15

There are three important sources of energy in planetary bodies (or their moons) that may be important in determining their suitability for life. All of these are evident in various bodies in the Solar System. The first is tidal heating. When one object orbits another then there will be gradient in the gravitational force across their finite sizes. If this ...


14

That's basically the Fermi paradox. It seems likely that there are numerous civilizations in the galaxy, and yet we see no trace of them anywhere. The Drake equation is often invoked to calculate the probability of existence of other civilizations, by compounding several other, more simple probabilities: the probability that a star has planets, that the ...


11

There is, believe it or not, a scientific theory regarding this: panspermia. According to the panspermia hypothesis, microbes "hitch" a lift on bodies leaving a planet. They then travel through space and eventually land somewhere else. Panspermia involves three difficult phases of travel: Launch (as well as the impact event) Travel in the harsh environment ...


9

Even if a virus came to Earth from space, it would likely be harmless to life on Earth. Let's look at some biology numbers: Life on Earth uses 20 amino acids (out of about 400 considered chemically potential alternatives). The median length of a protein on Earth is about 300 amino acids. That's 20^300 combinations. And some proteins are 30,000 amino acids ...


8

Direct observation of exoplanets (and then of traces of life on them) is still a big challenge. Up to now, there are several indirect methods (effects on the parent star or on other stars), and direct detection is performed by using devices such as coronagraphs on faint stars, where very bright planets are imaged. A way to image things such as as "...


7

Short Answer: We won't have to worry about the Galactic Empire any time soon. Long Answer: First we have to consider some of the properties of a Type III civilization - or, to maybe put it better, what kinds of things it would do. Some are shared properties of Type II civilizations, but on a larger scale. You can probably list some off the top of your head: ...


7

When you lose your keys on a dark night you look where the probability of finding them is highest (which is a combination of being likely to see them with their probability of being there), which is not necessarily where they are most likely to be. In the case of the search for extra-terrestrial life we have a fairly good idea what the signature of carbon ...


7

Using current technology (and by that I mean experiments and telescopes that are available now) we have not detected an "Earth-like" planet and we would probably be unable to detect life on Earth even if observed from a distance of a few light years. Therefore there is currently no prospect of detecting life on an "Earth doppelganger". I elaborate below: No ...


7

I'm not an expert in this, but it's a fun little blip in the history of SETI. Pretty much the only blip I think. I understand the incredibly high signal strength it entails. I wouldn't call it "incredibly high". It peaked at 30 times normal. source, and that's inside the "waterhole" a frequency range where the background radiation is the lowest in the ...


6

Lots of frontier science lectures to watch on nearby topics here: https://astrobiology.nasa.gov/seminars/ Your very question seems to be the hottest topic in astronomy today. My impression is that if oxygen gas and methane were on the same exoplanet, then it certainly must be living biological processing creating that there. Nothing else could explain the ...


5

Avi Loeb and Edwin Turner have written a paper about the possibility of detecting a civilization similar to our own on another world by looking for city lights. Their proposed method suggests observing the dark sides of planets when they transit in front of their parent star. Though they said that this method will require future generations of telescopes. ...


5

Reading Dyson's original argument gives some useful information. He says that such a sphere would have a surface temperature of 200-300 Kelvin, as it would reradiate some of the energy it absorbs at infrared wavelengths. That's a temperature comparable to cool Y-type brown dwarfs. If we can assume a black body approximation, and a radius of about 1 AU, we ...


5

It will be very important in several different ways. Not as in Messiah having descended to the World, and maybe not during one single human lifetime. But it will profoundly change the world in our minds, and thereby change our collective long term actions. The next generation would grow up taking alien life in space for granted, their minds will be more ...


5

Stars function by nuclear fusion. There is energy that isn't released by nuclear fusion, nor from the nuclear decay of elements produced by fusion. There is the cosmic microwave background. This is radiation, but it "cold", at about -268 *C. There is a lot of energy, but because it is so "cold" it is difficult to use it to power ...


5

ProfRob makes a good point about tidal heating, but you can have internal heat sufficient for life even without this. The heat I'm referring to is heat trapped in a planet's core from its formation, which slowly and reliably leaks out through geothermal vents. We observe this at the bottoms of Earth's oceans, where thriving colonies of deep sea organisms ...


