Transit of Venus

"Greg Hennessy" writes:

I'm not sure what it says at metaresearch.org, but since the black
drop effect was seen when Mercury transited the sun as observed by a
spacecraft, the black drop effect cannot be due to either the earth's
atmosphere or the atmosphere of the planet in transit.

I saw my first transit of Mercury and first black drop
effect in 1960. It has always been obvious that the atmosphere of the
transiting planet has nothing to do with the black drop effect because
Mercury has no atmosphere.

But think about what you are saying. Earth does have an
atmosphere, and the light from the transit must pass through it. Our
atmosphere slightly distorts all light passing through it. Why should
transits be an exception?

Lunar occultations prove that the apparent enlargement of
the Sun's and Moon's disks caused by irradiation does not occur in
space. So it must happen in Earth's atmosphere. And stellar "seeing"
disks show that it does happen here, caused by variable refraction in
moving air cells.

At the Meta Research site you will find the evidence and
details. See
http://metaresearch.org/home/viewpoint/blackdrop.asp.
Be sure not to be one of those people who can't unlearn things once
learned wrongly. Look at the evidence and draw your own conclusions
anew, without the influence of the bias of having previously held a
contrary position. -|Tom|-


Tom Van Flandern - Washington, DC - see our web site on replacement
astronomy research at http://metaresearch.org

"Tom Van Flandern" wrote in message
...
"Greg Hennessy" writes:

I'm not sure what it says at metaresearch.org, but since the black
drop effect was seen when Mercury transited the sun as observed by a
spacecraft, the black drop effect cannot be due to either the earth's
atmosphere or the atmosphere of the planet in transit.

I saw my first transit of Mercury and first black drop
effect in 1960. It has always been obvious that the atmosphere of the
transiting planet has nothing to do with the black drop effect because
Mercury has no atmosphere.

But think about what you are saying. Earth does have an
atmosphere, and the light from the transit must pass through it. Our
atmosphere slightly distorts all light passing through it. Why should
transits be an exception?

Lunar occultations prove that the apparent enlargement of
the Sun's and Moon's disks caused by irradiation does not occur in
space. So it must happen in Earth's atmosphere. And stellar "seeing"
disks show that it does happen here, caused by variable refraction in
moving air cells.

What about the spacecraft in orbit outside earth's atmosphere that
someone mentioned? It too saw the black drop effect in a Mercury
transit from outside
the atmosphere, according to whoever posted that.

rj

In article ,
Tom Van Flandern wrote:
But think about what you are saying. Earth does have an
atmosphere, and the light from the transit must pass through it. Our
atmosphere slightly distorts all light passing through it. Why should
transits be an exception?

You are proposing a logical fallacy.

Earth's atmosphere distorts light.
The black drop effect is a light distortion.
The earth's atmosphere causes the black drop effect.

The logical fallacy is because other effects besides the earths
atmosphere distort light.

If the black drop effect is from the earths atmosphere, how come the
TRACE sattelite saw the effect?

This replies to Greg Hennessy and Dave Tholen.


"Greg Hennessy" writes:

[tvf]: Earth does have an atmosphere, and the light from the transit
must pass through it. Our atmosphere slightly distorts all light passing
through it. Why should transits be an exception?

[Hennessy]: You are proposing a logical fallacy.
-- Earth's atmosphere distorts light.
-- The black drop effect is a light distortion.
-- The earth's atmosphere causes the black drop effect.
The logical fallacy is because other effects besides the earths
atmosphere distort light.

Earth's atmosphere produces an effect on starlight,
moonlight, and sunlight entering it that enlarges those visible disks.

The known effect produced by Earth's atmosphere is
qualitatively necessary and quantitatively sufficient to produce the
observed black drop effect.

Therefore, no other causes are needed in the case of
transits.

[Hennessy]: If the black drop effect is from the earths atmosphere,
how come the TRACE satellite saw the effect?

Thanks very much for mentioning the article you cited at
http://nicmosis.as.arizona.edu:8000/POSTERS/TOM1999.jpg, which I will
add to the bibliography for my article with an acknowledgement to you.
It is about space-based observations of transits of Mercury that
reported seeing the black drop effect. However, what the article says is
consistent with my own article and many others before it. The
investigators agree that the image spreading (their "point-spread
function" of PSF) is essential to the black drop effect, and that the
primary cause of the black drop for ground-based observers is
atmospheric "seeing" because that is the main cause of image spreading
(PSF) on the ground. Their point was that diffraction is also present
and, although much smaller than "seeing" effects, becomes the dominant
cause of image spreading (PSF) in space where there is no atmospheric
effect. (I had already mentioned diffraction as a secondary cause in my
section on image spreading for lunar occultations.) Therefore, a small
black drop effect is still seen by spacecraft unless one corrects for
limb darkening, in which case the black drop effect can be effectively
removed from the data.

