Is oxygen evenly dispersed across the planet? |
- Is oxygen evenly dispersed across the planet?
- What does mean sea level mean if you're thousands of miles from the sea?
- Can gamma rays break apart small nuclei?
- What better determines where lightning will strike: height, material, or some other factors?
- How can water go from being in a liquid state to being frozen by simply shaking it?
- If an object with a net force experiences a constant acceleration, why can’t it exceed the speed of light in a vacuum?
- What does the Maxwell term in the Ampere-Maxwell law physically represent?
| Is oxygen evenly dispersed across the planet? Posted: 31 Dec 2017 02:59 PM PST Is oxygen more prominent in the rain forest more so than the desert? Is there an area with the least and most oxygen? I mean low elevations of course. [link] [comments]  |
| What does mean sea level mean if you're thousands of miles from the sea? Posted: 01 Jan 2018 07:59 AM PST As I understand it, Mean Sea Level is defined by taking the time-averaged effective gravitational potential of the water-air boundary averaged over the world's oceans. Since sea levels are rising globally, we choose some datum and stick to that. This seems reasonably unambiguous. If the summit of Everest is 8848m above MSL, does that mean it's 8848m directly above a point within the crust on that same equipotential, or does it mean it's on the equipotential defined by the average of all points 8848m directly above the sea? Or does it mean something else? How much difference would there be? To rephrase the question: if you hollowed out Everest and made tunnels (sealed against groundwater) connecting that cavity to the oceans, would the water find a time-averaged level 8848m directly below the summit? [link] [comments]  |
| Can gamma rays break apart small nuclei? Posted: 31 Dec 2017 08:36 PM PST If fully ionized (electron free) nuclei of elements like hydrogen or helium or oxygen are hit with an extremely high-energy gamma ray, what happens? Would it cause the oxygen to undergo fission? Would it even interact with the hydrogen? Assuming it does interact, what happens? [link] [comments]  |
| What better determines where lightning will strike: height, material, or some other factors? Posted: 31 Dec 2017 02:06 PM PST I know that cloud-to-ground lightning generally speaking strikes from the negatively charged portion of a cloud to the positively charged portion of the ground below the storm, and that it will find the path of least resistance there, which usually means something tall. But does the material of the thing matter too? If the stepped leader is spreading out over an open field with an 80 foot metal pole vs a 100 foot wooden pole vs a 120 foot rubber pole near each other, does it just matter that it touches the rubber pole or wooden pole first, or would it still strike the metal one? (I also know that if something is really tall then it will send out an upward leader that can cause a ground-to-cloud strike, but I'm less clear about how that works) Thanks! [link] [comments]  |
| How can water go from being in a liquid state to being frozen by simply shaking it? Posted: 31 Dec 2017 07:23 PM PST |
| Posted: 31 Dec 2017 01:08 PM PST |
| What does the Maxwell term in the Ampere-Maxwell law physically represent? Posted: 31 Dec 2017 12:45 PM PST I'm trying to understand the Ampere-Maxwell law, in the form curlB = μJ + εμ ∂E/∂t [no subscript 0s on reddit]. I get how Ampere's law works for static currents, and I can also follow the mathematical steps that are used to add the Maxwell term. (The divergence of a curl is zero, so Ampere's law always results in the rate of change of charge density being zero. Then adding an unknown vector field to the original equation and rearranging everything using Gauss's law and the equation of continuity gives the Maxwell term of εμ ∂E/∂t.) But even though I can follow the maths, I can't shake the feeling that it's like using the same information twice in one equation. The μJ term is the current density, so it represents the movement of charge. And the εμ ∂E/∂t term is the change in electric field, so it represents... also the movement of charge? I can't get my head around why the rate of change of electric field means something fundamentally different to the movement of charge, since electric field is defined by the location of charge to begin with. I've tried doing research and looking for useful analogies and explanations. But I've found a lot of things talking about the displacement current, which all seems to lead to explanations about how electric fields can polarise a medium and cause a sort of opposing field - and I can't figure a way to relate that back to the Ampere-Maxwell law itself in any useful way. Can anyone help me understand the physical meaning of the Maxwell term, and how the change of electric field means something physically different from the movement of charge? [link] [comments]  |
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