I Would it be possible to observe an alien city? (1 Viewer)

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

momo666

Under what circumstances would a telescope be able to observe an alien city, supposing such a structure was present on a planet?
Are the requirements so high, say the mirror size, that this is simply wishful thinking or is this actually possible?
More specifically, suppose our imagined telescope is 15m in diameter. Is that a fundamental limit that prevents us from achieving such a feat? From what I gather, this kind of observation and detail would require an enormous diameter.

scottdave

Homework Helper
Gold Member
I don't recall the formulas for calculating the necessary mirror size. It might be possible to find evidence of alien activity (assuming they exist) through radio transmissions.

Last edited:

Staff Emeritus
This is far, far out of the realm of possibility. We can't image exoplanets, and indeed most stars.

berkeman

Mentor

Staff Emeritus
So there's your answer - for all but the very nearest stars, the mirror would need to be bigger than the earth.

momo666

Say the mirror is bigger than the earth or whatever huge diameter our thought experiment requires. Would that merely give us a picture of the star or would it allow us to observe structures on the orbiting planets?
If it only gives us a picture of the star, are we talking about 2 pixels added together or something like what Hubble gives us when we observe a crater on the Moon?

Edit: So this will clear it up I think.
Suppose the target is 1 light year away and our mirror diameter is 100m. What would be the angular resolution? My math is bad so I got 10m.
What if the mirror diameter is the size of the Earth?

Last edited:

berkeman

Mentor
Say the mirror is bigger than the earth or whatever huge diameter our thought experiment requires. Would that merely give us a picture of the star or would it allow us to observe structures on the orbiting planets?
If it only gives us a picture of the star, are we talking about 2 pixels added together or something like what Hubble gives us when we observe a crater on the Moon?

Edit: So this will clear it up I think.
Suppose the target is 1 light year away and our mirror diameter is 100m. What would be the angular resolution? My math is bad so I got 10m.
What if the mirror diameter is the size of the Earth?

The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving