Dark matter is more relevant to the evolution of the universe than to its age. The estimates of the age on the universe are based on what is loosely called the cosmic distance ladder. This is a chain of related observational data that eventually let us calibrate the value of the Hubble parameter (a.k.a. the Hubble constant, even though we're not sure that it *is* constant). If the universe were dense enough that its expansion since the Big Bang is slowing down, then dark matter would have a role in things. However, there are other observed phenomena, such as the relative lack of observed structure in the cosmic microwave background, that support quite the opposite conclusion. Overall, the question is still an open one, but the opinion of the astronomical herd seems to be that the universe is open (i.e., there isn't enough dark matter to slow down the expansion that started with the Big Bang).
Black holes are the result of a physical theory. Stars maintain their size and shape because the release of energy (mainly through fusion) is in the form of light that exerts a pressure outwards as it escapes. This balances the pressure of gravitation inwards. When the star can no longer produce enough energy to maintain this balance, the star collapses because the gravitational pressure is still there. Eventually, the surface gravity is so great that not even light can escape. This is what makes thes objects both "black" and a "hole".
Keep in mind that the orbital corrections are done with a significant time delay -- this is a situation where the speed of light *matters*:-).
Getting that close to Eros successfully is nothing short of remarkable IMO.
There was an article in Scientific American years ago about the mods made to the Voyager probes in flight (wish I could remember the specific issue), and it really gives you a feeling of wonder about the fact that we monkeys can do this stuff at all...
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Dark matter is more relevant to the evolution of the universe than to its age. The estimates of the age on the universe are based on what is loosely called the cosmic distance ladder. This is a chain of related observational data that eventually let us calibrate the value of the Hubble parameter (a.k.a. the Hubble constant, even though we're not sure that it *is* constant). If the universe were dense enough that its expansion since the Big Bang is slowing down, then dark matter would have a role in things. However, there are other observed phenomena, such as the relative lack of observed structure in the cosmic microwave background, that support quite the opposite conclusion. Overall, the question is still an open one, but the opinion of the astronomical herd seems to be that the universe is open (i.e., there isn't enough dark matter to slow down the expansion that started with the Big Bang).
Black holes are the result of a physical theory. Stars maintain their size and shape because the release of energy (mainly through fusion) is in the form of light that exerts a pressure outwards as it escapes. This balances the pressure of gravitation inwards. When the star can no longer produce enough energy to maintain this balance, the star collapses because the gravitational pressure is still there. Eventually, the surface gravity is so great that not even light can escape. This is what makes thes objects both "black" and a "hole".
Keep in mind that the orbital corrections are done with a significant time delay -- this is a situation where the speed of light *matters* :-).
Getting that close to Eros successfully is nothing short of remarkable IMO.
There was an article in Scientific American years ago about the mods made to the Voyager probes in flight (wish I could remember the specific issue), and it really gives you a feeling of wonder about the fact that we monkeys can do this stuff at all...