Science questions not worth a thread I: I'm a moron!
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So the staright walls would bulge out and the corners bend in? That would make sense.
Don't be sorry, what you said in the previous post was informative in many ways.
As to why? Not sure, sorry.
Don't be sorry, what you said in the previous post was informative in many ways.
Mise
isle of lucy
Yeah, what Cutlass said is what I was thinking too. So if you blew up a balloon into cube, the balloon would hit the centre of the walls first, exerting a force F on the centre of the wall. Now let's say the wall is 2w long: you now have w x F torque acting on the corner of the wall. So the bigger the cube, the more torque acting on the corners, the more likely it is to break at the corners, right?
That's modelling it in a "best case" scenario too, where there is zero force on anywhere other than the centre of the wall. While Atticus's argument might mean that the corners have less force acting on them directly, there's still quite a lot more energy ending up on the corners (due to [slightly less] direct pressure + torque) than on the centre of the wall (due to direct pressure only). Right????
How much $%^& am I talking here you guys?
That's modelling it in a "best case" scenario too, where there is zero force on anywhere other than the centre of the wall. While Atticus's argument might mean that the corners have less force acting on them directly, there's still quite a lot more energy ending up on the corners (due to [slightly less] direct pressure + torque) than on the centre of the wall (due to direct pressure only). Right????
How much $%^& am I talking here you guys?
madviking
north american scum
the way i'm thinking about it is that each corner has three faces pulling on it in three different directions.
In the conditions we are most probably talking about, this argument does not hold, anyway. The pressure should be the same on any surface.
The pressure should be the same. But materials and manufacture method would matter.
If, for example, your material was aluminum, if you started with sheet aluminum and made a fold in it for a corner, then you have already stressed the material at that corner. And if you stress it again and again, pressurizing and depressurizing the container, then you're repeatedly stressing a weak point. My landlord would have called that low cycle fatigue. He worked for 40 years in the failure analysis lab at Pratt & Whitney. Eventually running that department. But if you were doing cast aluminum, now the corner is rigid, but is also more brittle. So you can't flex that corner back and forth without stress fractures.
This may not hold true with all materials, I don't know enough to say. But it will with many materials. At least with the materials that are most common for use in a container.
If, for example, your material was aluminum, if you started with sheet aluminum and made a fold in it for a corner, then you have already stressed the material at that corner. And if you stress it again and again, pressurizing and depressurizing the container, then you're repeatedly stressing a weak point. My landlord would have called that low cycle fatigue. He worked for 40 years in the failure analysis lab at Pratt & Whitney. Eventually running that department. But if you were doing cast aluminum, now the corner is rigid, but is also more brittle. So you can't flex that corner back and forth without stress fractures.
This may not hold true with all materials, I don't know enough to say. But it will with many materials. At least with the materials that are most common for use in a container.
hobbsyoyo
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A lot of materials are stress-relieved after being formed into their near-net or net shapes, fyi. There are multiple ways of doing this (shot peening, heat treating, acid bathes, etc) and these methods relieve much of the stress induced by manufacturing.
Dark matter and dark energy seem to pervade the universe and most likely we are immersed in both. Why is it that their study is left to astro physicists looking millions of light years away and not by, say, biologists? Could we not find indirect evidence closer to home? Or do we need huge volumes to see their effects?
hobbsyoyo
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Part of the problem with dark energy and dark matter is that they are 'dark'. They are not easily observable and in the case of dark matter, we really can only (currently) make indirect measurements of it through its effects. Those effects being principally the gravitational pull exerted by dark matter.
So we can only 'see' dark matter when it tugs on galactic-scale objects. Currently we just don't have any way to observe it on smaller scales which would preclude biologists from studying it.
So we can only 'see' dark matter when it tugs on galactic-scale objects. Currently we just don't have any way to observe it on smaller scales which would preclude biologists from studying it.
That would provide an excellent opportunity for some entrepreneurial physicist
Biologist do not understand biological systems well enough to be remotely able to detect any subtle influence dark matter could have.
There actually are several experiments working in underground laboratories that try to detect dark matter here on earth. Whether these experiments will ever detect an unambiguous dark matter signal remains to be seen.
So do physicists recognize that dark energy and dark matter are "within us and without us" doing whatever it does? Would my "human space" be 73% Dark Energy; 23% Dark Matter, 4% "normal matter"?
They recognize the possibility and are trying to test that. There are different hypotheses out there, where dark matter and dark energy occur. Some say it is ubiquitous, others say it accumulates at certain places. But they will try to explore any possibility of detecting dark matter on earth.
Disclaimer: For most of these questions, the answer is going to be "we just don't know (yet)".
The normal matter in the universe is very much localized in certain spots. The distance between the earth and the moon is much larger than the size of the earth, and our solar system is mostly empty. A small part of the volume contains almost all of the mass. (Occupy would be angry.)
The same pattern holds true at larger scales, for example on the scale of galaxies. There are some areas that have a lot of mass but most areas are 'empty'.
As far as I know, the current hypothesis with regards to Dark Matter is that it less concentrated and distributed more uniformly. In particular, our galaxy is a disk but the dark matter around it is much more spherical. (see e.g. http://en.wikipedia.org/wiki/Dark_matter_halo)
member66170
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I read of an experiment, either on going or proposed to try and map the distribution of dark matter within the Sun. So physicists are looking at Dark matter on every different kind of scale they can think of.
Dark energy we know diddly squat about. There aren't even any theories that make any sort of concrete predictions about. Dark matter we at least have some ideas what it *could* be.
Dark energy we know diddly squat about. There aren't even any theories that make any sort of concrete predictions about. Dark matter we at least have some ideas what it *could* be.
Other than apples falling on heads, do we know how else gravity affects cells or cell activity?
There are probably more, but just as an example, some plants need gravity to know in which direction to grow.
So how can we use that bit of knowledge to formulate some thoughts on how dark matter affects gravity which affects affects plants? Would plant experiments at the ISS be useful?
Do we have the means/evidence to connect particle/quantum physics to cells? If not, what is needed?
Do we have the means/evidence to connect particle/quantum physics to cells? If not, what is needed?
Not at all. The plant just cares about the gravity, no matter where it is coming from. In principle you could try to build a gravity sensor with plants and discern that gravity is different what you would expect from normal matter. But such a sensor would certainly be worse than a normal gravity sensor, so there would be little point in doing that.
Yes. For example, there is evidence that quantum effects are used to enhance energy transfer in photosynthesis. But for a long time, people believed that there could not be any quantum effects in biological systems, so the field of quantum biology is in its infancy.
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