Comments by "Lawrence D’Oliveiro" (@lawrencedoliveiro9104) on "Scott Manley" channel.

  1. Yes, they had an uplink! https://youtu.be/Xtsrcc0c8Mo?t=3335 But they didn’t trust it.
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  2. 6:57 “Ap-helion” surely, not “af-e-lion”?
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  3. 4:56 Radio-semaphore!
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  4. No, light always follows a geodesic (aka “path of least action”). That doesn’t always mean a straight line.
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  5. In principle, the curvature of the Earth is visible from altitude zero. All you need is a patch of ground (or water) free of hills/waves/other bumps that block your view of the horizon. And consider: what is the shape of the horizon that you can see? Why, it is a circle, of course, going right round you. You only get that on a curved surface. QED.
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  6. 10:50 You mean ground vehicles? Spacecraft are vehicles, too.
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  7. It’s like How-To Dad ... in SPAAAACE!!
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  8. 3:49 What is this “Universal Standard Time” of which you speak? Do you mean “Coordinated Universal Time”, or “UTC”?
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  9. Not counting the dozens, hundreds of engineers and their slide rules.
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  10.  @battleoid2411  The computers were there to aid the engineers, not the other way round.
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  11. 8:19 Aperture defines how much light is captured only when expressed relative to focal length, not as an absolute distance measure. E.g. an aperture of 50mm with a focal length of 200mm is actually f/4, while if the lens focal length is 400mm with the same 50mm width, then that’s f/8, which means you only get one quarter the light.
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  12. 10:02 So the aperture is actually 50mm/360mm = f/7.2.
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  13. 10:42 Not to mention a longer objective focal length means a smaller aperture in f-terms (for the same aperture in absolute distance units), which means less light-gathering power!
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  14. 11:07 f/6, only slightly better than your Celestron.
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  15. 4:02 Also most phone customers live in urban areas, so the feature of total coverage of the surface of the Earth isn’t so important. I think Peter HIllary (son of Sir Ed) used an Iridium phone to stay in contact during an expedition in Antarctica.
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  16. 9:42 Collecting area is perhaps not so vital -- all that does is diminish the signal/noise ratio. What is probably more important is angular resolution, and you do that by widening the effective aperture. Which you can do by setting up multiple radio telescopes over a sufficient distance, listening to the same signal in sync. Hence the well-known radio telescope array projects.
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  17. They had multiple big IBM computers back at Mission Control. This on-board computer was really just interpreting sensor readings, little more.
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  18. Whereas nitrogen is repelled by a magnet. I think Toyota patented an idea some years ago about using magnets to increase the oxygen content in a car’s ventilation system, taking advantage of these properties of O₂ versus N₂.
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  19. 3:00 So in that picture, everything down to the box-like base is the MLP, and below that is the crawler transporter.
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  20. 6:44 MLP above, crawler below.
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  21. 18:04 Does Apollo 11 count? The switch to ignite the LM ascent stage was broken, so they used a pen to close the contacts.
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  22. Now do you think you can stop those journalists from saying “GMT”?
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  23. 1:03 “per-chlo-rate”
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  24. 7:20 Running shoes...? /me wonders if test labs have ever been fitted with ejector seats.
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  25. 14:45 Isn’t the orbital period chosen so that the same satellite is visible at the same apparent position in the sky at the same time each day?
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  26. 4:12 Because the gas is at low pressure, so it shows its Fraunhofer lines (absorption/emission spectra). At higher pressure, these disappear.
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  27. I think the name is a homage to Rutherford (for whom the engine is named). Interestingly, both NZ-born Nobel Prize winners went to the same primary school.
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  28. 4:47 Hey, looks like I was born and grew up in an extra-high-gravity field. ;)
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  29. I have a problem with the idea that light can disappear into a black hole and be lost forever. Light travels along geodesics. And geodesics are time-symmetrical. That means a light beam can travel in either direction along a geodesic. Therefore, if there is a light path from outside the event horizon leading into it, then there is a path in the opposite direction leading out. So if light can enter, it can just as easily escape. Since there is no escape, that must also mean there is no entry. QED.
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  30.  @scottmanley  Whatever it travels along, those trajectories are bidirectional. Either they cross the event horizon (which gives both entry and exit), or they don’t. Which is it?
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  31.  @scottmanley  Geodesics are time-symmetrical. Consider the orbits of the planets -- flip the time axis, and they go round the orbits the other way, and everything still conforms to the laws of physics. Every trajectory under gravity is time-symmetrical. That carries over to General Relativity too.
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  32. Think of “viscosity”. High mean free path means low viscosity.
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  33. Still waiting for intra terrestrial exploration to progress beyond (literally) scratching the surface...
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  34. 6:18 Interesting that they used 31 cells in series at a nominal potential of 1V each. I believe the power supply was nominally 28V. Maybe the extra 10% was to cater for quality variation and degradation over time.
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  35. 9:38 Thought: the rounding discrepancy between 0.965” and 24.5mm is maybe one part in 2000. Would there be any problem with a part made to one measurement fitting to one made with the other? On the other hand, 1¼” is exactly 31.75mm, so there should be no problem using SI units there.
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  36. Apple manages to design its computers to prevent users from doing things (like running alternative browsers). That sucks up a lot of computing power, too.
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  37. CAD software normally uses OpenGL for drawing on-screen, and that does indeed render surfaces as made up of triangles. The same would be true of Vulkan. It’s just easier for the hardware to work with triangles. Of course, the CAD software has much more elaborate mathematical structures, like surface patches, that it uses for calculations like FEA, BOM and so on. But all the on-screen visualization is still done with triangles.
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  38. 11:11 No love for Antarctica? ;)
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  39. 5:44 Some would argue that the most complex machine that humans have ever built is the Internet.
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  40. Anything to do with outer space immediately brings to mind the words “complicated”, “expensive” and “risky”.
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  41. 13:42 And no doubt there will be those claiming it’s all a political hoax or some kind of conspiracy, the threat is overblown etc etc. And threatening or committing actual violence against those trying to solve the problem. (Not something I would have seriously suggested a couple of years ago, but recent events, you know ...)
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  42. His sense of UI design was also a factor in the death of John Denver.
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  43. This is why the Earth’s surface is not covered with craters, the same way the Moon’s is. They’re in similar orbits, they would have been hit (and are still being hit) with similar densities of random objects. Erosion/deposition on the Earth tends to wipe out the traces in (geologically) short order.
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  44. He builds on the experience of those who pioneered it earlier.
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  45. This is why quoting lens focal length doesn’t really make much sense, it is better to quote actual angular field of view. Then you don’t have to keep qualifying your numbers with the sensor size.
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  46. 3:29 “Ullage” was the Apollo-era term.
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  47. 6:50 ... or, in this case, “spin safe”!
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  48. The electronic innards were buried in a thick mass of epoxy precisely to resist shock and vibrations. That epoxy is now an obstacle to fixing salvaged units that don’t work.
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  49. 1:22 Worth mentioning those green and powder-blue closed curves: are they polar orbits? But they don’t seem to precess?
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  50. 4:28 Ah.
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