Earth was almost flat disc - new Moon theory

[Cassel]

 

[Shpaget]

So how does it slow down to the rate we observe today?

Earth's spin is very from the tipping point the lady mentions.

Edited March 29, 2019 by Shpaget

[Cassel]

14 minutes ago, Shpaget said:

So how does it slow down to the rate we observe today?

Earth's spin is very from the tipping point the lady mentions.

No idea, youtube recommended me this video :-)
I am looking at her website, maybe there is more information http://sarahtstewart.net/origin-earth-and-moon/

Edited March 29, 2019 by Cassel

[Green Baron]

It is not a theory, neither is the giant impact hypothesis (Theia).

1 hour ago, Shpaget said:

So how does it slow down to the rate we observe today?

That is a problem i see too. And the cloud would loose much material at the edge.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JE005333

I didn't watch the video but overflew the corresponding article.

Theia is generally accepted but like any hypothesis not unquestioned. But it is the best explanation for the observations of the compositions of moon and earth, it was developed when we got samples from the moon during the Apollo programme. Earth was already differentiated at that point and the impact almost destroyed its mantel (one can find simulations), but left the core intact.

The  synestia proposal came up a year or two ago, being an extension to the Theia impact with a much bigger event that vapourized both bodies but was just not strong enough to fully disperse the resulting cloud. They say this explains better compositional differences, which exist but are few.

It has in my opinion three problems:

First the mentioned impulse that could keep the cloud from condensation. The impulse question is not addressed in the synestia hypothesis.

Second is that Theia explains better the slow receding of the moon to higher orbits over geological times because it formed very close to earth and has since then wandered to its current orbit. I would need more modelling because i'd expect an impact that vapourizes a differentiated planet's core would also disperse the resulting cloud, leaving nothing "valuable" behind.

Third is composition: The lighter material at the edge of the cloud would have a high probability of escape. I am unsure if the composition with volatiles and mantle material can be explained with subsequent impacts after such an event alone.

tl,dr: Theia is not unquestioned, but the most accepted hypothesis for moon forming for now. Which does not mean that this is a frozen state of research :-) We'll see if this approach will be discussed any further in the future.

 

Edited March 29, 2019 by Green Baron

[Cassel]

20 minutes ago, Green Baron said:

It is not a theory, neither is the giant impact hypothesis (Theia).

That is a problem i see too. And the cloud would loose much material at the edge.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JE005333

I didn't watch the video but overflew the corresponding article.

Theia is generally accepted but like any hypothesis not unquestioned. But it is the best explanation for the observations of the compositions of moon and earth, it was developed when we got samples from the moon during the Apollo programme. Earth was already differentiated at that point and the impact almost destroyed its mantel (one can find simulations), but left the core intact.

The "synestia" proposal came up a year or two ago, being an extension to the Theia impact with a much bigger event that vapourized both bodies but was just not strong enough to fully disperse the resulting cloud. They say this explains better compositional differences, which exist but are few.

It has in my opinion three problems:

 

I see a different problem here. Both hypotheses are based on the assumption that these rocks are from the moon.
This new hypothesis shows that there would have to be two objects hitting Earth. The first impact accelerated the rotation of the Earth to such an extent that it almost became flat. Second object was size of Mars, and that would create something that we have not seen so far (synestia) so we could explain the fact that the rocks from the moon are identical to the rocks from Earth.

I have a simpler answer how to explain this similarity :-)

As for the theory of the great collision, I am just reading about it and I do not understand why it is taken into account at all. Why could the Earth and the moon not be formed separately in the same orbit?

 

Edited March 29, 2019 by Cassel

[Green Baron]

38 minutes ago, Cassel said:

I see a different problem here. Both hypotheses are based on the assumption that these rocks are from the moon.
This new hypothesis shows that there would have to be two objects hitting Earth. The first impact accelerated the rotation of the Earth to such an extent that it almost became flat. Second object was size of Mars, and that would create something that we have not seen so far (synestia) so we could explain the fact that the rocks from the moon are identical to the rocks from Earth.

I have a simpler answer how to explain this similarity :-)

As for the theory of the great collision, I am just reading about it and I do not understand why it is taken into account at all. Why could the Earth and the moon not be formed separately in the same orbit?

 

Two impacts coinciding in that manner are improbable. In terms of parsimony the giant impact hypothesis is the "easier" variant.

