25 Aug 07
Originally posted by ArrakisSpace is not empty. In fact, [98%] ???of the universe is not visible to the human eye. The dark matter which we cannot see has a gravitational influence on all objects.
We all know this is true, but what we (I) don't know is how and why the last sentence is true?
The thinking is that the more mass an object has the more influence the dark matter exerts on it.
If this is true then the dark mass would hold the larger mass more stable? But if this is true it still doesn't explain why the dark mass would cause the smaller mass to move toward the larger mass?
So in your analogy it makes sense that the lesser mass object would move towards the heavier one.
Why does it make sense? Why wouldn't it just act like the planets that circle the sun? Which leads to why does that happen instead of collisions? Who invented this process anyway, Darwin? I'm going to file a patent and use the process to replace oil just as soon as you explain the process better.
25 Aug 07
Originally posted by Pawn QweenYou are totally right. Newton should have got the Nobel Prize for his gravitational theory..... not for Physics though, but for Medicine.
Gravity gets everybody down.
Gravity, like depression, is an illness, that only seems to worry we humans.
Prozac and Relativity have a lot in common.
25 Aug 07
Originally posted by MetBierOpTechnically, they will approach one another no matter the distance. However they won't start out accelerating very quickly.
I replied in the posers and puzzles forum on a thread about gravity but I think it belongs eihter here on in the debates forum.
Here it is:
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I never understood gravity at all.
"Gravitation" is the attractive influence that all objects exert on each other, while "gravity" specifically refers to a force which all massive o ...[text shortened]... away from it.
While I can learn that this is the truth, I simply cannot understand why.
I don't understand why either. Part of the problem is that any answer to "why X" just gives us more why questions.
26 Aug 07
Originally posted by AThousandYoungYou could even sweeten the pot by putting them at whatever incredible distance you can think up, then have them moving directly away from each other at as close to the speed of light as possible. In an otherwise empty universe, they'll still find each other.
Technically, they will approach one another no matter the distance. However they won't start out accelerating very quickly.
I don't understand why either. Part of the problem is that any answer to "why X" just gives us more why questions.
26 Aug 07
Originally posted by MetBierOpNobody knows the "why" of gravity yet; its existance is observed and its properties deduced. Quantum gravity still resists being shoe-horned into a grand unified theory, but the research continues! The elusive "why" stirs the imagination still.
(gravity) ... While I can learn that this is the truth, I simply cannot understand why.
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26 Aug 07
Originally posted by Sam The ShamThis isn't quite true. High speed objects can easily outpace the force of gravity, even though the force of gravity is felt over infinite distance. This is why there was such uncertainty for so long over whether the universe was open or closed, whether there was enough initial mass in the universe to overcome the expansion and one day collapse in a Big Crunch, or whether there was too little mass and the universe would continue to expand forever, slowly dying, slowly freezing, as the stars winked out one by one in an ever lonelier space. The key is whether the RATE of expansion outpaces the RATE of weakening of gravitational attraction as the physical objects get further and further apart.
You could even sweeten the pot by putting them at whatever incredible distance you can think up, then have them moving directly away from each other at as close to the speed of light as possible. In an otherwise empty universe, they'll still find each other.
The mind-blowing recent realization in physics and astronomy is the discovery that the rate of universal expansion is increasing!! Not that the universe is increasing, but that its RATE is increasing!! This is totally unexpected and shows that there are many mysteries yet to be uncovered. Physics is far from dead! 🙂
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26 Aug 07
Originally posted by Doctor RatDon't gravitational waves travel at light speed? How could an object outpace them?
This isn't quite true. High speed objects can easily outpace the force of gravity, even though the force of gravity is felt over infinite distance. This is why there was such uncertainty for so long over whether the universe was open or closed, whether there was enough initial mass in the universe to overcome the expansion and one day collapse in a Big Cr ...[text shortened]... and shows that there are many mysteries yet to be uncovered. Physics is far from dead! 🙂
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26 Aug 07
Originally posted by ArrakisThe 98% is too high now for dark matter. A little more mass of the universe has been found with the confirmation that neutrinos have mass. The Super-Kamiokande experiment in Hawaii (1998) and the confirmation from the Borexino Experiment (Italy) announced just this last week show that neutrinos oscillate and therefore have mass. It's a very very tiny mass, but because there are so many neutrinos out there, it adds up. But it doesn't add up to all the Dark Matter. I swear I read this last week that 75% of the matter was still "missing", but now I'll be darned if I can't find that number anywhere. Anyway, this is just a heads-up to the latest breaking news on the Dark Matter front and the appearance of low-mass neutrinos!
Space is not empty. In fact, 98% of the universe is not visible to the human eye. The dark matter which we cannot see has a gravitational influence on all objects. The thinking is that the more mass an object has the more influence the dark matter exerts on it. So in your analogy it makes sense that the lesser mass object would move towards the heavier one.
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26 Aug 07
Originally posted by Sam The ShamThe objects in our thought experiment (which are travelling at near light-speed) don't outpace the gravitational attraction itself (they will always feel some gravitational attraction to each other, no matter how far away they are), but that they move so fast that their distance between them increases faster than the RATE of gravitational attraction could ever slow them down to zero velocity. The objects will slow down, imperceptibly and forever, but slow down to a non-zero velocity asymptote. Grrr, I'm probably not making this clear. 🙁
Don't gravitational waves travel at light speed? How could an object outpace them?
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26 Aug 07
Originally posted by Doctor RatYou're making sense, though it's an explanation that needs math to explain properly.
The objects in our thought experiment (which are travelling at near light-speed) don't outpace the gravitational attraction itself (they will always feel some gravitational attraction to each other, no matter how far away they are), but that they move so fast that their distance between them increases faster than the RATE of gravitational attraction could ...[text shortened]... low down to a non-zero velocity asymptote. Grrr, I'm probably not making this clear. 🙁
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26 Aug 07
Originally posted by Doctor Ratmy head hurts now
The objects in our thought experiment (which are travelling at near light-speed) don't outpace the gravitational attraction itself (they will always feel some gravitational attraction to each other, no matter how far away they are), but that they move so fast that their distance between them increases faster than the RATE of gravitational attraction could ...[text shortened]... low down to a non-zero velocity asymptote. Grrr, I'm probably not making this clear. 🙁
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26 Aug 07
Originally posted by MetBierOpDark matter is hypothetical only in the sense that we think it is something entirely different than what we've ever seen before. If future observations were to show that all dark matter could be explained by, say Brown Dwarf objects and massive neutrinos, then everyone would say, "Well, dark matter was hypothetical after all. In the end, dark matter didn't really exist, it was just the stuff we've already known about but didn't detect until now."
well it seems logical that there is a other factor then only the 2 objects.
I am not really familiar with "The dark matter" but I thought that it was still hypotheticall. Do you have a source, so I can find more information on it?
You also triggered me for an off topic question,
if we cannot see 98% of the universe, then how do we know, that what we can see is 2% of the total?
What isn't hypothetical is the fact that gravitational effects are being observed in the universe where not enough observed matter is present to explain them. Gravitational lensing and galactic rotation speeds are two examples where this anomaly pops up.
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