?
If it's balanced, with the center of gravity below the balance point, why would it become unstable at any rpm? The lower the CG, the more stable it would be...even when stationary.

What I'm describing would 'hang' from the contact point, like the difference between a gyroscope on the table and one hanging by a string, the one hanging would never 'fall over' because gravity works to keep it upright.

Built the same as they built them here, but with the outer ring much lower, there should be no contact until it wobbles, which in my mind it never should.

Yes, I didn't think it would spin more, or faster, just be more stable, because lowering the CG ALWAYS makes things more stable, no? My design should self right if it gets off balance, gravity should pull it back into balance, rather than off balance like a normal top.

I just wondered if, somehow, centrifugal force coupled with some other forces might make it try to flip over....or maybe if the CG isn't above the contact point, it's not a 'top'?

Good question. I think that the entire device is unstable no matter what, its impossible to keep it straight no matter where the point of gravity as long as it needs to balance on a single tip. So zero speed would mean tip over in all cases unless you make a more stable tip (square) which would mean it cant spin very well which means you havent made a spinning top.

You can find more about the physics of the spinning top here:
http://hyperphysics.phy-astr.gsu.edu/hbase/top.html
and here:
http://physics.stackexchange.com/questions/271/why-dont-spinning-tops-fall-over

So what is the optimal distance of the center of gravity to the tip?

There are several things working at the same time. Most importantly is the energy. You need to store as much energy as possible so that the top can spin for as long as possible. When the top slows spinning the friction at the tip becomes larger (the precession becomes bigger) so it starts to lose more energy and slows the spinning even more. You store energy by adding weight with a center of mass that is further away from the tip. When the top then "falls" the center of gravity moves down and reduces potential energy. Due to energy conservation kinetic energy goes up meaning speed of precession or of spinning goes up and creates a force pushing the top back up.

Off course, more mass means more friction at the tip, so there is for sure an optimal here, most likely depending on mass, size and shape of spinning top, etc.

Last but not least, more rotation speed I assume also means more friction, so its a trade-off.

If you move the center of mass down below the tip, well, if you move it as far off as you would above, the energy you can save is about the same, but the entire thing would be harder to build and you would need to make sure the sides fit around the ground plateau. Also, when the precessions become bigger the sides will hit the plateau, meaning game over.

In the end you are better of keeping the center of gravity above the tip point.

I don't know about giving it a "fail" on gravity, but a "cheat" on the storm. If you are willing to give it a "cheat" on the storm, then the reality of filming on Earth should give the gravity a "cheat" as well. It would have been much much harder to replicate the gravity on Mars itself and maintain any sort of sense of budget etc. I'd be more inclined to fail it for the storm than the gravity, the storm is a cheat to setup the story, the gravity is a cheat due to the reality of filming on Earth.

Hmmm. I wonder why neither team decided to lower the center of gravity below the contact point, since they would be spinning on the tiny raised cylinders? It seems it would be easy to make the outer ring hang below the point, so it would stay upright at 0 rpm. Does that somehow make it unstable when you spin it?
*quality craftsmanship and design

Seldom get a 7" diameter clear hole directly down into the gas pocket. Because of gravity and subsidence, an earthquake tends to fill holes, not create them.

In case nobody caught it, this is not the first time a booster stage returns from space to land on its own power, not the first commercial launch booster landing nor even the first time it happened this year. Blue Origin's New Shepherd recently did just that. This lead to a bit of a war of words on twitter which quickly devolved to a "my rocket is bigger than yours" bragging competition. It's rather humorous therefore to hear this band of professional aerospace PR agents say that this is "history by being the first to fly back and land the first stage of our rocket to land" (@1:20).

Nonetheless an impressive mission and I congratulate their whole team for the accomplishment.

Congratulations! Your video, Smarter Every Day: Turning Gravity into Light, has reached the #1 spot in the current Top 15 New Videos listing. This is a very difficult thing to accomplish but you managed to pull it off. For your contribution you have been awarded 2 Power Points.

This achievement has earned you your "Golden One" Level 2 Badge!

Their specs say the LED runs at 100mw on "high".

1kg falling 1m is roughly 2.5 mwh, so yeah, you'll need either a lot of a rocks or a long fall to run much more than an LED for very long. Even then they can't be losing too much if they can have it running for 20 minutes.

