Voyager

[Bettina]

This is too awesome not to be put here. These instruments were launched before I was born, and one of them is over 6 billion miles from our sun and still has power.

 

Bee

 

http://www.cnn.com/2005/TECH/space/05/25/voyager.space/index.html

[luc]

Voyager 1 recently crossed the Termination shock, and is currently in a zone called the heliosheath. Its next goal is to cross the heliopause (it will cross it in about 10 years), and then it will go on forever gosh knows where. A true adventurer

[insane_alien]

luc, its crossed the terminator shock about 10 times already(or rather the terminator shock has crossed voyager about 10 times, it moves). isn't pioneer 10(or 11, not sure) about a billion kilometers further out or something?

[Bettina]

According to Wiki, Voyager 1 and 2 were launched in 1977 and is the farthest man made probe in earth history, passing the pioneers launched earlier, because of something called "Heliocentric radial distance." The pioneers 11 and 12 carry a gold plaque and recordings of earth sounds and human figures.

 

From Wiki on Pioneer 10......

 

The last, very weak, signal from Pioneer 10 was received January 23, 2003. A contact attempt February 7, 2003 was not successful. The last successful reception of telemetry was on April 27, 2002; subsequent signals were barely strong enough to detect. Loss of contact was probably due to a combination of increasing distance and the spacecraft's steadily weakening power source, rather than failure of the craft. One final attempt was made on the evening of March 4, 2006, the last time the antenna would be correctly aligned with Earth. So far, no response has been received from Pioneer 10.

 

The Voyagers are still communicating...

 

Something even more interesting...... Yoo Hoo.. calling Martin...

 

http://en.wikipedia.org/wiki/Pioneer_anomaly

 

Bettina

[insane_alien]

oops...

[Martin]

...

 

Something even more interesting...... Yoo Hoo.. calling Martin...

 

http://en.wikipedia.org/wiki/Pioneer_anomaly

 

Bettina

 

I'm not so good on the Pioneer anomaly:embarass:

 

We should wait and see if Swansont or some of the others will discuss it.

If not, I will make a stab.

 

I personally SUSPECT that the effect is real and that it may lead to a slight but significant modification of the equations we have for gravity.

But it could just be an artifact due to some engineering defect of some not-understood kind.

 

I feel more confident that more probes will be sent out to specifically study the Pioneer anomaly, to be sure whether it is real or not.

 

Does anyone want to say in more detail what is known about this?

[[Tycho?]]

According to Wiki' date=' Voyager 1 and 2 were launched in 1977 and is the farthest man made probe in earth history, passing the pioneers launched earlier, because of something called "Heliocentric radial distance." The pioneers 11 and 12 carry a gold plaque and recordings of earth sounds and human figures.

 

From Wiki on Pioneer 10......

 

[i']The last, very weak, signal from Pioneer 10 was received January 23, 2003. A contact attempt February 7, 2003 was not successful. The last successful reception of telemetry was on April 27, 2002; subsequent signals were barely strong enough to detect. Loss of contact was probably due to a combination of increasing distance and the spacecraft's steadily weakening power source, rather than failure of the craft. One final attempt was made on the evening of March 4, 2006, the last time the antenna would be correctly aligned with Earth. So far, no response has been received from Pioneer 10.[/i]

 

The Voyagers are still communicating...

 

Something even more interesting...... Yoo Hoo.. calling Martin...

 

http://en.wikipedia.org/wiki/Pioneer_anomaly

 

Bettina

 

Yeah thats an interesting question. They've been pretty rigorous in trying to explain whats causing it, but so far nothing has come up. And its been observed in other probes as well, making it unlikely it has to do with the construction of the probe.

[reor]

I'm not sure it's a good idea to sign a probe that may crash into something important for some aliens.

Imagine it hits their emperor or some powerplant, causing a disaster.

Do we really want an "Independance Day"?

[Klaynos]

Hopefully if they're that advanced they'd have some shielding against such things as asteroids...

[Sisyphus]

Ah, but they might interpret it as a grave insult. Anyone familiar with the Hitchhiker's Guide to the Galaxy should know about such dangers.

