# Series K- Kinetics

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1033092.  Mon Nov 04, 2013 11:55 am

 dr.bob wrote: This was something that occurred to me after I'd done the maths, but it served as a useful checksum to reassure me that I'd got my figures straight :)

...or indeed curved...

:-)

Actually I think that's a relevant point. In most systems you can apply a relativity view as to which bit is "static" and which is "moving" to make the sums or the comprehension simpler - all that matters is what one does in relation to the other so you can cast your frame of reference for convenience.

But this case is one of the exceprtions where it DOES matter and the static/moving elements are not interchangable because one view is in a linear frame of reference whilst the other is in a rotating frame of reference - epople seem to have missed that point.

PDR

1033094.  Mon Nov 04, 2013 12:01 pm

 Ian Dunn wrote: Stephen is 6ft, 4.5in tall and weighs just over 14 stone. If Stephen were 44,000 miles tall his penis would be 3,384 miles long. Using that you can probably calculate his real penis length.

I do not believe that Stephen can have gone through this calculation for himself. If he had, I doubt that he would have allowed such an unflattering number to be broadcast.

My husband is not as tall as Stephen. But if he were scaled up to be 44,000 miles tall, his penis would be 4,086 miles long. If I were so scaled up, I'd have a 21,500 mile bust - which would be enough even for the likes of Dr. Know!

 1033111.  Mon Nov 04, 2013 1:12 pm I feel a comment like "That's a mountain I'd like to climb!" is due. About the episode, though: I will now refer to (at least to myself) the instances where Stephen tries to prove a very simple thing and Alan throws all the research of the Elves out the window Alan's Law. (And if someone can reword that to apply to the world at large I would be very thankful.)

1033124.  Mon Nov 04, 2013 4:20 pm

dr.bob wrote:

 djgordy wrote: Surely the only things you need to know is how fast the Earth is spinning (1,000 mph at he equator) and the escape velocity* (25,000 mph).

You seem to be implying that, if you're travelling any less than the escape velocity, you'll never leave the surface of the Earth.

This is clearly not true. If I jump into the air, I temporarily leave the surface of the Earth without ever getting close to escape velocity.

Don't be ridiculous. I'm not implying any such thing.

 1033155.  Mon Nov 04, 2013 11:54 pm This was a good episode which, if nothing else, suggested Marcus Brigstocke deserves a third go. He said on Twitter that he choked his first time (although, frankly, he did better than many then), but his polar bear story and genuine engagement of the QI concept and format was laudable. I can genuinely see him becoming another staple of the series, esp. as so many of them (Clive Anderson, Sean Lock, Rob Brydon, even Dara O Briain) seem to be getting escorted out. It was good to see from Marcus a truly Quite Interesting thing said, by the A or B series sense of that. Definitely the best non-regular this series so far -- although we've still not seen Ms. Coren or Rev. Coles who impressed so well with their first times.

1033159.  Tue Nov 05, 2013 3:20 am

 vantheman wrote: This was a good episode which, if nothing else, suggested Marcus Brigstocke deserves a third go. He said on Twitter that he choked his first time (although, frankly, he did better than many then), but his polar bear story and genuine engagement of the QI concept and format was laudable. I can genuinely see him becoming another staple of the series, esp. as so many of them (Clive Anderson, Sean Lock, Rob Brydon, even Dara O Briain) seem to be getting escorted out. It was good to see from Marcus a truly Quite Interesting thing said, by the A or B series sense of that. Definitely the best non-regular this series so far -- although we've still not seen Ms. Coren or Rev. Coles who impressed so well with their first times.

That's one of the reasons why the earlier series are more fun to watch. Guests like Clive Anderson and Dara O Briain are the soul of QI. They are the ones who are both interesting and funny. Although Brigstocke did fine, I really hope that QI isn't going down the same path as all the other panel games. The guests were what elevated QI above the rest.

1033186.  Tue Nov 05, 2013 6:38 am

djgordy wrote:
dr.bob wrote:

 djgordy wrote: Surely the only things you need to know is how fast the Earth is spinning (1,000 mph at he equator) and the escape velocity* (25,000 mph).

You seem to be implying that, if you're travelling any less than the escape velocity, you'll never leave the surface of the Earth.