I suppose its also worth remembering that gravity is harnessed on a massive scale for the generation of electricity by dams, so yeah, in some parts of the world its quite possible your computer would be gravity powered.

Nice idea, although LEDs have an extremely low power draw. Not sure if the gravity plus gearing would generate enough watts for the Pi.

USB is 5 volts at usually under 1 amp (.5 amps for USB 2 and .9 for USB 3). So I think that suggests about a 2.5-5 watt draw for USB, although I could be wrong -- long time since I took any EE classes. With very quick googling, I'm not getting a concrete number on the wattage of the (single?) LED in the Gravity Light, but one result suggested in the milliWatt range (60-80mW). Same post says that a cheap hand crank generates about 1 watt with vigorous cranking that will wear out your arm/hand quickly.

So, I'm thinking that 2.5-5 watts would require a much more heavy-duty and less portable gravity-fed system. Very much doable (bicycle pedaling can generate 50 watts fairly easily), but probably only with more bulk than what can power LED lighting.

Your video, Smarter Every Day: Turning Gravity into Light, has made it into the Top 15 New Videos listing. Congratulations on your achievement. For your contribution you have been awarded 1 Power Point.

Smarter Every Day: Turning Gravity into Light has been added as a related post - related requested by eric3579 on that post.

A Light That Runs On Gravity has been added as a related post - related requested by eric3579.

*related http://videosift.com/video/A-Light-That-Runs-On-Gravity-very-cool

To address your points:

>> Bush: Disaster. Remember, remember the Patriot Act?
GW is not up for re-election and to the best of my knowledge Jeb had nothing to do with writing the Patriot Act. He supports it, but almost all the candidates do. I'm not a huge fan of Jeb, but he actually seems like the smart one in his family. Would still prefer him not to be president.

>> Clinton: Lying, manipulative, currently under Federal investigation by America's FBI department. Really?
@newtboy already addressed the so-called "email-gate" or whatever. As for "lying, manipulative"? You're kidding, right? She's a politician. They're all lying and manipulative. Ultimately, I think Hillary will probably get the democratic nomination and while I'm not a huge fan, she's an order of magnitude better than any of the republicans.

>> Bernie Sanders: Self-purported Socialist. Lovely.
So what? "Socialist" is not a bad word. Many of the highest ranked countries for citizen health and happiness are socialist. America needs to grow the fuck up and get over it's childish clinging to McCarthyism. A bit of socialism would do it the world of good.

>> Ben Carson: I have no particular qualms, by all means intelligent, however, doesn't say anything beyond the bloated party line.
Ben Carson, "intelligent"? Are you fucking kidding me? The guy's borderline insane. How he ever got to be a surgeon baffles me.
This is a guy who thinks that "Joseph built the pyramids to store grain", that doesn't understand fucking magnets, er, gravity and believes evolution was ‘encouraged by’ Satan. He's a fucking moron.

>> That brings us full circle back to Trump... He has a real, tangible plan...
to fuck everything up? Seriously, Trump is an idiot and would be the worst thing to happen to the USA (and by extension the world) in decades. His ignorance is matched only by his ineptitude.

>> As for Obama, and I include him because many seem to think he is great for some reason..
a) I don't think he's great, he's been a huge disappointment and
b) he's irrelevant to this debate
but anyway...

>> His healthcare plan failed(look it up)
I did and it hasn't.

>> America is now over $18 Trillion in debt.
I wonder if the previous president starting two wars has anything to do with that?

>> And he insists on throwing pebbles at ISIS while the EU does all the fighting
Way too big a topic to address here. Post on another video if you want to discuss it further.

>> I am not necessarily saying that Trump is a good person, or would make a good President, but he would me loads better than the other shrimps for candidates...
He's not, he wouldn't and better than an invertebrate with a brain only barely recognisable as such is not a sufficient bar for the presidency.

@Jerykk
capital punishment much?
look,i get it,eye for an eye,choices have consequences,violence should be responded to with violence.

i do not necessarily agree with that premise but i can understand why someone would adopt that premise, but YOU....you take it to a whole new level.

"You threaten to stab someone, you are executed"

really?
you really feel that this is a justifiable stance?
in your world merely threatening violence should be countered with actual execution?

have you even considered the gravity and weight of what you are proposing? the implications alone are horrifying.

i struggle to understand your commentary.
you consistently seem to promote an extremely fascist worldview.i wonder if you are even aware of this facet.