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theengineer

The Engineer

The Life and Times of Donald F. Simmons


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theengineer

Space!!!

Last night's meeting of the Canadian Space Society was quite good.

We started off with baited breath watching a live webcast of the second attempted launch of a Falcon 1 rocket (the first failed last year due to a fuel leak in the engines). Unfortunately, it was aborted with just under 2 minutes to go due to a communications problem. They are trying again tonight.

UPDATE: The launch was successful, but a second-stage roll problem kept the rocket from achieving full orbit. This was a test launch, and it was only carrying two very minor payloads.

The main talk was by Prof. John Moffet, a physicist who been working for the last 30-odd years on modifying the Einstein-Newton theory of gravity. 

When astronomers study the behavior of star clusters, galaxies, and galaxy clusters, they find that they behave as it they were much more massive than we expect, judging from the amount of stars and dust we can see in them. This has lead to the theory of  "dark matter", non-luminous matter we can't see that bulks up these objects. Also, the study of supernovas has lead us to believe that the expansion of the universe is speeding up, which requires the presence of a "dark energy", unrelated to "dark matter", filling all of space.

Prof. Moffet says we can get rid of both of these ideas if gravity doesn't behave the way we think it does. Instead of the strict inverse-square law (double the distance and force of gravity falls by a factor of four), gravity over long distances actually weakens less than this, so it's stronger over long distances then we currently think. He's created a new theory of gravity that so far explains galaxy rotation curves, gravity lensing, cosmological effects, and even the Bullet Cluster (the best evidence to date that dark matter actually exists). 

He's also the first to say that so far, what he's done is pretty much just advanced curve-fitting, impressive as it is. The test of any scientific theory is that it must make predictions that can be experimentally verified. The best way to check out his theory would be to investigate the Pioneer Anomaly (which his theory also explains).

Basically, the space probes Pioneer 10 and 11 (launched in the early 70s, first spacecraft to Jupiter and Saturn) while travelling thru the outer reaches of the Solar System, both slowed down very slightly more than they should have. As the Wikipedia entry referred to above shows, the cause of this is hotly debated, as is if it is a real effect at all. Unfortunately for various reasons, mainly with how they are stabilized, we can't get reliable enough data from the Voyager probes to check for an effect with them. But one explanation is that our theory of gravity is incomplete.

There's an increasing push to design a space probe specifically to test for such an effect, and fire it off straight out of the solar system, as if Prof. Moffat is right you'll have to get at least away as Saturn to start detecting it. In any case, because gravity is such a weak force we've pretty much run out of experiments we can perform to investigate it here on Earth, trying to screen out all other influences is just too hard.  We only know the Gravitational Constant(?) to a lousy four decimal places. Practically all other physical constants we know to 9 or 10 places. 

Unfortunately, as Prof. Moffat said last night he's unlikely to still be around when such a mission manages to start returning data (10 years away at least). 


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It's an interesting theory, I'll grant, but I'll wait until a few more data points have been validated. ;)

The Wiki article on the Pioneer Effect was interesting, but it makes it sound like the scientists studying it think that only one of the possible causes is responsible. Why couldn't it be a cumulative effect caused by several of them?

OTOH, I also have a problem with dark matter and dark energy - and that's that they're basically fudge factors. When astrophysicists can actually point at something and say, "There it is!", I'll accept it fully. Until then, it seems to me to be the modern equivalent of "Here there be dragons." They don't know what it is, but the effects are there, so they have to be explained.

It's an interesting theory, I'll grant, but I'll wait until a few more data points have been validated.

I agree. But we desperately need to send some gravity experiments into the outer solar system just to get a better handle on it. Right now we've got bilions being tied up in dark matter physics experiments on Earth. If they come up negative, the modified gravity people will hopefully get a shot.


Why couldn't it be a cumulative effect caused by several of them?


That's what it might be. But any indication of new physics will get people's saliva going.


OTOH, I also have a problem with dark matter and dark energy - and that's that they're basically fudge factors. When astrophysicists can actually point at something and say, "There it is!", I'll accept it fully.

And that the big thrill and curse of astronomy / cosmology. We're getting more and better data than ever these days, but it's not enough or not good enough to come to a clear conclusion, because everything we really need to see is a million light years away.

I predict that cosmology in particular will be overturned and built up again several more times in the next 200 years as our instruments get better and better.


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