physics question

[2hats]

A better explanation for showing how curved space time can lead to effects of gravity is in this video. The 'bending' of the time part of space-time is another thing missed by the rubber sheet analogy, when this actually explains nearly all of the everyday effects of gravity.

It is a better illustration, a better visualisation in many ways. However, ultimately the only complete* explanation is one laid out by working through the mathematics, the Riemann tensors, that describe the warping of spacetime. Which of course brings us back to … the cartoon in post 58.
(* as best we currently know it).

 

[DotCommunist]

I've heard of him. Something to do with functions.

 

[moon]

What is the role of gravity on the formation of the earths crystal core? Does gravity affect it, did it create it?

 

[existentialist]

What is the role of gravity on the formation of the earths crystal core? Does gravity affect it, did it create it?

Gravity's role was critical, as for the formation of any body in the Universe.

The solar disc started out as a large cloud of dust. Over time, the gravitational attraction between those dust particles pulled them together, and they will have started to form small objects, which would then have been pulled together - by gravity - to form larger ones, that we often call planetesimals, which in turn would have collided with each other to form larger bodies, and so on. Various other forces - not least the kinetic energy of sizeable objects slamming into each other - will have caused heating, which will have affected the structure of bodies such as the earth.

So yes, its own gravity created it. And the Earth is affected by its own gravity - if you take into account the slightly increased diameter at the Equator, caused by the rotation of the Earth, it is a perfect sphere, and that shape is a direct result of the way the gravitational attraction of all of the matter composing the earth interacts. The reason all stable astronomical bodies are spherical is because that is the most stable shape they can assume under their own gravity.

 

[Signal 11]

It causes the denser elements like iron to sink towards the centre. Planetary differentiation - Wikipedia

 

[moon]

So the effect of gravity is to concentrate mass into a smaller denser space over time?

 

[NoXion]

So the effect of gravity is to concentrate mass into a smaller denser space over time?

I'm pretty sure it just causes the denser stuff to sink down to the centre and the lighter stuff to float up, while the body in question still has a molten component.

 

[existentialist]

So the effect of gravity is to concentrate mass into a smaller denser space over time?

It's more subtle than that. Time is not a factor in regard to gravitation, in the classical (Newtonian) sense: put enough matter together in one place and gravity will do its work instantaneously (allowing for the propagation across the space at the speed of light, per relativity theory). But the mechanical properties of the matter may mean that the process of accretion takes a finite amount of time to take place.

The density will be limited by other factors, too, such as the compressibility of the matter - which is why the matter at the core of the earth is (albeit highly-compressed) iron and nickel, rather than degenerate matter such as you might find at the heart of a neutron star.

 

[moon]

Well it seems to me that gravity is a process by which space seeks to complete itself, mass being areas of 'negative space' which the universe tries to compress into a smaller form through crystallisation.
Its also interesting that the process of crystallisation or lattice energy is exothermic, whilst the opposite process entropy?? is endothermic, as it relates to the photosynthesis thing I was talking about earlier.

 

[existentialist]

Well it seems to me that gravity is a process by which space seeks to complete itself, mass being areas of 'negative space' which the universe tries to compress into a smaller form through crystallisation.
Its also interesting that the process of crystallisation or lattice energy is exothermic, whilst the opposite process entropy?? is endothermic, as it relates to the photosynthesis thing I was talking about earlier.

Space doesn't "seek" to do anything - I think it is dangerous to infer some kind of goal or intention on physics in this way, because it leads us into thinking about it in an unhelpful way. Gravity is a property of spacetime, and influences the way in which matter interacts with it; no more than that.

Crystallisation is a red herring here - that's a property of matter, and nothing really to do with spacetime. And I am completely at sea with this idea of "negative space"

I think you are confusing three completely unrelated subjects - crystallisation, entropy, and photosynthesis.

I would really, really urge you - if you are seriously interested in understanding the subject in any practical way - to go and study some basic texts on spacetime, relativity, and so on. I fear that what you may be doing is to try to assemble a few slightly-understood snippets into something that looks like it fits. That just isn't going to work in the real world.

ETA: you could do worse than to incorporate some reading on the philosophy of science into your researches, too - you may thereby get a better understanding of why it is that people like me are challenging what probably seem to you like core concepts.

 

[moon]

Well it sort of stems from the fact that plants don't grow so well in space, which lead me to ask whether photosynthesis was dependent on gravity.
The whole energy capture through protein folding cascade appears to be a process similar to crystallisation.

