We know that some solar systems in the Universe have planets within them known as the “Goldilocks Zone”, just like Earth. How is it the same technology used to discover these planets is not able to detect if life, especially the intelligent type, also inhabits them?

Question

Scientists are able to observe these planets from vast distances. You would think with technological capability like this that we would also be able to detect if planets in these zones possess life on them. Trying to understand how or why this is the case.

In: Planetary Science

Answer 1

There is a big difference between being able to tell if there is a large ball of rock orbiting a star, and whats on said rock. The farther out into the universe you go the less information that gets back to you. Most of our discoveries of distant planets is more like a blip of data in a spreadsheet rather than an actual photo.

Take earth for example, assuming we try to locate our own planet in the distant galaxy. 70% of our surface is just water. Of the remaining 30% of land, greenland and antarctica are just blobs of ice, as is much of northern asia and north america. and very large portions of North American, Asia, Africa, and Australia are desert or mountains that don’t appear green from space. So there’s not a lot of green reflecting off into space to signal plant life, and while we could probably determine to some extent that earth might have water oceans and a thick atmosphere based on how light reflects, determining oxygen(a major sign of life) would be harder, and even farther out, determining that the planet has oceans might not even be possible. This also doesn’t take into account that on an alien plant, photosynthesizing organisms might not be predominantly green. We have lots of red, purple, yellow, and even blue plants on earth, as well as lots of blue, gray, yellow, and orange lichens, and red and yellow is a fairly common color in space at times.

Now as for our structures. Concrete and metal aren’t going to reflect any unusual colors into space and most of our planet’s surface is not covered by man-made structures. And no far off telescope is going to spot any of our satellites or the international space station. Artificial lighting at night would be a different case, but even then our lights are not nearly bright enough to make it very far into space past our solar system. Radio waves we emit go farther, but by the time you reach our closest neighboring star, our radio waves have degraded and faded to the point where our current technology likely wouldn’t be able to discern it from the background radiation in the universe.