Jump to content


Senior Members
  • Posts

  • Joined

  • Last visited

  • Days Won


Prometheus last won the day on July 14 2021

Prometheus had the most liked content!


Profile Information

  • Interests
    Building statistical models for Raman spectroscopy.

Recent Profile Visitors

24949 profile views

Prometheus's Achievements


Primate (9/13)



  1. Is immune and hormonal response physical enough? This review has a nice little section on it. I think the line between psychological and physical is a little more blurred than our Western dualistic upbringing would suggest.
  2. We really know nothing about the effect of low gravity on the body. What research we have regards the micro-gravity environments of LEO. It would be folly to interpolate between these 1G and 0G environment data points. Another reason to go to the moon first, and get intermediate data points.
  3. That was from the 2015 study I gave. They didn't get those number themselves but provide these references to justify it: Seifritz W. Mirrors to halt global warming? Nature. 1989;340(6235):603. 10.Early JT. Space-based solar shield to offset greenhouse effect. Journal of British Interplanetary Society. 1989;42(567–569). 11.McInnes CR. Minimum mass solar shield for terrestrial climate control. JBIS. 2002;55(9–10):307–11.
  4. But it would threaten to knock the structure off the L1 point and so require a significant amount of fuel to keep it in place.
  5. Why the equator? I thought the Earth's tilt took it out of the ecliptic plane?
  6. Additionally geostationary orbit wouldn't work. This orbit means an object is always above the same point on Earth which means at night time its pointing away from the sun.
  7. I remember seeing a back of the envelope calculation that estimated the amount of mass needed for such a shade to be effective at cooling would require an orbital infrastructure of epic sci-fi proportions (and didn't even attempt to calculate the warming caused by building a launching all those rockets). I think it was a science communicator called Scott Manley if you want to have a google around to find it. Can't find it, but i have an envelope handy. Found this study that estimated the mass of a sun shield needs to be 10^7–10^8 tonnes. Let's take 10^7. That's 10^10 kg. The current cheapest vehicle per kilo is currently the Falcon 9 at $1400 per kilo. The cost of just launching this structure would be $14 trillion. Pretty expensive but economically possible i guess, if we ignore politics. A Falcon 9 can launch 22,800 kg per launch, which would require ~ 440000 launches. Space X have one of the best launch cadences in the world but only managed 31 last year. If we started now we might get it done in 30 years if we can increase the launches to 15000 a year. Apparently a Falcon 9 produces 360,000 kg of C02 per launch. So we'd be adding 10^11 kilos, or 10^8 tonnes, of C02 into the atmosphere by the end of the project. All this is based on costs to launch to LEO. L1, the most feasible place it could sit, would be far more expensive (both $ and C02) - but those numbers aren't so easy to get. I conclude that it's not feasible with current tech, and by the time it does become feasible it would be too late to significantly contribute i.e. the damage would be done. But feel free to check these numbers because i haven't.
  8. I heard that its lifespan, if all goes well, will be determined by the amount of fuel it has to keep it in its L2 orbit - because the Ariane 5 rocket did such a good job on its infection burn that is anticipated to be 10 years.
  9. By convention, in the fields i'm familiar with - medicine, biology and computer science - the first author will have contributed the most and the last author will be the most senior academic, usually the head of a lab. The middle authors will have contributed the least. I've been on papers where the squabbling of who goes where on the author list gets pretty intense and petty. Many publications require that the contribution each author makes is explicitly stated, unfortunately PLOS biology doesn't seem to be one. Karl Friston is a pretty reputable name though, I can't believe he would have tolerated too much jockeying.
  10. Accuracy is a terrible metric to assess these things: fine for classifying dog and cat images, but for law and health it misses so many nuances. There's also no mention of how well the AI generalises to data not in the original train/test distribution. I can't find the original publication, if it has been published in a peer reviewed journal, so can't dig into any details. Until then I wouldn't believe these numbers any more than my claim that i just developed an AI with 99.56% accuracy for predicting a bull's bowel habits.
  11. Ghana were awarded a penalty, which they missed. The game then went to penalties and Suarez, who was one of their main penalty takers, couldn't take one, so there were plenty of downsides, Ghana were just unable to capitalise on them. Additionally, Suarez was banned from the semi-final against the Dutch, which Uruguay lost. As to whether it's right - i can see both sides, but seeing Suarez celebrate the penalty miss was pretty galling.
  12. I've not the foggiest. Check out the lecture - The Royal Institution has a good reputation so i presume he's not talking total quack. As i remember he just mentions it near the end without many details.
  13. There are perhaps lessons we can learn from cellular automata - take rule 30 for instance. The generating process is perfectly known and simple, yet the manifestations of it are anything but. The central column the rule produces can only be modelled as a stochastic process (currently - £10k prize if you prove otherwise), so much so it is used as the random number generator in Mathematica. We could say that, in this case, the randomness is emergent from the rule. There was an interesting Royal Institute lecture on time - the lecturer ended by speculating that time was an emergent property based on our psychology - or something close to that effect..
  14. Putting aside that i know no physics - perhaps we can think of it in terms of how we model phenomena. Taking the Mexican wave as an example, each person could be understood in terms of simple up and down motions, but to capture the wave we might want to use sinusoids (ignoring that we might use sinusoids to understand the initial up and down motion). So a property is emergent when we decide, for whatever reason, to apply a new model to understand it. Emergence then isn't a property of the universe, but a property of how we understand it.
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.