In principle you are correct. The earth will move up towards the apple with a smaller acceleration than the apple moves down towards the earth.
This is because the force F between two objects is given by
Since F = ma, then the acceleration of each mass m1 and m2 will be dictated by the other mass.
I.e. m1 x a1 = K (M1 x m2)
or a1 = K x m2 (because m1 cancels on both sides)
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JonnyMcA
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Laboratory
QuoteThe core is a great deal hotter than the melting point of iron at 1 atmosphere, but the greater pressure on the inner core is what keeps it solid supposedly.
This to my mind is physically true. The thermodynamics of phases can be complex particularly when you introduce pressure, stress and strain into the equations. Generally speaking though, high pressure will prevent most materials fr
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JonnyMcA
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Laboratory
As Far as I am aware there is no plasma in the core of the core of the earth. Earths magnetism comes from a combination of certain things. Wiki syas it best
QuoteThe field is similar to that of a bar magnet. The Earth's magnetic field is mostly caused by electric currents in the liquid outer core. The Earth's core is hotter than 1043 K, the Curie point temperature above which the o
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JonnyMcA
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Laboratory
Earths magnetic field is thought to be generated in the liquid ferrous shell that surrounds the solid ferrous core. As the planet rotates, so too does this shell, which acts like a electric current, and it is this electric current that reinforces the earth's magnetic field. What I was pointing out preciously is that the crust of the earth is composed of metallic compounds that are chemical
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JonnyMcA
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Laboratory
QuoteSo... where is the magnetic friction of the earths ferrous core? Or is it correct what I dimly recall reading looong ago that the spin of the earth is gradually slowing? (Though i think I recall the casue being cited as the moon's tidal friction)
Most metals found in the earth's crust are found in mineral compounds. Just because they are in these compounds doe not make them con
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JonnyMcA
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Laboratory
Indeed it is. The furthest I have been on conference was Boston. I had a wonderful time, as it was the first week in December with the all Christmas decorations going up. I thought it was a lovely city.
Jonny
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JonnyMcA
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Laboratory
There have been some conferences that I know of have had "video conferencing" facilities. It isnt common, though.
Jonny
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JonnyMcA
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Laboratory
It looks like an interesting symposium. Im looking forward to trying to get the proceedings from it (fingers crossed there will be some, and I will have access to it). I would love to be at it just to soak in the inevitable heated debate given the different factions there.
Jonny
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JonnyMcA
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Laboratory
Hi Paul,
I was not meaning to assert that Giampaolo Giuliani successfully predicted the earthquake (though some media like to imply he did), and I am aware of the issues of earthquake prediction. I was merely using this as an example to illustrate that those pushing for indictment against geologists for not being able to predict an earthquake is ridiculous, and indeed the details of the case
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JonnyMcA
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Laboratory
I think I am confusing myself here, and perhaps the issue. I will have to think about this more before further comment.
Jonny
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JonnyMcA
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Laboratory
Hi Paul
And yet, one Giampaolo Giuliani, who apparently predicted the earthquake was dismissed by authorities before it occured for spreading panic! Surely the powers that be cannot have it both ways?
QuoteThe technician, Giampaolo Giuliani, who could not be reached for comment, had predicted that a massive earthquake would strike based on measurements of radon emissions. Skeptical Itali
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JonnyMcA
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Laboratory
As far as I am aware, A, C are the same thing since the celestial poles are the extension of the geographical poles to teh celestial sphere, and the inclination of the planet is the angle between E and A/C. B is the figure axis and tells us how the mass is balanced (one can think of it as the centre of mas axis in a way). Thus one can have the figure axis itself rotating with respect to the pri
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JonnyMcA
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Laboratory
As far as I am aware the polar axis and the spin axis are the same thing.
Also, the precession of the earth's polar axis is caused by the tidal forces of the moon and the sun (and to a lesser degree the other planets). This has the related effect of altering the inclination of the polar/spin axis to the ecliptic over time.
Finally, for the chillean earthquake effected the figure axis
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JonnyMcA
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Laboratory
The polar axis I refer to is not the magnetic axis, but rather the spin axis. If you are talking about friction, it is most likely that it will redistribute itself throughout the planet, with very little, if any effect upon the spin axis of the planet, though it will most likely speed or slow the planets rotation.
The fact is though, that these shifts so far have only been inferred from mod
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JonnyMcA
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Laboratory
The chilean earthquake only affected the figure axis of the earth not the actual polar axis. The figure axis is the axis about which the mass of the earth is balanced. Thus with the large earthquake the mass on the earth was redistributed which caused a shift in the figure axis, not the polar axis.
