What are the ways we can search for alien life?

[Zentrails]

It's possible that intelligent aliens could decide to send a highly directional signal to Earth if they already had a good reason to suspect there was a liklihood of the message being received.

Or maybe by accident, say if aliens are using a directed energy source of some sort to power "light sail" like spacecraft ?

 

[rootone]

Or maybe by accident, say if aliens are using a directed energy source of some sort to power "light sail" like spacecraft ?

It's a possibility.
The first detections of pulsars had people wondering for a while.
Those produce highly directional EM beams, although whether or not we by chance happen to intercept one is random of course, no intelligence behind it.

 

[DaveC426913]

It's quite possible that there is intelligent life in our solar system and we just don't have the capability to perceive it. If "God(s)" exists, that would be a good example.

It would not be a good example.
God is, by nature, beyond science. A being detectable only if and how he chooses is beyond the scope of both scientific analysis and this forum.

Or maybe beings made of dark matter, hive minds, etc. There are a lot of possibilities that I can imagine. I think it is a little arrogant for humans to assume that intelligent beings have to be like us or at least have technology/artifacts similar to ours.

No, it would be arrogant to assume creatures don't exist when there's evidence that they might.
But without any conceivable way of detecting them, let alone finding evidence, it would not be an arrogant assumption. It might be a faulty one, but it would not be an arrogant one.

Not sure why having a hive mind would change the equation in any way. Would it mean they would not produce evidence of their civilization - heat signatures, organization, consumption, waste?

 

[Hugh Parker]

rootone wrote: Only Mars could be possibly be survivable given an enclosed habitat and adequate shielding from radiation - Mars' atmosphere doesn't cut it as a radiation shield like Earth's does, and it completely lacks any effective magnetic field. Primitive life might be possible in the subsurface water oceans of some gas giant moons, but there is no evidence at present suggesting that this is so.

Reference https://www.physicsforums.com/threads/what-are-the-ways-we-can-search-for-alien-life.834005/

Well, perhaps the lava tunnels of giant volcanoes are places where life thrived when Mars had water. Deeper sites mean warmer sites. If Mars has lava tunnels, as Earth does, at what range of depths would salty waters be liquid now? What would be the current partial pressures of oxygen and carbon dioxide at those depths?

 

[Monsterboy]

Is it possible to launch Kepler like space telescopes that can orbit the sun in several different planes other than the plane of the orbits of the planets in our solar system ? This way we might be able detect more exoplanets that are undetectable by Kepler today.

 

[Vanadium 50]

Sure. It's more difficult, but it can be done. But why do you think that would help?

 

[Monsterboy]

Sure. It's more difficult, but it can be done. But why do you think that would help?

An exoplanet that orbits in a plane which is inclined such that it does not obstruct the light from the star from reaching the Kepler telescope is undetectable right ? Is it possible to detect those planets by rotating the telescope someway?( i don't think so) can this problem be solved by telescopes orbiting in different planes? now that you asked i feel like it doesn't really help or maybe it does.

 

[DaveC426913]

An exoplanet that orbits in a plane which is inclined such that it does not obstruct the light from the star from reaching the Kepler telescope is undetectable right ? Is it possible to detect those planets by rotating the telescope someway?( i don't think so) can this problem be solved by telescopes orbiting in different planes? now that you asked i feel like it doesn't really help or maybe it does.

The star is 1500 light years away. The farthest we've ever sent a man made object is about 4 light hours.
A telescope launched in a polar orbit (after about ten years travel) would have a better angle of this distant star by about one ten thousandth of a degree.

Nice idea, but no.

 

[Monsterboy]

The star is 1500 light years away.

You are talking about that alien structures thing right ? This may not work in that case but this was actually a general question whether such an orbit might help us detect more number of exoplanets.

The farthest we've ever sent a man made object is about 4 light hours.

Voyager 1 &2 are quite far away than that right ? You are talking about space telescopes?

 

[DaveC426913]

You are talking about that alien structures thing right ? This may not work in that case but this was actually a general question whether such an orbit might help us detect more number of exoplanets.

The nearest star to us is 4 light years away, making an angle of about 1 one-hundredth of a degree.

Voyager 1 &2 are quite far away than that right ? You are talking about space telescopes?

13 light hours. And it took 40 years to get there.

 

[newjerseyrunner]

It would not be a good example.
God is, by nature, beyond science. A being detectable only if and how he chooses is beyond the scope of both scientific analysis and this forum.

I think he was not referring to gods in a religious sense, but more in the sense of a creature so advanced they appear to us as a god. Q from Star Trek for example.

In fact, I don't think you need to even go that far, I would think a species only a thousand years in our future would be able to walk the Earth undetected fairly easily, I would think a creature that evolved has surpassed the technological singularity and entered a post-biological civilization. I see no reason a conscious computer with robot building abilities of 1000 years from now would be in any way distinguishable than the person sitting next to you... How do you know they aren't?

Unfortunately, I think a creatures ability to disguise itself will inherently come out of their progress. They'll probably have to fight wars, misdirection is critical to any war, regardless of species.

 

[Fallen-S36]

Most planets have an atmosphere. Even pluto has one.

 

[mfb]

You are talking about that alien structures thing right ?

Did you read the paper? The authors suggest many possible ideas what could cause this light curve. What do they say about alien structures?

Spoiler

Those are not mentioned at all. Not even with a single word.

This may not work in that case but this was actually a general question whether such an orbit might help us detect more number of exoplanets.

It doesn't help. Take the ideal conditions - an Earth-like planet around Alpha Centauri. The half-shadow of this planet is a cone with an opening angle of 0.0046. We have to be within this cone. Voyager has a viewing angle that differs by 0.0004, that is 1/10 this value. A Kepler-like telescope at the distance of the Voyager probes would increase the change to find that planet by a few percent (I guess 3, but didn't calculate it in detail). At least if we ignore all other issues, like the tiny data transfer rate, the limited lifetime of Kepler (~5 years, we need 40!) and so on. Star #10 ranked by distance is 8 light years away, the additional discovery potential there drops to something like 1.5%, and before we reach star #50 the effect is below 1%.

Compare that with simply launching a second Kepler close to Earth: Kepler watched about 1/400 of the whole sky. A second telescope can watch a different patch, and double the discovery rate (assuming data analysis can keep up with it).
Even better: Send a telescope that can observe more stars than Kepler did. Or, send more than one.

NASA works on TESS, roughly 3 times the number of stars Kepler watched, with a focus on bright stars nearby.
ESA is planning PLATO, it will observe 7 times the number of stars Kepler watched, over a much larger area in the sky so it can focus on brighter (and closer) stars as well.
CHEOS is another ESA spacecraft , with a focus on accurate radius measurements for planets that have been discovered before.