I would like to reserve the right to reopen the reconnection debate at a later date while I focus on a key issue that I believe needs to be addressed. This is not a thread about reconnection or dark energy, though it relates to both topics, it is a thread about imagination vs. experimentation. Birkeland experimented with electrical discharges on spheres over 100 years ago. Alfven also experimented with plasma physical model in controlled laboratory conditions. Each of them formed an opinion based on careful study of their theories in controlled laboratory conditions.

Exactly what value is experimentation in astronomy today? When does it become "ok" to posit a new form of physics, or a new form of energy? When would it be appropriate to *require* laboratory conformation, and when is that inappropriate?

Partly it depends on exactly what you mean by experiment. If you mean experiment in a lab under extremely controlled conditions, then it is a bit less important than it was in Birkeland's or Alfven's time. You still need a good theoretical model, but now, whenever possible, an in-situ measurement is preferred. Alot of the preference in measurements in space is caused by the fact that lab experiments are very restricted in the conditions they can simulate. Even the best ground vac chambers are going to be higher pressure than space, and the scale of the experiment is extremely limited. That is the main driving force for alot of sattelite experiments.

Bear in mind that if you are trying to simulate the whole Earth with a plasma experiment on the ground, you may have a ball 6cm in radius. That is 1/100000 scale. At that scale, a kilometer wide effect out of the experiment is only 10 microns wide in the experiment. You may miss fairly important effects in your experiment simply due to scale.

And this assuming that you can scale planet-wide effects down to laboratory scales.

For example, with a three meter high setup, they did not even come close to simulate the Earth's dynamo.

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papageno


"Why waste time learning, when ignorance is instantaneous?" - Hobbes (Calvin and Hobbes)

"It's all about context!" - Vince Noir (The Mighty Boosh)

"I've never heard of such a brutal and shocking injustice that I cared so little about!" - Zapp Brannigan (Futurama)

Why is this an ATM idea?

"Exactly what value is experimentation in astronomy today?" is, it seems to me, an excellent question!

Perhaps it could be re-expressed as "what are the strengths and limitations of experimental tests of the theories used in modern astrophysics?"

After all, astrophysics contains a great deal more than just plasma physics!

Not according to most of the TM threads on here

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'The eye can only see what the mind is prepared to accept'

Because I am of the impression that things will get ugly for your side pretty quickly and you'll want to muzzle me sooner or later.

Here's where I think things get interesting. There is often a difference between "observation" and "interpretation" even in controlled experiments. I will grant korjic's point about direct in-situ measurement being preferred, and in fact I would say that those measurements are required if we are to make valid "interpretations" of the data based on experiments. In other words, we would need to test our various models to see if they jive with in-situ measurement, and if they don't jive, then we know we have a problem with the model or the theory.

There is a distinct difference here between observing something like an aurora and attributing it to electrical activity vs attributing that same activity to "magnetic reconnection". Likewise there is a distinct difference between observing or measuring acceleration, and positing dark energy as the cause.

When is it acceptable to infer that a specific observation is "caused" by a specific force of nature without experimenting to find out if that is even possible?

ugly in what way?

are you saying that this is a deliberate attemptto get silenced? is this a deliberate troll?

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'The eye can only see what the mind is prepared to accept'

No. I simply think there is an experimental disconnect between many "mainstream" beliefs, and scientific reality. I think that will become quite apparent as this thread drags out.

Are you making this as a claim, or is it just a thinking out loud?

... a completely unstructured list of areas where astrophysics and lab physics have interacted, over the past few decades ...

* neutrino physics (the solar neutrino problem, neutrino oscillations)

* nuclear reaction cross-sections

* line spectra - oscillator strengths, forbidden lines, Stark effect, Zeeman effect, ...

* strong field tests of GR (and many weak field ones too)

* quantum physics in extreme environments - magnetic fields, high temperature/low density, high temperature/high density, neutron degeneracy, ...

* astrophysical masers

* high-energy particle physics (cosmic rays).

Oh, and plasma physics too.

Why should the focus of this thread be on just one branch of physics? Or, if it should focus on just one branch, why not edit the title to reflect that narrow scope?

Keeping with this example. Nowadays we have multiple spacecraft observations of the processes that occur while auroras are being viewed.

Indeed, Mr. B expected that electric currents were the cause (gotta find time to read his biography). And in the 70s of the last century the first real measurements of these currents were made, but these measurements did not show what was driving this current.

