Starship Asterisk*

Jerome68 wrote: ↑Wed Jun 03, 2020 9:13 am I did not know about that fact, super interesting. Sad is not possible to appreciate it because of the clouds in Venus.

By the way, do you know any source where I can read, why Venus rotation is so slow compared with the rest of the planets? That is another fact that has always got my attention about this planet

JohnD wrote: ↑Wed Jun 03, 2020 10:04 am The APOD blurb, that says that the Earth "surprisingly dominates the Sun's tidal effect" leads to a 1969 article, whose abstract starts, "The observed spin-orbit resonance of Venus, whereby the same side of Venus faces the Earth at each inferior conjunction, cannot be explained adequately by gravitational interaction with the Earth alone." It then goes on to speculate (I think, I cannot read the entire article, thanks to Elsevier's ridiculous publishing policy. I mean, charging you to read a fifty year old paper!) that a "solar atmospheric tide" may contribute to the orbital locking.

I don't understand that - solar? In the Sun's atmosphere? Or in that of Venus, caused by the Sun? And after fifty years, do we have no more certain an explanation?

Chris Peterson wrote: ↑Wed Jun 03, 2020 1:19 pm

JohnD wrote: ↑Wed Jun 03, 2020 10:04 am The APOD blurb, that says that the Earth "surprisingly dominates the Sun's tidal effect" leads to a 1969 article, whose abstract starts, "The observed spin-orbit resonance of Venus, whereby the same side of Venus faces the Earth at each inferior conjunction, cannot be explained adequately by gravitational interaction with the Earth alone." It then goes on to speculate (I think, I cannot read the entire article, thanks to Elsevier's ridiculous publishing policy. I mean, charging you to read a fifty year old paper!) that a "solar atmospheric tide" may contribute to the orbital locking.

I don't understand that - solar? In the Sun's atmosphere? Or in that of Venus, caused by the Sun? And after fifty years, do we have no more certain an explanation?

https://en.wikipedia.org/wiki/Atmospheric_tide

JohnD wrote: ↑Wed Jun 03, 2020 6:23 pm

Chris Peterson wrote: ↑Wed Jun 03, 2020 1:19 pm

JohnD wrote: ↑Wed Jun 03, 2020 10:04 am The APOD blurb, that says that the Earth "surprisingly dominates the Sun's tidal effect" leads to a 1969 article, whose abstract starts, "The observed spin-orbit resonance of Venus, whereby the same side of Venus faces the Earth at each inferior conjunction, cannot be explained adequately by gravitational interaction with the Earth alone." It then goes on to speculate (I think, I cannot read the entire article, thanks to Elsevier's ridiculous publishing policy. I mean, charging you to read a fifty year old paper!) that a "solar atmospheric tide" may contribute to the orbital locking.

I don't understand that - solar? In the Sun's atmosphere? Or in that of Venus, caused by the Sun? And after fifty years, do we have no more certain an explanation?

https://en.wikipedia.org/wiki/Atmospheric_tide

Thank you, Chris! So, caused by Venus' atmosphere. I'm amazed, dumbfounded. The Moon has no atmosphere but has been locked into synchronous rotation with the Earth, and I understand that the Earth's rotation is slowing down so that one day it will be locked to the Moon. But not for millions of years (?). So intuitively it's unimaginable that Venus, 25 million miles away its closest, should be influenced as much as the Moon, which is a hundred times nearer all the time! And so affected by Earth's gravity 10,000 times less! Quantum chromodynamics? Trivial compared to orbital mechanics!

Ann wrote: ↑Thu Jun 04, 2020 4:33 am I didn't pay all that much attention to this APOD. So, is it correct that the ultra-slow rotation of Venus is actually caused by the fact that our sister planet is tidally locked to the Earth?

Or have I misunderstood everything?

Ann

Chris Peterson wrote: ↑Thu Jun 04, 2020 1:25 pm
The slow rotation of Venus is probably unrelated to the Earth. Something happened early in the formation of the Solar System that flipped its rotation axis and resulted in a slow retrograde rotation.

https://en.wikipedia.org/wiki/Venus#Orbit_and_rotation wrote:
<<Alex Alemi's and David Stevenson's 2006 study of models of the early Solar System at the California Institute of Technology shows Venus likely had at least one moon created by a huge impact event billions of years ago. About 10 million years later, according to the study, another impact reversed the planet's spin direction and caused the Venusian moon gradually to spiral inward until it collided with Venus.>>

JohnD wrote: ↑Thu Jun 04, 2020 3:30 pm Oh! So it's coincidence, nothing to do with tidal locking, atmospheric tides or the Great Venusian Panjandrum?
John

Chris Peterson wrote: ↑Thu Jun 04, 2020 4:01 pm
The near orbital resonance is just a coincidence. But that same near resonance might play a role in the orbital-rotational relationship that seems to keep the same place on the surface rotating into the same position at each inferior conjunction... meaning the latter might not be a coincidence at all, but something that follows physically as a consequence of a coincidence.

Jerome68 wrote: ↑Thu Jun 04, 2020 4:30 pm

Chris Peterson wrote: ↑Thu Jun 04, 2020 4:01 pm
The near orbital resonance is just a coincidence. But that same near resonance might play a role in the orbital-rotational relationship that seems to keep the same place on the surface rotating into the same position at each inferior conjunction... meaning the latter might not be a coincidence at all, but something that follows physically as a consequence of a coincidence.

I normally will agree with you, but it also shows the history of science that a coincidence is hiding some big discover, wouldn't be this the case? (I don't pretend to say I know it, but, why not? also, the moon is showing us the same face, why not a way to interact we don't know would explain it?). Coincidences in science are very rarely (in my opinion) :)