Jonny
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JonnyMcA
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Laboratory
Hi Pete,
No probs, fire away and I will get it to you asap!
Jonny
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JonnyMcA
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Laboratory
Thanks Hermione. I have that paper already (and have most of his comet related work,a nd any that i dont have is covered in his three books).
I think that some of the Celtic legends and gods can be seen as cometary in nature, as can many other ancient gods can be, however, the problem with this is that with most myths one can make them fit specific templates. In this respect one should not t
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JonnyMcA
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Laboratory
If one reads the two most recent papers of Baillie's, then you will see that he has suggested in light of new measurements of by Larson et al of the ice cores, that the two periods of environmental downturns in the tree-ring record (Ad 536 and 540) could be down to volcanoes.
Larson has identified a volcanic signature at AD 529 and one at AD 533/534 +/- two years. In the first paper, Bai
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JonnyMcA
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Laboratory
QuoteAnd in the Principia iirc Newton imagined that if you fired a cannonball from a mountain top fast enough that it would circle the earth and come back to it's original position.
A rather elaborate way to commit suicide really! Surely looking into teh business end and shouting FIRE! would be much easier
Indeed there was indeed a woodcut of this principle in the Principia. Whats mo
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JonnyMcA
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Coffee Shop
Dont forget that Jupiter is also responsible for throwing things our way too. Look at Comet Encke for example which is an earth crosser, and is thought to be a remnant of debris from a larger progenitor comet, along with the Taurid meteor complex of which the Tunguska bolide is thought to have been a member of.
So while Jupiter is useful, he does like to scare us or spank us once in a while
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JonnyMcA
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Laboratory
I found these nice sources which details the physics and maths behind all the different sorts of trebuchets (and yes there is more than one type) for those who are interested. As one of them points out the trebuchet was developed before the methods of calculus were discovered, but yet it evolved over hundreds of years to become a more efficient weapon. War does seem to be one of the greatest dr
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JonnyMcA
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Coffee Shop
Just take a sphere of Uranium 235 of diameter 17 cm, and you dont need to worry about being all that accurate at all. Just launch it in the general direction of your enemy! Mind you, it will weigh about 52 Kg (114 pounds) though.
Jonny
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JonnyMcA
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Coffee Shop
Two amateur astronomers have caught Jupiter being hit again.
Check out the videos in the above link.
Jonny
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JonnyMcA
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Laboratory
Ok, some will think me a bit sad, but it is how my brain works. I woke up last night and realised that the original statement about the variation of gravity not effecting the range is indeed correct. What I posted is correct for projectile motion, but it does not take into consideration how that projectile motion is created in the first place.
Normally in projectile motion problems, some one
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JonnyMcA
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Coffee Shop
Hi Warwick
It is fun, but there is an error in the physics I believe. It states after the first round that altering gravity will not effect the projectiles range. This is not correct, if gravity is less, then the projectile will go further.
If we have an object projected at an angle q to the horizontal with speed V, then we can resolve the motion into two components, a vertical one and a
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JonnyMcA
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Coffee Shop
Hi Hermione,
Yes, Electromagnetism is a very technical area of physics. It is the bane of most physics students. Its very much a Marmite subject, either you love it or hate it, but it is so intrinsic to the core of physics that you just cant ignore it, no matter how much you try. I was one of the ones who hated it, but it has grown on me over the years, and I have come to appreciate the sub
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JonnyMcA
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Laboratory
It seems to me that this gentleman is need of a good basic electromagnetism text book. I say this because electromagnetism is a "Newtonian" theory, and one that Tesla used, but he has not understood one of THE most fundamental implications of it, namely the speed of light and why it is what it is, and its origin. I shall try to explain.
We all know that light is an electromagnetic
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JonnyMcA
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Laboratory
Dont forget that when making measurements there is a difference between accuracy and precision. I could measure a line 30 cms long to be 29.6 +/- 2.2 cms, or I could measure the line to be 32.567 +/ 0.063 cms. The first is accurate but imprecise, the second is precise but inaccurate. A measurement of 30.225 +/- 0.025 is both more accurate and more precise than either the previous two, even t
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JonnyMcA
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Alternative Geometry and Numerology
That is perfectly true, and shows the value of obtaining more data. If one or models fits the current data, then you need to extend the data to try to discern the difference, or look at some other way of investigating the problem that will separate the models. Thats where the excitement and challenge in any science lies.
Jonny
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JonnyMcA
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Alternative Geometry and Numerology