5

I can't detect you simultaneously! I have no way of knowing if you are alive or dead, as you are not in the same room as me I can assume you must be at least 10 meters from me. That means you are more than 30 light-nanoseconds If you have died in the past 30 nanoseconds, I could not know about it! However 30 nanoseconds is a very short period of time, ...


4

Certainly it's a function of astronomy - chances are, if you're doing science outside the Earth then by definition it's astronomy in some form or another. There are many sub-fields of astronomy that are useful in the search for extra-terrestrial life: Astrophysics is used to discover exoplanets, and to make crude approximations as to their habitability. ...


4

The search for extraterrestrial life is usually covered by "exobiology". But astronomy can provide clues of whether a planet or an exoplanet provides some of the conditions, which allow life or indicate life. The habitable zone - in its various versions - defines, in which distance from a star a planet needs to be to allow for e.g. liquid surface water, a ...


4

In short, no. It is impossible for an infectious agent to come from another planet. Comets formed in space, and while they may have some carbon based chemicals, nothing as complex as life could form on a comet. Some meteoroids have been ejected from planets, and it is at least conceivable that something could survive "launch". It is not likely that ...


4

I think it's a fun question and I can kind of give a layman's answer. (though reading the above answer, there is some overlap). It seems likely that "tiny", life or viruses could survive/hibernate for a long time if blown into space on space rocks, so it follows that life could travel to earth that way, but I think we could apply a modified version of the ...


4

No. The light curves don't look at all like anything transiting. The ingress and egress profiles and the timing are way beyond that kind of explanation. Not planets, not comets, not clouds, not alien super structures. No infrared light from dust or gas has been detected, as they should've been if the starlight had heated small particles. And since this is ...


4

It's not hard to calculated brightness to distance, but that doesn't take into account cloud cover, which is important for Titan. Just looking at distance first, Titan (based on Saturn's distance) averages 9.6 AU from the sun, or about 1/91st as bright as the sun appears from Earth, assuming equal atmospheres. 1/91st isn't a bright sunny day, but it's ...


4

I don't think you can prove that aliens have never visited Earth. It's theoretically provable if one had a time machine, but without one, we can't really prove that aliens didn't visit Earth (say) 2 billion years ago. The physical evidence would be long gone (especially with plate tectonics). What you can say is that the burden of proof is on the person ...


4

An amino acid is any acid that has an amine in it. They are not necessarily found in proteins. They can be found in conditions similar to deep space, for example: In a laboratory at NASA Ames Research Center in California’s Silicon Valley, the team of astrobiologists shone ultraviolet light on deep-space-like "ices," simulating conditions that are ...


3

The simplest reason why your proposed explanation is not really that obvious, and thus was not considered is that the dimming of KIC 8462852 was not an isolated event. The dimming is a pattern that has been observed over years. There is no known phenomenon in interstellar space that would cause a repeated obstruction of that star, so it doesn't make any ...


3

I was fortunate enough to spend the past week at a workshop held at the Green Bank Observatory (GBO), so I can give you a partial answer based on how the Breakthrough Initiatives affects it in particular. Telescope time The GBO actually operates a selection of telescopes, of which the most widely-known (and largest) is the Green Bank Telescope (GBT). The GBT ...


3

In the opposite direction (RA= 07h 25m 31s ± 10s, +26° 57′ ± 20′, J2000.0, seen from Earth) of the positive horn of the Wow!-signal (RA= 19h 25m 31s ± 10s, −26° 57′ ± 20′, in J2000.0 coordinates), Iota Geminorum, aka Propus, (RA= 07h 25m 43.6s, +27° 47' 53") is within a 3-sigma error ellipse (1.26 sigma in RA, 2.54 sigma in Dec, 2.84 sigma total error). ...


3

"probably not". Unless it were so close that television or radio signals like we've been inadvertently sending out can be detected above background radiation levels we can't know about the civilisation. The signals are extremely weak, and not on any band scientifically interesting (deliberately of course, because we don't want our televisions to pick up ...


3

I think you're question is incorrect, and what you should be asking is "Which of these is plausible", in which case, all of them are. I think you are also missing other options: There is alien life, who have already visited, but have not made formal contact with us, for any one of a number of reasons. We are the alien life, who has forgotten how we arrived ...


3

A significant portion of SETI's work is done through a program known as SETI@home, which takes signals that have been received and processes them for responses, such as recurring patterns. Here is a page on how to download its source code. I grabbed the most recent nightly tarball and it turns out the program is coded in C++. I offer this as evidence that C++...


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