Is it possible for a planet to have a perpetual solar eclipse if a satellite orbits at the same speed as the planets rotation?
Kind of, but it's not very stable.
In this arrangement, the satellite is at the "L1 Lagrange point". This is where the gravity from the planet, the gravity from the star, and the effective centrifugal force from movement of the planet and the moon all cancel out, and the moon is at an equilibrium point in-between the planet and the star.
However, this is not a stable equilibrium. Although all the forces add up to zero (in a rotating frame), if you give the moon a tiny push, then it will drift away further and further and faster and faster until it's not near the L1 point anymore.
This means that you don't get moons naturally hanging out at the L1 point. But you can put an artificial satellite there. You do need to constantly give little boosts to correct the orbit to keep it there, but they only need to be small boosts.
Quakes are generally accompanied by very sight rearrangement of a body's mass which is accompanied by a movement of the center of mass.
For a thought experiment, imagine one half of a planet were hollow, but then the whole thing collapsed uniformly in space. The new center of mass would be moved significantly towards the former empty space, resulting in the gravitational effects being different. Real quakes do the same thing, just many orders of magnitude smaller.
Do Earth earthquakes, or crustquakes of other bodies, perturb the Solar System's dynamics at all?
Technically, yes. Practically, no. Our Solar System is very spread out and Earth is nowhere near the biggest player among the planets; pretty much no earthquake it could possibly experience would have any kind of practical impact on the orbit of any body (even the Moon would barely be disturbed).
To put this in context, if you performed the "doomsday scenario" of a "planetary alignment"—that is, line up every single body in the Solar System perfectly—so that their gravitational fields were all as impactful upon one another as possible, NASA calculated that it would be enough to cause Earth's tides to rise... 1/25th of 1mm.
What earthquakes certainly can do is affect the rotational speed, tides and axial tilt of a planet, because it's a redistribution of mass within one system over a relatively small area. However, even there, the effects are generally very minor. Remember the 2004 Christmas Day tsunami and earthquake that killed over 200,000 people in Indonesia? That earthquake did actually cause the Earth's rotation to speed up somewhat, and shortened a day by about 3 microseconds (3 millionths of a second) because the Earth got a bit less oval-shaped. However, since the Moon is consistently stabilizing our orbit, that change in rotational speed was lost likely within a couple of weeks.
we named the planet "dirt". an earthquake is a quake of earth not a quake of the earth so an earthquake on mars would still be an earthquake.
(edit- ...i guess it wouldn't translate to for example planets "made of ice" instead of a quake of some kid of rocky crust (like if a miles deep glacier shifted), if you're being overly literal with the roots at least. common use would probably still call it earthquake as long as 'the ground' is shaking regardless of what the ground is made of, like how acid rain on venus is still rain. but it might matter scientifically since I'm not sure if ice layers can really be described as having plate tectonics /edit)
changing it by planet would be silly, like how fireman is linguistically correct even if ignorant people who don't know what the word actually means decided it wasn't pc. I'm sure somebody would insist on calling it a marsquake but they'd be wrong
"Earth" translates if you think of the meaning as being "our earth, our planet." If there were Venusians or Martians and they had a word for their own planet it would mean the same thing, it would be the translation of "earth" in their local language. "Earth" is a relative term.
Isolated cultures don't themselves give a proper-noun to their own island or their own people; the word they use in the local language just means "the land" or "the people." Because for them it's the only land, the only people. Or you'll find the name was given by outsiders and eventually adopted by the locals, because we do give proper names to other places, to other people.
So "earth" should be written with a lower-case e because it's not a proper noun.
What about on the other side? Is it more stable if a planet is in the L1 point between a smaller moon and its parent star? So if we lived on a planets moon could a planet permanently eclipse the moon and be relatively stable or because the planet has greater mass would it be even less stable than a smaller object in the L1 point?
Also side question how many Legrange points are there where Gravities cancel each other out? Are they just in smaller star-planet-moon systems or do Galaxies and star clusters have legrange points?
When the moon is "behind" the planet, it's in the L2 point. The Lagrange points are defined relative to the planet because it has a stronger gravity. But it's also unstable.
There are five Lagrange points in total. Wikipedia has a nice plot but I'll list them here:
L1 - satellite is between planet and star
L2 - planet is between satellite and star
L3 - satellite is on opposite side of star from planet
L4 - satellite is partially anticlockwise around the orbit from the planet
L5 - satellite is partially clockwise around the orbit from the planet
Out of these, only L4 and L5 are stable, and they only exist if the planet is sufficiently small compared to the star. This is the case for all the planets in our solar system - even Jupiter - but it means that two stars orbiting each other do not have L4 and L5 points.
However, for Jupiter they are quite deep and stable, and they are home to two "camps" of asteroids: the Trojan asteroids and the Greek asteroids, who hang out in the same orbit as Jupiter, one "camp" in front, and one "camp" behind. Again, wikipedia has a nice plot.
