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Our moon has been slowly drifting away from Earth over the past 2.5B yrs
- hinkley 4y agoWould Pangea have resulted in less tidal locking due to less resistance to the flow of the oceans? I would think ice ages also slowed things down.
- londons_explore 4y agoI would suspect the effect of tidal forces in the rock of the earth has more impact than in the seawater. Simply because there is a lot more rock, and as molten magma deforms it absorbs a lot of energy - it has a pretty high viscosity.
- Daub 4y agoMy poor old eyes. Read this as ‘Our mom has been slowly drifting away from Earth over the past 2.5B yrs’
- saagarjha 4y agoYours might be large enough to affect the planet's rotation, but leave the rest of our moms out of this.
- picsao 4y ago
- elevaet 4y ago> We found that the moon was around 60,000 kilometers closer to the Earth then [2.46 billion years ago] (that distance is about 1.5 times the circumference of Earth). This would make the length of a day much shorter than it is now, at roughly 17 hours rather than the current 24 hours. I wish they explained why the moon being that much closer would have such a dramatic effect on the day length. Can someone explain this? Seems off to me, but I'm very physics-naive. Also, good to know it's drifting away, and not towards the earth!
- mgraczyk 4y agoTo first order I think the explanation is just conversation of angular momentum. The moon earth system has to have it's angular momentum constant over time. If the moon is further away in a stable orbit, the earth must rotate slower.
- morsch 4y agoIt's explained here: https://en.m.wikipedia.org/wiki/Tidal_acceleration https://en.m.wikipedia.org/wiki/Tidal_acceleration
- FiatLuxDave 4y agoSure. The earth is spinning faster than the the moon is going around the earth (earth rotates in one day, the moon goes around in about a month). When the tides transfer energy and momentum to the moon from the earth's spin, it slows down the earth's spin and gives the moon more energy. This moves the moon to a higher orbit, so it moves a bit farther away from us. The source of energy for the whole process is the earth's spin. It takes a lot of energy to lift a moon, relative to the amount of energy in the earth's spin, which is why it has such a dramatic effect on the day length.
- redact207 4y agoIf the moon wasn't drifting away and was in a static orbit, would the Earth's rotation slow and the moon's orbit speed up to the point where they're in sync?
- yellowapple 4y agoEventually, yeah; just as the Moon is tidally locked to Earth, Earth would be tidally locked to the Moon. I don't know offhand whether that would happen before the Moon drifts too far away to remain in Earth's orbit, however.
- sliken 4y agoMoon is below escape velocity, so it's not leaving. In fact when 1 day = 1 lunar month the movement away will stop, and reverse. It will continue to get closer to earth until it hits the Roche limit and becomes a ring.
- Proven 4y ago
- apengwin 4y ago
- divbzero 4y agoA curious effect of this is that total solar eclipses past and future look different from total solar eclipses today. We live in a time when both the Sun and the Moon are roughly the same size (~32 arcminutes) when viewed from Earth. This coincidence results in the image we associate with total solar eclipses where the Sun’s corona is visible as a ring around the Moon.
- deleted 4y ago[deleted]
- charcircuit 4y agoIn even 1000 years that would only be an offset 38 meters. That wouldn't meaningfully change the ratio.
- consp 4y agoWhile not overwhelming an orbit change of 38000km per 1b years sounds more than enough to change that image.
- d0mine 4y ago38000km is just 10% of the current Moon-Earth distance and on the time scale of billions years, there are other things to worry: "the Sun will likely engulf Earth in about 7.59 billion years." https://en.wikipedia.org/wiki/Future_of_Earth#:~:text=Earth%20will%20interact%20tidally%20with,in%20about%207.59%20billion%20years https://en.wikipedia.org/wiki/Future_of_Earth#:~:text=Earth%....
- User23 4y agoRoughly the same size is understating it severely. They are uncannily similar in apparent size.
- TheSpiceIsLife 4y agoThe surface of the Earth is the only place we know of where a natural satellite appears exactly the same size as the primary / only star.
- kuramitropolis 4y agoAnd good riddance!
