Activity for dsrâ€
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Edit | Post #288711 | Initial revision | — | over 1 year ago |
| Answer | — |
A: Determining a Practical Bridge Design for a Wide River and Heavy Traffic Neopanamax beam is just under 52m, with a height of just under 60m. Let's give it about 50% margins on each side, and that give you 100m between bridge supports. A suspension bridge with a 100m span would not appear on a list of notably long bridges in our world. Suddenly this is not looking like ... (more) |
— | over 1 year ago |
| Edit | Post #288211 | Initial revision | — | over 1 year ago |
| Answer | — |
A: Could there be a way for a solar system to be very precise, so that the lunar calendar and solar calendar align? Something you may not have thought of: the Earth-Luna system has the barycenter inside the Earth's radius. Fairly deep inside, in fact -- about 25% of the way down from the surface. Your system as described is less binary-like than our own. Either the moon is smaller than Luna, or farther away, or... (more) |
— | over 1 year ago |
| Edit | Post #286966 | Initial revision | — | over 2 years ago |
| Answer | — |
A: Price's Law Sanity Check For the sake of a fictional story, you should be thoroughly aware that the author is playing as a god. The laws are what you want them to be, and what you say happens is what happens. I am not aware of any experiments to determine the validity of Price's hypothesis. If you want it to be true in yo... (more) |
— | over 2 years ago |
| Edit | Post #286002 | Initial revision | — | almost 3 years ago |
| Answer | — |
A: Could a high-pressure, low oxygen atmosphere reduce fire risk while still being breathable? Your intuition is correct. Let's suppose that at STP, a human needs to breathe 1L of O2 in 200 minutes. That's 1.43g of gaseous oxygen. If the pressure is raised to 5 bar, a human still needs 1.43g of O2 -- but it will only take up 0.2L of volume, and the other neutral gas mass will have to increase ... (more) |
— | almost 3 years ago |
| Edit | Post #283980 | Initial revision | — | over 3 years ago |
| Answer | — |
A: Human elytra flying off a cliff An average human masses 60Kg. The largest bird ever to fly, Argentavis, massed about that much. https://en.wikipedia.org/wiki/Argentavis So it seems reasonable that flying creatures the same weight as a human need to be reasonably close to Argentavis's size. Argentavis' wingspan was about 6m, a... (more) |
— | over 3 years ago |
| Comment | Post #283382 |
The food supply in the US uses about 10Kcal of energy in transport per Kcal of food value. This is relatively extreme in the current world... but in the world-farm scenario, the problem would be worse by a factor of about 24, as only cities next to the world-farm would have local food.
Waste will ... (more) |
— | over 3 years ago |
| Comment | Post #283382 |
Let's pretend that we aren't contributing to global warming because 100% of the power for this building comes from solar power systems with no production resource costs.
We still have 24TW of heat to transport away, or else the building will rapidly turn into an oven. The natural world has huge he... (more) |
— | over 3 years ago |
| Edit | Post #281984 | Initial revision | — | over 3 years ago |
| Answer | — |
A: Could a habitable planet lit by the cosmic microwave background plausibly exist? A back of the envelope calculation suggests that you need a velocity relative to the CMBR of more than 0.9c. (1mm microwaves blue-shifted to 570nm light typical of yellow dwarves) This is a problem for several reasons: - there is no known mechanism to create a planet with that velocity relative... (more) |
— | over 3 years ago |