The Problem with Gravity.....

worthj1970 · Oct 18, 2004

I have a question about this article on Space.com. The article says the Pioneer craft are not accelerating at the rate we believe they should, and say another mission is needed to verify this. Why can't we perform the same basic experiment with comets? Thanks! John W.

newtonian · Oct 18, 2004

worthJ1970 - May I address the problem with gravity part of your thread? We don't know what is going on. There are a number of theories on why those space probes are slowing down. I had a thread going on that for some time in the old SDC which crashed. Borman had posted a way to punch in a formula for the cosmological constant, aka vacuum energy, aka dark energy. The result was consistent: dark energy can be causing the decceleration (sp?) of the probes while also causing acceleration of our universe. It had to do with reference points and it was way over my head (literally also), but Borman understood it. He also acknowledged it was just one possible explanation and not yet proven. Now, on to comets. Comets do not have any such unknown decelleration factor, nor do any other bodies in our solar system. So, why would our space probes be slowing down - there is a supernatural explanation, but I will avoid that for now. I suspect it is natural, and that it has to do with the fact that the probes are in escape velocity from our solar system. In other words, it is not gravity that is causing the effect because the probes are not gravitationally bound. I don't know why this would cause that effect. But it is the only factor I have noted that would distinguish the probes from objects like planets, moons, asteroids, comets, etc. To repeat: the probes are not gravitationally bound.

newtonian · Oct 18, 2004

How could escaping a bond that slows down cause more slowing down? Here is one example: What if someone is swinging you around with a strong rigid bar while at the same time a strong wind caused by a strong updraft where that someone is located is pushing you towards said person. You cannot be moved towards that person because the bar is rigid. Now, let go of the bar. The bar is gravity. You are in escape velocity. The bond is broken. Instead of flying off, as you would intuitively expect, you move towards the person- caused by an invisible wind that you ignored because it was stopped from causing an effect on your motion because of the bar: gravity. Just a thought.

newtonian · Oct 18, 2004

What if gravity is somewhat independent of the bending of space-time, such that gravity has an anti-gravity component. The effect we call gravity would then be: A + B + C = observed gravitational effects. Where A is positive gravity, B is antigravity and C is an additional independent effect of the bending of space-time. Let C cause motion towards the slope of space-time caused by our sun's gravity. However, A and/or B prevents C from having an effect unless the mass has escaped being bound by gravity. It could be something like surfing on a wave, where motion occurs in a specific direction even though the body of water is not moving in that direction. Now, as long as you, the surfer, remain bonded to the sand at your feet, you will have zero motion towards the shore. But break that bond and lift off and..... And, yes, your motion can be towards the shore even if the tide is going out! You all - can we increase a probes speed by 'surfing' on some sort of energy wave? Back to your question - Yes, if we can send a probe to Pioneer, we should be able to send a probe to a comet. I think we just did that, didn't we? Was it Wild?

CalliArcale · Oct 19, 2004

One point bears mentioning.... ...there us not only disagreement about why the Pioneers slowed down during the period that they were observed, but also disagreement about whether or not they've slowed down at all. It may be an error in the measurements, given the challenges involved in measuring their distance and velocity with the minimal data available (their very weak carrier signals, both of which are now undetectable). <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

glutomoto · Oct 20, 2004

Do you mean, not gravitationallly bound to sol ? Does body B, have to be gravitationally bound to body A to be affected by the gravity of body A ? Off the top I would say No, the bodies do not have to gravitationallly bound. Otherwise slingshot orbits wouldn't work. Perhaps the Pioneers are now bound to some other gravity source ? Certianly they are still part of the Milky Way. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

glutomoto · Oct 20, 2004

I guess you aren't talking about the heliopause are you ? I would also guess that I would be way off base here for thinking the spacecraft are starting to feel the effects of the galactic medium, in other words are they far enough out yet to be near the heliopause ?? <div class="Discussion_UserSignature"> </div>

glutomoto · Oct 20, 2004

Same stuff different thread. Pioneer anomaly <div class="Discussion_UserSignature"> </div>

Saiph · Oct 20, 2004

the reason we suspect it in the pioneer craft and we don't check with comets is: Precision. THe pioneer craft are set up in such a way that the radio signal we recieved from them was very, very consistent. So any deviation was due to their motion. We don't get radio signals from comets, and while we could bounce radar off of them, we won't get nearly as precise a signal. Since the discrepancy is small, we'd never be able to detect it. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

worthj1970 · Oct 21, 2004

This was what I suspected, but wasn't sure. In thinking about it I suppose the random surface of comets would complicate things. Would it be possible to in some way attach a probe to a retreating comet to test the theory? John W.

lewcos · Oct 21, 2004

Couldn't solar wind from other star systems slow down the craft?

Saiph · Oct 21, 2004

The only way to save energy/money on a probe using a comet is to have the comet hit the probe, hard. Likely damaging any precision instrumentation in the process. The best method is to send a probe out, that is specifically designed to send back a very specific and very well controled signal. The candidates for the slowing of the pioneer craft: 1) Craft is venting from somewhere, creating thrust of it's own. 2) The medium out there (gas dust etc) is much thicker than previously thought (unlikely). This sorta goes in with other stars solar winds. 3) Gravitational Constant "G" isn't as well determined as previously thought. It may have slight variation even. This is a BIG speculation. IF this is true, a lot of things have to get tweaked, so it's basically a last resort. 4) Umm...the catchall for odd things in astronomy: Magnetic fields? <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

tom_hobbes · Oct 22, 2004

This must be either complete nonsense or already accounted for: You mention the possibility of the very thin medium out there being a little denser than thought, but discount it immediately. One thought I had is that perhaps there might be some point, out toward the edges of the solar system, where what gas and dust there is tends to become denser, equally poised between pressure from the solar wind and the gravity of the sun/planets etc. If so would such a point occur well within the orbit of the main bodies of the solar system and any material present swept up long ago? <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

Saiph · Oct 22, 2004

solar radiation and winds already push a lot of that stuff far out beyond the solar system, creating a boundry called the Heliopause. The reason I discount it, is for this medium to have an effect it would have to be so dense that it would easily show up in any attempts to detect it. Even the dense star formation nebulae (think Pillars of Creation) are far better vacuums than we can create on earth. That isn't going to slow the Pioneer spacecraft well enough to be detected. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

tom_hobbes · Oct 22, 2004

I see. Thanks. <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

newtonian · Oct 24, 2004

Saiph - Well, on the old SDC these classic causes for the slow-down were discounted because no such slow-down is noted on planets, moons, comets, etc. We do not need probes on these bodies to calculate their motion. Are you sure we cannot note the motion of planets like Jupiter and its moons to the degree where the rate of slowing would be observable? I know the links I examined last year on this did not indicate any problem with observational accuracy of these other solar system bodies. Alas, I forget the links!

Saiph · Oct 24, 2004

No, I don't think we can know it that precisely, since we cannot know the distance or velocity of the planets to a great enough precision. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

newtonian · Oct 24, 2004

Saiph - Acknowledged. I will research that further and get back to you. In search of good links on this subject, btw. You all - Any good links?

The Problem with Gravity.....

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