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Fifteen years of radar reveal Venus’s most basic facts
- oaiey 5y agoWhat about the protomolecule?
- science4sail 5y agoHaving each day be 3 minutes longer/shorter than the previous one is pretty crazy, even if it's mitigated by the fact that 1 Venusian day is ~243 Earth days. That really makes me wonder how timekeeping would work for civilizations that evolved on planets with variable day length. Earth has variable periods of sunlight depending on latitude, but Earth's day length itself is relatively constant.
- tintor 5y agoWater clocks and sand clocks could still work, or some other periodic natural phenomena (like moon phases).
- cdumler 5y agoEarth already has this problem. Years aren't consistent both because the number of rotations don't evenly go into a single revolution, but also because Earth's rotation time is variable. For instance, above normal fresh water accumulation on land will measurably change the length of a day. Generally, there are two solutions. One is to track absolute time by increasing the clock as necessary to realign the day to the year. There are Earth days with where the last minute of the day is 61 seconds long. Daylight Saving Time makes days with 23 hours or 25 hours. And, of course, leap years add a day. Unfortunately, a lot of software/hardware is built by people with misconceptions about time, like a minute can have only 60 seconds or a day can have only 24 hours. So, the second solution is to update the system periodically. Computers often poll internet time to update the clock and will jump to the new time. Alternatively, some systems skew the system clock with additional milliseconds per second until it catches up with the time change. As long as the values are valid typical ranges, most software doesn't care about sudden changes.
- anticristi 5y agoVery well summerized. For those who care about the longer version: https://en.m.wikipedia.org/wiki/International_Atomic_Time https://en.m.wikipedia.org/wiki/International_Atomic_Time https://en.m.wikipedia.org/wiki/Universal_Time https://en.m.wikipedia.org/wiki/Universal_Time https://en.m.wikipedia.org/wiki/Coordinated_Universal_Time https://en.m.wikipedia.org/wiki/Coordinated_Universal_Time
- benpbenp 5y ago> Very well summerized. Actually, in Sumer, they used an intercalary month every three years or so, much like the leap year in the Gregorian Calendar. https://en.wikipedia.org/wiki/Sumer https://en.wikipedia.org/wiki/Sumer
- dotancohen 5y ago> Years aren't consistent both because the number of rotations > don't evenly go into a single revolution, but also because > Earth's rotation time is variable. Lots of civilizations have found novel solutions to the fact that the number of days in a year is not an integer. Adding an occasional leap month (Hebrew calendar) or leap day (Gregorian calendar), or just letting the calendar get out of sync with the seasons (Islamic calendar). However, it should be noted that although the Earth's rotation time is measurably variable, such measurements require precision instruments that have only been available for a bit over a century. Human senses could not notice such small changes over the course of a lifetime or even over the lifespan of an empire.
- dfsegoat 5y ago> Human senses could not notice such small changes over the course of a lifetime or even over the lifespan of an empire. I don't disagree in this case. But I am continually amazed at how resourceful and technical past civilizations could be. For instance early polynesian navigators ("wayfinders") could look at patterns in wave refraction across the ocean surface, to locate islands over the horizon [1]. They also memorized the setting and rising positions of hundreds of stars. [1] Unfortunately, much of this knowledge was lost, as the polynesians did not have a written system of language. 1 - https://manoa.hawaii.edu/exploringourfluidearth/physical/navigation-and-transportation/wayfinding-and-navigation https://manoa.hawaii.edu/exploringourfluidearth/physical/nav...
- sandworm101 5y agoStart the clock at zero and just start counting seconds. The problem only occurs when you are trying to calculate sunrise/set times. Your solar power system doesn't care about leap seconds/days/years. It knows to expect sunrise at 353478515 seconds without regard for human concepts of a particular day or month.
- munk-a 5y agoWell I assume the drift based on atmospheric anomalies doesn't tend toward a total delta of +/- 0 over time - or at least we're not accurately accounting for it yet. As such we'd face the same january in summer problem the romans faced right? Slowly midnight will move further and further from the time when you're furthest from the sun.
