Some questions about Venus

[Bikkembergs]

Hi,

I ended up reading a book the other night, looking at a section on Galileo and his discoveries that Venus has similar phases which emulate our moon and it left me a little puzzled

Venus has a "full face" and is at its smallest when on the far side of the sun, hence it's fullness. And it's biggest and most thin crescent shaped when nearest. Are these observations what was needed to confirm that Venus has an orbit inside Earth's? Otherwise it could have a full face and be right next to Earth, if it was orbiting the Sun behind Earth...right?

Then I thought..(and this is silly! ) How can we even see anything that inside Earth's orbit at all? No matter where Venus (Or Mercury for that matter) are, doesn't the Sun get in the way?

Lets say Venus is in it's full phase, so its on the other side of the Sun. The Sun is inbetween, and when you're facing Venus (wherever you are on Earth) it's daytime....? And when you're able to see the night sky, you have your back to the Sun and you're facing Mars, Jupiter and the rest of the pack behind?

Similarly, If Venus was at it's closest, thin crescent stage, to face Venus will you not be also facing the Sun too, as Venus is inside Earth's orbit?

Blimey

[SteveL]

Then I thought..(and this is silly! ) How can we even see anything that inside Earth's orbit at all? No matter where Venus (Or Mercury for that matter) are, doesn't the Sun get in the way?

"inside earth's orbit" doesnt mean "directly in line with the sun". You can quite happily see venus in the morning sky before the sun comes up or the evening sky after the sun has gone down (depending on where in its orbit venus is at the time). If Venus' orbit is 90 degrees offset to earths, it will appear to be to the left or the right of the sun, and is so quite visible, despite it orbiting inside the earth. Varying offsets in the orbits produce varying offset from the diretc line of sight with the sun. It only has to be to the left or the right of the sun to see it when the sun is obscured, or even when it isnt (if you know where to look and if its safe to do so!).

The moon spends half its time closer to the sun that the earth (as it orbits the earth), and that is quite plainly visible.

[brantuk]

I've seen venus's phases (well three of 'em) in my telescope and it's dead easy. The crescent phase was mid spring from the Lake District. The sun had just gone down behind a hill and there was venus trailing behind. Got a good hour's vewing before it set too.

It's not allways in line with the sun or behind it. Often venus appears to either side. Same for mercury too

[Dave Smith]

Here are some pictures of Venus that I have taken recently showing it's different phases and apparent size.

They were taken on 5 July, 17 Aug, 30 Aug, 16 Sept this year.

They may help you visualise what is going on. They were all taken in daylight hours.

Dave

[Bikkembergs]

Thanks for the replies