It is taken into account (and widely favoured) because orbital mechanics almost exclude a capturing. A planet clears its path, throwing smaller objects out or in or incorporates them, that's what makes it a planet. And the fact that earth and moon are so similar in their isotopic compositions suggest a common origin, there is little doubt. The moon started orbiting close to earth, slowly leaving since then in exchange for friction energy from tidal forces. Simulations suggest that the moon initially might have been very close to earth, like a couple of radii, though this has great uncertainties. I am not sure if capturing of the moon is in discussion any more.

The web has a lot of information on the Theia impact hypothesis and its development, in publications, on the space agencie's sites, EGU and AGU publications and almost all of the geoscience journals. It will not be easy to replace it ;-)

Edited March 29, 2019 by Green Baron
Uncertainties, uncertainties :-)

[Cassel]

39 minutes ago, Green Baron said:

Two impacts coinciding in that manner are improbable. In terms of parsimony the giant impact hypothesis is the "easier" variant.

It is taken into account (and widely favoured) because orbital mechanics almost exclude a capturing. A planet clears its path, throwing smaller objects out or in or incorporates them, that's what makes it a planet. And the fact that earth and moon are so similar in their isotopic compositions suggest a common origin, there is little doubt. The moon started orbiting close to earth, slowly leaving since then in exchange for friction energy from tidal forces. Simulations suggest that the moon initially might have been very close to earth, like a couple of radii, though this has great uncertainties. I am not sure if capturing of the moon is in discussion any more.

The web has a lot of information on the Theia impact hypothesis and its development, in publications, on the space agencie's sites, EGU and AGU publications and almost all of the geoscience journals. It will not be easy to replace it ;-)

Why you exclude "capturing" moon?

First of all, there is no evidence that the oceans of magma existed on Earth, it negates the hypothesis of a great impact.

"This lunar origin hypothesis has some difficulties that have yet to be resolved. For example, the giant-impact hypothesis implies that a surface magma ocean would have formed following the impact. Yet there is no evidence that the Earth ever had such a magma ocean and it is likely there exists material that has never been processed in a magma ocean."

https://en.wikipedia.org/wiki/Giant-impact_hypothesis

Secondly, you suggest that the moon was accelerating, where was this observed?

The simplest hypothesis is one that says that these rocks, on which the great impact hypothesis rests, do not come from the moon.

Edited March 29, 2019 by Cassel

[kerbiloid]

In the beginning both the Earth and the Moon were one cloud.
And the cloud was a torus.
And the torus was around the Sun.

[Shpaget]

32 minutes ago, Green Baron said:

Two impacts coinciding in that manner are improbable.

Generally speaking, I find low probability of something happening to be entirely irrelevant and a poor argument, when speaking about the sample size of 1, as is the case with the only planet we know of that has life on it.

I believe that we can all accept that the relatively large moon (such as Moon) was a significant factor in evolution of life on Earth, hence the presence of Moon should not be surprising. With billions of galaxies, each with billions of stars in it, (and likely) each with numerous planets it's not surprising that something unlikely happened, but the fact that it's a low chances for it happened on the planet that we just happen to be is not important, since we are on this planet because we have such a big moon.

Anyway, anybody feel like throwing some numbers on the paper to calculate how much would the Earth's spin change if the entire momentum of the Moon was converted to the rotation of the Earth?

[Cassel]

4 minutes ago, Shpaget said:

Generally speaking, I find low probability of something happening to be entirely irrelevant and a poor argument, when speaking about the sample size of 1, as is the case with the only planet we know of that has life on it.

 

If the chances of something does not matter to you, I might as well create a hypothesis based on 6 hits in Earth.

The fact that we are dealing with a sample of size 1 should make us skeptical about every hypothesis.

7 minutes ago, kerbiloid said:

In the beginning both the Earth and the Moon were one cloud.
And the cloud was a torus.
And the torus was around the Sun.

Exactly, could not the Earth and the moon form in such a way from the beginning?

[Green Baron]

Yeah, don't let this get too wild. Ease of explanation is what drives research. If you start thinking around several corners to support an upcoming hypothesis (edit: while simpler explanations are there) something is wrong with your base model. The Theia hypothesis is around for several decades now and not widely doubted, though maybe in need of more adjustments. The paper in the OP also misses out on some things there.

Here's some reasonable pop science:

Very basic: https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question38.html

A variant: https://www.nasa.gov/topics/solarsystem/features/moon_formation.html

The classic model: http://curious.astro.cornell.edu/our-solar-system/the-moon

(skip down to questions in that link, @Cassel, they are answered there)

 

Somewhat advanced, just to show that the ideas are in development, without any preferences from my side:

http://advances.sciencemag.org/content/3/1/e1602365

Addressing the angular momentum problem with many impacts instead of a big one:

https://www.nature.com/articles/ngeo2866

 

... and so on. You see, nothing is carved in basalt or iron ;-)

 

Edit: this is the second time in my life that i recommend a Wikipedia article. Changing times ...

