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About Neil9327

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  • Birthday 08/05/1970

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  • Location
    London, UK
  • Interests
    Wacky science and engineering ideas
  • College Major/Degree
    Cambridge University, UK
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  1. That's true - but slightly misses the point - probably because I haven't explained it properly. Climate change. Could you grow plankton or other biomass on the surface of the oceans to cover them completely, with the aim being to absorb carbon dioxide from the atmosphere at a much greater rate than algae can under the water? For two reasons: 1. At the surface there is greater availability of CO2 from the air compared to the water, because fresh air carrying new CO2 arrives constantly by the wind, whereas dissolved CO2 has to make its way to the plankton via diffusion, which is a slow
  2. That's interesting. Quoting from that Wikipedia page, it says: "Phytoplankton account for about half of all photosynthetic activity on Earth". Now, I wonder how efficient that process is? It occurs to me that for ocean phytoplankton to photosynthesize light, that light has to first travel through a certain distance of water. But (from: https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water), we know that a fair amount of the light will instead be absorbed by the water and dissipated as heat, before it has a chance to reach a phytoplankton cell. I wonder whether the efficie
  3. Maybe. How would you hold the sheets in position though, and stop them either rising to the surface (where they might dry out) or moving deeper into the ocean?
  4. Ah yes, nutrients. That would explain it. Thanks! Now that example you have given, about lava added to water giving rise to chlorophyll, is interesting. "Once the lava stopped flowing into the ocean, the patch dissipated within a week" I wonder why this was? One reason might be that the plant growth used up all of the nutrients, leaving none left to support additional growth. But I think the more likely explanation, perhaps, is that the nutrients diffused away in every direction until they became too dilute for the plants to use - and growth stopped. I wonder wh
  5. This is a question that has puzzled me for some time. It is that on land in every part of the world where there is abundant water and sunlight, there is vegetation everywhere (rainforests typically). But on the oceans in the same parts of the world (tropical and equatorial regions) there is typically very little, if any, floating seaweed. Given that floating seaweed is able to live in salt water, has access to abundant amounts of water (obviously), and has the same access to the air to support photosynthesis, why hasn't floating seaweed grown to the same extent as the plants on land?
  6. Is there a link here? So on the one hand, the energy stored in the electromagnetic field created by a (constant DC) current passing through a coil (from its inductance L), and the kinetic energy of the electrons themselves passing around the link. And a follow-on question (assuming no such link) is whether there is any effective contribution to the inductance of a wire from the kinetic energy of the electrons in the (constant DC) current flowing through it. What are the equations?
  7. I think I've got it now, after reading this .doc file. It is all to do with the fact that the accelerating twin starts to receive faster return time pips immediately after the change in velocity (the turnaround) whereas the stationary twin has to wait for <distance>/c until they see the turnaround and start getting the faster blips. It is weird yet so simple to conceptualise once you've "got it". I wrote my own version of how this happens using my Andy&Brian scenario without using worldlines, but I now see that Janus's post above explains it more succinctly than I have. Still
  8. So are you saying that during these one-second periods of acceleration of the travelling twin, that time speeds up? (the time of the stationary twin as observed by the travelling twin) Below are some notes in italics I wrote, to follow up my question - am I on the right lines here? OK so we are agreed that in my scenario that at the end of the journey, Brian and Andy (now standing next to each other) will look at their respective clocks and see that Brian's only shows 100 days (100 pips), and that Andy's shows 200 days (200 pips). And that this is because Brian's movement and heavy acc
  9. Special relativity says that a clock on a spaceship moving relative to a stationary observer appears to be running more slowly than if it was stationary. So if this is true, what would you get in the following scenario? Stationary observer Andy and moving observer Brian are both initially stationary and in the same location, and each has an atomic clocks measuring time in days, and displaying what they can see on a large monitor visible to both. In addition both clocks emit an electronic "pip" whenever one day passes to the next, and each records the number of pips made since reset. Day =
  10. I asked this question a week ago or so on Yahoo Answers (OK don't scoff). Got 10 replies http://uk.answers.yahoo.com/question/index;_ylt=AgMMhwzI6WpSsLJz.m3smFAhBgx.;_ylv=3?qid=20100212145607AAtahRr
  11. http://en.wikipedia.org/wiki/Trinity_(nuclear_test) On the right of the link is a photo taken a few milliseconds into the Trinity atom bomb test. You can see the smooth surface of the fireball shock wave expanding out, and you can see the rough dusty base where it (presumably) is interacting with the ground. But what is the paler band between the two? Also there are some blotches on the surface of the fireball. Are these as a result of the tower or bomb casing perhaps?
  12. Interesting. This raises a question: Discounting the moon's gravity, is there any centrifugal force experienced by someone on the moon's surface by virtue of the rotation of the moon?
  13. If the entire mass of the universe was compressed into a single point, it would form a black hole. What would be the radius of its event horizon? I calculated this from a mass of the universe of 10^52 kg, and it came out as around 10 billion light years. Is this right? If it is right then perhaps the whole universe is inside its own black hole. In which case where abouts is the singularity, and why aren't we sucked into it?
  14. You say that rocket B only has to give rocket A 1000 joules to accelerate B from 10 m/s to 20 m/s relative to earth (0 to 10 relative to it). But this isn't true, due to the conservation of momentum: What would happen is that rocket B would be slowed to 5 m/s and rocket B to 15 m/s because the effort of pushing forward A would equally push back B. So the combined kinetic energy of the two rockets relative to earth would be: 0.5 * 20 * (0.5)^2 + 0.5 * 20 * (1.5)^2 = 0.5 * 20 * 0.25 + 0.5 * 20 * 2.25 = 2500 Joules. Hmmm seem to have got something wrong here. But there is more to it th
  15. wow I didn't realise that the rate of flow was proportional to the square root of the pressure differential. That definitely makes it more complicated. This all started with an arguement I was having with my mother about whether you can water plants faster holding the watering can still, or whether to swing it to and fro. I'm still not sure. Could someone please do an integration of the square root function - that must surely reveal the answer to the question - it was too long ago when I studied integration. Thanks:D
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