Society for Popular Astronomy

At the Earth's core
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Author:  brian livesey [ Thu Jan 12, 2017 5:11 pm ]
Post subject:  At the Earth's core

These days we know how complex and dynamic the internal structure of our planet is. Recently, a Japanese team of researchers discovered that Earth's inner core has its own core.
More recently, a team at Tokyo University claim to have detected the "missing element" in the inner core.
The scientists studied how seismic waves passed through the inner core region and believe they've found silicon present. Lead researcher Eiji Ohtani said: "We believe that silicon is a major element ... about 5 per cent [ of the Earth's inner core ] by weight could be silicon dissolved into the nickel-iron alloys."
The inner core is thought to be a solid crystalline ball with a radius of about 745 miles, but is too deep to be examined directly. The region consists of mainly iron at 85 per cent and nickel at 10 per cent. To account for the missing 5 per cent, Professor Ohtani and his team made alloys of iron and nickel with silicon added, and subjected them to the enormous temperatures and pressures existing in the inner core. The Professor said that the results matched the data that was obtained by the core seismic results that indicated silicon.
Professor Simon Redfern at Cambridge University, said: "These difficult experiments are really exciting because they can provide a window into what Earth's interior was like after it first formed, 4.5 million years ago, when the core first started to separate from the rocky parts of Earth."

Author:  Cliff [ Sun Jan 15, 2017 3:18 pm ]
Post subject:  Re: At the Earth's core

Dear Brian - PART ONE
I just read your topic "At the Earth's core".
"Rivers of iron flow near the Earth's core" in New Scientist magazine 7th January, suggests a molten jet of iron deep below Earth's surface is speeding up. Why the jet is getting faster is a mystery?
Apparently the Earth's magnetic field has been weakening since the 1840s at a rate of 5% per century.
Knowledge of the molten core jet stream might help us predict when the Earth's magnetic field might flip ! Although I vaguely recall reading somewhere that the magnetic flip might not be instantaneous (ie a year or two ?) So the event might mean that much of life on Earth could be exterminated by cosmic ray bombardment !!!!
Best of luck from Cliff

Author:  brian livesey [ Mon Jan 16, 2017 10:51 am ]
Post subject:  Re: At the Earth's core

The NS article you mentioned is interesting Cliff, and it's a further confirmation of just how dynamic our planet's interior is.
Regarding reversed polarity. Is there any data to show that mass extinctions have coincided with this process?

Author:  Cliff [ Mon Jan 16, 2017 11:25 am ]
Post subject:  Re: At the Earth's core

Dear Brian
That's a good point you make - about any connections with mass extinctions and magnetic field flips previously. I don't really know much about previous Earth magnetic field flips, nor previous mass extinctions. It actually only occurred to me (after reading the NS article) whilst considering my recent reply to your post that (if my memory about the little I've read in the past is correct ?) the Earth's magnetic field protects life on Earth from cosmic ray bombardment. That being correct (?) then assuming a magnetic flip occurs in the future life will\may be at risk (?).
Off hand I cannot recall reading when previous Earth magnetic field flips occurred, or how many magnetic flips there have been in the past.
Anyway if there were previous magnetic flips does anyone know how long changes take ?
It might be a bit annoying if the World sorts out its energy\climate change problems only for all life (or in particular humans) to be then quickly be wiped out by an Earth magnetic flip, asteroid crash alien invasion, or something else we haven't even thought of ?
These possibilities all really bother me, particular since I gather I may be someone lucky enough to be short listed to live until I'm more than a THOUSAND years old.
Best of luck from Cliff - The above is not PART TWO by the way.

Author:  Cliff [ Fri Jan 20, 2017 6:55 pm ]
Post subject:  Re: At the Earth's core

Dear Brian
I decided against sending what might have been PART 2.
However, I was in a Waterstones book store the other day and noticed a new book (at least newish to me) written by a lady I think (can't remember her name) can't even remember the book's title properly but it was something like "the Sixth Extinction".
I quickly glanced at its contents (paperback £9-99 I think). Might be interesting but I'm a slow reader. I couldn't read much - not wanting to get chucked out the shop.
However, if I got things right I think the book suggests there have been five previous serious mass extinctions (over the last half billion years). I think the book gives an outline of those previous 5 extinctions and that Number SIX is the next extinction which might have already started and is human caused.
Best wishes from Cliff

Author:  Alastair McBeath [ Fri Jan 20, 2017 8:56 pm ]
Post subject:  Re: At the Earth's core

Regarding geomagnetic field reversals on Earth, these happen with variable, but quite common, frequencies over geological time (roughly once every 200,000 to 300,000 years during the past twenty million years or so). There's no evidence linking them with extinctions.

