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Everything posted by StringJunky
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Why 2 men can't lift a 2 ton car but can push it for even 1000 meters
StringJunky replied to shaks's topic in Physics
What's that got to do with anything? It was a thought experiment. You disagreed that the force of gravity was too high on Earth and I illustrated that it is. Weight is function of gravity. Note that I didn't say 'mass'. -
When you define some thing like time it must encompass everything and the problem with using 'change' in a definition is it doesn't, for example, cover the spontaneous decay of a radioactive atom. It decays in an unpredictable manner, when viewed as a single unit, but time still passes until it does.
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Why 2 men can't lift a 2 ton car but can push it for even 1000 meters
StringJunky replied to shaks's topic in Physics
If the two people were very strong, they could probably lift a car of 2000kg (Earth weight) on the moon since the weight - which is due to gravity - would only be 1/6th of that on Earth ie about 300kg each. -
Why 2 men can't lift a 2 ton car but can push it for even 1000 meters
StringJunky replied to shaks's topic in Physics
Yes, it becomes a car3 -
Why 2 men can't lift a 2 ton car but can push it for even 1000 meters
StringJunky replied to shaks's topic in Physics
They can't lift it because the force of gravity is too high but they can push it because that force is mediated by the wheel assembly so all they have left to overcome to move perpendicular to the gravitational force is the inertia. Once this is overcome that effort is stored as momentum and that's what keeps it going and makes it feel easy; in gravity-free space that stored momentum would keep the car going indefinitely without any more pushing because there aren't any frictional forces to slow it down. -
Aim to answer a scientific question within the attention-span of your audience; addressing only the salient points. After that let them ask more questions to fill the gaps. This way you are actually having a conversation instead of presenting a lecture.
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Yes, the steps of progress have become shorter...and shorter. The christamas tree has been erected and now we are hanging the decorations.
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Haven't we been here before?
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The thing is though that most things now aren't paradigm-changing ideas and that's probably what the OP alludes to. i think it's just too technical now for casual readers for the most part.
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The first thing that I notice is that the RAM in your machine is way too low for Windows 7. It wants to be at least 1GB preferably 2GB as a minimumum. Your computer is just going to run a bit and then hang then run all the time whilst it swap files info between the RAM and virtual hard drive it has to use because there isn't enough RAM. As a speculation, your connection might be timing out because your computer keeps hanging from the VERY low RAM.
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If you clone cells from a person who is fifty years old the age of the baby they are made from starts at fifty years old and all the concomitant issues that go with that age appear prematurely. The baby's biological clock is not set to zero in cloning. Is it ethical to condemn a person to a preset shortened lifespan? "...But in January, the first mammal cloned from an adult cell, Dolly the sheep, was reported to have prematurely developed arthritis." "Ogura's team cloned 12 male mice and these were compared with seven males from natural matings and six others produced using in vitro fertilisation. The clones appeared active and healthy, gained weight normally and matched the control animals in 14 of 16 physiological measurements. But the first cloned animal died after only 311 days and, by day 800, 10 (83 per cent) of the animals were dead. In contrast, only three (23 per cent) of the controls died during the same period. The dead clones showed high rates of pneumonia, liver disease, cancer and a lower level of antibody production, suggesting they had an immune system defect". http://www.newscientist.com/article/dn1903-cloned-animals-meet-early-deaths.html One or two of the problems expressed in the mice in this research might be inherent in the methodology used but some of those are also likely to be down to the advanced preset age of the cloned subjects.
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Stochastic vs Natural Selection
StringJunky replied to StringJunky's topic in Evolution, Morphology and Exobiology
If they want to do that they are welcome. I'm happy with the answers now I've received so if you want to take it further I don't mind. -
Stochastic vs Natural Selection
StringJunky replied to StringJunky's topic in Evolution, Morphology and Exobiology
What do you mean? -
Does evolutionary theory need a rethink?
StringJunky replied to starlarvae's topic in Evolution, Morphology and Exobiology
Confirmation bias would be the potential problem there wouldn't it? If one pursues a line of research that ignores, or doesn’t test for, one of the two possible causes then it’s obvious what the outcome will be. -
Stochastic vs Natural Selection
StringJunky replied to StringJunky's topic in Evolution, Morphology and Exobiology
Understood. Cheers. -
Stochastic vs Natural Selection
StringJunky replied to StringJunky's topic in Evolution, Morphology and Exobiology
So, soot is a selective pressure because it advantages dark moths and therefore not stochastic. -
Stochastic vs Natural Selection
StringJunky replied to StringJunky's topic in Evolution, Morphology and Exobiology
Thanks Is there a distinction between the soot and the predatory element in the selection process or are they both classed the same? A stochastic event causes population change regardless of genetic makeup? -
Stochastic vs Natural Selection
StringJunky replied to StringJunky's topic in Evolution, Morphology and Exobiology
I was seeing the sooting as a random effect. which happened to cause a change in the choice of the predators. The predators caused the actual change in the allele frequency not the sooty environment the predator and prey exist in. I'm not arguing, just putting up a scenario that I have a rudimentary familiarity with as a focus for learning the difference. -
Spooky alignment of quasars across billions of light-years
StringJunky replied to StringJunky's topic in Science News
Exactly my thoughts. It's nice when something as big and complex as the universe has some linearity in it to focus on. -
In the evolution of the changing prevalence of the colour of peppered moths in the industrial revolution – light versus dark - was the sooted surfaces of their habitats a stochastic effect or classed as natural selection? To my mind the sooted surfaces is stochastic and the predation on the poorly camouflaged whites was natural selection. Is this correct?
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New observations with ESO's Very Large Telescope (VLT) in Chile have revealed alignments over the largest structures ever discovered in the Universe. A European research team has found that the rotation axes of the central supermassive black holes in a sample of quasars are parallel to each other over distances of billions of light-years. The team has also found that the rotation axes of these quasars tend to be aligned with the vast structures in the cosmic web in which they reside....Read More>>> Arxiv: Alignment of quasar polarizations with large-scale structures
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Temperature as a function of pressure?
StringJunky replied to Science Student's topic in Homework Help
I was curious about this question and what happened at the molecular level so I looked it up. When you increase pressure the velocity of the enclosing moving surface(s) adds momentum to the molecules that collide with it and hence heat; rather like a swinging bat hitting a ball as opposed to a balll bouncing off a stationary wall. The heat rise will only be temporary however due to the usual heat loss pathways. -
Temperature as a function of pressure?
StringJunky replied to Science Student's topic in Homework Help
I think the OP is but doesn't realise it but that's what it necessitates if one is to increase the temperature via increasing the pressure...it seems to me anyway. -
And you can control amounts or omit ingredients
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A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of a star's rays, preventing them from hitting a planet and thereby reducing its insolation, which results in less heating of the planet. A sunshade is of particular interest towards mitigating global warming through solar radiation management. Such shades could also be used to produce space solar power, acting as solar power satellites. Proposed shade designs include a single-piece shade and a shade made by a great number of small objects.[citation needed] http://en.wikipedia.org/wiki/Space_sunshade