October 8, 2018
JFK: After the Shot
When Air Force One's crew Learned of the Kennedy assassination, They refused to put his body in the cargo hold and modified the plane with a hacksaw to be able to take the coffin in the cabin.
The position of the Dallas police was that it was the law that the body could not leave city limits.
The position of the federal government was that, since Attorney General Bobby Kennedy was officially the highest ranking law officer in the U.S., then he could overrule them.
I Am Not A Lawyer, but if Lee Harvey Oswald had gone to trial, this all could have been an important point -- the Law is supposed to keep all evidence under its direct control and not let anyone or anything tamper with it.
The book "Best Evidence" by David Lifton has a theory that was good at keeping me up at night.
Note that they refused to take the casket in the cargo hold. What could happen if it was up in the cabin? Lifton describes the surgery that could be done on the body during the flight back to D.C. that would make it look like the exact opposite of what happened.
They could take a body that had been shot from the front and make it look like it had been shot from the back. Then at the autopsy in D.C. there would be no question of multiple shooters on a grassy knoll. One shooter in the Texas School Book Depository would be the conclusion.
If the body had stayed in the hands of the Dallas police, there would be safeguards against that happening.
A crime has occurred. A man has been murdered in Dallas City limits, Dallas PD has jurisdiction. A federal official in line of duty is murdered, FBI has jurisdiction.
How this gets settled out, is normally a matter of priority.
The FBI will typically take the murder jacket but the locals will run the autopsy and report because it's easier.
i'd have to talk with the Local ME's see if the FBI even runs their own coroners. The only ME's I know of in the federal system are typically Military.
I imagine the proper approach would be to run the autopsy at Parkland or at the Dallas Coroners office, with FBI/Secret service as recipients of chain of evidence, and Dallas PD as witnesses.
That would mean leaving JFKs corpse in Dallas for a day, and LBJ flying to DC. But nobody was thinking very clearly.
LBJ needed to take AF-1 to DC immediately, and a USAF Cargo jet needed to take JFKs body back to DC later.
I don't exactly blame a whole lot of people for being upset and making bad decisions. They were humans in a terrible minute.
The autopsy is one of the main reasons there is such confusion and controversy about the Assassination. Partially because it was so farcically done.
The two pathologists who performed it had never done a single gunshot wound autopsy in their entire careers. They never spoke to the doctors at Parkland Hospital (who’s recollections of Kennedy’s wounds are different to what the autopsy concluded), the original autopsy report was burnt, and then a new one was made from the doctors memory. The locations of none of jfk’s wounds are known with any precision. The back wound, for example, was not measured against a standard anatomical feature, and was photographed with the body in a distorted position. The fundamental question, of whether or not the back and throat wounds were caused by the same bullet, could have been answered by dissecting the wounds and the connecting tissue, but the pathologists were ordered not to do this according to sworn testimony.
IIRC he was in the hospital dying and the local police & authorities wanted to take possession of the body as he had died in Texas, and the shooter had committed murder in Texas. They would have then performed an autopsy on the body of the president, kept him in their freezer until the investigation was complete, etc., before releasing it to the family for burial.
USSS said nope, and were basically willing to draw their weapons and defend the body of the president with force. The local cops didn't want to get down like that, so they let them take possession of the body and put it on a plane back to DC.
Not 100% sure if it was a federal crime to kill the president at that time or not, i.e., it Lee Harvey Oswald may not have been guilty of a federal crime so it was unclear who had "jurisdiction" of the investigation.
Aircraft structural mechanic here. We seal any parts that get attached to the skin and fasteners that go through the skin and load any possibly leaky areas with sealant. When we're done with major work we do a pressurization test where we pressurize the whole plane and see how bad it leaks. We're allowed a certain tolerance like 1psi in 15 mins for example so the leaking is pretty miniscule and the way the pressurization system works more than makes up for that small bit of leakage. Unfortunately there's pretty much no way to entirely seal a 150+ foot-long airplane with millions of rivets and screws going through it.
The coffin is typically taken out in order with the other items, but is also ceremoniously escorted by military personnel to its final destination. They fly with them and ride with them to the final resting location. On occasion they will also be one of the military members to do the final salute and assist with the folding of the flag and delivery of it to the family.
Source: Was present at a funeral as a kid and asked one of the soldier there.
The escorts and coffin may not be on their last stop or will be picked up by a hearse and local Honor Guard at the tarmac, so things might be delayed. It's also a matter of respect. You aren't asked to do much other than wait for the coffin to be removed and transferred and so the escorts can disembark and salute the fallen service member as they go.
As far as being the last out of the cargo hold, most of the coffins have a space for them to be specifically in the plane or are the last things interred before takeoff, all of this is observed by the escorts and local Honor Guard of the particular location.
