Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Did Earth coalesce from 2 medium sized planets?

LOL, I see instead of actually replying to the criticism you've instead chosen to propagate your insult. And on that note, what kind of science I'm involved in is clearly outlined in my profile - no need for you to guess.

What you have shown us is where you stand on the topic of peer-review...and on the topic of the relationship between potential energy and work.

Bryan

PS: how's that paper coming?

It is finished. You can download it from http://preearth.net/worlds-collide-A4-bw.pdf

Hi Bryan,

Last night I didn't have time to explain things fully and I spent all today chatting with geophysicists from Auckland University. I left Sydney about a week ago.

So, where were we?

Question 1) What exactly is your definition of gravitational potential energy?

Here is mine: The gravitational potential energy is the work done against the gravity force in bringing a mass in from infinity (so the gravitational potential energy is negative). It is defined to be zero at infinity.

Now, you calculate the gravitational potential energy of one planet relative to the other, at the time when they touch, and then swing this about as if it means something that it probably doesn't, without saying exactly what you mean.

Question 2) What exactly do you think this number you calculated means?

I tried to guess what you meant by this and assumed you were talking about the kinetic energy Heaven would have if it fell to PreEarth from infinitely far off. Which is negative the same number.

But apparently, that is not what you meant.

So, what exactly do you mean?

I could hazard another guess, but don't think it wise, until you have made what you think it means clear.

Try submitting that to peer review; without that it's not a scientific paper, just ramblings...



Sorry, but there is only one definition for gravitational potential energy, and that is the one defined by physicists. You don't get to make up your own scientific definitions on a whim, or to re-write basic physical laws so they fit your mis-understanding of physics.

The one and only definition of gravitational potential energy is the one I gave, and is the one defined by the formula I used - "stored energy determined by an object's position in a gravitational field".

The key word there is "position". "Position" is not infinity, but rather is the exactly defined distance between the centers of mass.



It means exactly what the math and science says it means - that is the amount of energy available to the system, in its given configuration. The exact same math is used by scientists and engineers all over the world to calculate things like the amount of energy that can be derived from hydroelectric dams. They don't have to move the water an infinite distance away in order to extract the gravitational potential energy determined by U=G[m1*m2]/R. Nor do your imaginary planets need to be moved to an infinite distance apart for the gravitational potential energy that exists between them to be converted, in its entirety, into work.



Its the amount of potential energy available in the system to do work, given the spatial relationship of the two planets and their mass. As in exactly what gravitational potential energy calculates.

I'm thinking you may need to pick up a high school textbook; potential energy and the conversion of it into work is one of the most basic of physical concepts, and you have absolutely zero understanding of how they work.



Exactly what I've been saying all along, and exactly what the physics of gravity dictate I am saying. You really need to learn about the relationship between potential energy and work.

Bryan

Here is a typical definition of gravitational potential energy:

Gravitational Potential Energy

The general expression for gravitational potential energy arises from the law of gravity and is equal to the work done against gravity to bring a mass to a given point in space....

From the work done against the gravity force in bringing a mass in from infinity where the potential energy is assigned the value zero, the expression for gravitational potential energy is:

U = - [G * M * m]/R, etc.

http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html

It is from a site dedicated to high school students so should be easy to understand.

Bryan;

In the case being considered, the gravitational potential energy is as you calculated;

U = - [G * Mp-e * Mh]/R = -5.95 X 10^25 MJ.

This is exactly the kinetic energy (apart from the sign) that Heaven would have if it fell to PreEarth from infinitely far off, i.e., Heaven would have kinetic energy

KE = 5.95 X 10^25 MJ.

(the loss in potential energy equals the gain in kinetic energy)

So your estimate of the energy transfer to PreEarth is the largest possible and thus not very realistic.

I don't know how many times one has to say this till you wake up,....

So? As pointed out to you repetitively, kinetic energy is not the only form of energy which potential energy can be converted to, and ergo is not the only mechanism by which the gravitational potential energy between pre-earth and heaven will be translated into work (i.e. turning your planets into molten orbs of goo).



Its actually the measure of the free energy available to do work. Without proof, you have no idea as to how much or little of that will actually be translated into the destruction of your planet. But keep in mind, you need to explain away roughly 99.99% of that energy just to get to an energy transfer equivalent to the amount of energy thought to have created the moon - and that collision completely melted the earth's surface.

To get into territory where the earths crust has a chance of actually remaining intact (to be generous, 1000 dino-extinction asteroids worth) you need to explain away 99.999995% of that potential energy.

Pretending that because it cannot all get converted into kinetic energy, and therefore can be ignored, is bad science at best; idiocy at worst.



Get what? That you don't have the vaguest idea of what potential energy is and how its translated into work, or that you are so married to your hypothesis that you are unwilling to take criticism and analyze your possible errors?

Bryan

Bryan; Perhaps the following will help you out.

Yes the gravitational potential energy of the system at impact is equal to

U = - [G * Mp-e * Mh]/R = -5.95 X 10^25 MJ.