[Martin]

.

 

Something even more interesting...

 

http://en.wikipedia.org/wiki/Pioneer_anomaly

 

Bettina

 

this is not a particularly good source about Pioneer anomaly' date=' but it appeared on the preprint archive today and it has some links. I should get a link to one of the well-illustrated survey articles that came out earlier. But here this is:

 

http://arxiv.org/abs/gr-qc/0605141

[b']Time Delay Predictions in a Modified Gravity Theory[/b]

J. W. Moffat

5 pages

"The time delay effect for planets and spacecraft is obtained from a fully relativistic modified gravity theory including a fifth force skew symmetric field by fitting to the Pioneer 10/11 anomalous acceleration data. A possible detection of the predicted time delay corrections to general relativity for the outer planets and future spacecraft missions is considered. The time delay correction to GR predicted by the modified gravity is consistent with the observational limit of the Doppler tracking measurement reported by the Cassini spacecraft on its way to Saturn, and the correction increases to a value that could be measured for a spacecraft approaching Neptune and Pluto."

 

 

=====here is some general discussion========

Before we lost contact with them the Pioneer probes behaved as if they were subject to a slightly greater-than-expected pull towards the sun.

 

they werent "accelerating" towards the sun in the usual sense, but the trajectory wasnt normal. Maybe you could say that they were expected to decelerate as they drifted away, and they did keep on drifting away, but decelerated a tiny bit MORE than expected------so it was slightly harder for them to break away than expected.

 

physicists describe this as showing some extra sunward acceleration (i.e. extra pull towards sun)

==================

 

but it is very tiny amount and could be an error in measuring, or could be caused by some ordinary on-board thing, like a gas leak somewhere on the probe giving a gentle push that happened to be towards the sun. like an unintended little rocket thrust.

 

=================

 

over the years dozens of savy professional people have studied this and concluded that it doesnt seem to be a mistake. the grav pull of the sun could very well actually BE slightlystronger out there than our gravity theory (general relativity or newtonian either) predicts

 

THIS I THINK YOU ALREADY KNOW maybe or [TYCHO] Klaynos and the others know. I am just saying it to have it said.

=========what is John Moffatt doing?============

Now this guy John Moffatt is somebody at PERIMETER INSTITUTE who has kept on trying to devise some modification of standard gravity that would FIT THE DATA. Maybe that is wise and maybe it is foolish, but anyway he is trying. I guess since there is this anomaly maybe somebody ought to be doing that.

 

Most scientists would I think just wait till they send another probe and get better data, but he is marching to a different drummer and he has been struggling to devise a slight modification of gravity theory that will fit it. He seems to think that his modified model of gravity could be TESTED by its predicting slight differences in the time-delay of the signals communicating with probes. At least it is good to have a TESTABLE theory that you can chuck it out if you measure different numbers from what it predicts. I wish everybody's theory would do that!

==============

I cant say much more as the situation puzzles me.

[SmallIsPower]

It would seem that since the anomoly has been noticed in many probes, that one could compare the anomolies between different probes. If the anomoly is much bigger than the ones near to the sun, then it could easily be a MOND, or (could it be) that its because of the pull of other stars? If there is a bigger anomoly in the nearer probes, amybe it's a miscacluation in the solar wind or the pull of the planets.

[Martin]

It would seem that since the anomoly has been noticed in many probes, that one could compare the anomolies between different probes. If the anomoly is much bigger than the ones near to the sun, then it could easily be a MOND, or (could it be) that its because of the pull of other stars? If there is a bigger anomoly in the nearer probes, amybe it's a miscacluation in the solar wind or the pull of the planets.

 

I think you have the right idea, Small. AFAIK the data is consistent between the two Pioneer probes. people have constructed various models to fit it. further observations, gathering more data, will hopefully either

 

1. help choose between different modified gravity models, by seeing which fit the new data best

 

or 2. show the whole thing was just a fluke accident and no modification of gravity is needed

 

or 3. something else is going on that nobody thought of yet

 

I guess a lot of people must be feeling impatient to see the anomaly resolved, one way or the other.