The moon is drifting farther and farther away from the earth. will it ever work

One caveat to the moon’s recession rate is that it hasn’t always been what it is now. Our current estimate comes from NASA’s Apollo mission in 1969, which placed five reflective plates on the lunar surface. Scientists shine laser pulses at the reflectors from Earth and record the round-trip times to get distance measurements with an accuracy of about 3 centimeters.

But if you extend the 1.5 inch regression rate backwards in time, the Moon and Earth would collide 1.5 billion years ago, while we know the Moon formed about 4.5 billion years ago. This shows that the speed at which the moon drifts away varied in the past.

To better understand how far away the Moon was in our planet’s past, geoscientists from Utrecht University and the University of Geneva studied ancient rock strata in the gorges of Karijini National Park in Western Australia.

The paper, recently published in the Proceedings of the National Academy of Sciences, shows that about 2.46 billion years ago, the moon was about 60,000 kilometers closer to Earth than it is today. This means that our days were shorter back then, only around 17 hours instead of the 24 hours we expect.

The scientists’ look into the past is based on the study of erosion patterns in rock formations that are related to fluctuations in the earth’s climate in connection with so-called “Milankovitch cycles”.

Proposed a century ago by Serbian scientist Milutin Milankovitch, these orbital cycles link small, periodic changes in the shape of Earth’s orbit and the orientation of its axis to how the sunlight received by the planet is distributed over time.

The changes can lead to extreme cold or warm periods and wetter or drier regional climate conditions. Notably, the rock record tracks these cycles in the way sediments are deposited, and their frequency is related to the distance between Earth and the moon, the scientists demonstrated.

Interesting Engineering (IE) spoke to the new study’s co-author, Dr. Margriet Lantink from the University of Utrecht in the Netherlands, on the methodology of the work and the implications of its results.

The following conversation has been edited slightly for clarity and flow.

Interesting Technique: Are the Milankovitch Cycles Linked to the Climate Changes We Observe?

dr Margaret Lantink: The Milankovitch cycles have nothing to do with the sharp increase in atmospheric CO2 concentration and associated global warming that we have been observing since the Industrial Revolution. Milankovitch cycles play a role on time scales from tens of thousands to millions of years – the recent increase in CO2 and global warming are many orders of magnitude faster and of greater amplitude than what has ever been observed in geological history, and for which we humans they are responsible.

Of course, the shape of the Earth’s orbit and the orientation of its axis of rotation are still subject to slow periodic changes (originating from gravitational interactions with the other bodies in our solar system), and these will slowly alter the distribution of incoming solar radiation on the Milankovitch timescales. Earth is currently near a 405,000-year eccentricity cycle minimum—so its orbit is relatively circular—and close to a precession maximum—meaning relatively low seasonality and low summer insolation in the northern hemisphere. The tilt angle of the Earth’s axis is medium.

In the figure below, you can see how glacial-interglacial cycles have followed a ~100,000-year pattern attributed to Milankovitch cycles over the past 800,000 years. We are now in an interglacial period, and we should be slowly moving towards the next ice age. However, the recent human CO2 entry is visible as an almost vertical, very high spike on the chart. As a result, we are very unlikely to enter this Ice Age for the next ~50,000 years due to the unprecedented amounts of CO2 we have been emitting into Earth’s atmosphere.

IE: Can you predict the distance from the earth to the moon in the future, another 2.46 billion years?

lantin: Our estimate of the Earth-Moon distance 2.46 billion years ago is based on empirical data stored in geological records, but of course there is no geological record for the future, and so we have to rely on models for Earth. Tidal evolution of the moon, which is certainly not my area of ​​expertise.

The Earth’s rotational speed and the Moon’s orbit evolve over time as a result of the dissipation of tidal energy (primarily in Earth’s ocean). This tidal derivative (or frictional drag) depends on many different parameters and complex processes that vary with time and on different time scales and have therefore been very difficult to constrain accurately in the past, such as B. Changes in the configuration of the continents (due to plate tectonics). Because of this, there is much uncertainty about the tidal history of the Earth-Moon system and the associated evolution of the lunar orbit.

The fact that we were able to obtain information about the Earth-Moon system 2.46 billion years ago does not mean that we now understand what happened between then and now: With our study we “only” provided an important snapshot Situation 2.46 billion years ago. We now need more reliable geological data points that can be compared to robust theoretical models (such as the recent model by Farhat et al., 2022: The resonant tidal evolution of the Earth-Moon distance) to predict the Moon’s evolution over time and try to understand what were/are the main parameters that control its development.

For the future, predictions about the development of the earth-moon system and the lunar orbit are possible. But these predictions are being misunderstood because of the many unknowns in the Earth’s geophysical state, such as of plate tectonic evolution, may be less accurate/include a larger margin of uncertainty than past predictions.

IE: Is there a point where the moon would be too far away and drift out of Earth’s orbit?

lantin: First, let me be clear that it is not the moon’s recession that is causing the Earth’s rate of rotation to decrease – both of which occur as a result of tidal dissipation. This tidal dissipation (frictional drag exerted on the Earth’s tidal bulge) slows the Earth’s rotation, and by transferring angular momentum, the Moon is accelerated to a higher orbit.

Whether it’s possible for the moon to drift out of Earth’s orbit: in infinite time, yes, but we’ll reach the end of our solar system in less time — simply lacking the time for the moon to move far enough away from Earth’s gravitational pull escape. The tidal dissipation effect slows down over time as the moon moves farther away.

Study Summary:

The long-term history of the Earth-Moon system, as reconstructed from the geological record, remains unclear when based on fossil growth bands and tidal layers. A potentially more robust method offers the sediment record of Milankovitch cycles (climate precession, obliquity, and orbital eccentricity), whose relative ratios of periodicity change over time as a function of decreasing Earth’s rotation rate and increasing Moon distance. However, for the critical older part of Earth’s history, where information on Earth-Moon dynamics is sparse, suitable sedimentary sequences in which these cycles are recorded remain largely unknown, leaving this method unexplored. Here we present results of cyclostratigraphic analysis and high-precision U-Pb-Zircon dating of the Joffre member of the Lower Paleoproterozoic of the Brockman Iron Formation, NW Australia, the evidence for the Milankovitch force of regular lithological alternations associated with Earth’s climatic precession and the provide orbital eccentricity cycles. Combining visual and statistical tools to determine their hierarchical relationship, we estimate an astronomical precession frequency of 108.6 ± 8.5 arcsec/year, which corresponds to an Earth-Moon distance of 321,800 ± 6,500 km and a day length of 16.9 ± 0 .2 h at 2.46 Ga. With this robust cyclostratigraphic approach, we extend the oldest reliable date for the history of the lunar recession by more than 1 billion years and provide a critical reference point for future modeling and geological investigations of the Precambrian evolution of the Earth-Moon system.

Read the full study here.