However, not all that potential energy will be converted to heat (something you keep telling me I don't believe,... but its actually you who assume all the potential energy is turned to heat, thus giving the largest possible increase in heat).

A lot of this potential energy will be used in reshaping the 2 planets into one.

For example, a cubic kilometer of mass on the surface of Heaven (radius 4800 km, say) needs to be "lifted" one and a half thousand kilometers to the surface of Earth (radius 6371 km), or more, if the cubic kilometer of mass started below Heaven's surface.

This takes a huge amount of energy.

So you get the idea.

Its not as simple as one may think.

It is this sort of thing that forced me to adopt the approach using gravitational binding energy (in the paper).

Based on what I've seen, I highly doubt these conversations ever took place. But it would be easy enough for you to confirm - names please.

Try re-reading my past posts; I never once said it would all be converted to heat. Some portion of the potential energy in the initial state will remain as potential energy, simply because the entirety of the two planets masses will not be collapsed down into a point-mass. Ergo, the mass "supported" above the core will not loose all of its potential energy.

However, enough of it will be. Keep in mind that just 1% of the energy in you starting state is 100X the energy needed to get a moon-making impact. But since you seem to have trouble following the bouncing ball, I'll slow it down even more for you:

Gravitational potential energy of your initial state: 5.95 X 10^31 J.

Energy of the collision that made the moon, and melted the entirety of the earth: 10^27J

Energy of the collision that killed the dino's: 10^23J

So the amount of potential energy you need to have magically disappear, just to get to an earth-melting, moon making collision: ~99.99%

Energy that has to magically disappear, to get to a dino-killing impact: ~99.999999%

A rough guess as to the amount of energy that has to magically disappear to get the maximum energy absorbed without melting the earth: ~99.999%

Now I'll buy that upto 60%, maybe even a bit more, of the potential energy in the original configuration will be left after formation. That still leaves you a few orders of magnitude above what it takes to make a moon.

You see, it is comments like the one above which confirm you have no grasp of basic physics, which is also why I doubt you ever talked to a real scientist about your ideas.

Firstly, no "lifting" is taking place - the surface of one planet is not being lifted towards the other. What physics dictates must happen, given your initial state, is both planets fall towards the center of mass of the combined system - which assuming equal density of both planets, will be located a few hundred km below the surface of pre-earth. The planets ***fall*** towards each other, due to their mutual gravitational attraction. There is no "lifting", and thus no "lifting energy" is required.

Secondly, you seem to have forgotten your thermodynamics, and the role of entropy. Heat (or more accurately, increased entropy) is a given in all physical systems. In the case of two planets merging, all of the energy generated in the interactions between the two bodies will ultimately end up has heat. For example, as the two planets merge the magma comprising the two planets will be forced to flow due to the displacement by the other planet. That flow is subject to friction, which over time will bring the flow to a halt, transferring that energy into heat. Likewise, any waves created during merger will be slowed by friction, converting their energy into heat. Heat is the eventual end for all of the potential energy translated into work, with one exception. That one exception is any material actually ejected into space - in this one case energy escapes not as heat, but rather as kinetic energy.

Oh, but it is. You have a very simple situation - an initial state containing a large quantity of potential energy. You can pontificate all you want about gravitational binding energy or whatever other irrelevant phenomena you want, but at the end of the day that energy MUST BE ACCOUNTED FOR. Bringing up irrelevant physical phenomena doesn't change that one simple fact.

Bryan

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Sorry Bryan but you are totally hopeless.

You believe random incorrect stuff and refuse to believe correct stuff.

First your 10^27J for the collision that made the moon (and supposedly melted the entirety of the earth) is basically unsourced and CLEARLY WRONG.

Take 1300 J/kg°K as the average specific heat for the Earth.

Then if all of the 10^27J is converted to heat we get a temperature rise of:

(10^27)/(5.97369 x 10^24 x 1300) = 1.3 degrees (the mass of Earth is 5.97369 x 10^24 kg)

And a 1.3 degree rise in temperature, just ain't going to melt the planet.

Now lets get back to the gravitational potential energy of the system just before impact.

Then if ALL the potential energy, i.e., the entire 5.95 x 10^31 Joules, is converted to heat we get a temperature rise of:

(5.95 x 10^31)/(5.97369 x 10^24 x 1300) = 7662 degrees.

And this is not so unreasonable but is clearly enough to eventually melt the planet.

Prove me wrong then. Saying it is so, does not make it so.


It was not unsourced, as I provided the link to the scientific paper from which I got the source the first time I brought up the number. that's the opposite of unsourced - its cited fully, the first time it was given. The link, again:

http://www.nature.com/nature/journal/v412/n6848/full/412708a0.html

Any errors in that calcification are theirs, not mine. Any errors in interpreting their numbers are mine...



