Slashdot Mirror
New Gravity Theory Dispenses with Dark Matter
Darkness Matters writes "According to New Scientist, a theory of modified gravity, which has no need of dark matter, has just explained why the Pioneer 10 probe is 400,000 miles off its expected course as it leaves the solar system. It sounds pretty convincing, although in dispensing with dark matter, they've had to utilize the theoretical particle, called a graviton, which appears from the vacuum of space wherever stars are densely packed, making gravity stronger."
However, we're still left with the age old question: If gravity is manifest as a particle, why can't we shield against it?
There could be lots of reasons for this. The mechanism certainly isn't the same, but as an example of a particle which cannot be shielded, you need look no further than a neutrino, which can pass through the entire Earth.
It's only a theory folks. We shouldn't be teaching it because it hasn't been proven. It's not a fact.
(For the humor impaired I'll give you a few moments to let the words sink in)
We will bankrupt ourselves in the vain search for absolute security. -- Dwight D. Eisenhower
I read physics at university. An optional Third year course was 'General Relativity'. In the little booklet they gave us to help in choosing what courses to 'major' in (it was an english university), there was an asterisk next to 'General Relativity', as well as 'Cosmology' as a matter of fact. The asterisk denoted 'mathematically rigorous - to be considered only by students with particularly strong mathematical backgrounds'. My friends and I didn't take it - we did things like Computational Physics and Astrophysics instead. In fact, one afternoon, for a laugh (crazy guys that we were) we sat in on a General Relativity lecture to see if we could even keep up. It was a thirty minute lecture on 'Aphelion Procession Using the Scwarzchild Geodesic'. We didn't stand a chance - ball-breakingly tensor analysis. My point is, at that time I knew a hell of a lot more physics than your average guy in the street and I didn't have a clue what was going on in that General Relativity lecture. I read around, spoke to people smarter than I was, spent a fair bit of time trying to get my head around General Relativity I didn't even scratch the surface. And I was a straight-A student back then. I just don't think there exists such a thing as a layman explanation of our understanding of gravity. That other splendid bugger Dr Richard Feynman once said something like 'If a theory can't be reasonably well explained in a single undergraduate lecture then we don't really understand it at all.' It may be that we don't really understand the theory of General Relativity - maybe there is a far more elegant theory explaining gravity that could be explain gravity in simpler terms. For certain, though, that theory does not currently exist. It's a shame, because like you I was always frustrated by the absence of a simple answer to 'How does gravity work?', Why is it always attractive and never repulsive? Some things are just really, really difficult to model and the only models we have are 'mathematically rigorous'. In the words of JBS Haldane 'The universe is not only stranger than we imagine, it is stranger than we can imagine'. http://en.wikipedia.org/wiki/Richard_Feynman http://en.wikipedia.org/wiki/General_relativity http://en.wikipedia.org/wiki/Tensor_analysis
"More of the 'uh... well, it went away when you came in. It's only around when you're not looking. And it knocks things over when I'm the only one in the room' variety..."
This sounds more like the work of a quantum physicist.