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The Official "Quick Question" Thread


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#261 Lord Antares

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Posted 9 February 2017 - 09:09 PM

Yes, that's exactly what I'm asking. Yeah, that's what I thought.

 

Hm, the Wikipea article states that the downward one comes first. All the other GIFs show it that way too. It would make more sense as well, as the cloud is the supercharged body, so it would make more sense that the discharge is initiated by it, right?

 

You either misheard, misremembered, they mis-explained or I stumbled onto an unlucky string of coincidentally wrong explanations.


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#262 Lord Antares

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Posted 31 March 2017 - 08:22 PM

In a thunderstorm, is the sky between the clouds and the ground negatively charged or NET negatively charged?

 

What is the maximum distance of attraction  between a proton and an electron?


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#263 EdEarl

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Posted 8 April 2017 - 12:37 PM

The proposed SpaceX Earth-Mars Luxury Liner has a top stage of 17m diameter with a booster stage of 12m diameter. What is the benefit of having a 12m dia booster? I believe material and weight could be saved by having the booster 17m dia.


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#264 Manticore

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Posted 12 April 2017 - 06:09 AM

Yes, that's exactly what I'm asking. Yeah, that's what I thought.

 

Hm, the Wikipea article states that the downward one comes first. All the other GIFs show it that way too. It would make more sense as well, as the cloud is the supercharged body, so it would make more sense that the discharge is initiated by it, right?

 

You either misheard, misremembered, they mis-explained or I stumbled onto an unlucky string of coincidentally wrong explanations.

A couple of months ago I saw an inverted stroke of lightning ie. forked upwards rather than down. I assume that in this case the leader propagated from the ground upwards & the actual strike was downwards.

(Apparently this is caused by metal masts and towers which concentrate the Earth's charge at a single point.)


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#265 Lord Antares

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Posted 12 April 2017 - 11:19 AM

I THINK (not 100% sure) that we almost always see the upward stroke, even though both the downward one and the upward one happen. 

So it might have been a normal lightning and you saw the upward one pronounced. I would have to go back to research that as I'm speaking from memory.


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#266 Manticore

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Posted 12 April 2017 - 06:49 PM

I THINK (not 100% sure) that we almost always see the upward stroke, even though both the downward one and the upward one happen. 

So it might have been a normal lightning and you saw the upward one pronounced. I would have to go back to research that as I'm speaking from memory.

 

A quick search for "ground to cloud lightning" shows that the phenomenon is more common than I would have thought. And that, yes, this gives lightning that forks upward.


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#267 Lord Antares

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Posted 12 April 2017 - 09:32 PM

I know, but we have cloud-to-ground and ground-to-cloud in both types of lightning. I think both need to be there.

So you may have witnessed ground-to-cloud lightning or the return stroke of the regular cloud-to-ground lightning.


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#268 Manticore

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Posted 13 April 2017 - 05:43 AM

I think you will find that the stepped leader causes the forked shape of the lightning. Therefore, in an inverted forked bolt, the leader must be propagating upwards rather than downwards as in a normal strike. Presumably the main discharge is also in the opposite direction to that of a cloud to ground discharge.

 

(When I took my (French) pilot exam, there was only one question related to thunderstorms. The question was 'What is this?' with a picture of a Cumulo-Nimbus. The correct answer was 'Dangerous'.)


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#269 EdEarl

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Posted 20 April 2017 - 10:21 AM

There are now estimates of how many Earth like planets exist in the Milky Way. Do we know enough about the history of our galaxy to estimate how many of those worlds have been sterilized by stellar explosions, whether such worlds may recover enough to support life after sterilization, and how such events affect our expectation of finding aliens.


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#270 Velocity_Boy

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Posted 20 April 2017 - 11:31 PM

I have a quick question. One that I really should know the answer to. And am almost embarrassed to ask. But I was watching a documentary on the history of our space program the other night, and this question came to me. I could look it up but this is more fun.

So....here goes.....Gravity. as in....The Earth's. Does our planet's gravitational field lessen as one rises in altitude toward the boundary of space? Or is it uniform all the way up? Until we escape it totally and enter the weightlessness of Space. Which, if memory serves, is agreed upon you be about 60 Miles up?

So....Yeah, do you weigh less up at, say, thirty miles than you do at one mile? Or is it all uniform and equally spread? Like going through a jar of honey till you break the surface?

Thanks.

Edited by Velocity_Boy, 20 April 2017 - 11:33 PM.

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#271 Lord Antares

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Posted 20 April 2017 - 11:35 PM

No, it is always dependent on the distance from the object, hence the inverse square law. So, the higher you are, the lesser the effect of gravitation on you. There's even a greater effect at sea level than, say, on a mountain.


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#272 Velocity_Boy

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Posted 21 April 2017 - 12:13 AM

No, it is always dependent on the distance from the object, hence the inverse square law. So, the higher you are, the lesser the effect of gravitation on you. There's even a greater effect at sea level than, say, on a mountain.

Really? I never heard about the lesser gravity at altitude? For instance, I used to live in a town that was 7200 ft. Elevation. And while we all knew about the thinner air and it's effects....I'm a runner!...I never heard about less gravity. I'm sure it's negligible though, eh? Like I maybe weigh half of an oz. Less in Flagstaff than in Austin?

So, Denver. The Rockies baseball team. Their stadium Coors Field. Renowned for balls going farther, more home runs, a pitcher's nightmare. I always attributed all that to thinner air. Do you mean to say lesser gravitational pull is also part of the equation? How can I never have heard this? LOL

Edited by Velocity_Boy, 21 April 2017 - 12:16 AM.

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#273 Lord Antares

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Posted 21 April 2017 - 12:36 AM

No, the effects are much too negligible. I really don't know how you've never heard of it, it has been well known for a few hundred years that gravity falls off with distance.

See Newton's inverse-square law: https://en.wikipedia...sal_gravitation

 

How else would gravity work if it didn't fall off with distance? Everything would be one body in the universe.


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