Small problem with your math - most of the earth is already molten; it is only the surface which has to be warmed to melt the surface. Had you read the article I linked to before you'd know the collision was a glancing one, and thought to have transferred most of its energy to the crust (which is why the moon is iron-poor, BTW). Had you bothered checking the citation you claimed I never gave, you'd not have made such an obvious mistake. It's late and I'm feeling lazy, but I'd be willing to bet the fairly thin crust (30km on average today; less back then) would easily be melted by that impact.



If the planet was entirely solid to start, I'd agree. But since all but <1% the planet was already molten, and since a lot of the energy was applied to the solid surface, I don't see the relevance of your calcs. Heat transfer takes time - in the case of the earth today, core-surface transfer takes place of tens of thousands to hundreds of thousands of years.



So lets see:

You agree that the potential energy is sufficient to melt the planet.

Finally, some progress!

Now, lets do some kindergarden math. The average temp of magma is 700-1300C according to wikipedia. Lets give you the best-case scenario, wherein the entirety of pre-earth and heaven are at the freezing point of water; from the core on out. This means that to melt the whole of the new planet you'd need 9-17% of the total potential energy of your initial state to be transferred into any other form of energy, to eventually get this degree of warming. Keep in mind, this means that in this impossible scenario you still have an excess of potential energy nearly 6X that needed to melt earth.

But once again, most of the planet is already molten. According to wikipedia, 1% of the earths volume (and therefore approximately the same % of mass) is crust. The top of the crust averages ~18C, the bottom ~400C. Call it an average of 200C for simplicity. So to melt the crust of earth you actually need between 0.07 to 0.14 percent of the potential energy present in your initial condition.

Now tell me, where the hell do you think the other 99.85-99.93% of that potential energy goes?

Bryan

If facing the world with a critical mind, and demanding proof of claims makes me "hopeless", than I'm damned proud to be hopeless.

Bryan

The opening of the Atlantic.



Cool, eh?

Nice animation. How does your model account for the fact that the crust along the base of the Atlantic radiodates in a matter consistent with continued expansion over millions of years (i.e. the crust nearest shore dates much older than crust near the mid-atlantic ridge), instead all aging to the same date (as your model would predict)?

Bryan

If you had read the paper, you would know that my model does not necessarily predict that all points of the Atlantic ocean basin should age the same.

Why don't you read the section called: Radiogenic Dating.

In fact, under certain circumstances one would expect to see an argon gradient across the Atlantic, just like one sees today.

The argon gradient used to date the sea-floor, can be interpreted as a geochemical gradient, one which can be explained by the mixing of mantles with different initial argon concentrations.

I did - and like the rest of your hypothesis you ignored all the contravening data and looked only at the one form of radiodating you could twist to your desires.

And even with argon you did a half-assed job - you pretty much ignored the potassium side of the equation. You need both - not just the argon - to date the rocks. I'd like to see you explain both the argon and potassium, without you ignoring basic physics this time.

And if you can do that, try searching the scientific literature - 2 minutes in it found three papers which dated the Atlantic floor using four other methods - Samarium-neodymium, Rubidium-strontium, Uranium-Lead and even Uranium-thorium of the area closest to the ridge itself.

They all show the same thing - explaining how mixing could give the argon gradient is one thing, explaining how 8 other radionucleotides could all end up in exactly the right mixes - given their different half-lives - is going to be much harder.

If you can do that, then lets see you explain the magnetic anomalies which also support conventional continental drift, in a non-radioactive manner.

Bryan

Good. Then lets have the web addresses of the sites you found (and consider good enough).

And, no more (false) claims from links the general public can not access.

Start with the Uranium-Lead and Uranium-thorium, please.

So basically your reply is "please do my homework for me". You'd think someone claiming to be presenting a "scientific" hypothesis would be familiar with scientific journals and how to find them. Or that the burden of proof is on you - reviewers of scientific work (i.e. me) simply provide critisim; its upto those doing the "work" to prove/disprove those critisism.

Speaking of which, why the deafening silence on the potassium issue? It is, after all, a direct product of your work - no references needed...

But I'm feeling generous today, so here's a hint - you can find scientific literature using google scholar: http://scholar.google.com

Heck, I'm feeling so good today I'll even give you some help, and start your home work for you:

Best place to start, is with the man who single-handedly discovered most of what we know about oceanic ridges:
Cesare Emiliani's [u]The Oceanic Lithosphere[u]. Great book, been a scientific staple for 30 years.

Then, how about some actual studies, published in one of the most prestigious scientific journals out there:
http://www.sciencemag.org/cgi/content/full/sci%3B323/5917/1048

--and--

http://www.sciencemag.org/cgi/content/ab...pe2=tf_ipsecsha

Between Emiliani's book and those two papers, you should have data and references galore.

Bryan

You claimed you had already these links/papers.

Were you just lying?

Is it too hard to provide the links you claimed you had?

And the one link you did provide states:

Approximately 75% of the gabbros accreted within error of the predicted seafloor magnetic age, whereas ~25% are significantly older. These anomalously old samples suggest...

So fully one quarter of the dates were ANOMALOUS.

Is that what you call collaborating evidence? Hmmmmm?