Science questions not worth a thread I: I'm a moron!

[hobbsyoyo]

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?

They do perform plant growth experiments on the ISS but AFAIK they have nothing to do with quantum biology.

 

[Birdjaguar]

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.

Yes when i heard about quantum effects related to photosynthesis a while back I was very excited. I've nothing more though. IIRC it was related to entanglement.

 

[Samson]

Yes when i heard about quantum effects related to photosynthesis a while back I was very excited. I've nothing more though. IIRC it was related to entanglement.

I think it is quantum tunneling through the photosynthetic complex. I am not at all sure, but I think while the whole process of energy transfer down the various chromophores from initial photon capture to electron transfer is down the energy gradient, there are significant energy "cliffs" that would make it it occur too rarely if quantum tunneling did not occur. Or something like that.

 

[uppi]

I think it is quantum tunneling through the photosynthetic complex. I am not at all sure, but I think while the whole process of energy transfer down the various chromophores from initial photon capture to electron transfer is down the energy gradient, there are significant energy "cliffs" that would make it it occur too rarely if quantum tunneling did not occur. Or something like that.

I would not call it quantum tunneling. It is about finding the most efficient way through a disordered potential. It is also not a pure quantum effect, because that would lead to Anderson localisation, which would negate the advantage. It uses the decoherence inherent in a biological system to overcome the localisation.

 

[daft]

Could anyone light up some knowledge about possible type(s) of fuel needed for spacecraft to enable quick and safe travel for earthlings to other planets in our solar system and beyond.

 

[Arakhor]

There's no such thing as 'quick' in space without using superscience devices.

 

[Cutlass]

Hydrogen fusion is the best that any current theory could call realistic. Unless you can get to antimatter. But from what I've heard, the making of antimatter is prohibitive.

 

[uppi]

Hydrogen fusion is the best that any current theory could call realistic. Unless you can get to antimatter. But from what I've heard, the making of antimatter is prohibitive.

Current designs of energy generating fusion reactors are way to massive to use it on a spaceship. You could hope for the development of a compact fusion reactor in the future, but you could also hope for a device that efficiently produces antimatter. I am not sure which has a better chance of success.

 

[Cutlass]

Current designs of energy generating fusion reactors are way to massive to use it on a spaceship. You could hope for the development of a compact fusion reactor in the future, but you could also hope for a device that efficiently produces antimatter. I am not sure which has a better chance of success.

Wouldn't a fusion reaction engine be less massive than a fusion reactor? It doesn't have to contain the reaction, it just has to channel it in a specified direction.

 

[Michkov]

Antimatter, fussion, fission, chemical in that order if you want to carry the fuel onboard. Have a look here for a list of engine/fuel combinations

 

[uppi]

Wouldn't a fusion reaction engine be less massive than a fusion reactor? It doesn't have to contain the reaction, it just has to channel it in a specified direction.

For fusion reactions to occur you need a very hot plasma. You need to contain the plasma long enough in such a state that you can recover the energy spent heating it. To actually gain energy you want the plasma to ignite, so that the heat from fusion reactions heats the plasma enough to keep the reactions going. So you could make a small hole to spew out plasma in a certain direction to accelerate the spaceship, but you still need the confinement and I do not see a reason why it could be considerably less massive.

 

[El_Machinae]

Well, then you just need a bigger spaceship to justify the engine size!

 

[hobbsyoyo]

Could anyone light up some knowledge about possible type(s) of fuel needed for spacecraft to enable quick and safe travel for earthlings to other planets in our solar system and beyond.

Fission-based designs are really the only viable way to do relatively fast way to get to other planets in our solar system.

There currently isn't any viable designs for interstellar travel as you'd need a prohibitively massive fission based system to get to other stars and even then you'd be going pretty slowly.

Fusion designs don't work because we can't make fusion work well enough at the moment. Antimatter designs are the stuff of science fiction as we can't produce antimatter or store it in the quantities we would need it at. There are some electric-based designs that could provide for relatively quick travel times to other planets such as VASIMIR but they're still in the R&D phase and many people just think they won't work.

Wouldn't a fusion reaction engine be less massive than a fusion reactor? It doesn't have to contain the reaction, it just has to channel it in a specified direction.

Fusion reactors still produce radiation using the types of fuel available (read: NOT He3), so you'd still have to protect the engine from degradation caused by that.

