Why Major Comets Don't Fall Into The Sun

Why Comets Don’t Fall into the Sun

To understand the fantastic nature of what we are asked to accept as commonplace about the orbits and especially those of long-period comets, we must place such motions in a vivid framework of perspective, something we can visualize and play with in our minds and conversations. Earlier it was discussed that Comet Kohoutek's orbit was originally calculated as 3,600 AU (Astronomical Unit=93 million miles) long and 44 AU wide. Thus, the shape of the orbit has an 81-to-1 ratio.

Let us fashion a little solar system using that scaled-down orbit as a basis. This representative solar system is 81-miles deep. That is a radius of 81 miles from the outer edge of the solar system to the sun in the center. Looking down on this scene from a god’s eye view, the sun is a reduced version of our own, tiny, bright sphere about 1.1 feet in diameter as seen from our position at the aphelion point for the comet. (The aphelia point of a comet is its turn around point, its furthest distance reached from the sun before it starts back.) From this position we will launch comets to pass in through the planets and round the sun as we are told comets are supposed to do.

Normally, it would be very difficult to hit a 1.1 feet target from a distance of 81 miles away. But this target is different. It has almost all of the local gravity working for it. Actually, the gravity would so overwhelming that the problem would be in avoiding its pull. If we let go of our atom-sized comets and let only gravity to energize them, they would go smack! Dead center into the sun without fail every time.

It goes without say that our supply of comets would be assuredly depleted at that rate. It would be one released, and one automatically lost, gobbled up by the little, but relatively weighty sun . Having been allotted a given number of the strange little cometary bodies at the creation of the solar system, we became fearful that eventually we would run out of them before the rest of the solar system was worn out.

We recall that the planets in our system have survived the millennia by rotating around the Sun. We decided to steal that wisdom of the planets and apply it to our operations. We would do what they do, but in a highly exaggerated form that would allow us to continue our little game indefinitely.

We ran an analysis of the physics involved and found that the planets continue to exist because they have achieved a fairly balanced relationship between solar gravity and themselves. They are captives of the sun to be sure, but they continue in place by having thwarted the singular, constant hunger of the gravitational attraction of the primary.

We note that in any given instance three factors are involved: distance from the primary, speed of the planet, and the direction of motion in relation to the primary. These factors are closely interrelated, we learn. A very interesting point we pick up on is that a given orbit may display a great deal of variation of these three factors at various points in its track.

We have a Eureka! idea. Can a lop-sided orbit be created so that a comet will not only successfully orbit our sun but be sent back our way, so we can snatch it up and use it again? A check with pencil and paper confirms that hunch. Yes, physics does allow such a motion. When pressed to the absolute limit, physics--on paper--allows us to have the comet return back like a rebounding yo-yo time and time again.

Amazingly, all that is required is that the comets be allowed to fall toward the sun at almost the normal velocity for that distance. The only difference is that the speed must be slightly increased and the exact direction of travel must be slightly altered from off center. Instead of a straight-line flight to the near middle of the solar body as pure, unmolested Nature would dictate, the line of motion must be directed to pass somewhat outside the rim of the sun. As our little comet comes into close proximity with the sun, the determined but limited intense gravity will pull the comet around it in a very sharp turn in a futile attempt to eat it. But our clever and perfect blend of distance, speed, and direction of motion will prevent being drawn in, and the comet will subsequently break away from its sharp turn that increased its velocity and head back toward its incoming direction.. It was a beautiful piece of theoretical physics on paper. But would it work in our miniature solar system?

reply to post by Aliensun


Part Two:
Maybe. We sit there for eons dropping comet after comet into the void and giving them little nudges this way and that in hopeful attempts to set up the right amount of speed, distance, and angle to beat the gravity well at the other end. But everything goes wrong and nothing goes right. We see our comets committing three types of behaviors. Some curve down into the sun anyway because they were not endowed with enough independent actions to remain free. Some curve around the sides somewhat before they impact at an angle into the surface, but they still die.

Some are lucky enough to miss the sun on the first pass, but they lack the precise interrelationship of the three critical factors to achieve the orbital motion we want for them to return to us. These comets round the sun in varying degrees, but fly off into all manners of haphazard and every-changing motions, destined for the most part to crash before too many more passes.

A few comets are so enthusiastically launched that they attain escape velocity. The faster ones only slightly curve around the sun before shooting away toward a new direction never to return. But never among our many, many launches would we have a nice, docile comet which would go down to the sun, turn a tidy 180-degree 'hairpin" curve and return back our way for reuse. Never would it happen.

Slowly, it dawns on us that the random spewing of comets is not every efficient for gaining our desires. In pondering the situation, we conclude that our goal is far more difficult to obtain than the hardest of the early ballistic missile satellites launches into space. We have no manner of in-flight correction capabilities. Our little comets are similar to a rifle bullet's flight. Our projectile must be perfectly aligned toward the sun and every minute, course-diverting obstacle considered and factored in at the instant of release or all is for naught, a clear miss.

We call upon our friends in Science for aid. They use mighty instruments to measure the mass and diameter of the 81-mile distant sun in order to know exactly what our flight parameters must be. After the computers quit spewing out their seemingly endless amounts of decimal places for any given combination of the critical factors, we come to learn that the exact figures are useless and the situation is hopeless.

We have in hand the exact required components of our equations, x distance, y speed, and z angle, but we won't have the ability to produce them as required when required. Even if we were to draw upon the best computers and rocket technologies of today, a ballistic shot as we require simply cannot be achieved. There is no way an inert, little body can be sent down that long corridor of 81 miles with the accuracy to hit the precisely required "window" so that it will round the sun and then break away to return exactly to us.

People working in that field wouldn't even consider trying such foolishness. They argue that a little onboard computer and some navigational thrusters would solve the problem nicely. We refuse such help. We stubbornly hold to the idea of wanting to bring the orbit about naturally. "Dammit, comets do it in the real world, why can't we do it here?" They shrug and ignore the question. They counter-argue that in addition to the precise amount of initial control needed for a successful return of our little natural comets, the intervening variables which would act on the situation after a correct release of a come had been achieved would always subtract further from any possible chance of the mission being successful. These other factors include changes in the mass of the comet as it lost material to the sun, rotational spins by the nucleus which can retard or advance the orbit, pockets of jet actions of erupting gases which can change the body’s rotation rates, perturbations from the major planets (especially Jupiter), fracturing of the nucleus, collisions and near misses with other bodies, resisting medium in space, passing stars, solar wind, etc.

In sum, our attempt to produce a returning little comet would be a very noble concept,, true to the science of physics, and clearly theoretically possible on paper it the above several altering factors are ignore. But alas, the probability for error would always be hugely greater than the probability for success such as to make the feat impossible in the real area. We would be shooting for a theoretical point unobtainable in reality via our natural methods. This situation is akin to the theoretical stationary point at the exact center of a rotating circle. Theoretically, it can be proven to exist, but try the physical approach of trying to stick a pin into it.

If all we had to draw upon for experience was this little solar system and our bright idea about what we thought we could do with our comet bodies, it would never occur to us that nature is apparently, consistently, and unwittingly performing the same feat time after time. Long-period comets have the remarkable record of precisely hitting the impossible-to-hit window for return 100 per cent of the time. How does nature do it? Perhaps a better question: Does nature do it?

The foregoing example of a miniature but relatively accurate solar system was fashioned after the original elements of Kohoutek's orbit were published. They supposed an orbital length of 3,600 AU. This is an extremely short orbit for a long-period comet. A subsequent official revision of its orbital motion revealed that figure was many factors of ten too low. And that it, like most long-period comets, has a supposed turn-around point out beyond 90,000 or more astronomical units from the Sun.

For further amusement, you may want to fashion a solar system yourself based on these larger measurements (which would make the diminutive sun 25 times further away than on our scale model used here) and consider how much harder it would be to correctly launch a ballistic comet around it at such a distance and have it complete the equally arduous task of returning back from where it had originated.

By now it should be clearly evident that the real world of comets is hard to reconcile with the paper world of theoretical physics and conic geometry. The only safe assumption which comes to mind is that something is wrong with comets, not physics.

So we must wonder aside from what we are told, if theoretically possible but realistically impossible events are commonplace with the motions of comets, then there must be a clear-cut, ever-present, and all-encompassing reason. The reason, of course, is simple. Comets are not naturally produced balls of frozen space fluff adrift in a sea of gravity. Instead, they are controlled bodies, nothing less. And basic physics is honest and true. That is the only way these two at-odds aspect of our Universe can be reconciled.

(Detractors will want to mention the many SOHO, SOLWIND, etc. records of comet-like minor bodies noted to have fallen into the sun. They are not to be confused with a typical long-period comet of considerable more substance and presence.)

For further stimulation of thought pro and con, see these other threads:
Rethinking Comets
Trouble with Comet Halley
Motions of Comets

Just my opinion of course but the fact that sun isn't stationary would impart a curvature to the comet's trajectory making it a difficult, but not impossible, target to hit from a vastly distant starting point and once an elliptical orbit is established it tends to remain predictably elliptical unless something gets in its way or gravitationally alters its course.