This Wikipedia page has some useful notes on geomagnetic reversals, while the 2011 Nov 30 item on this NASA webpage has a snappier summary. There's a link on the latter page that's worth following too, to here, which goes into a bit more detail, but a little more readably than the Wikipedia page.

As for mass extinctions, Wikipedia again has a useful outline here, including details of the big five in geological history.

Cliff, I also came across this Wikipedia page which handily summarizes that Sixth Extinction book you'd been glancing over.

Author:  Cliff [ Mon Jan 23, 2017 11:21 am ]
Post subject:  Re: At the Earth's core

Dear Alastair and Brian
Alastair; I have looked at two of web pages that you pointed us to.
Last night I looked at the Wiki reference about "The Sixth Extinction" book by Elizabeth Holbert in particular and am pretty sure that is the book I perused in a Waterstones book store a couple of weeks ago. This morning I looked at your NASA magnetic field flip webpage. I previously felt a bit vague about the frequency (or infrequency!) about the magnetic field flip regularity and the NASA gen (like you said - snappy) left me feeling a bit happier about my previous vagueness. Incidentally regarding the NASA quip about about a magnetic flip being good for compass manufacturers, I disagree with that. Possibly all an old compass owner needs do is just remember the compass pointer colour is a different way round - or is it more complicated than that. (Just vaguely remembered - I think compasses are corrected for magnetic tilt or whatever they call it so it might be best to buy a new compass eventually ?) I must confess in my enthusiastic hill going days I had compass problems several times. In particular twice I felt certain the compass was wrong - fortunately my companions were sure it was me who was wrong.
However, if I read the NASA gen correctly, it seems although Magnetic field flips might occur once every 200,000 to 300,000 years, it is now about 800,000 years since the last flip occurred - if that is correct then the last magnetic flip might have happened long enough ago not to affect "modern" humans too much but a another flip happening soon might affect us more sophisticated humans more severely (eg having to turn our mobile phones upside down).
Whatever, I liked the Wiki thing about "The Sixth Extinction" book by Elizabeth Holbert.
I even feel a bit inclined to buy it but I always was a slow reader and these days I'm even slower so I suspect I might give it a miss.
I think she could be right in suggesting the sixth extinction may have already started. However, if the criteria for the start is when the human population actually peaked or peaks then starts to decline I am not sure if we've actually peaked yet or it will take another year or two ?
Best wishes from Cliff

Author:  Alastair McBeath [ Mon Jan 23, 2017 7:58 pm ]
Post subject:  Re: At the Earth's core

Cliff wrote:
...Incidentally regarding the NASA quip about about a magnetic flip being good for compass manufacturers, I disagree with that. Possibly all an old compass owner needs do is just remember the compass pointer colour is a different way round - or is it more complicated than that. (Just vaguely remembered - I think compasses are corrected for magnetic tilt or whatever they call it so it might be best to buy a new compass eventually ?)

It's a bit more complicated, unfortunately, because the magnetic pole is constantly shifting slightly anyway. If you look at an OS map, for instance, you'll find it has three different "norths" shown (usually in a little diagram among the various keys along one side), "true north", "grid north" and "magnetic north". True north is the Earth's rotational pole direction. Grid north is north as used on the OS grid, to help fit the maps to the paper sheets better. Magnetic north is the direction a compass will point, roughly speaking. If you read the accompanying notes on the map, you'll find the direction for magnetic north is also given as an approximate bearing direction compared to grid north for a specific month and year, and for each corner of the map and its centre (because each spot is different). At one time, the average shift in magnetic north per year was also stated, but that doesn't seem to be the case on the newer OS maps, quite sensibly, because it can be misleading, given the shift in magnetic north isn't at a constant rate. This BBC News page from 2014 has some more discussion, and if you're keen for more detail, there's a handy Wikipedia page, "Magnetic declination" that has more.

For that "Sixth Extinction" book, maybe you could borrow it from the library (assuming you still have a public library with books like this you can borrow, of course; we no longer do here...).

