# Tag Info

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If you are indoors, then... Seal all cracks or openings in the ceiling and in the walls above the mid-point. This includes the gaps around junction boxes and between drywall panels. Caulk and duct tape are your friends here. Extinguish any open flames and get rid of any possible spark sources. No smoking either! Release a quantity of hydrogen equal to 1/2 ...

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In theory the pressure of air decreaes with altitude. So if your balloon is fully inflated, inelastic and does not burst it will float up to a given height and stay there. The problem is that the pressure variation over the range of heights you are working with is tiny. Also the pressure of air is not constant, it's weather dependent. So what can we do ...

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if we confine our discussion to weather balloons, like this one and assume the Ideal Gas Law, we can greatly simplify the problem. The balloon is limp; it is not under tension, and the pressure and temperature of the hydrogen or helium are the same as those of the surrounding air. Assume that we put 2 grams of hydrogen (or 4 grams of helium) into the ...

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You might be interested to have a look at my answer to Why do helium balloons rise and fall? where I answer a closely related problem. The change in bouyancy with pressure depends on how rigid the skin of the ballon is. If the skin is very rigid, i.e. the balloon volume doesn't change as the external pressure changes, then the bouyant force is proportional ...

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If you have a "slack" balloon (one with no elasticity, like is used for some extreme altitude work like the one Felix Baumgartner used for the highest free-fall) then the pressure inside is the same as the pressure outside, and the balloon will not find an equilibrium position due to pressure (the volume of air displaced will change with altitude, and the ...

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Ideal gases (of which real gases are only an approximation) obey the relationship $PV = const$ (at constant temperature). This won't work because pressure falls as altitude increases. As the balloon rises, the pressure outside the balloon falls, and it will expand, increasing its volume, and decreasing the density of the gas inside. In the real atmosphere, ...

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Nope, there's no way for this to work unless you want to tie a string. The reason being this: There's no different between the density of air between 1m to 5m or similar range. So if the balloon's net density is less than that of air, it would continue to rise. Similarly if its more than air's density, it would sink to the ground. The best chance you have ...

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The work being done on the surroundings is because the air parcel expands as the pressure decreases. There would be some heat transfer if the parcel of interest has a different temperature than the surrounding air. This effect is smaller because gases are poor conductors of heat, as mentioned by @gerrit. We take advantage of this with fiberglass and ...

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I'd like to know what would happen if Venus was flung into a highly eccentric orbit like Sedna (except maybe with its current perihelion) with an orbital period measured in thousands of years. It's kind of a weird question but the first thing to consider is whether the orbit crosses any other planetary orbits, cause if it does, the biggest effect of ...

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A star with a temperature of 50.000 °K would have to be much larger than our sun to sustain that rate of fusion, and our Earth as we know it would not exist. It would have to be much further out and it would be unlikely to form a similar atmosphere. There would probably be more ozone as a direct result of more UV to break stuff, though all emission at UVB ...

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To me it's quite difficult to imagine that this greenglow would be caused by atomic reactions, like explained in "Airglow". There are various aspects which speaks against this. Wavelengths emitted from such a reactions, are variable. And this glow is clearly only green. The light emitted from such a reactions are spread to all direction, but this glow is ...

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If you actually look at (atmospherically) scattered light, you will see that even at ground-level, there is a distinct blue tint. How do you see that, you ask? Any old shadow will do - find some building that throws a nice big shadow, make a photo with a decent camera, and analyze it thoroughly - you'll find that there's indeed a blue tint, as expected. Why ...

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It's because you're not looking far enough. From personal experience, it takes at least 10 km of atmosphere to build up a really obvious blue (see, for example, this picture), and if you're not in hilly country, the horizon is only 5km away. In contrast, most of the sky has distances to space on the order of hundreds of kilometers.

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Two reasons: The scattering separates red/orange and blue in different directions. At sunset you'll see the red parts that are missing from the blue skies by day. This isn't noticeable for objects close by, because those objects surround you. The blue from some objects mixes with the red from others. Secondly, there is a lot of air between you and the ...

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If I understand you right, you're referring to the phenomenon seen in this picture (from the first Google hit), that near the horison the color of the sky is more light-blue (not exactly white): Rayleigh scattering The scattering in the atmosphere is for a large part Rayleigh scattering off of nitrogen and oxygen molecules, which are much smaller than ...

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According to these lecture notes, the Coriolis parameter at mid-latitudes is on the order of $f_c = 1\times10^-4 \text{s}^{-1}$ and this needs to be multiplied by a wind speed to get a force. This is the first important note -- Coriolis forces do not create wind/motion, they merely change the direction of it. For a pressure force, let's look at a ...

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It is true that the most contribution to heat comes from compressing the air. The temperature of a falling meteor was in fact in my aerodynamics II exam where I had to predict its temperature using shockwaves. According to my estimation it was about 10,000 K. You need a proper understanding of compressible air flows in order to answer this question. And I ...

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Presuming it's a clear day (ie. no clouds, fog, or smog), then there are certain wavelengths (colors) of light that will transmit through the atmosphere with minimal loss. Of course, there is Rayleigh scattering that preferentially scatters shorter wavelengths at 90 degrees (this is why the sky is blue and sunsets are red).

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You can see through many things: glass, water and other liquids etc.. What you see however is a matter of what is being transmitted or re-transmitted by the particles present in the medium, after some waves-lengths will be reflected or absorbed.

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Interesting question which even made me laugh. As already pointed out the Power of an hurricane is too high to be connected to any grid. My laugh came about this; "Giant heaters out to sea which dump heat into sea water?" -Why? Because it's basically the heat of the sea which feeds the energy to the Hurricane, and thus this kind of system would not do ...

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How much of the Earth's atmosphere is visible from its surface All of it. Though you need either a lot of observers or a lot of time. I assume you mean without taking into account clouds, haze and other atmospheric issues. Or not, depending on what wavelengths are "visible" to our observer(s). It kinda depends on whether the observer is a cat or a ...

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If you know the distance (15km) the approximate computation is easy with a bit of trigonometry. A quarter of the night sky is a bit imprecise: apparent sizes are measured in angle units, that is, degrees or radians. The sky (night or day) is a maximum of 180º, so a quarter of that would be more or less 45º. Now, assume the following: the trail is a ...

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The plot below shows a model of how an isolated mass of gas (planet, brown dwarf) cools down with time, taken from Baraffe et al. (2003). The cooling tracks are labelled with mass in Jupiter masses. The time axis is logarithmic in years, the luminosity axis is lograrithmic in units of solar luminosities. Young brown dwarfs and giant planets are governed by ...

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I'm not an expert but I believe the following is correct. The object PSO J318.5-22 is referred to as a "young L dwarf." An L dwarf is a type of brown dwarf, meaning a mass of hydrogen and other elements that is not large enough to fuse hydrogen. PSO J318.5-22 is Jupiter-sized, but I guess there is no particularly important difference between "failed stars" ...

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A quick Google search turns up a couple of additional resources besides the free paper abstract. Stanford has a summary of the paper, and the University of Delaware has slides associated with a talk on the paper. Offshore wind turbines currently exist and do act the opposite of an aircraft propellor: wind energy is converted into electricity, slowing the ...

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