For fusion reactions to occur you need a very hot plasma. You need to contain the plasma long enough in such a state that you can recover the energy spent heating it. To actually gain energy you want the plasma to ignite, so that the heat from fusion reactions heats the plasma enough to keep the reactions going. So you could make a small hole to spew out plasma in a certain direction to accelerate the spaceship, but you still need the confinement and I do not see a reason why it could be considerably less massive.

Pretty much this. Though if you dump the requirement that you need to have a fusion reactor that is power-positive, then you could conceivably construct a fusion reactor used to drive the spaceship that makes up for being power-negative by being powered by a fission reactor. I think this could work for solar exploration though I'm sure it won't work for exploring other solar systems as you'd need too large of fission reactor (and it's fuel) to power the contraption across interstellar distances.

As for the logistics of a fission/fusion system, well they are somewhat answered by this:

Well, then you just need a bigger spaceship to justify the engine size!

_____________________

For further reference, actual nuclear fission-powered rocket engines were produced and tested in the 60's as part of Project Rover. The final models had somewhat OK thrust/weight ratios (and further research in the 80's as part of the Star Wars program made the ratios even better and modern designs would be better still if we chose to go this route) and were planned as 'drop in' replacements for the 3rd stage of the Saturn V. Such an arrangement or similar arrangements would have made exploration of the solar system viable.

A fission based system essentially uses a nuclear reactor to heat hydrogen propellant to super-high temperatures (higher temps = greater efficiency) but in the process irradiates the propellant and also emits radioactive bits of uranium or other radioisotopes that escape via the propellant. Plus, the engines are relatively heavy so they aren't so useful for launch vehicles. But as an upper stage or interplanetary transfer stage, they are very, very useful and much better than any chemical system.

Basically, nuclear fission can work and has been tested but political considerations and public fear of anything nuclear has prohibited any country from seriously developing or using these systems since the 60's.

 

[daft]

Thanks!, I appreciate the responses/answers.

That story about the anomaly found last year on the bottom of the Baltic is just a YouTube scam?

Are robots going to replace soldiers in the future? (are such designs already underway?)

 

[Timsup2nothin]

Are robots going to replace soldiers in the future? (are such designs already underway?)

In the most tech advanced countries unmanned air vehicles (UAV) have already taken over many mission functions formerly filled by manned aircraft. I would have to assume that unmanned ground vehicles that could make inroads into land mission functions are being actively pursued. If that counts as 'robot soldiers' would be a matter of definitions.

 

[Cutlass]

Is there a theoretical upper limit on how large an implosion type atomic bomb can be?

 

[dutchfire]

I would expect that all of the pre-implosion pieces have to be less than critical mass, which puts some severe engineering constraints on the size of the total thing.

 

[Flying Pig]

Could you not theoretically increase the number of pieces ad infinitum, though?

 

[uppi]

Could you not theoretically increase the number of pieces ad infinitum, though?

You could, but they also need to be a minimum distance apart to stay below criticality. That means that you have to increase the size if you want to increase the yield. At the same time you need to ensure that the fissile material combines before all flies apart. Given the speed of the explosions that are used to do that, one could probably come up with some theoretical limit, but that would not be an easy calculations and depend very much on the parameters that are assumed.

 

[Timsup2nothin]

So, I have an observed phenomenon and a theory.

Background: I was a pool man for a long time. In the spring I find myself helping out friends in the business who have too much repairs and such. So, black pools. A black pool is actually just dark green, but in the pool biz the term 'green pool' is used for a pool that has somehow gotten out of whack and has started some algae. A black pool is the 'yeah I abandoned it last fall, thought about getting it dosed up with chems before it started getting warm, but didn't, and now it is effectively a stagnant pond of muck...so I called you guys'.

Phenomenon: If you pull out leaves and such with a net when you can't see more than a couple inches into the water you are gonna miss a lot. If you then produce an obscenely high chlorine level in the water all the leaves and such will pop to the surface.

Theory: The chlorine reaction with organic material produces gaseous nitrogen, and at a high enough concentration of chlorine it produces it faster than it can escape the cells so they become buoyant.

I used this theory for years when explaining to customers, who all swallowed it whole as customers should, but I just made it up on the fly one day and it occurred to me today that I don't really know if that's what is happening, and I'm having trouble finding shortcut references to chlorine/organic interactions. It seems like I would need to read entire chemistry texts and just hope they touch on it somewhere. Any ideas?