B Top 3 brighest planets as seen from other planets

[lifeonmercury]

I'd have to think Jupiter from Mars would be the brightest but after that it's hard to say. Any guesses?

 

[tony873004]

Venus from Mercury.
Earth from Venus.

 

[lifeonmercury]

Good point there. I would have guessed Saturn from Jupiter and Jupiter from Earth.

 

[mfb]

Wikipedia has an article.
Assuming we go by peak brightness:

From Mercury, Venus would be by far the brightest object, Earth would be very bright as well, with the Moon nearby. Jupiter would look similar as from Earth, with Mars a bit dimmer.
From Venus above the clouds, Earth is the brightest planet, with Jupiter, Mars and Mercury all very similar in their peak brightness.
From Earth, Venus wins, then Jupiter and Mars with nearly identical peak brightness.
From Mars, Jupiter and Venus will have a very similar brightness, with Earth a bit behind that.
From the outer planets, the inner planets will have their peak brightness when they are in opposition. Venus will always be the brightest inner planet, followed by Earth, with Mars being quite dim.
As seen by Jupiter, Saturn should win over Venus by a small margin. Various nice moons in the sky.
As seen by Saturn, I would expect Jupiter to win, but didn't calculate it.
As seen by Neptune and Uranus: Jupiter or Saturn I guess.

 

[lifeonmercury]

Could some of Jupiter's moons be seen with the naked eye from just above the Martian atmosphere?

 

[mfb]

If you block the line of sight to Jupiter, you can see Ganymede from Earth with the naked eye - its maximum brightness is 4.3 magnitude. The contrast to Jupiter is so large that you don't see them together. The situation is similar on Mars.

 

[DaveC426913]

If you block the line of sight to Jupiter, you can see Ganymede from Earth with the naked eye - its maximum brightness is 4.3 magnitude.

Really! I've got to try this.

 

[mfb]

The maximal angular separation is 1/10 of a degree, or 1/5 the diameter of Moon. A single human eye has an active size of a few millimeters, your shield should be at least 3-4 meters away, and placed with a precision of a few millimeters (which means move your eye around until Jupiter is just out of sight). And even then you need good viewing conditions, and you have to close the other eye unless your obstacle is really far away or exactly in the right orientation.

Callisto has about twice the maximal separation, but its maximal brightness is at the limits of the human eye even in perfect viewing conditions.

Here is a blog article discussing it

 

[epenguin]

Gosh that's interesting! The first question that was occurring to me as I read was 'and nobody saw these satellites before Galileo?!'. When it is so simple. You would expect quite early men to have seen it, since they were far more aware of the heavens than are we, who are often rarely see them through living in artificial light. People living in the desert are no doubt the most likely. But then it is surprising if the ancient Egyptians did not notice. Perhaps it will be found that they did.

(I was not able to open your link yet.)

 

[mfb]

There are some reports that could be interpreted as earlier sightings of Ganymede or Callisto. You have to block the line of sight to Jupiter while keeping the line of sight to the moons, which is not trivial. If you don't know what you are doing (and why), why should you do that?

 

[epenguin]

There are some reports that could be interpreted as earlier sightings of Ganymede or Callisto. You have to block the line of sight to Jupiter while keeping the line of sight to the moons, which is not trivial. If you don't know what you are doing (and why), why should you do that?

Well I just thought that if you have 2000 years in which there is never anything entertaining on the telly somebody might have watched the planets disappear behind an obelisk or pyramid during one of the many clear nights they have in Egypt. And then Ptolemy surely watched the planets in a more than casual way, tabulating their movements. As usual the knowledge of most of us of him is thirdhand (we mostly hear about his theory) and I have no idea how he obtained his tables. If I had to do it with means I imagine available to him, I think it would involve watching the planet and other stars go behind a plumbline, and he might notice a little speck very near it. It is the kind of observation not part of your project you tend to dismiss at first, but if you see it often, if on Monday it is on the right and on Thursday it's on the left and so on, its period is only a week, you might start thinking...