Customer Discussions > Science forum

What's the speed of dark?


Sort: Oldest first | Newest first
Showing 1-25 of 35 posts in this discussion
Initial post: Nov 16, 2012 5:18:20 PM PST
Monk says:
Are there any physics experts who could chime in? Since light is energy, and 'darkness' is the absence of light.. Shouldn't /c/ be the same for both light and dark?

In reply to an earlier post on Nov 16, 2012 5:37:42 PM PST
Doctor Who says:
"Dark" isn't a thing. Its an absence of light. It doesn't move or have a speed.

In reply to an earlier post on Nov 16, 2012 8:12:28 PM PST
barbW says:
that's a curious answer, but I defer to the expertise you've offered here in the past.

The speed of gravity has been quarreled about and the experiment involving that quasar and a Jupiter moon is still being argued about. So, how fast does a gravitational field recede?

If you tell a kid to jump into bed before the light fades in their room - as you're turning off the switch, they're very impressed when you tell them that light travels 7 and half times around the planet every second!

Posted on Nov 16, 2012 8:39:48 PM PST
Re OP: Doctor Who is basically correct here, but we can imagine a gedankenexperiment which may help. Suppose you have a lantern with a shutter which is initially open. An observer is watching, with a suitable clock. You close the shutter, and shortly later the observer sees the darkness. The velocity with which the darkness travels is, of course, the speed of light.

In reply to an earlier post on Nov 16, 2012 8:44:43 PM PST
Last edited by the author on Nov 16, 2012 8:46:15 PM PST
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

Posted on Nov 16, 2012 8:51:32 PM PST
Pure Darkness does not exist!

In reply to an earlier post on Nov 16, 2012 9:20:33 PM PST
Last edited by the author on Nov 16, 2012 9:33:47 PM PST
Doctor Who says:
Actually, for anyone who cares to know this, the above is wrong. A photon is not a vibration in the aether and the Morley-Michelson experiment proved this with great precision[1]. All aether physics is about a century old and discarded by just about everyone who actually knows what they are talking about. There is no evidence for one and there is mountains of evidence against one.

A photon is a packet of energy which is stored in electric and magnetic fields. (An electric and magnetic field is actually the same thing, but that is a different story). It does not have a physical mass. What it is is a wavicle. That is to say, it has properties of both a wave and a particle. It undergoes diffraction like a wave and it undergoes collisions like a particle. These two properties cannot be observed at the same time, which may imply that at the level of photons these properties as we understand them break down. A few things are fairly certain: photons are not vibrations of something and they always travel at a velocity c with respect to every observer.

Photons are actually not the only small things to defy "common sense." Any quantum system may actually not have a momentum and a position at the same time. This is one interpretation of the uncertainty principle that is favored by one professor I know.

[1] Actually, they proved that photons always moved at speed c within their detector. That is, they never saw a photon traveling at c+v where v is the velocity of their apparatus through the aether. This eliminates all theories with the aether being a universal rest frame, but leaves so called "frame dragging" theories. These theories can be trivially discarded because they predict that the fluid should interact with matter, which would cause the planets to crash into the sun. They would also cause optical aberrations which would be visible to the naked eye and also change the direction you need to point a telescope. Since we don't observe these, we can through out frame dragging theories. Thus we see that space is not filled with something and there is no experiment that can pick out any one frame as better than another.

EDIT:

Reference on frame dragging.

http://en.wikipedia.org/wiki/Aether_drag_hypothesis

In reply to an earlier post on Nov 16, 2012 9:20:53 PM PST
that is so meaningless

and illogical

the speed of dark is many times faster than c
light = photons are limited in speed to c
but the universe is expanding at rates far faster than c
and that is dark that is expanding not light

In reply to an earlier post on Nov 16, 2012 9:21:26 PM PST
gravity field does not recede
it is everywhere and you are stuck in it

In reply to an earlier post on Nov 16, 2012 9:28:51 PM PST
Re Doctor Who, 11-16 9:20 PM: "the above is wrong." It is a waste of time to respond to MFEH on any topic whatever: he is ALWAYS wrong. Save yourself some grief and put him on Ignore.

In reply to an earlier post on Nov 16, 2012 9:35:05 PM PST
Last edited by the author on Nov 16, 2012 9:48:36 PM PST
Doctor Who says:
True, but in this case I wasn't posting to him. I was posting to anyone who might actually believe him. After an 8 hour exam on Lienard-Wiechert potentials posting anything is a relief.

