Debunked: Venus is abnormally bright

Astro

Senior Member
I'm not entirely sure which sub-forum this subject best fits. This claim does sometimes crop up in youtube videos and comments, but it's a more generally held psuedoscientific belief that can be found on a variety of conspiracy forums across the internet. Here are just a few examples to illustrate how widespread the belief is that Venus is now brighter than normal:
http://www.davidicke.com/forum/showthread.php?t=51432
http://www.godlikeproductions.com/forum1/message1850362/pg1
http://www.abovetopsecret.com/forum/thread787463/pg5
Of course Venus' apparent magnitude varies as a function of its phase angle and distance from the earth and sun, but many seem to believe that it's brighter than it should be or has been historically. Most are going based on their own personal memory, which is both fallible and prone to bias. I have seen some debunkers use old photos of Venus to show that it has indeed been quite bright in decades past. Old photographs of Venus can be interesting in an anecdotal sense, but in and of themselves do not typically provide hard data on the apparent magnitude of Venus; film is notoriously non-linear in its response to light. In order to definitively determine if the brightness of Venus is normal compared to its historical brightness or not, two things are necessary; accurate, quantitative measurement of the current brightness of Venus (photometry) and a way of comparing this measurement to an expected value based solely on historical data (Danjon's formula).

In astronomy, an object's apparent brightness is measured in terms of apparent magnitude and can be determined using the following formula:

m(x)=-2.5*Log10(F(x)/F(x,0))+m(x,0)
where
m(x) = magnitude of unknown
m(x,0) = reference magnitude
F(x) = flux of unknown
F(x,0) = reference flux

Human estimates of an object's magnitude are lower in accuracy than they are in precision; the human eye can fairly accurately detect changes in brightness while monitoring an object like a variable star, but observer to observer variations can be quite high. On page 4 of the book "Astronomical Photometry: Past, Present, and Future" within the article titled "Photometric Precision and Accuracy" by Christiaan Sterken, E.F. Milone, and Andrew T. Young, it states the following:

"Although the visual estimates mimic changes of the variable quite closely, they demonstrate significant systematic zero-point deviations - in other words, they have good precision, but very poor accuracy. In particular, the estimates obtained by the two visual observers differ by 0.2m to 0.5m in 2007-2008."

Figure 1 of this article shows the precision of naked eye measurements to be no better than .1 magnitude, so because these anecdotal reports of Venus being "too bright" are themselves naked eye "measurements" (generally by untrained observers, no less), that is the minimum accuracy I aimed to achieve both with my own quantitative measurement of Venus' magnitude as well as with the method by which I compared this to its historically expected value.

I used CCD photometry to measure the brightness of Venus on the morning of September 17th, 2012. On that date, the star Sirius had about the same altitude over the horizon as Venus, which simplified the measurement by allowing for a direct comparison (since they would both experience similar amounts of atmospheric extinction). Sirius served as my reference flux, and since it has a known magnitude (and since it is bright enough to not be under-exposed in a fast exposure needed to avoid over-exposing Venus), it allowed me to solve for the magnitude of Venus.

At 05:38 UT on September 17th, I imaged both Venus and Sirius back to back using a Planewave 20" Corrected Dall-Kirkham Astrograph with a FLI ProLine PL11002M CCD camera and a photometric V filter, the T-11 telescope on the itelescope.net network. Venus had a measured intensity of 118458.254726 and Sirius was 10586.866282. These are arbitrary units, so we need to plug them into the above formula to calculate the magnitude of Venus. Given that Sirius has a photometric V magnitude of -1.47 (http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=sirius&submit=SIMBAD search ), Venus had a V magnitude of about -4.09 that morning.

To compare this to the historically expected magnitude of Venus, I utilized the Danjon formula. In 1949, Andre-Louis Danjon published a formula for calculating the variation of Venus' visual magnitude (V) based on the solar phase angle using data he had collected over the previous 10 years.
http://i319.photobucket.com/albums/mm477/ngchunter/Planetmagnitudes2.jpg
Plugging the result into the general formula for calculating the magnitude of a planet, seen here (http://i319.photobucket.com/albums/mm477/ngchunter/Planetmagnitudes1.jpg ) allows one to calculate the expected magnitude of Venus given data from the first half of the 20th century, long before Venus supposedly started becoming "abnormally bright." Danjon's formula agrees with later determinations of Venus' magnitude (Knuckles, CF., Sinton, MK., and Sinton, WM 1961, "UBV Photometry Venus," Lowell Obs. Bull., 5, 153-156) to within about .1 magnitudes, the accuracy I'm aiming for. Given the distance of Venus from the sun and earth at that time (0.721802 and 0.957722 AUs respectively) and a phase angle of 71.9646 degrees, Venus' apparent V magnitude should have been about -4.03, agreeing with the measured value above well within the accuracy expected for the Danjon formula, and far beyond the accuracy and precision attainable by naked eye visual measurements.

I summarize all of this in the following YouTube video and also show the analysis of the images I took of Venus and Sirius (I used the astronomy version of ImageJ):
 
Very nice. This reminds me of the "Boat Moon" thread on Above Top Secret, where a few people became convinced that the Moon had tipped over a bit, and was showing up as an incredibly rare Boat Moon. An incredible amount of patient explaining went into trying to set them straight, but they were entirely immune to reason. (Edit: wrote that before watching your video, and I see that's mentioned in the first few seconds. Nice music:) )

It also reminds me of "the sky is less blue now" threads. Like you say, people are good at judging relative differenced (precision), but not absolute value (accuracy). And they also rely on highly unreliable memory and color photographs.