Author:  Cliff [ Tue Jan 24, 2017 6:04 pm ]
Post subject:  Re: At the Earth's core

Dear Alistair
Thanks for your recent comments & interesting information. Excuse my relative brevity replying now (at least by my standards!) Unfortunately my earlier attempt some hours back got "time outed"
Believe it or not I do like Maps - and one of my older hill-going companions actually worked for the OS for several years.
However, my more recently acquired OS maps are largish scale - I mainly use now for "armchair hill-going", like I use my old star charts occasionally for doing "armchair astronomy". I admire the detail of the new OS maps and wonder how we managed with the old inch to a mile OS Maps. Whilst there are also GPS, Smart phones and various tablets. So how does anyone get lost these days.
As far as I'm concerned one of the few advantage of experiencing dotage, is the luxury of admiring anything whilst understanding nothing.
But I do wonder if Po;aris bothers about the Earth's north pole wandering.
I have rarely borrowed any books from our local library, being a slow reader - always taking them back before reading them properly.
Best wishes from Cliff
PS - Having got one - I don't like the double sided OS maps.

Author:  Alastair McBeath [ Tue Jan 24, 2017 7:58 pm ]
Post subject:  Re: At the Earth's core

Cliff: The double-sided OS maps do at least let you feel you're getting your money's worth though! I tend to agree, as they're beasts to use indoors alone; outdoors and they become unworkable.

As for the apparently more detailed modern OS maps, actually, very large-scale OS maps go back to the 19th century. The six-inch-to-the-mile series started in the 1840s, covering all of England and Wales by the early 20th century, with some rural areas mapped at 25 inches to the mile, and urban areas at an incredible 10 foot 6 inches to the mile, according to the OS's own "history" page for the 1855-1935 period. If you just want to view some of the old 6-inch maps, there's a handy site from the National Library of Scotland (ironically!), where you can browse and view to your heart's content, here. The modern 1:25,000 scale Explorer OS maps are simply following in those illustrious footsteps, even if not at quite the same expansive scale.

Author:  mike a feist [ Wed Jan 25, 2017 7:11 am ]
Post subject:  Re: At the Earth's core

Re Maps. I too love maps, star maps especially although as folded sheet maps they also fail outdoors. This was well demontrated during a talk I gave at the FTAG many year ago, pointing out the various types of star charts anf map that observers could use. I borrowed a Philips star-map from a member and when folding it up, and pointing out how difficult it could be, I managed to tear it accidentally...I guess it made the point! Even carefully folded maps soon fail at the corners and edges between folds, even the old folded cloth-backed OS maps eventually lost the detail at the intersections as the printed paper rubbed off at that point. There is also another weak area, where the cardboard cover is attached to the thinner paper of the map itself...rips to easily! Or am I just too clumsy! regards maf

Author:  David Frydman [ Wed Jan 25, 2017 5:41 pm ]
Post subject:  Re: At the Earth's core

I was surprised to see a T.V. programme that showed France was mapped well before Britain.

When both countries mapped the Channel ports they got the same results with different instruments. The British machine engraved the French hand engraved but multiple measures.

I like maps.

When the GPS and the internet switches off the whole world will be lost.


Author:  Cliff [ Wed Jan 25, 2017 8:56 pm ]
Post subject:  Re: At the Earth's core

Dear Alastair, Mike & David
I suppose I have really been talking about the maps readily available to me and my friends which we used,in our hill-going days, starting 67 years ago. Now some stores, I occasionally visit one at Nelson near Burnley sell a range of what I'll call replica old OS maps shops (not even a specialist book shop). I haven't been up a decent hill for about 20 years now. However, I don't think I would have wanted to use old maps and we found the one inch to a mile pretty good really. However, one point I'd make about map reading and compass bearings is that in difficult conditions it can be quite tricky trying to read a map and compass.
Mike, yes indeed and from what I gather even the new paper maps tear quite easily. I think I have one of these new "indestructible" maps somewhere - but they are quite expensive.
David, I didn't see the TV programme you referred to but it sounds quite interesting.
I have "The Measure of All things" by Ken Alder, but I'm ashamed to say Ive never got round to reading it properly. If I recall correctly there was a very sad fiasco when the French did some remapping, one surveying north parts the other south. Unfortunately I think it was the south guy did a good job surveying but unfortunately re-adjusted his calculations at several places to make his survey fit the previously less well surveyed important locations. It really messed his excellent survey work up. He eventually realise what he'd done but never admitted his mistake. Only after he died was the problem discovered. I think the astronomr Mechain was the north surveyor. Was that story mentioned in the TV programme ?
Best wishes from Cliff

Author:  Cliff [ Thu Feb 09, 2017 9:19 pm ]
Post subject:  Re: At the Earth's core

Dear al(L)
I just edited my 25th January post. The only thing I changed I realised I had once typed "is" which should have been "his" - I had also accidentally double posted the whole post, so I got rid of one version.
Best wishes from Cliff

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