I think its helpful to look at things in new ways, otherwise you get stuck in old thinking..

 

[gosub]

Well it sort of stems from the fact that plants don't grow so well in space, which lead me to ask whether photosynthesis was dependent on gravity.
The whole energy capture through protein folding cascade appears to be a process similar to crystallisation.

I think its helpful to look at things in new ways, otherwise you get stuck in old thinking..

Not photosynthesis per say but the equation requires water and the supply of that through osmosis might be the issue

 

[existentialist]

Well it sort of stems from the fact that plants don't grow so well in space, which lead me to ask whether photosynthesis was dependent on gravity.
The whole energy capture through protein folding cascade appears to be a process similar to crystallisation.

I think its helpful to look at things in new ways, otherwise you get stuck in old thinking..

I think you'll find that scientists (and especially those in the fields of relativity/quantum mechanics) are already rather good at looking at things in new ways. And - per the whole "philosophy of science" thing - science itself, done properly, is very good at fostering and developing new ideas, in a way that is pretty much unique in most fields of knowledge.

Where new ideas don't gain traction in science, there's usually a very good reason why.

 

[moon]

Yeah I have studied science, focusing on photosynthesis in Arabidopsis, its why I like to question things.

 

[existentialist]

Yeah I have studied science, focusing on photosynthesis in Arabidopsis, its why I like to question things.

Good-oh. Well, I wish you luck in your researches.

 

[moon]

yeah see yah man...

 

[Signal 11]

Well it sort of stems from the fact that plants don't grow so well in space

That's a claim not a fact. You've shown no evidence to support it and you've been shown evidence to contradict it: physics question

which lead me to ask whether photosynthesis was dependent on gravity.

There may be more to it but a quick search suggests it's not...

Effects of the Extraterrestrial Environment on Plants: Recommendations for Future Space Experiments for the MELiSSA Higher Plant Compartment
"Plant gas exchange, metabolism, and photosynthesis mechanisms were not affected by microgravity when provided with satisfactory environmental control"

https://lsda.jsc.nasa.gov/Experiment/exper/508
"There was no difference to ground controls when measured for canopy level photosynthetic rates"

Microgravity effects on thylakoid, single leaf, and whole canopy photosynthesis of dwarf wheat. - PubMed - NCBI
"Canopy level photosynthetic rates of plants developing in microgravity at approximately 280 micromol m(-2) s(-1) were not different from ground controls."

 

[moon]

That's a claim not a fact. You've shown no evidence to support it and you've been shown evidence to contradict it: physics question



There may be more to it but a quick search suggests it's not...

Effects of the Extraterrestrial Environment on Plants: Recommendations for Future Space Experiments for the MELiSSA Higher Plant Compartment
"Plant gas exchange, metabolism, and photosynthesis mechanisms were not affected by microgravity when provided with satisfactory environmental control"

https://lsda.jsc.nasa.gov/Experiment/exper/508
"There was no difference to ground controls when measured for canopy level photosynthetic rates"

Microgravity effects on thylakoid, single leaf, and whole canopy photosynthesis of dwarf wheat. - PubMed - NCBI
"Canopy level photosynthetic rates of plants developing in microgravity at approximately 280 micromol m(-2) s(-1) were not different from ground controls."

But, but, but..
Brassica rapa plants adapted to microgravity with reduced photosystem I and its photochemical activity.
Brassica rapa plants adapted to microgravity with reduced photosystem I and its photochemical activity. - PubMed - NCBI

 

[NoXion]

One paper versus three, meaning 75% of all studies considered showed no significant effect. It's not enough papers in total to be conclusive, but there are definitely more data points in favour of one interpretation over the other.

 

[moon]

The number of studies has zero relationship to the fact that the phenomenon may be occurring, are you saying that unless a paper has been written it didn't happen?
Besides all the papers that mention no change in photosynthetic rates compared to ground controls have obviously not taking into account the Brassica rapa study.

 

[NoXion]

The number of studies has zero relationship to the fact that the phenomenon may be occurring, are you saying that unless a paper has been written it didn't happen?
Besides all the papers that mention no change in photosynthetic rates compared to ground controls have obviously not taking into account the Brassica rapa study.

You can't generalise from a single study.

 

[Signal 11]

It's probably still early days with the plant experiments. I'll be surprised if lack of gravity turns out to have much effect on photosynthesis, but some things will probably need it for strength. They will be able to use rotation for it if it's needed so it shouldn't be a big deal.