- Vanit 4y agoRelated; Kurzgesagt recently released a nice animation demonstrating where Earth "is" once you consider orbital dynamics https://youtu.be/Pj-h6MEgE7I https://youtu.be/Pj-h6MEgE7I
- Zecc 4y agoI initially missed the B in the title and thought the moon's been drifting away over the past 2.5 years. Which I guess is also true.
- NKosmatos 4y agoI feel sorry for our future colleagues software developers, that will have to deal with calendars, public holidays and all other stuff related to the lunar calendar. There are many religions that use the lunar cycles as basis for their calculations: https://en.wikipedia.org/wiki/Lunar_calendar https://en.wikipedia.org/wiki/Lunar_calendar
- teawrecks 4y agoLunar calendar? How about the rotation of the earth? I imagine the further out it gets, the further out our moment of inertia, the slower the earth spins. Days get longer, but the length of a year stays the same. That'll be a fun one. We would probably have day length deniers/365 purists who believe nothing is changing for centuries.
- mtlmtlmtlmtl 4y agoA 360 day year would be kind of neat. We could ave a perfect 6 week calendar, with 60 weeks, 5 per months, every month 30 days.
- waste_monk 4y agoAll nations of the world must band together to build a harpoon, of immensity and grandness the likes of which has never seen before. The moon cannot be allowed to escape.
- beebeepka 4y agoYou would have her imprisoned, covered in metal burka, hosting terran colonists till her end? If you really love her, you should let her go.
- egberts1 4y agoDespite the rapid devolvement of the Moon’s rotational at its own polar axis (to a point of having one face of the Moon being tidal locked toward Earth) since its birthing from Earth, I remain curious about the breakage of such tidal locking as Moon’s orbit dramatically continues to expand.
- doubleunplussed 4y agoNah it won't. The timescale for it to lock is much faster than anything else - it'll stay locked the whole time.
- jb101 4y agoThe universe is expanding almost as fast as the Moon is moving away from the Earth.
- soliton4 4y ago-- quote -- These have shown that the moon is currently moving 3.8 cm away from the Earth every year. If we take the moon's current rate of recession and project it back in time, we end up with a collision between the Earth and moon around 1.5 billion years ago. -- end quote -- 3.8 cm * 1.500.000.000 = 5.700.000.000 cm = 57.000.000 meter = 57.000 km distance between earth and moon = 384,399 km according to https://en.wikipedia.org/wiki/Lunar_distance_(astronomy) https://en.wikipedia.org/wiki/Lunar_distance_(astronomy) what is wrong here?
- JaimeThompson 4y agoThe rate at which the moon moves away from the Earth isn't constant. I can't find the details right now so I could be totally wrong.
- soliton4 4y agothats true, however the author explicitly stated that the collision point of earth and moon at 1.5 billion years was calculated by assuming the moons CURRENT rate of recession
- zenexer 4y agoAt no point does the author make any assertion that the rate was constant. Presumably, the current rate of recession is just one variable that gets plugged into an equation.
- soliton4 4y ago"If we take the moon's current rate of recession and project it back in time" is a very straight forward way of saying, lets assume the moon receeded from the earth at the current rate.
- snowwrestler 4y agoNo it’s not because you are projecting backward in time in the presence of a gravitational field that varies with square of radius. The path of the moon away from the Earth is not a straight line, it is a tightly wound spiral.
- bradleyankrom 4y agoThe moon is quiet quitting us
- andrewstuart 4y agoHow would the moon have looked to someone looking into the night sky billions of years ago? Dramatically bigger, or not noticeably? What would have been the effect on tides?
- sliken 4y agoI was disappointed in this article that doesn't really explain what's going on. Yes, the moon is moving away from earth, because the energy transferred by tides. Said energy transfer is slowing the spin of earth, which lengthens the day. This transfer will stop once a day = a lunar month. At which point the moon will slowly decrease it's orbit until it hits the Roche limit and becomes a ring. Fun to think about, granted it's billions of years and the sun may become a red giant before then and either alter earths orbit or consume it.