Here are three paragraphs with the actual words of these authors:

[from abstract]: ". we examined the images in and around the point of
internal tangency for evidence of the historical 'Black Drop' effect.
After calibration (including careful removal of image/instrumental
artifacts and flat-fielding) the only radially directed brightness
anisotropies found were due to the interacting effects of diffracted
limb-darkened photospheric light around the Mercurian disk and the
instrument's Point Spread Function (PSF). We discuss, and model, these
effects as they would have applied to earlier ground-based observations
of Mercurian transits (also including the effects of atmospheric
"seeing") to explain the historical basis for the Black Drop effect."

[from text]: "Shortly after the 1769 transit of Venus [i], De la Lande
identified the origin of this effect in blurring due to atmospheric
turbidity (i.e., 'seeing'). Today, space-based transit observations are,
of course, devoid of, (time variable) atmospheric seeing effects,
previously modeled [3]. Nonetheless, the Black Drop effect arises due to
the finite instrumental resolution (blurring by the instrumental PSF)
convolved with the solar limb-darkening profile."

[from conclusion]: "The principal cause of the Black Drop effect, which
has historically impeded ground-based planetary transit measurements, is
optical broadening due to the convolution of the systemic PSF with the
planetary and limb-darkened solar disks. TRACE [satellite] observations
are free from PSF instabilities due to 'seeing' in the terrestrial
atmosphere and allow mitigation of the Black Drop effect from the
intrinsic disk images."

"Mitigation" means "lessening". The ground-based black drop
effect caused by "seeing" is not present in space, but a lesser effect
from a different cause (diffraction) is still present there. Unlike
rapidly time-variable "seeing" effects, diffraction and limb-darkening
effects can be easily modeled and corrected for. The ground observers
have no such luxury.


and writes:

[Tholen]: Why don't you practice what you preach and think about what
you are saying. Greg said the effect was observed by a spacecraft,
therefore your entire reference to the Earth's atmosphere is irrelevant.

Tholen, you are a professional, and are supposed to be
helping matters, not spreading disinformation. In this case, I'm taking
about information that has been known for over 200 years, not some
theory of mine. See for example the references in Peter Abraham's first
message in the current thread "black drop, longer explanation" in
newsgroup sci.astro.amateur.

You could have read my article, the other references, or the
spacecraft article, and set matters straight yourself, even if you have
never personally seen the black drop effect. Instead, you opted for the
chance to take another shot at me, rather than helping to get the
science right. Pathetic. When will you get that this isn't about you or
me, but about advancing science? -|Tom|-


Tom Van Flandern - Washington, DC - see our web site on replacement
astronomy research at http://metaresearch.org

Tom Van Flandern writes:

Why don't you practice what you preach and think about what
you are saying. Greg said the effect was observed by a spacecraft,
therefore your entire reference to the Earth's atmosphere is irrelevant.

Tholen, you are a professional, and are supposed to be
helping matters, not spreading disinformation.

I did help matters by noting that the effect was observed by a spacecraft,
therefore your entire reference to the Earth's atmosphere is irrelevant.

In this case, I'm taking
about information that has been known for over 200 years, not some
theory of mine.

You're talking about some explanation that involves the Earth's
atmosphere, which cannot explain the effect seen by a spacecraft.

See for example the references in Peter Abraham's first
message in the current thread "black drop, longer explanation" in
newsgroup sci.astro.amateur.

Unnecessary. In a nutshell, we have the following:

Q: What causes the black drop effect?
A: The Earth's atmosphere.
Q: But a spacecraft observed the black drop effect, so doesn't
that invalidate the claim that it's caused by the Earth's
atmosphere?
A: Think about what you are saying. Earth does have an atmosphere,
and the light from the transit MUST [emphasis added] pass
through it.

Sorry, but from the spacecraft's perspective, the light does not
have to pass through the Earth's atmosphere, which means that you
didn't think about what you said.

You could have read my article, the other references, or the
spacecraft article, and set matters straight yourself,

The matter had already been set straight. I was merely recommending
that you practice what you preach and think about what you are saying.

even if you have
never personally seen the black drop effect. Instead, you opted for the
chance to take another shot at me,

That's rather ironic, coming from someone who has taken shots at me.

rather than helping to get the science right.

That's rather ironic, coming from someone saying that the light from
the transit must pass through the Earth's atmosphere, even for a
spacecraft.

Pathetic.

My sentiments exactly.

When will you get that this isn't about you or
me, but about advancing science? -|Tom|-

The science had already been advanced, Tom. It's about you telling
someone to think about what they're saying while not doing so yourself.

wrote:
The science had already been advanced, Tom. It's about you telling
someone to think about what they're saying while not doing so yourself.

