>>Apophis was discovered in 2004. At 2mph it would be moving outward at 50 miles per day. Over 11 years, that would be an orbital change in the order of about 193,000 miles .... something that would be easily detected. In the other discussion, Dave also proposed a speed of 8 mph which would lead to the orbit being about 800,000 miles off. We will get another chance to test this as Apophis will have two close approaches to Earth between now and 2036.>>
RE and solar wind cannot propel high density objects...just low density (high surface/mass) objects. That is why they need a SAIL to propel spacecraft. The spacecraft alone is FAR less dense than an asteroid...so no surprise if we don't see asteroids affected by RE or SW. So you are dead wrong to think Apophis refutes the RE idea. The cloud of stuff surrounding the "seed rock" of the "rockpile" would serve as the sail for that object. And contrary to your former claim...that would not strip the seed rock of its cloud of gases. If the force against the cloud was small, the cloud would move away but then pull (or be pulled by...actually it is BOTH) the seed rock to keep them together as both move outward.
>>What about stuff that is launched above or below the plane of the lunar orbit? How is the moon going to intercept that? How is the moon going to intercept material that is going to be "ahead of Earth" when the moon is beside or behind Earth?>>
OOPS, you said "intercept"...that means a crater on the Moon! You'd better go back to Craters-Moon to discuss that.
My answer would be that I did not say (nor does Brown) that ALL (or even MOST) of the lower speed stuff gets intercepted by the Moon. It just would intercept more of it (which is on the ecliptic) than you say it would. There would NOT be a 13.5x multiplier. Also there would be a flattening of their trajectories, just as I explained on the Craters-Earth site when SN asked that.
>>How is the moon going to intercept material coming from the direction of the Sun when the moon is ahead of Earth, behind Earth, or away from the Sun? You keep making your assertion without ever responding to this issue.>>
I have too responded, several times IIRC. If I have to go back to show you, just repeat this again, and I'll hunt it down.
>> It would be much more impressive if you were to address these problems once rather than repeating your mantra over and over and over.....>>
First, I haven't said or implied that ALL the stuff on the ecliptic would get intercepted by Moon. You may think my saying THIS is a mantra too. But you keep misrepresenting me. That is your MISUNDERSTANDING of what I've said. I just say that much more of stuff moving outward ONCE is intercepted by Moon than you say...and it would bring the 13.5x multiplier down to about 1x. Here's how Moon could get hit by an object that has no chance to hit the Earth. Suppose the object is coming outward (slowly outward due to RE but in a FAST orbit around the Sun) from the Sun (in a retrograde solar orbit), finally getting to 1 AU and misses Earth by being ahead of or behind E in the solar orbit. (That is, it is not in the 8000mi wide "slice" that Earth occupies.) But that object could still be hit by the Moon as M is inside 1 AU, at 1 AU or BEYOND 1 AU, at any point along the 500,000 mi swath of the Moon. (I'm not saying ALL would be...just that more would be than the 13.5x multiplier suggests. Most might miss BOTH E and M). Any object within 500,000 mi ahead of or behind Earth could be hit by the Moon. OOPS AGAIN...I'm discussing a cratering event...maybe we need to switch this paragraph to one of the other topics!
>>In very eccentric orbits, it's much more likely to hit the Earth with no chance to hit the moon. >>
Most likely you haven't pictured what I'm describing. Picture some very eccentric orbit (around Earth) that goes out beyond the Moon but still is in E's gravity, so that it will (if it misses the Moon) come back to sling around Earth again, and again. It NEVER could hit Earth, but it COULD and probably WOULD eventually hit the Moon.
>>Dave: This is ridiculous. Firstly, the Earth is a "moving target" so wherever it was (in its solar orbit) when the stuff was launched, would NOT be where it would be as a comet makes its first return. And secondly, the return path would be determined by whatever object has the greatest gravitational pull at the aphelion (when the object stops its outward path to start its fall back)...which of course would be the Sun. Pi is picturing what might be the case if the Sun were to be obliterated and the Earth were to be stationary. Maybe he should have asked some expert to help him. But if he HAD, they would have missed this too like Pi did I expect, so I would have had to correct them also.
Pi: Maybe you should get some first year engineering student to help you. If you had, you wouldn't be so completely wrong on the orbital mechanics and the moon having "many chances" to be hit while the Earth would have only one.>>
If I did that, I would FIRST be sure he could repeat what I am asserting rather than constantly DISTORTING it as you do. Ask your expert if I'm right that if you launched an object from Earth, the Sun would pull the object back to it, rather than the Earth pulling it back...so that object would end up being in orbit around the Sun on its second trip outward. It would NOT (as you say it would have to) come back to where the Earth is, swing around the Earth, and then head back out. That is absurd. That is NOT what we would expect to see if HPT is right. Comets would return to, and then around, the SUN..even though they came from Earth. If you disagree, explain what force the Sun would have compared to the Earth when the comet is out beyond Jupiter's orbit distance and it has stopped all outward motion and now is starting to fall back inward. Why in the world would the comet return toward Earth rather than toward the Sun? (Have your expert read this paragraph and then inform you.)