And of course we also have "contrails last much longer nowadays". It seems there is fertile ground in the human mind for any theory that's along the lines of "X is a bit different now".
 
Very nice Video, Mr. Astro. the Title "Episode 1" suggest that there is more to come.

Thank you! Indeed, I'm currently working on "Episode 2" which will focus on the "boat moon" issue Mick mentioned above. I'll try to cover the whole range of claims which tie back to field rotation and the moon; some people focus on the apparent orientation of the moon's terminator, particularly during crescent phases (boat moon madness), while others seem to focus on the orientation of lunar surface features. Once the moon's phase returns to something I can work with, I'll show both the effect of field rotation (as well as how it vanishes from a polar aligned point of view) and how the orientation of the lunar terminator with respect to lunar surface features is still the same as it was a long time ago.
 
Very, very nice. Is "The YouTuber's Guide to Astronomy" your invention? You should open every video with it. Either way, I've subscribed.
Yes, I recently started this channel for the purpose of producing videos debunking common or popular YouTube astronomy myths. I plan to use that intro sequence for all the episodes and make it a continuous series of shows. The tricky bit is deciding what to go after first, it's a target rich environment. I'm currently working on field rotation for episode 2, but the end of the year's also fast approaching and I'm sure "Nibiru" will resurface as a popular topic by mid-December, so I'd like to get an episode out about that before then.
On the topic of people "noticing things for the first time and jumping to the conclusion that it must be part of some conspiracy" comes these mind-boggling examples from one channel:

http://www.youtube.com/watch?v=-5EOWcuji3I

http://www.youtube.com/watch?v=LbdQuoIKPYM

Wow. That's depressing. At least most of the people making comments seem to get it.
 
The tricky bit is deciding what to go after first, it's a target rich environment. I'm currently working on field rotation for episode 2, but the end of the year's also fast approaching and I'm sure "Nibiru" will resurface as a popular topic by mid-December, so I'd like to get an episode out about that before then.

Yeah. A YouTube search for Nibiru sorted by upload date is very depressing. Common claims I've seen are that it only emits in the infrared so that's why we can't see it with the naked eye (WTF???) and it's approaching from south of the ecliptic so we can't see it from the northern hemisphere (which is why the evil seekrit gubmint built the South Pole Telescope).
 
Very, very nice. Is "The YouTuber's Guide to Astronomy" your invention? You should open every video with it. Either way, I've subscribed.

On the topic of people "noticing things for the first time and jumping to the conclusion that it must be part of some conspiracy" comes these mind-boggling examples from one channel:

http://www.youtube.com/watch?v=-5EOWcuji3I

http://www.youtube.com/watch?v=LbdQuoIKPYM

That guy scares me. He may be a danger to himself and others:

http://www.youtube.com/watch?v=IyHcKeGZchY&feature=plcp

I identified the shopping center in that video. It is on Cheshire Bridge Road in Atlanta, GA.
 
Thank you! Indeed, I'm currently working on "Episode 2" which will focus on the "boat moon" issue Mick mentioned above. I'll try to cover the whole range of claims which tie back to field rotation and the moon; some people focus on the apparent orientation of the moon's terminator, particularly during crescent phases (boat moon madness), while others seem to focus on the orientation of lunar surface features. Once the moon's phase returns to something I can work with, I'll show both the effect of field rotation (as well as how it vanishes from a polar aligned point of view) and how the orientation of the lunar terminator with respect to lunar surface features is still the same as it was a long time ago.

I imagine you've seen the ATS thread on that, with numerous visual aids created to try to explain things to the beleivers
http://www.abovetopsecret.com/forum/thread783771/pg1

This is the one I participated in (as Uncinus)
http://www.abovetopsecret.com/forum/thread771886/pg1

The sad thing is that even though they seemed to be being deliberately obtuse, I don't think the believers were actually trolling.
 
Thanks, these sorts of things fascinate me.
(ATS threads where people rabidly defend erroneous views because they've invested so emotionally in it being true.)
 
I imagine you've seen the ATS thread on that, with numerous visual aids created to try to explain things to the beleivers
http://www.abovetopsecret.com/forum/thread783771/pg1

This is the one I participated in (as Uncinus)
http://www.abovetopsecret.com/forum/thread771886/pg1

The sad thing is that even though they seemed to be being deliberately obtuse, I don't think the believers were actually trolling.

I think Pete may be right; it seems like they're so emotionally invested in their erroneous views that they can't admit when they're wrong. I suspect that you're right as well and that they're not merely trolling, but I suspect that they also know when they're cornered on a point.

They're so emotionally invested in being "right" that they will never admit that the evidence contradicts them and will either alter their claim to explain it or claim the evidence itself is part of a conspiracy to hide the truth. I think I saw one of the posters alternate between one and then the other "solution" for the same piece of evidence in those threads. In other words, they're experiencing a large amount of cognitive dissonance, but will resolve that dissonance not by discarding their erroneous beliefs, rather by discarding the offending evidence.

There will always be believers who are too emotionally invested to restructure their beliefs to fit the facts rather than the other way around, but hopefully a point-by-point debunking such as this can provide a clear explanation to those who are willing to understand it before becoming too emotionally invested.
 
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