- BitwiseFool 5y agoI'm imagining a system where you have two different lengths of time units. You can have a "scientific second" which is defined by distance and the speed of light. Just like we have now in SI. When the rotation of the planet changes slightly you need to compensate by adding leap seconds every few years for things to sync up. Eventually they will need to add a leap second every day as the earth's rotation slows down. Some planet with high variation would be adding and removing these frequently. But, you can define a second as 1/86400th of a "day". For most civil purposes you just want to know when an event happened relative to the day/night cycle and the year. In which case the order of events is more important than the precise amount of time between the events. If precision is needed, you can always measure in scientific seconds and convert accordingly. I figure the "civil second" is fine for such a purpose because it's not like living beings can consistently and accurately keep track of time in their heads. Now for a planet with a rotation as slow as Venus the concept of a "day" is probably meaningless. It would be more like a season of light and darkness. So I suppose you'd just only use scientific seconds and count upwards?
- brandmeyer 5y agoTurns out that this standard already exists. UT1 (and its close cousin UT1R) track Earth's rotation using radio astronomy techniques. The basis for adding leap seconds is the wind up between UTC and UT1. I agree, we ought to align UTC to UT1 instead of TAI. Doing so is not trivial on a technical level, though. At the very least, the GNSS broadcast time parameters wouldn't support such a revision for decades.
- harywilke 5y agoInteresting. Noon is when the sun is highest. I had fun explaining time zones to my son the other day. I think he got lost in my train analogy: If the train travels around the earth at the same speed the earth turns, then it's always noon on the train.
- ArnoVW 5y agoConceptual stuff like that is tricky if you don't already know it. I've found that visual explanation works best for building an intuition. My approach for day / night type of questions: - a soccer ball - a toilet roll - the lamp in your phone When you shine your lamp through the toilet roll on the ball, you get a neat 'terminator'.
- Pxtl 5y agoIt gets better. Venus' atmosphere superrotates far faster and so an airship city over Venus would have a different day/night cycle too.
- anticristi 5y agoWith such a huge transfer of momentum -- a day on Venus is +/- 3 minutes the previous one -- the winds on the ground must be crazy!
- munk-a 5y agoYea actually, prior to reading this article I always thought of the atmosphere as a mostly static shell that just sorta floats around planets - it's interesting to consider how, when the wind pushes on a mountain the mountain pushes back (not literally of course) and that can cause subtle variations in day cycle on earth that could be influenced by spikes in externally acquired heat in differing parts of the atmosphere - but it's crazy to think how much more dramatic the effect is on Venus.
- qayxc 5y agoThe winds on Venus' surface are actually pretty tame ("light breeze", 1 Beaufort, 0.5 to 1 m/s) [1]. Problem is, that even this very slight wind packs a considerable punch at 92 bars of pressure and is comparable to a category 4 hurricane on Earth in terms of power (i.e. it would roughly translate to about 90 m/s; 325 km/h; 200 mph on Earth). [1] https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.ht...
- BurningFrog 5y agoObviously, the planet as a whole rotates at a very constant speed. But the "hard" planet and the atmosphere can move in very different ways. The 3 minute difference comes from not seeing the atmosphere as part of the planet.
- mrfusion 5y agoWhy does the atmosphere rotate faster than the planet?
- qayxc 5y agoBecause unlike Earth, Venus receives a whole bunch of solar radiation on one hemisphere for months on end. This drives a substantial temperature differential that causes strong winds. Since a day on Venus is longer than a year on Venus, it doesn't take much for the atmosphere to rotate faster, either.
- emc3 5y agoToday NASA also announced new missions to Venus, discussed here: https://news.ycombinator.com/item?id=27374233 https://news.ycombinator.com/item?id=27374233
- alexpotato 5y agoAt a past job, they used to call phases of a software project "Days" e.g. "That's a Day 2 feature, not a Day 1 feature." Since the "Days" seemed to last forever, I used to joke "Are we measuring project progress in Venusian days? Those are like 243 days per regular day"
- Shadonototro 5y agoif the Sun looses intensity over time, Venus is the perfect planet to teraform
- sulam 5y agoExcept for the whole expansion phase thing that comes along with it.
- Thiez 5y agoBut the opposite is the case. The sun will get hotter for the foreseeable future until the earth will also become uninhabitable. And then the sun will expand and swallow Venus and probably also our planet. So if we base the choice only on the expected future intensity of the sun Mars would seem the better choice.
- bullfightonmars 5y ago> We illuminate it with an extremely powerful flashlight—about 100,000 times brighter than your typical flashlight Wow! How much of this hits the atmosphere/surface of Venus. Is this the amount of energy output from the Radio Telescope or that hits the surface.