One-off: "Black drop" problem an SR effect?

[OneEye]

From a Reuters science article (http://story.news.yahoo.com/news?tmpl=story&cid=585&e=1&u=/nm/20040511/sc_nm/space_venus_dc)

Reuters Science, Scientists Prepare for Rare Astronomical Event:

[The solar transit of Venus] will allow scientists to study the famous "black drop" problem which makes timing the transits difficult. As the black disc of Venus appears on the sun it seems to have a dark neck, or become pear-shaped, for a short time. The opposite occurs when it leaves the sun.
This sounds like something one would want to explain through SR - perhaps GR.

Any comments from anyone?

[Nereid]

No, it's an atmospheric phenomenon (Venus' atmosphere, that is!).

Here's (http://www.vt-2004.org/Media/vt-comm-03.html) a more suitable site for following this rare event ... a bit like Halley's comet - most people will see such a thing only once in their lifetime (and many, not even that!).

You might find the Teachers' Guide, on the VT site, of interest (and there are plenty of links to explore the whole thing in much more detail). :biggrin:

[Creator]

Yes, I always thought it was an optical phenomena due to a slight refraction of the light at the solar edge passing through the atmosphere of Venus.

[OneEye]

Okay, thanks.

Boy, I sure made that simple question complicated, didn't I?

I must be management material!

[Nereid]

Glad we could help.

Don't stop asking questions! Questions are good; curiosity is good. :smile:

Perhaps more managers should ask more questions?

Kind Regards
Nereid

[Creator]

Okay, thanks.

Boy, I sure made that simple question complicated, didn't I?



Actually, it's apparently not that simple.

I've just been corrected by an article that I came across which stated that the TRACE satellite recently detected the same black drop phenomena in the recent solar transit of Mercury,.....which casts doubt on the previous explaination since Mercury has NO atmosphere.

So apparently, the effect is still considered an unresolved (and somewhat bothersome) paradox.

Thanks for the question; it made me re-check my assumptions.

Anyone thought this one through....and come up with OTHER possibilities??

[Nereid]

With the benefit of more than a century in observational astronomy (equipment, techniques, detailed understanding of 'seeing', ...), and many thousands of high quality images of the transit, from many locations and using a wide variety of equipment, ... the conclusion (so far) on the 'black drop effect' is ....

"Scientifically, solar photographers confirmed that the black drop effect is really better related to the viewing clarity of the camera or telescope than the atmosphere of Venus."

Source: Astronomy Picture of the Day (http://antwrp.gsfc.nasa.gov/apod/ap040623.html)