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posted by mrpg on Wednesday June 20 2018, @09:40PM   Printer-friendly
from the density=density+1 dept.

Submitted via IRC for BoyceMagooglyMonkey

Time is out of joint on Venus. The planet's thick air, which spins much faster than the solid globe, may push against the flanks of mountains and change Venus' rotation rate.

Computer simulations show that the thick Venusian atmosphere, whipping around the planet at 100 meters per second, exerts enough push against a mountain on one side and suction on the other side to speed the planet's rotation rate by about two minutes each Venus day, according to a study in Nature Geoscience June 18.

That's not much, considering that the planet rotates just once every 243 Earth days. By comparison, Venus' atmosphere rotates about once every four Earth days. Precise measurements of the planet's rotation rate have varied by about seven minutes, however. The push and pull of the air over the mountains could help explain the mismatch, with some other force — possibly the gravitational influence of the sun — slowing the planet's spin back down.

Source: Venus’ Thick Atmosphere Speeds Up the Planet's Spin


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  • (Score: 0) by Anonymous Coward on Thursday June 21 2018, @10:50AM (1 child)

    by Anonymous Coward on Thursday June 21 2018, @10:50AM (#696129)

    heating won't act on the center of mass.
    due to local conditions the atmosphere may accept a different percentage of the energy input (which can be considered a constant times some factor that depends on "Sun's angle in the sky").
    therefore the atmosphere can in principle be rotated by a feedback mechanism if the rotation emphasizes the conditions that lead to the initial differential heating.

    I don't know if this is actually happening here (no time to read the paper), but a mechanism for differential heating does exist.

  • (Score: 2) by deimtee on Thursday June 21 2018, @12:45PM

    by deimtee (3272) on Thursday June 21 2018, @12:45PM (#696162) Journal

    The point was that there is no mechanism postulated to change the total angular momentum of the planet. If the atmosphere speeds up for any reason that doesn't involve an interplanetary force, then it must have been by reaction against the planet. Newtons third law. Without an external force - not just an energy input - the atmosphere cannot accelerate without pushing back on something else. That something else is the planet.
    If the wind is continually pushing against a mountain in one place, then it must be pushing against something else in the opposite direction somewhere else. Saying the wind can accelerate the planet is as valid as saying that if you pull on your boots hard enough you can lift yourself off the ground.

    --
    If you cough while drinking cheap red wine it really cleans out your sinuses.