After 30 years in space, America's oldest spacecraft,Pioneer 10 and 11, are being held back from visiting distantstars by a mysterious force.
Robin McKie writes in The Observer that some scientiststhink this may be the first real evidence of the "darkmatter" that some scientist theorize permeates the universe. A simpler explanation could be that gas from fuel tanks maybe leaking, slowing the craft down. Astronomer MartinBarstow says, "Unless there is really good evidence to thecontrary, we should stick to simple ideas like these and notgo around blaming strange new types of particle or flaws ingeneral relativity."
But NASA's John Anderson says, "It's hard to imagine such aleak happening on both probes at the same time in such a wayas to produce an identical acceleration."
Another explanation may be that the laws of physics are notconstant, and the force of gravity may work differently inouter space than we think it does.
Whatever is causing the slowdown, astronomer Bernard Haischsays, "The effect is real."
There areforcesright here on Earth that are holding some of us down (atleast this one is onsale!)
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