Whoops. Here's the DIRECT link to a response to the news item at the top. It contains some interesting revelations about the experimenter's methods: Not exactly... It bitches about a particular application of an equation, but it doesn't really go into details about the "experimenter's methods".
Without more discussion of those actual methods, it's impossible to say whether Van Flandern has a valid objection or not.
However... Looking over Van Flandern's website, other works, and his specific piece on the gravity experiment, I can't say that I'm impressed.
Generally, while Van Flandern clearly has a lot of knowledge of the field of astronomy (he ought to, he has a PhD in it), and is capable of making some good points, he also is clearly more than a bit of a crank. For example he's an evangelist for the proposition that there are artificial structures on Mars, which he presents with unshakable belief based on the slimmest of evidence and yet calls "proof".
He follows the crank pattern of having a naysayer's argument against nearly every established theory (the Big Bang, origin of the asteroid belt, cometary formation, the possibility of a tenth planet, etc. etc.). Most scientists are lucky if they ever manage to revolutionize even a *single* bit of conventional wisdom -- Van Flandern has the crank's arrogance of thinking he can overturn *all* of it. And has built a personal website to preach it.
He also has the crank's paranoid mantra down pat: In his own words, he writes that his website's "[...] goal is to do astronomy research wherever promising avenues of advancement are blocked by funding authorities solely because the research results might conflict with an accepted paradigm." Yeah, sure, you can't get your theories published because of the *conspiracy*, and not because they appear to be crackpot ideas.
But let's get specific...
In his argument against the results of the recent gravity experiment, he gets some *basic* astronomical concepts astoundingly wrong, which does not bode well.
In his overview of alleged previous findings in the field, he claims:
The propagation speed of gravitational force is bounded by six experiments to be much faster than the speed of light [5]
The work cited in footnote five was written by... Van Flandern himself (didja ever notice how often cranks cite their *OWN* works for supporting evidence?).
That work can be found here.
In it, while describing his claim that "Laplace determined that the minimum speed of gravity consistent with observations was at least 10 million times the speed of light", he writes:
As viewed from the Earth's frame, light from the Sun has aberration. Light requires about 8.3 minutes to arrive from the Sun, during which time the Sun seems to move through an angle of 20 arc seconds. The arriving sunlight shows us where the Sun was 8.3 minutes ago. The true, instantaneous position of the Sun is about 20 arcs seconds east of its visible position, and we will see the Sun in its true present position about 8.3 minutes into the future. In the same way, star positions are displaced from their average position by up to 20 arcs seconds, depending on the relative direction of the Earth's motion around the Sun. This well-known phenomenon is classical aberration, and was discovered by the astronomer Bradley in 1728.
This is just... wrong. (Although it's clearly where Aruanan's earlier post came from.)
While it's true that light from the sun exhibits an apparent aberration (i.e., false visual displacement) of 20 arc seconds of angle, and while it's true that Bradley discovered this in 1728, just about everything in between is nonsensical twaddle.
Note how much Van Flandern harps on "8.3 minutes" (the time it takes light to travel from the Sun to the Earth). One has to wonder why, because the aberration has *NOTHING* to do with how long it took the light to get from the Sun to the Earth. If the Sun were half as far away (and its light took 4.25 minutes to get here), the amount of aberration would *STILL* be 20 arc seconds. Furthermore, light from distant stars shows the same 20-arc-second aberration (when the Earth's orbit is traveling perpendicular to the Earth-star line), even though the light from those stars took *years* (some, thousands/millions of years) to arrive here. "8.3 minutes" is *entirely* irrelevant to the issue of aberration.
Even worse, he constantly misrepresents aberration as having something to do with 8.3 minutes in the "past" or "future", when aberration has NOTHING to do with where anything was or will be, timewise. It's simply an optical illusion caused by the fact that the orbiting Earth is traveling "crosswise" (at 29.79 Km/s) to the path of the incoming photons (streaming in at the speed of light). It's similar how rain appears to be angling downward at you as you drive your car through a straight-down sprinkle. There's a good discussion of this phenomenon (as opposed to Van Flandern's mangled version) at: http://www.newtonphysics.on.ca/Aberration/Aberration.html.
Keep in mind that light aberration from a star/Sun depends *only* on the speed which the Earth is cruising along in its orbit. Now let's take Van Flandern's errors and nonsense line by line:
Light requires about 8.3 minutes to arrive from the Sun, during which time the Sun seems to move through an angle of 20 arc seconds.
No, sorry. Here Van Flandern confuses parallax with aberration. "Seeming to move" is caused by parallax, and by coincidence the apparent motion of the Sun "around the Earth" due to the Earth's orbit is 20.45 arc-seconds per 8.3 minutes, which is reasonably close to the 20.49 arc-seconds of stellar aberration. BUT THEY ARE IN NO WAY RELATED (and if the Sun's gravity were greater/lesser, they wouldn't be even approximately the same size).
