Well how far is extremely far? The article you linked says
This would give a resolution of about 10 square kilometers for objects 100 light-years away.
The galaxy is 87k light years across. Is such a resolution good enough to determine the atmospheric composition of any planet in our galaxy? What about other galaxies?
Obviously there is a delay based on the speed of light where time needs to pass before changes can be seen, but I’m wondering what the radius is where these things become invisible no matter how much time passes, if there is such a limit. There might be intelligent life elsewhere in the universe but not in our galaxy, so if the edge of the galaxy was the limit that would be relevant to our security.
You don’t need resolution to do spectral analysis. They’re talking about identifying specific features, which isn’t what we’re talking about.
An ideal situation would be to look at a star (you only need to be able to pick out a single star, which you can do in other galaxies in the right conditions) and have a planet pass between that star and us. You’d see the change in color of the light and from that you can determine a lot about the planet’s atmosphere.
With our current technology, you have to get pretty lucky to have gravitational lensing opportunity along with a planetary transit, but that’s just assuming our level of tech.
With a powerful enough telescope, if you can pick out the specific planet and not get overwhelmed by it’s star’s light, you can do it without being lined up with the star.
If you’re a high tech enough civilization to be an actual threat to another planet, then you can build telescopes in space. If you build telescopes in space, they can be giant, and positioned wherever you want them. If that’s the case then you can likely directly measure the atmosphere of any planet big enough to support life in the entire galaxy, along with plenty of samples in the nearby galaxy.
But also, if you are assuming an alien race that has the capability to transit intergalactic distances in an amount of time that would make them a threat to us, then that means they already have some sort of technology that is so far beyond anything we can currently imagine, that we can already assume they know we are here.
If they can’t traverse those distances, then it doesn’t matter if they know we’re here.
the capability to transit intergalactic distances in an amount of time that would make them a threat to us
I would say that amount of time is anything less than the remaining lifespan of the universe, if we are in this for the long haul. Even with the speed of light as the limit, it’s still something to worry about that we could build a thriving civilization for 20 million years which then is wiped out because that’s how long it took for them to get here after they saw us and we were doomed from the beginning.
Well how far is extremely far? The article you linked says
The galaxy is 87k light years across. Is such a resolution good enough to determine the atmospheric composition of any planet in our galaxy? What about other galaxies?
Obviously there is a delay based on the speed of light where time needs to pass before changes can be seen, but I’m wondering what the radius is where these things become invisible no matter how much time passes, if there is such a limit. There might be intelligent life elsewhere in the universe but not in our galaxy, so if the edge of the galaxy was the limit that would be relevant to our security.
You don’t need resolution to do spectral analysis. They’re talking about identifying specific features, which isn’t what we’re talking about.
An ideal situation would be to look at a star (you only need to be able to pick out a single star, which you can do in other galaxies in the right conditions) and have a planet pass between that star and us. You’d see the change in color of the light and from that you can determine a lot about the planet’s atmosphere.
With our current technology, you have to get pretty lucky to have gravitational lensing opportunity along with a planetary transit, but that’s just assuming our level of tech.
With a powerful enough telescope, if you can pick out the specific planet and not get overwhelmed by it’s star’s light, you can do it without being lined up with the star.
If you’re a high tech enough civilization to be an actual threat to another planet, then you can build telescopes in space. If you build telescopes in space, they can be giant, and positioned wherever you want them. If that’s the case then you can likely directly measure the atmosphere of any planet big enough to support life in the entire galaxy, along with plenty of samples in the nearby galaxy.
But also, if you are assuming an alien race that has the capability to transit intergalactic distances in an amount of time that would make them a threat to us, then that means they already have some sort of technology that is so far beyond anything we can currently imagine, that we can already assume they know we are here.
If they can’t traverse those distances, then it doesn’t matter if they know we’re here.
I would say that amount of time is anything less than the remaining lifespan of the universe, if we are in this for the long haul. Even with the speed of light as the limit, it’s still something to worry about that we could build a thriving civilization for 20 million years which then is wiped out because that’s how long it took for them to get here after they saw us and we were doomed from the beginning.