EARTH is shoving the moon away faster now than it has done for most of the past 50 million years, says a new model for the way tides influence the lunar orbit. The result helps solve a mystery concerning the moon's age that has long vexed astronomers.
The moon's gravity creates a daily cycle of low and high tides. This dissipates energy between the two bodies, slowing Earth's spin on its axis and causing the moon's orbit to expand at a rate of about 3.8 centimetres per year. If that rate has always been the same, the moon should be 1.5 billion years old, yet some lunar rocks are 4.5 billion years old.
Enter Matthew Huber of Purdue University in West Lafayette, Indiana. His team gathered data on ocean depths and continental contours that existed 50 million years ago, and fed that into a model to simulate ancient tides. Energy dissipation back then was only half what it is today, so the moon was pushed away at a slower rate (Geophysical Research Letters, doi.org/mjz).
The key is the North Atlantic Ocean, which is now wide enough for water to slosh across once per 12-hour cycle, says Huber. Like a child sliding in a bathtub, that creates larger waves and very high tides, shoving the moon faster.
This article appeared in print under the headline "Tides are pushing the moon away faster"
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
Have your say
Only subscribers may leave comments on this article. Please log in.
Only personal subscribers may leave comments on this article
Subscribe now to comment.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
meghan mccain wilson chandler bristol motor speedway prometheus grand canyon skywalk tonga pid
No comments:
Post a Comment