>>As has been pointed out many times... the 13.5x multiplier is for objects with velocities relative to Earth that would cause them to be single pass events.... as they will exit the solar system. As relative velocities go down, the Earth's "target size" increases. DaveB came up with a multiplier of about 52x for objects with velocities relative to Earth of 6 km/sec. Indy now proposes velocities of only 2mph (less than 0.001 km/sec). This is a really slow approach that will increase the comparative target size of Earth to something near the maximum... about 300x.>>
The slower speed also increases the Moon's target because of the Moon's gravity. But we are NOT talking about slow-speed objects because higher speeds are needed to form the large craters (OOPS!...wrong topic again) on the Moon. So these are fast objects, going retrograde and hitting the Earth or the Moon head on at HIGH SPEED...so the target factor would be far less than 19x...more like about 14 to 14.5.
>>Actually, under the Laws of Conservation of Energy and Conservation of Momentum, the material returning to the Earth will have the same velocity as when it left Earth. We have established that stuff just past escape velocity will still be moving along at 1.44 km/sec (about 3200 mph) when it reaches the moon's orbit. It should be moving at least that fast when it returns to the Earth-moon system. If you propose it's going to cross the moons orbit at only 2mph, you have a lot of unexplained energy loss to contend with.>>
After now TWENTY ONE times trying to explain this... I have never SAID stuff RETURNS at only 2 mph. Only a tiny part would EVER return...the fastest stuff like comets. Asteroid-stuff gets moved outward slowly ONE time...pushed by RE and solar wind. It is moved outward slowly at 2-8mph MINIMUM (based on 4000 years to get to the A-belt) but the orbital speed or CLOSING speed for E/M is higher than that...especially retrograde stuff.
>>I do think I understand what you are saying... and I do (obviously) disagree with it. You are simply dismissing the disagreements as a "failure to understand.">>
If you DID understand, you wouldn't still be making arguments filled with things I do NOT say...like stuff would return at 2 mph. You want to PRETEND you understand but you don't. Not even after 21 times. If you really DO understand, they you are building a straw man and purposefully deceiving.
>>Momentum = mass * velocity. As has already been pointed out, anything passing the moon on an outward trajectory will already be moving along at at least 3200 km/hr. Adding 2 mph to that isn't going to do much to change that trajectory.>>
You don't understand me. That is not what I assert at all. The stuff moving out from the Sun at 2-8mph takes years to hit E/M on its ONE trip outward. And not ALL of that stuff would hit either...most might miss both.
>>In other discussions, Dave has also pointed out the the outward push from the Sun will tend to "flatten" the trajectories of these objects. Well.... that is true to some extent. >>
Um...I think you just got done mocking me for saying it would flatten...when you said "What about stuff that is launched above or below the plane of the lunar orbit? How is the moon going to intercept that?" Not ALL the stuff gets intercepted. If it misses both E & M, then it would head outward, never to return, and it would be flattened by its solar orbit velocity as well as by gravity from planets in the ecliptic. That is why the a-belt (and TNO's) is like a donut...flattened and circular.
>>Let's take the special case of an object launched from Earth at escape velocity 11 km/sec) on a path at right angles to the ecliptic (the plane of Earth's orbit around the Sun). Let's also treat it as if it is getting pushed outward from the Sun at 2 mph. The 2mph outward push will not change the 3200 mph vertical velocity. >>
No, but the TWO velocities combined alter the initial vector, curving the direction to make a flatter orbit. And it would not just be the RE force...but also the force of the solar orbit that does the flattening.
>>The vertical velocity will be influenced almost entirely by Earth's gravity which, at the orbit of the moon is only 0.0025 m/sec2. For all practical purposes, this material is not going to "flatten" its trajectory to the extent necessary to get it into the asteroid belt. It's orbit will still be inclined by some 2.75o from the ecliptic. >>
Where do you get that number?
>>The inclination of the moon's orbit to the ecliptic is 5o. The angle of the sky covered by the moon is only 0.5o. One doesn't need to be a math major to see it is much more likely this stuff will miss the moon entirely if it is on a path toward Earth.>>
The stuff which is "flattened" and which I say has more op's to hit Moon than Earth is NOT stuff which returns. (22 times) It is stuff that goes past EV but is still in E/M's vicinity until it gets pushed outward (to never return) ONCE. You have NOT understood me. Before declaring me to be stupid or ignorant, try FIRST to understand me such that you could repeat what I say in such a way as I will agree you "got it." So far you haven't been able to do that. That makes YOU the un-smart one.
So if the stuff is headed up toward the North Star when it escapes Earth...do you think it will continue moving only North? Or will it (if there is a radiometer effect or solar wind effect) be pushed outward so that it is not going around the Sun on a perfect North-South (polar) solar orbit, but rather it is going to be nearer to the ecliptic? The centrifugal force of its solar orbit (which it had before launch) as well as the new outward momentum of RE/solar wind would flatten it. And this would be not even counting what effect gravity of all the planets has. I am not even saying that the stuff shot to the North, would nec. hit or even have a chance to hit the Moon. Maybe most of that would go past the Moon before it flattens much. But stuff shot so as to start out at (say) 1 AU - 10 million miles COULD get flattened a lot, especially if you include the gravity effects of Venus and Earth pulling it downward. (Do you agree they would? I never heard back from SN on that point...which is VALID). So that by the time (years? DECADES?) when they got back to 1 AU, they may have a chance to hit either one. AND if you say "no...the North-launches could NEVER hit the Moon"...then fine. They also would never hit Earth either.