I'm not a big fan of Tom's (I think he's a borderline nut and I sure
wish he'd ask more informed questions at the MER briefings), but I must
say your response to him is both childish and personal. In the end it
is *you* who aren't paying enough attention to what is being said before
commenting (or thinking). Tom explained clearly enough how this affect
has the same basic cause with or without the atmosphere, only that the
atmosphere exacerbates it. I think you should ask yourself one simple
question: do you have anything to offer regarding this phenomenon other
than ridicule?

Greg Crinklaw writes:

The science had already been advanced, Tom. It's about you telling
someone to think about what they're saying while not doing so yourself.

I'm not a big fan of Tom's (I think he's a borderline nut and I sure
wish he'd ask more informed questions at the MER briefings), but I must
say your response to him is both childish and personal.

No more childish and personal than Tom's response to Greg Hennessy. I
have often found that the best educational tool is to use that which
the person being educated uses himself.

In the end it
is *you* who aren't paying enough attention to what is being said before
commenting (or thinking).

Incorrect, Greg, and ironically, you have demonstrated that you haven't
paid enough attention to what was said before commenting. See below.

Tom explained clearly enough how this affect
has the same basic cause with or without the atmosphere, only that the
atmosphere exacerbates it.

I suggest you go back and read Tom's original reply to Greg Hennessy
(reproduced below for your convenience). Nowhere did he say that the
atmosphere exacerbates it. Indeed, he stated quite unambiguously
that the effect "must happen in the Earth's atmosphere". It was only
*after* Greg Hennessy and I called attention to his failure to think
about what he was saying that he changed his explanation.

I think you should ask yourself one simple
question: do you have anything to offer regarding this phenomenon other
than ridicule?

I am offering the facts on the sequence of statements that have
occurred during the course of this discussion. Here is the
relevant portion of Tom's original response to Greg Hennessy:

] But think about what you are saying. Earth does have an
] atmosphere, and the light from the transit must pass through it. Our
] atmosphere slightly distorts all light passing through it. Why should
] transits be an exception?
]
] Lunar occultations prove that the apparent enlargement of
] the Sun's and Moon's disks caused by irradiation does not occur in
] space. So it must happen in Earth's atmosphere. And stellar "seeing"
] disks show that it does happen here, caused by variable refraction in
] moving air cells.

wrote:
Tom explained clearly enough how this affect
has the same basic cause with or without the atmosphere, only that the
atmosphere exacerbates it.

I suggest you go back and read Tom's original reply to Greg Hennessy
(reproduced below for your convenience). Nowhere did he say that the
atmosphere exacerbates it. Indeed, he stated quite unambiguously
that the effect "must happen in the Earth's atmosphere". It was only
*after* Greg Hennessy and I called attention to his failure to think
about what he was saying that he changed his explanation.

Actually, had you taking the time to read his elaboration it should be
obvious that he simply didn't make himself very clear in his first post.
I don't understand why you are intentionally ignoring his
clarification, preferring to attack him based on your erroneous
interpretation of his poorly worded original statement. That, sir, is
not the sign of someone being rational...

I am offering the facts on the sequence of statements that have
occurred during the course of this discussion. Here is the
relevant portion of Tom's original response to Greg Hennessy:

Are you a lawyer by trade? You seem intent on using his words against
him even after he later clarified what he meant. I'll ask one more
time: do you have anything relevant to offer regarding the topic at
hand? Because I've got to say I find Tom's remarks and links far more
insightful than your continued childish personal attacks against him and
I doubt I'm the only one...

If you two have some sort of personal feud, then please consider that
the rest of us don't give a damn!

In article ,
Tom Van Flandern wrote:

The known effect produced by Earth's atmosphere is
qualitatively necessary and quantitatively sufficient to produce the
observed black drop effect.

False. The earth's atmosphere CANNOT be necessary to produce the black
drop effect, since the effect is seen from TRACE.

If you want to argue that the earth's atmosphere INCREASES the black
drop effect, you can, but you cannot aruge it CAUSES it.

(Greg Hennessy) wrote in message ...
In article ,
Tom Van Flandern wrote:

The known effect produced by Earth's atmosphere is
qualitatively necessary and quantitatively sufficient to produce the
observed black drop effect.

False. The earth's atmosphere CANNOT be necessary to produce the black
drop effect, since the effect is seen from TRACE.

If you want to argue that the earth's atmosphere INCREASES the black
drop effect, you can, but you cannot aruge it CAUSES it.

The TRACE photos are very interesing. There is some obvious additional
darkening in the subject area over and above limb darkening.

If I had seen these pictures before seeing pictures of the real black
drop effect, I'd have thought "cool, the black drop effect".

But I have seen black drop effect photos taken from the ground. IMO,
we need a new name, something like the "grey drop effect", for what
TRACE recorded.

LB