HST and 'dark matter' |
HST and 'dark matter' |
Guest_PhilCo126_* |
May 11 2007, 05:13 PM
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Guests |
ASA Updates Plans for Hubble 'Ring Of Dark Matter' Briefing
GREENBELT, Md. - NASA will hold a media teleconference at 1 p.m. EDT on May 15 to discuss the strongest evidence to date that dark matter exists. This evidence was found in a ghostly ring of dark matter in the cluster CL0024+17, discovered using NASA's Hubble Space Telescope. The ring is the first detection of dark matter with a unique structure different from the distribution of both the galaxies and the hot gas in the cluster. The discovery will be featured in the June 20 issue of the Astrophysical Journal. |
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Mar 11 2010, 05:47 PM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
Is it just me, or is this a catastrophically screwed up analogy?
"Fill a bucket with water, grab it by the handle and whirl it in an arc above your head. If you do it right, you will stay dry. A mysterious force seems to glue the water into the upside down bucket. Scientists are still unsure about where this force comes from" Errr - F=MA and A=V^2 / R Nothin mysterious about it. |
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Mar 11 2010, 06:04 PM
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#3
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Member Group: Members Posts: 723 Joined: 13-June 04 Member No.: 82 |
That was my first thought too, but how does the water 'know' that it is experiencing circular acceleration? The magnitude of the 'centrifugal' (or conversely, centripetal) force is easily calculated, but the reason it exists is apparently much harder to understand. Einstein never could. As the example stated, if the Earth were rotating in an otherwise empty universe, would it still be considered to be rotating? And would it still experience polar flattening as a result? If it does, how does it 'know' how quickly it is rotating (to generate that degree of flattening) with nothing to act as an external reference frame, and if it does not, why does the presence of some other random object(s) in the universe affect the shape of the earth, to a far larger degree than those caused by tidal effects? And is one other physical object in the universe enough to establish a reference frame, or is an entire universe equivalent to ours necessary? If so, why?
Inertia is very easy to handle mathematically, it's practically the first thing taught in high school physics, but its origin is apparently much more difficult to explain. It appears that this new theory of gravity by Verlinde has inertia fall out almost automatically, in terms of entropy gradients. |
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Mar 11 2010, 07:13 PM
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#4
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Senior Member Group: Members Posts: 1592 Joined: 14-October 05 From: Vermont Member No.: 530 |
Inertia is very easy to handle mathematically, it's practically the first thing taught in high school physics, but its origin is apparently much more difficult to explain. It appears that this new theory of gravity by Verlinde has inertia fall out almost automatically, in terms of entropy gradients. Yes, but I don't understand why an balanced entropy gradients are so much more gee-whiz than balanced forces. Someone will be unsatisfied with not knowing the origin for the 2nd law of thermodynamics, right? I understand the elegance of describing inertia in terms of entropy, but in my mind, it's just saying that this thing we think is fundamental is just like this other thing that is fundamental. It's still fundamental. I would think that if some young einstein asked his physics teacher "why is there inertia?" the answer would be "it's fundamental." Upon reaching university, a physics professor might say, "actually, it can be expressed as a manifestation of entropy." At which point the young einstein says, "why is there entropy?" Does the physics professor say, "it's fundamental?" Is the reason it's so gee-whiz because entropy is a fundamental property of everything, not just matter and energy, but also information? We're better linking in the concepts of data and uncertainty with matter and energy? |
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