Don't be ridiculous. I'm not implying any such thing.

No, that's a fair point. Having re-read your post, you seem to be implying that, if you're travelling any less than the escape velocity, you'll never head out into space.

That's still wrong since ICBMs are fast enough to enter a low Earth orbit, but they're still a fair way short of escape velocity.

1033187.  Tue Nov 05, 2013 6:39 am

 vantheman wrote: This was a good episode which, if nothing else, suggested Marcus Brigstocke deserves a third go. He said on Twitter that he choked his first time (although, frankly, he did better than many then), but his polar bear story and genuine engagement of the QI concept and format was laudable.

Hear hear!

I hope the Powers That Be are reading this and ensure that Mr Brigstocke is booked for the 'L' series.

 1033192.  Tue Nov 05, 2013 6:45 am Having a quick a calc, the measurements are pretty bang on wht you often see as "average" size given, so I'm guessing that's what was used, as opposed to someone measuring Stephen. When men are usually measured, they tend to round to the nearest inch, often up :) If Stephen was the same as the "average" size often quoted, he'd more likely had rounded it up to the nearest inch, and the size would have been quoted as 3,450 miles. As for the mountain ranges mentioned above... :)

1033198.  Tue Nov 05, 2013 7:16 am

 Naughtyhorse wrote: Instead we were treated to Stephen (or elves) making a massive schoolboy error - which is related to the massive schoolboy error that lies behind the elevator:

Schoolboy error, eh?

 Naughtyhorse wrote: "If stephen was 44,000 miles tall his CofG would be outside earths gravitational field, ergo he would be weightless."

The slight problem here is that's not what Stephen said on the show.

What he actually said, quite correctly, is that, if he were 44,000 miles tall, his centre of gravity would be in orbit. Things that are in orbit around the Earth are certainly not outside the Earth's gravitational field, but they are effectively weightless.

 Naughtyhorse wrote: In this case the body in question experiences differing gravitational attraction depending on the location - an effect so small in everyday experience that it can be neglected.

This is quite correct.

 Naughtyhorse wrote: in the case of a 44,000 mile tall man it cannot be ignored. the soles of his feet would experience g of 9.806 m/s while his knees might experience g of 7.5something m/s and the top of his head would see g of nought point bugger all. Summing all these would result in a weight of considerably more than 0

This is incorrect.

The point at which Stephen's giant body would experience weightlessness would be at a point around 22,000 miles up. This is the distance to a geostationary orbit. At this point, the centripetal acceleration caused by the earth's spin would be precisely balanced out by the gravitational pull of the Earth. Beyond this point, Stephen's giant body would experience negative gravity. That is, the centripetal acceleration of the Earth (due to his feet being on Terra Firma) would overcome the gravitational pull of the Earth, trying to force anything above (roughly) his belly button further out into space.

Summing all these points, from the positive gravity at the Earth's surface, through the weightlessness of 22,000 miles up, out to the negative gravity out to 44,000 miles, would result in a weight of zero.

Of course, this assumes that Stephen is perfectly rigid. However, we're already imagining a 44,000 mile high Stephen, so clearly some suspension of disbelief is already at play here.

1033209.  Tue Nov 05, 2013 7:42 am

 djgordy wrote: *"Escape velocity" should really be called "escape speed" because velocity is a vector quantity.

If it refers to escaping the earth's gravitational field, then using the term "escape velocity" is correct, as you'd not get very far travelling at "escape speed" if your direction of travel was towards the surface of the earth.

1033219.  Tue Nov 05, 2013 8:14 am

dr.bob wrote:
 Naughtyhorse wrote: Instead we were treated to Stephen (or elves) making a massive schoolboy error - which is related to the massive schoolboy error that lies behind the elevator:

Schoolboy error, eh?

 Naughtyhorse wrote: "If stephen was 44,000 miles tall his CofG would be outside earths gravitational field, ergo he would be weightless."

The slight problem here is that's not what Stephen said on the show.

What he actually said, quite correctly, is that, if he were 44,000 miles tall, his centre of gravity would be in orbit. Things that are in orbit around the Earth are certainly not outside the Earth's gravitational field, but they are effectively weightless.