 

 

Edited March 29, 2019 by Green Baron

[kerbiloid]

I find the practice of naming hypothetic bodies (say, so-called "Theia") highly disgusting and unfair.
It makes the audience to think about it as about a real, proven thing. This is an absolutely misleading advertising, and its authors should be banned from the science forever.

[Green Baron]

You get that impression if you only read the popular headlines. As soon as you look into it it becomes clear that it is the name for a hypothetical body from the giant impact hypothesis, nothing more and less.

Edit: I used it only because it is common and i ddidn't want to cut&paste giant impact hypothesis over and again.

Edited March 29, 2019 by Green Baron

[kerbiloid]

1 minute ago, Green Baron said:

You get that impression if you only read the popular headlines. As soon as you look into it it becomes clear that it is the name for a hypothetical body from the giant impact hypothesis, nothing more and less.

There is a bunch of >1 body hypotheses, and most of them don't use this name.

[Green Baron]

Oh, you've noticed :-)

Many of them are adjustments or extensions of the giant impact hypothesis, as is the one in the OP. Good news: it is all in discussion. There is a lot of info on it in the links in this thread.

[Starstruck69]

Hypothesis (a proposition made as a basis for reasoning, without any assumption of its truth.)

It is of course an idea that may or may not be true.

This is very important as either outcome is possible without facts.

This is where i am very sceptical about the accuracy of these ideas as we are limited by the information needed to formulate an accurate opinion due to the absence of critical data.

It is great that this is being discussed, imagination is a wonderfull thing however science requires cold hard unbiased facts and they seem to me to be absent here. 

Again it is just an idea thats all..

 

[sevenperforce]

When the giant impact took place, the crusts of proto-Earth and Theia were mixed to such a degree that they became undifferentiated. The core of Theia merged with the core of proto-Earth. Our moon formed rather rapidly from the debris cloud and has very little core to speak of.

We know without question that the Moon has been receding since its formation. This is observable.

[Green Baron]

A hypothesis is a testable assumption about a phenomenon, based on observation.

The giant impact hypothesis for the moon is founded on chemical analyses and orbital mechanics. It has been refined with observations of other moons, meteorites, our model of the forming of the solar system and its bodies, and undergoes modelling and simulations. It has its unresolved problems. That's why people are working on it and on possible alternatives. 3 of which have been ruled out, as one can take from the links. I will not bore you with reciting their contents ;-)

Edited March 29, 2019 by Green Baron

[Rakaydos]

2 hours ago, Cassel said:

 

Exactly, could not the Earth and the moon form in such a way from the beginning?

Earth-Sun L3, L4 and L5 makes it likely that the initial torus will form multiple bodies, well separated in orbit. But those bodies are usually unstable relative to each other, and over astronomical time, will eventually "clear their orbit" and collide/combine.

I suspect the spin of the rock-plasma disk actually gets tidally transferred to the moon, gradually shifting the moon  to a higher orbit.

[Starstruck69]

The observation bit is where i become sceptical because we weren't measuring/observing in that instance.

If i were to drive 100 miles and we only observed the last 10. Can i accurately describe what happened in the first 90?

 

[Rakaydos]

Just now, Starstruck69 said:

The observation bit is where i become sceptical because we weren't measuring/observing in that instance.

If i were to drive 100 miles and we only observed the last 10. Can i accurately describe what happened in the first 90?

 

We can observe the mud on our wheelwells, the bugs and leaves on our windshield and grill, and our tracks in the road and weather that may have washed out the tracks.

[Green Baron]

18 minutes ago, Rakaydos said:

... But those bodies are usually unstable relative to each other, and over astronomical time, will eventually "clear their orbit" and collide/combine....

True, but we think that earth was almost "ready" ~ 4.5 billion years before now, at the beginning of the Hadean

[Starstruck69]

Thats a fair point Rakaydos!!

[kerbiloid]

1 hour ago, Rakaydos said:

1 hour ago, Starstruck69 said:

If i were to drive 100 miles and we only observed the last 10. Can i accurately describe what happened in the first 90?

 

We can observe the mud on our wheelwells, the bugs and leaves on our windshield and grill, and our tracks in the road and weather that may have washed out the tracks.

80 miles ago we have washed the car.

P.S.
After hitting a Moon deer, lol.

Edited March 29, 2019 by kerbiloid

[Starstruck69]

Lol those pesky moon deer get everywhere:)