No, talking about the project I am working on at the moment (paper needs to be finished by the end of June) I have Cluster 18 radii behind the Earth, and then I have DoubleStart TC1 and TC2 at 10 radii behind the Earth, and I have Polar at 8 radii but a little lower in z, and I have ground magnetometers and EISCAT radar data, and last but not least the very good model of the magnetic field of the Earth from Tsyganenko. We have never before had such a complete view of the magnetosphere/tail, untill THEMIS is in its final orbit.

Now, in this time and place we can see all that is happening, reconnection at Cluster, with fast plasma flows, dipolarization of the magnetic field, which reach TC1 and TC, which both show field aligned currents at exactly the time that the aurora brightens, and the ground magnetometers show that there are electrical currents flowing overhead, by of the negative bay in the data.

We have already gone much further than just sending one satellite to do experiments, we are presenting views of the whole magnetotail in this case, and can directly link reconnection to field aligned currents to aurora.

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Optimism does not change the laws of physics. (T'Pol)
A good scientist has freed himself of concepts and keeps his mind open to what is. (Dao De Jing 27)
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Martin ( http://www.geocities.com/DrMartinV )

Thats all very well, but you aren't doing it in the Lab, so it doesn't count as an experiment.

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'The eye can only see what the mind is prepared to accept'

You're mean, captain swoop! :-)

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Optimism does not change the laws of physics. (T'Pol)
A good scientist has freed himself of concepts and keeps his mind open to what is. (Dao De Jing 27)
************************************************** *************************
Martin ( http://www.geocities.com/DrMartinV )

Just out of curiosity, how does the state of knowledge of the Earth's magnetosphere* in 1980, derived from in situ observations, compare with that today?

Not a dissertation, just a one sentence (or one para) summary.

*bow shock, magnetosheath, magnetotail, magnetopause, plasma sheet, neutral sheet, polar cusp, ...

Order or orders of magnitude better info today. Tusenfem could tell you better tho.

You dont understand what is being said. No one has thought that aurora are anything other than field aligned current flow for a couple of generations. The in-situ measurements off of balloons and sattellites solved that a long time ago.

I personally have explained dark energy to you before, and you still dont understand it. Dark energy is a name for an unknown effect that appears to cause the expansion of the universe to accelerate. That is all that dark energy is. It is an unknown. When it gets known (if ever) it will get a different name.

When you have an observation, something caused it, or there is an error in your observation. If the observation refuses to go away even after you fix all the possible errors, then there is something there, no matter wether you know what it is or not. Then, since you have something, you start trying to figure out what it is. If there is nothing obvious, and there isnt a good theory to tell you what you are seeing, it generally ends up with some sort of somewhat silly name until the theory and other observations catch up.

Dark energy is a classic example. IIRC, they were looking to measure the deceleration of expansion over time, but they could not get their curve to fit a deceleration, only an acceleration, no matter what they did. So, courting professional suicide and wide spread mocking for a crazy idea, they presented their data. All their i's were dotted and all their t's were crossed (their data and analysis were airtight). So people went 'thats wierd.' Others confirmed the observations, and someone, drawing a parallel to dark matter, proposed the name dark energy for this unknown effect. It probably did help that Einstein's greatest blunder was the correct term in GR to explain the acceleration, but that dosent change the fact that an unexpected, unwanted, and unusual observation forced a change in theory, forced all of physics to change to account for observation.

It just occured to me that it is somewhat odd that you basically label all scientist as mindless slaves to orthodoxy, when you are the one who refuses to accept the biggest change in cosmology in the last 20 years.

http://mrx.pppl.gov/

This is a perfect example of what I mean by imagination vs. experimentation. Birkeland experimented with electric discharges on charged terralla in a vacuum. With the power turned on, he created experiments that showed surface loops on the terella in the shape of coronal loops when the surface was positively charged. He also created aurora above the terrella when the surface of the sphere was negatively charged. When he turned the power off, the party was over. No more coronal loops and no more aurora.

It seems as though PPPL is imagining what they want to believe, whereas Birkeland experimented and showed that current flow was the real force behind these effects. How come PPPL gets to rewrite history?

It's pretty clear from the conversations that nobody "understands" it. I got a million different definitions of it. Bjoern was convinced it was a negative pressure energy thingamabob. Nereid refused to even describe it. Nobody could explain how it tied back to particle physics. I think Van's explanation was the most "honest" answer I got. It's a placeholder term for ignorance. You might imagine otherwise, but then we need an "experiment" that can take us from our imagination to actually demonstrating that such a thing exists in reality.

I really don't want to debate dark energy or reconnection. I'm more interested in how you intend to demonstrate some of the more important aspects of current theory via experimentation. Do you really think any of those PPPL discharges are going to occur if no electricity is used in the experiment?