Trees grow layers on the outside, just underneath the bark. This is the only part of a tree trunk that is actively growing and is part of the plant’s circulatory system. All the older wood toward the center of the tree is basically only structural support.
There’s a technique called “collaring” used to remove invasive trees, if you cut a shallow, 4 inch tall ring from the bark around eye level, everything above that ring will die, because you’ve severed the circulatory system between the roots and everything above the collar
So, the inner rings are actually the oldest. I’m no botanist, but I know that with your average deciduous tree, you have a layer right between the bark and first wood layers, and that thin layer is where the cell division for growth is mostly occuring. So, it actually is the exterior, just right beneath the bark.
Other kinds of plants are probably different, and again, I’m no botanist. Just have some basic biology study.
Generally in trees you have the xylem in the middle which transports water and minerals from the roots to the rest of the plant. You have the phloem on the outside, it transports photosynthetic products and nutrients to all parts of the plant. The cambium where growth happens sits between them, because there they get easy access to water minerals and nutrients. The xylem is a mix of living and dead cells. The tracheids and vessel elements in the xylem, which are responsible for water transport, are dead at maturity. So it’s probably too hard to move them to grow from the inside out for trees. This whole process of growing thicker is called secondary growth as opposed to primary growth at the tips of stems and roots.
Also if were the other way around and trees would grow from the inside out, you’d have to have vessels going from the leaves to the center of the stems to deliver nutrients, which just complicates everything. And the tree wanted to grow from the inside by 1cm, every “ring” in the xylem would have to grow one centimeter longer in circumference or crack. It’s much easier to just add a layer on the outside. Also having living layer around the tree probably helps it defend itself from pathogens. If all the mostly dead woody stuff was on the outside fungi etc would have an easier time invading, I think.
OP phrased it weirdly but what they mean is that trees have all growth happen at the surface, not in the middle.
which is actually the opposite of how our skin grows, skin cells grow at the bottom of the skin and are pushed upwards by the new growth and mature as they go, until they reach the surface and die so that they can protect us and easily be shed to make space for new cells.
which is why you’ll see hollow trees being perfectly happy and healthy, whereas a human with an empty space underneath their skin is going to be uncomfortable at best.
Yeah my question was wrongly put but I thought trees did what you described skin does: I thought new tree cells were created in the middle and the outermost layers were the oldest ones.
well i’d say that trees grow in both ways: the stem grows on the outside because it’s acting more like our bones, but the bark acts like our skin and indeed grows in the same way, new matter being created at the base and pushed outwards, hence why a lot of bark has tons of cracks in them from the stretching.
I suspect the answer here is yes, and there’ll be a lot more hydrogen and oxygen in the star afterwards… but really I’m posting to see what a proper scientist will say.
Am keen to know if this would pretty much include anything. For example, if I gathered a great enough density of chocolate eclairs in one place, would that become a star?
I believe anything lower from iron will make a star, when enough material added. Of course, one material from iron will give a much smaller lifespan for a star rather than hydrogen only.
I think that an iron ball wouldn’t start a fusion. Might just jump right to a black hole if you added even more iron 🤔
There is a way to find that out. We can use Schwarzschild radius to find the point at which an objects radius crosses the event horizon and thus becomes a black hole; Rs=2GM/c^2^, Rs being the Schwarzschild radius, G being the gravitational constant (6.67xe^-11^), M being the things mass, and c being the speed of light.
Stars have a lot of mass. The Sun loses almost 5 billion tons of mass every second and has enough fuel to last another 4-5 billion years. Adding a single ton of anything would make no appreciable difference. If you were to drop Jupiter into the Sun, it would have an effect, but Jupiter is only 0.09% the Sun's mass, so the effect would be small.
Depending on how you define a star, you could smush ~13 Jupiters together and make something that is maybe a star. To make a definite star you need ~80 Jupiters. To make it the same size as our Sun you’d need almost 250 Jupiters.
A literal ton wouldn’t do anything measurable but yeah, adding more material of lower atomic numbers would in theory work considering it’s a fusion engine and wouldn’t exactly scoff at having to break the water molecule before using it.
Edit: like maybe if there was a star with a bunch of particularly wet planets around it and you somehow deorbited them, since as far as I’m aware the elements heavier than iron are just dead weight, they wouldn’t put out the star or anything.
I mean, if you add enough iron I believe it would eventually disrupt fusion, but you’d need an incredible amount, far more than you’d ever get from orbiting planets.
As I understand it, the problem isn’t the presence of iron, but rather when it starts fusing silicon into iron, as that particular process consumes more energy than it releases, thus eating away at the radiation pressure that keeps the star “held up.”
I was thinking that the added inert mass would decrease the likelihood of individual fusion reactions as well as eventually overpower the radiation pressure due to its effect on total gravitational force, but honestly I don’t really know what I’m talking about so I could be completely wrong.
Your question made me realize I had never thought about this at all so I spent some time searching. If I am understanding this article correctly it essentially boils down to the factors that would cause rotational symmetry at a smaller scale ie spinning sand on a plate apply at the galaxy scale as well.
The fact they spin and the bits interact gravitationally makes them symmetric. There are almost certainly some asymmetric galaxies as we know galaxies collide and they will be asymmetric for a bit afterwards, but the spinning and fiction of gravity will make them symmetric again fairly quickly on galactic time scales.
I believe there have been multiple sci-fi stories written about such concepts. It would go to assume that any civilization still around in 10^43 years from now will have no choice but to live around black holes while harnessing their rotational energy. My current favorite series, Xeelee Sequence by Stephen Baxter, explores some possible endings of life in the long-term life cycle of the universe. There is also the final book of the Three Body Problem, which if I remember correctly, shows civilizations in pocket universes around black holes.
There is a YouTube video you may want to watch by Isaac Arthur. It mentions the possibility of combining black holes to elongate their life, and I won’t spoil the final answer for you. But like always, entropy prevails.
There’s a lot of oxygen in water by star standards, so keep that in mind. It’s possible the change in metallicity will offset any change to equilibrium temperature, although I don’t really know the details.
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