As far as I know, civilians are not given the same treatment, but I might be wrong.
Same process is observed for nonviolent passing overseas, but in country, they likely live and will be interred at a location near their current station.
The position of the Dallas police was that it was the law that the body could not leave city limits.
The position of the federal government was that, since Attorney General Bobby Kennedy was officially the highest ranking law officer in the U.S., then he could overrule them.
I Am Not A Lawyer, but if Lee Harvey Oswald had gone to trial, this all could have been an important point -- the Law is supposed to keep all evidence under its direct control and not let anyone or anything tamper with it.
The book "Best Evidence" by David Lifton has a theory that was good at keeping me up at night.
Note that they refused to take the casket in the cargo hold. What could happen if it was up in the cabin? Lifton describes the surgery that could be done on the body during the flight back to D.C. that would make it look like the exact opposite of what happened.
They could take a body that had been shot from the front and make it look like it had been shot from the back. Then at the autopsy in D.C. there would be no question of multiple shooters on a grassy knoll. One shooter in the Texas School Book Depository would be the conclusion.
If the body had stayed in the hands of the Dallas police, there would be safeguards against that happening.
A crime has occurred. A man has been murdered in Dallas City limits, Dallas PD has jurisdiction. A federal official in line of duty is murdered, FBI has jurisdiction.
How this gets settled out, is normally a matter of priority.
The FBI will typically take the murder jacket but the locals will run the autopsy and report because it's easier.
i'd have to talk with the Local ME's see if the FBI even runs their own coroners. The only ME's I know of in the federal system are typically Military.
I imagine the proper approach would be to run the autopsy at Parkland or at the Dallas Coroners office, with FBI/Secret service as recipients of chain of evidence, and Dallas PD as witnesses.
That would mean leaving JFKs corpse in Dallas for a day, and LBJ flying to DC. But nobody was thinking very clearly.
LBJ needed to take AF-1 to DC immediately, and a USAF Cargo jet needed to take JFKs body back to DC later.
I don't exactly blame a whole lot of people for being upset and making bad decisions. They were humans in a terrible minute.
The autopsy is one of the main reasons there is such confusion and controversy about the Assassination. Partially because it was so farcically done.
The two pathologists who performed it had never done a single gunshot wound autopsy in their entire careers. They never spoke to the doctors at Parkland Hospital (who’s recollections of Kennedy’s wounds are different to what the autopsy concluded), the original autopsy report was burnt, and then a new one was made from the doctors memory. The locations of none of jfk’s wounds are known with any precision. The back wound, for example, was not measured against a standard anatomical feature, and was photographed with the body in a distorted position. The fundamental question, of whether or not the back and throat wounds were caused by the same bullet, could have been answered by dissecting the wounds and the connecting tissue, but the pathologists were ordered not to do this according to sworn testimony.
IIRC he was in the hospital dying and the local police & authorities wanted to take possession of the body as he had died in Texas, and the shooter had committed murder in Texas. They would have then performed an autopsy on the body of the president, kept him in their freezer until the investigation was complete, etc., before releasing it to the family for burial.
USSS said nope, and were basically willing to draw their weapons and defend the body of the president with force. The local cops didn't want to get down like that, so they let them take possession of the body and put it on a plane back to DC.
Not 100% sure if it was a federal crime to kill the president at that time or not, i.e., it Lee Harvey Oswald may not have been guilty of a federal crime so it was unclear who had "jurisdiction" of the investigation.
Aircraft structural mechanic here. We seal any parts that get attached to the skin and fasteners that go through the skin and load any possibly leaky areas with sealant. When we're done with major work we do a pressurization test where we pressurize the whole plane and see how bad it leaks. We're allowed a certain tolerance like 1psi in 15 mins for example so the leaking is pretty miniscule and the way the pressurization system works more than makes up for that small bit of leakage. Unfortunately there's pretty much no way to entirely seal a 150+ foot-long airplane with millions of rivets and screws going through it.
The coffin is typically taken out in order with the other items, but is also ceremoniously escorted by military personnel to its final destination. They fly with them and ride with them to the final resting location. On occasion they will also be one of the military members to do the final salute and assist with the folding of the flag and delivery of it to the family.
Source: Was present at a funeral as a kid and asked one of the soldier there.
The escorts and coffin may not be on their last stop or will be picked up by a hearse and local Honor Guard at the tarmac, so things might be delayed. It's also a matter of respect. You aren't asked to do much other than wait for the coffin to be removed and transferred and so the escorts can disembark and salute the fallen service member as they go.
As far as being the last out of the cargo hold, most of the coffins have a space for them to be specifically in the plane or are the last things interred before takeoff, all of this is observed by the escorts and local Honor Guard of the particular location.
As far as I know, civilians are not given the same treatment, but I might be wrong.
Same process is observed for nonviolent passing overseas, but in country, they likely live and will be interred at a location near their current station.
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