 Naughtyhorse wrote: In this case the body in question experiences differing gravitational attraction depending on the location - an effect so small in everyday experience that it can be neglected.

This is quite correct.

 Naughtyhorse wrote: in the case of a 44,000 mile tall man it cannot be ignored. the soles of his feet would experience g of 9.806 m/s while his knees might experience g of 7.5something m/s and the top of his head would see g of nought point bugger all. Summing all these would result in a weight of considerably more than 0

This is incorrect.

The point at which Stephen's giant body would experience weightlessness would be at a point around 22,000 miles up. This is the distance to a geostationary orbit. At this point, the centripetal acceleration caused by the earth's spin would be precisely balanced out by the gravitational pull of the Earth. Beyond this point, Stephen's giant body would experience negative gravity. That is, the centripetal acceleration of the Earth (due to his feet being on Terra Firma) would overcome the gravitational pull of the Earth, trying to force anything above (roughly) his belly button further out into space.

Summing all these points, from the positive gravity at the Earth's surface, through the weightlessness of 22,000 miles up, out to the negative gravity out to 44,000 miles, would result in a weight of zero.

Of course, this assumes that Stephen is perfectly rigid. However, we're already imagining a 44,000 mile high Stephen, so clearly some suspension of disbelief is already at play here.

I think we may be missing a point here. If we assume the internal composition of the 44,000 mile Super-Steviebabes is the same as that of the more common 6'4" version, and that the common-or-greenroom version weighs around 16stone (~100kg) then the mass of the Super-Steviebabes will be in proportion to the cube of the scale factor.

The scale factor is 6'4":44,000 miles, or roughly 1.9m:7*10^7m which approximates to 37million:1., so the cube of the scale factor is roughly 50*10^30, which means that the mass of the Super-Steviebabes would be in the region of 5*10^33kg (5*10^30 tonnes) - clearly he needs to cut back on the pies.

Now the mass of the Earth is usually taken as around 6*10^21 tonnes, so the Super-Steviebabes has a mass which is about eight and a half million times that of the earth and so the effect of Earth's gravity on the Super-Steviebabes would be insignificant compared to the effect of the Super-Steviebabes' gravity on the Earth (to put it in very sloppy language). There isn't really any question of the Super-Steviebabes orbitting the Earth - it would be more a matter of the Earth trying to orbit the Super-Steviebabes. This might be possible around the midriff region where (thanks to the aforementioned pies) the shape will be roughly circular, but it would be almost impossible to estanlish a "head-to-toe axis" orbit due to the uneven and radially asymetric nature of the gravitational field.

Of course if we could pursuade him to curl up into a foetal position then we'd have a near-enough approximation to a sherical object and the Earth could then orbit the Super-Steviebabes (or more correctly he and the Earth would both orbit their mutual centre of mass, which would be a point on the line joining their individual centres of mass roughly an 8.5millionth of the distance from the Super-Steviebabes' centre of mass, which is small enough to ignore of our purposes). But if he didn't *want* to curl up into a ball I'm not offering to try to force him to do it - at 5*10^30 tonnes he's much bigger than my dad and even bigger than SWOT, so whatever he wants to do is just fine by me...

PDR

 1033230.  Tue Nov 05, 2013 9:06 am I think perhaps it might be worth illustrating the respective sizes of the super-steviebabes and the planet earth so that people can better grasp what I mean: PDR

1033267.  Tue Nov 05, 2013 11:14 am

 PDR wrote: so the Super-Steviebabes has a mass which is about eight and a half million times that of the earth and so the effect of Earth's gravity on the Super-Steviebabes would be insignificant compared to the effect of the Super-Steviebabes' gravity on the Earth

That's a very good point, maybe one for the mythical Retractions Special in series 'R'.

Mined ewe, it simply tends to highlight the shortcomings (ironically!) of examples of problems that are easily and quickly explained in the format of a comedy panel show. Having said that, at least it's sparked a bit of debate and got people thinking in more depth, which is at least one of QI's stated aims.

1033274.  Tue Nov 05, 2013 11:53 am

 dr.bob wrote: Of course, this assumes that Stephen is perfectly rigid.

But of course. Isn't that the usual way to measure a chap's membrum virile?

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