Furthermore, while it makes some sense to talk about apparent motion due to parallax and how "fast" things seem to move, stellar aberration DOES NOT SHOW ANY APPARENT MOTION. It's a fixed displacement. For example, distant stars show no apparent motion relative to the Earth (due to their enormous distances), and yet *still* appear displaced due to stellar aberration. Objects that are entirely at rest even show aberration. It's as wrong to try to pin aberration on movement so many minutes ahead/ago as it is to claim that the angled glass of the side of an acquarium visually displaces the rocks in the acquarium because of where the rocks were "a minute ago".
It's a very bad sign that Van Flandern starts out a discussion of stellar aberration by discussing orbital parallax -- they're unrelated.
The arriving sunlight shows us where the Sun was 8.3 minutes ago.
No, since the Sun *hasn't moved* in the past 8.3 minutes. It's right where it always was. The Sun would appear at the same apparent spot in the sky no matter how long it took its light to reach us.
The true, instantaneous position of the Sun is about 20 arcs seconds east of its visible position, and we will see the Sun in its true present position about 8.3 minutes into the future.
Again he confuses apparent position in the sky (due to the changing position of the Earth) with "true position" (actual physical coordinates), and parallax with aberration.
The "true position" *doesn't change*. The Sun doesn't go zooming around the solar system. It sits right there in the middle, century after century. Therefore it's nonsense to talk about its "true position 8.3 minutes in the future", as if that's any different from its "true position" right now. And again, the *apparent* displacement due to stellar aberration has nothing to do with movement "8.3 minutes" in the future or past.
In the same way, star positions are displaced from their average position by up to 20 arcs seconds, depending on the relative direction of the Earth's motion around the Sun.
Suddenly, Van Flandern admits that distant stars show the *same* visual displacement, without drawing attention to the fact that his fixation on 8.3-minute-old light (which he presented as being key to the Sun's visual displacement) can't possibly be the case for the years-old light arriving from the stars.
Sigh.
But on to his point, even if he has done an amateur's job of confusing the crap out of his audience (and maybe himself) about stellar aberration...
His main point is that although the Sun does indeed appear 20.49 arc-seconds away from where it really is, gravity doesn't. And from this he concludes that gravity propagation must therefore be faster than that of light.
But the mistake is that while the sun's apparent (visual) position is indeed offset due to an optical illusion caused by the Earth's motion, the Sun was never really "there" in the first place. It's not moving, his confused paragraph above notwithstanding. Thus, no matter how long it may take the gravitational force (or field gradient) to propagate, the Sun's "gravity well" is unmoving and unchanging, it's like a standing wave. Thus it's no surprise that the Earth will always find itself gravitationally pulled towards the "true" position of the Sun. This tells us nothing about how fast the gravitational force "adjusts" to changes, since the Sun ain't changing appreciably.
And it's no surprise (and thus not significant) that the gravitational force doesn't demonstrate a 20.49 arc-second aberration like light does, because gravity is presumably a result of space-time curvature, and thus its effects are independent of the lateral motion of an affected body, *unlike* the manner in which incoming photons are encountered as they stream in.
"The "true position" *doesn't change*. The Sun doesn't go zooming around the solar system. It sits right there in the middle, century after century. Therefore it's nonsense to talk about its "true position 8.3 minutes in the future", as if that's any different from its "true position" right now." - Dan Day
That's wrong.
The Sun, Earth, and the rest of our Solar System ARE moving, it's just that they are moving uniformly, so even as the Earth orbits the Sun, both the Earth and the Sun are simultaneously moving together in yet another direction.
This is easy to visualize if you have a toy model of our Solar System. Place that toy model on a ship and start the ship moving. Now, the Earth will circle the Sun in that toy model, but in 8.3 minutes the entire model will be in a new position due to the movement of the ship. However, to an observer on the Earth of that toy model, the Earth would merely have revolved a little around the Sun, while the Sun remained stationary.
Of course, we know that since the ship moved during that time period, that the Sun is actually in a new position. A GPS unit would record two different positions for our toy model, after all.
Likewise with our actual Solar System, one could visualize the entire System moving North/Vertical/towards Polaris for the purposes of a thought exercise. However, just like the toy model on the ship in the example above, whereas an Earth-based observer would percieve that the Sun was in the same position no matter how much time had passed, in reality we know that the Sun will be in a new position above its old location.
And because we know that our Sun is moving North over time, we can discern if Gravity has the same delay as Light simply by detecting if the Earth is orbiting the actual or the perceived (i.e. the "old") position of the Sun.