3 ms·

Completely missing the point of analogy, I know, but skyscrappers would fly if they were tall enough, right? The center of gravity far enough should make them

by ajuc 12y ago

Completely missing the point of analogy, I know, but skyscrappers would fly if they were tall enough, right? The center of gravity far enough should make them sattelites, if they were made from something that can withstand the forces involved?

fchollet 12y ago
Your "skyscraper" would need to have its top in geostationary orbit, or else it would be wrapping up around the earth as its top would be in LEO or HEO and thus would be moving at a different speed than its base. I.e. your skyscraper (or cable) would be crashing down. So that's a space elevator. But can a space elevator be said to be "flying"? It stays above a single spot the whole time.
- ajuc 12y ago
  But then you can take one brick from the bottom, throw it out, and you launch into space.
- bjornsing 12y ago
  BS. ;) First of all before a (hypothetical) "skyscraper" could fly it would have to have its top beyond geostationary orbit. How so? Because a skyscraper is geostationary and if its center of mass is below geostationary orbit then it's simply not orbiting. It doesn't have enough kinetic energy. Secondly, there's no law that an object revolving around earth must do so at "orbit" speed/altitude. You and I are perfect examples of that: we're going far too slow. Only consequence of that is that earths gravitational pull must constantly be counteracted by a supporting force. If an object were to revolve around earth at a speed faster than "orbit" that's also fine, as long as there's a force keeping it down. So, no, this "skyscraper" could have its top well below geostationary orbit as long as it rests firmly on mother earth. Once its center of mass is beyond geostationary orbit though it would need to be held down.
fchollet 12y ago
In any case, I think that's a point very much relevant to the analogy: when you do more of the same, but at a scale a few orders of magnitude larger, you do get qualitatively different results. That's very much applicable to AI. As an illustration, when we started to use GPUs for training neural nets with the exact same algorithms as a decade earlier but with an order of magnitude more parameters, we got dramatically better results (see Ciresan et al. 2010 [1]). Building the same dumb skyscrapers but making them 100 times taller might in fact get them to fly. [1] http://arxiv.org/abs/1003.0358 http://arxiv.org/abs/1003.0358

by ajuc 12y ago

fchollet 12y ago

Your "skyscraper" would need to have its top in geostationary orbit, or else it would be wrapping up around the earth as its top would be in LEO or HEO and thus would be moving at a different speed than its base. I.e. your skyscraper (or cable) would be crashing down. So that's a space elevator. But can a space elevator be said to be "flying"? It stays above a single spot the whole time.

ajuc 12y ago
But then you can take one brick from the bottom, throw it out, and you launch into space.
bjornsing 12y ago
BS. ;) First of all before a (hypothetical) "skyscraper" could fly it would have to have its top beyond geostationary orbit. How so? Because a skyscraper is geostationary and if its center of mass is below geostationary orbit then it's simply not orbiting. It doesn't have enough kinetic energy. Secondly, there's no law that an object revolving around earth must do so at "orbit" speed/altitude. You and I are perfect examples of that: we're going far too slow. Only consequence of that is that earths gravitational pull must constantly be counteracted by a supporting force. If an object were to revolve around earth at a speed faster than "orbit" that's also fine, as long as there's a force keeping it down. So, no, this "skyscraper" could have its top well below geostationary orbit as long as it rests firmly on mother earth. Once its center of mass is beyond geostationary orbit though it would need to be held down.

fchollet 12y ago

In any case, I think that's a point very much relevant to the analogy: when you do more of the same, but at a scale a few orders of magnitude larger, you do get qualitatively different results. That's very much applicable to AI. As an illustration, when we started to use GPUs for training neural nets with the exact same algorithms as a decade earlier but with an order of magnitude more parameters, we got dramatically better results (see Ciresan et al. 2010 [1]). Building the same dumb skyscrapers but making them 100 times taller might in fact get them to fly. [1] http://arxiv.org/abs/1003.0358 http://arxiv.org/abs/1003.0358