In reply to an earlier post on Nov 16, 2012 9:48:01 PM PST
Last edited by the author on Nov 16, 2012 9:48:58 PM PST
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

In reply to an earlier post on Nov 16, 2012 10:16:21 PM PST
he is to funny to put on ignore

scanlon on ignore for sure
drm on ignore
not yet meh

In reply to an earlier post on Nov 16, 2012 10:17:12 PM PST
there is no gravity

it is an artifact of time perturbations your waves do not get right

In reply to an earlier post on Nov 16, 2012 10:26:54 PM PST
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

In reply to an earlier post on Nov 17, 2012 3:43:00 AM PST
Charlie T. says:
Gravitational radiation travels at the speed of light.

In reply to an earlier post on Nov 17, 2012 5:18:17 AM PST
Bubba says:
The darkness in the hearts of the anti-SSM people is quite pure.

In reply to an earlier post on Nov 17, 2012 7:00:46 AM PST
barbW says:
the strength of a gravitational field changes, with respect to an observer, due to collisions and explosions

are these changes instantaneous or limited to the SOL? These are hints for unifying GR and QM. Most likely the changes are limited to the SOL, but not only because all the speeds of the masses are limited to the SOL.

In reply to an earlier post on Nov 17, 2012 7:02:40 AM PST
barbW says:
then how was that experiment supposed to give us the speed of gravity?

In reply to an earlier post on Nov 17, 2012 7:18:48 AM PST
tell me again after somebody actually has united gravity GR and QM with Mtheory

In reply to an earlier post on Nov 17, 2012 7:37:06 AM PST
Last edited by the author on Nov 17, 2012 7:46:19 AM PST
[Customers don't think this post adds to the discussion. Show post anyway. Show all unhelpful posts.]

In reply to an earlier post on Nov 17, 2012 7:39:55 AM PST
andthehorseirodeinontoo? wrote:
"tell me again after somebody actually has united gravity GR and QM with Mtheory "
=====================

I already told you that Chicken JJ in England did so, but you cannot read English or write in English.

http://www.amazon.com/forum/science/ref=cm_cd_et_md_pl?_encoding=UTF8&cdForum=FxZ58KVEERYS5E&cdMsgID=Mx1KL2O95T9TVYP&cdMsgNo=4&cdPage=1&cdSort=oldest&cdThread=Tx3FSTNPE0REPD5#Mx1KL2O95T9TVYP

Mohamed F. El-Hewie

In reply to an earlier post on Nov 17, 2012 7:51:55 AM PST
barbW says:
Newton 'needed' the propagation speed of gravity to be infinite. The experimenters figured that they should be able to rule that out completely. They did get a good estimate for the speed of gravitational waves, but critics say they didn't measure the speed of the force -- which has been determined, by more than one prior experiment, to be faster than the SOL.

In reply to an earlier post on Nov 17, 2012 8:08:53 AM PST
Last edited by the author on Nov 17, 2012 8:09:11 AM PST
werranth413 wrote:
"Newton 'needed' the propagation speed of gravity to be infinite. The experimenters figured that they should be able to rule that out completely. They did get a good estimate for the speed of gravitational waves, but critics say they didn't measure the speed of the force -- which has been determined, by more than one prior experiment, to be faster than the SOL. "
====================

I am willing to start my education anew if you put up with my delinquency.

Force having speed? That leads to either

(1) Force x speed = F.v = m.a.v = m (∂²x/∂t²) (∂x/∂t)
...........................> that is energy / time = power of gravitation

Or

(2) Rate of change of force with respect to time = ∂F/∂t = m (∂/∂t)(∂²x/∂t²)
............................> that implies either force applied to mass change or irregular gravitational field.

I never saw any publication claiming that gravitational speed was anything other than the speed of light and wikipedia left many [edit] fields open for revisions.

Mohamed F. El-Hewie

In reply to an earlier post on Nov 17, 2012 8:48:17 AM PST
Re werranth413, 11-17 7:51 AM: "[the speed of the gravitational force] has been determined, by more than one prior experiment, to be faster than the SOL." No, it hasn't. I posed a question of interest pertaining to this some time back, specifically: Does the earth fall toward where the sun is NOW, or toward where it was eight minutes ago? This is something of a trick question, as the concept of NOW is of course relative. Nevertheless, the answer is important because it has implications on the nature of the earth's orbit.
‹ Previous 1 2 Next ›
[Add comment]
Add your own message to the discussion
To insert a product link use the format: [[ASIN:ASIN product-title]] (What's this?)
Prompts for sign-in
 


 

This discussion

Discussion in:  Science forum
Participants:  11
Total posts:  35
Initial post:  Nov 16, 2012
Latest post:  Nov 18, 2012

New! Receive e-mail when new posts are made.

Search Customer Discussions