is patently incorrect and is likely to cause students of get things WRONG.
Please RE-read carefully what I said above...and discern the explicit distinction I made between FIELD and FORCE aspects.

See? You fell into the unwary students' common trap of conflating the two totally different things. PHys1 understands it. Cheers. :)

Oct 04, 2016
@ Really-Skippy. How you are Cher? I am good me, thanks for asking.

Cher, RNP-Skippy and Phys1-Skippy are having a nice conversation that I am really enjoying. Why you want to disrupt it with your usual "I-me-my-I" stuffs? You are conflating how smart you think are with how smart you really aren't. See? Everybody understands it but you.

Oct 04, 2016
Hi Ira. :)
Cher, RNP-Skippy and Phys1-Skippy are having a nice conversation that I am really enjoying. Why you want to disrupt it with your usual "I-me-my-I" stuffs?
I reminded everyone, including RNP, of the KNOWN SCIENCE understandings that EM 'field' is ONE field; and that EM 'forces' involve TWO forces/actions which manifest as a result of the ONE EM field.

In this instance Phys1 understands the KNOWN SCIENCE I reminded everyone of so the discussion didn't continue confusing/conflating the 'field' and 'forces' aspects.

But you, Ira, being a bot-voting ignoramus wouldn't understand any of it, hence wouldn't understand the need for the KNOWN SCIENCE reminder from me. :)

PS: It's a pity RNP kneejerked to '1' (along with your '1' bot-vote from gnorance of known science).

PPS: Ira, do realize that Phys1 DOES understand/agree re my known science reminder; which makes your above Ira-Crap all over the PO floor just more smelly irrelevance from a bot-voting ignoramus. :(

RNP
Oct 05, 2016
@Phys1
I note that this is not my area of expertise. I think the problem lies in the interpretation of statements like:

"electricity and magnetism are different manifestations of the same phenomenon. (i.e. electromagnetism)"

Such statements are made in virtually discussions of the subject.

I have read this as saying that electomagnetism generates two forces (that are separable in all inertial reference frames), whereas you are reading it as saying that they are manifestations of the same force. I confess that the more I think about it the less sure about it that I become.

HOWEVER, regardless of which of the above interpretations you accept, it still wrong to say that the electrostatic "manifestation" is the SAME as the magnetic one (which was the claim that I was originally contesting).

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