Do you think any aliens exist in the universe?

[Loren Pechtel]

You're assuming detecting a signal.

No, Frank Drake is. He defines L as:

"the length of time for which [technological] civilizations release detectable signals into space"

But Earth absolutely shines in the radio spectrum

No, it really doesn't. Where do you get the idea that it does?

for no apparent reason.

Indeed, no reason why it should is apparent to me.

You don't have to be able to detect individual signals to see that.

If we were somehow emitting enough RF radiation to swamp individual signals, radio would be useless to us, as every signal was swamped by the noise.

Compared to other planets, we shine.

We don't get swamped because we are closer to the transmitters we care about and many of the others are below the horizon. ET is going to see everything blurred together. (And it does happen--that's why you're not supposed to use cell phones in the air--too high up they'll end up stomping on many cells and causing problems for the network.)

 

[Shadowy Man]

You're assuming detecting a signal.

No, Frank Drake is. He defines L as:

"the length of time for which [technological] civilizations release detectable signals into space"

But Earth absolutely shines in the radio spectrum

No, it really doesn't. Where do you get the idea that it does?

for no apparent reason.

Indeed, no reason why it should is apparent to me.

You don't have to be able to detect individual signals to see that.

If we were somehow emitting enough RF radiation to swamp individual signals, radio would be useless to us, as every signal was swamped by the noise.

Compared to other planets, we shine.

Do you care to quantify that? For example, compare to radio emissions from Jupiter’s magnetosphere.

 

[unapologetic]

Frack Musk. Quote Sagan directly.
The two vids together suggest there are no other civilazations in the universe because our alian programer didn't think we would notice.
It's one of the reasons the alien kid who programmed us, got an 'F' on this science project.

not even the most intelligent aquatic life is going to struggle to harness fire as a tool.

That ain't it. If you could surf all day and grab food out of the air space around you, You wouldn't bother building a messy 'Civilazation' either.

The current idea for the moon’s formation was the collision between earth and a mars-sized object. We know for sure that earth sized and mars sized objects can form (because of the existence of earth and mars in the solar system) so for me it isn’t “hard to imagine” a scenario in which two of these objects collide.

I was about to bring that up. Yes I call that rare. It is not just the collision itsself. It needs to be at the correct angle to eject the right amount.
And such that it doesn't shoot away or crash back into earth. Pure luck in my opinion.

So far the most fun thing I've learned from this thread is that it's raining diamonds on Uranus.

OUCH. Stop that.

 

[Shadowy Man]

The current idea for the moon’s formation was the collision between earth and a mars-sized object. We know for sure that earth sized and mars sized objects can form (because of the existence of earth and mars in the solar system) so for me it isn’t “hard to imagine” a scenario in which two of these objects collide.

I was about to bring that up. Yes I call that rare. It is not just the collision itsself. It needs to be at the correct angle to eject the right amount.
And such that it doesn't shoot away or crash back into earth. Pure luck in my opinion.

Did you read those papers I cited? We do not have to rely on your opinion to assess the odds.

 

[unapologetic]

Did you read those papers I cited? We do not have to rely on your opinion to assess the odds.

TLDR.
Are the papers any more than someone's opinion? Any hard data? Do they take the angle of collision into account?
"so for me it isn’t “hard to imagine”
Sure, I can imagine that too. It seams to have actually happened... Once.
What you or I imagine is not a valid assessment of the odds.
Stating my opinion. We don't need to argue opinions that will never be proven.

 

[excreationist]

Frack Musk. Quote Sagan directly.
The two vids together suggest there are no other civilazations in the universe because our alian programer didn't think we would notice.
It's one of the reasons the alien kid who programmed us, got an 'F' on this science project.

If there are many alien civilizations being simulated the simulation would be a lot more expensive. Games are often about cutting corners.

 

[Tannhäuser Rover]

The idea that large tides may be *necessary* for the development of intelligent/technological life, seems even more of a stretch based on extremely little information.

That's true, but unavoidable; By necessity all of our thoughts on the subject are highly speculative and woolly, and are more likely than not to be contradicted by future observations and data. It's hard to imagine a scenario in which moons like ours are common, though, however they may arise.

Personally, I don’t think there’s enough information to make a statement like “hard to imagine a scenario in which moons like ours are common”. My expertise is not in planetary system formation but my understanding is that in the early days of a protoplanetary disk, many objects may form. Some may collide, some may be ejected.l due to the developing gravitational dynamics at play.

The current idea for the moon’s formation was the collision between earth and a mars-sized object. We know for sure that earth sized and mars sized objects can form (because of the existence of earth and mars in the solar system) so for me it isn’t “hard to imagine” a scenario in which two of these objects collide.

There just isn’t a large enough sample size to tease out the underlying probabilities. Let’s say there was a 50% chance of a large moon forming, then the fact that of the three major rocky planets only one has a large moon is eminently consistent with such a probability. It is consistent with a wide variety of (as yet unknown) probability distributions.

I don’t know on what basis you can appear so sure as to the rarity of large moons like the earth’s. If there’s a study or paper you can point me to that discusses this I would happily read it. As I said it’s not my expertise. But I do know from my experience that dealing with have call “small number statistics” can lead one to erroneous conclusions. And I can give a specific example from my research if you’re interested.

Correct me if I'm wrong, but it is my understanding that tides are caused by the Moon's gravity, and gravity is a function of mass and the square of the distance. Thus a much smaller moon closer to Earth could exert the same gravitational effect of our Moon. For instance a moon that has a mass 1/4 of our Moon and it is half its distance from earth. So there is no need for a large moon, unless there are some restraints on the distance. Of course I'm no expert so maybe I just wrote a load of BS

 

[bilby]

The idea that large tides may be *necessary* for the development of intelligent/technological life, seems even more of a stretch based on extremely little information.

That's true, but unavoidable; By necessity all of our thoughts on the subject are highly speculative and woolly, and are more likely than not to be contradicted by future observations and data. It's hard to imagine a scenario in which moons like ours are common, though, however they may arise.

Personally, I don’t think there’s enough information to make a statement like “hard to imagine a scenario in which moons like ours are common”. My expertise is not in planetary system formation but my understanding is that in the early days of a protoplanetary disk, many objects may form. Some may collide, some may be ejected.l due to the developing gravitational dynamics at play.

The current idea for the moon’s formation was the collision between earth and a mars-sized object. We know for sure that earth sized and mars sized objects can form (because of the existence of earth and mars in the solar system) so for me it isn’t “hard to imagine” a scenario in which two of these objects collide.

There just isn’t a large enough sample size to tease out the underlying probabilities. Let’s say there was a 50% chance of a large moon forming, then the fact that of the three major rocky planets only one has a large moon is eminently consistent with such a probability. It is consistent with a wide variety of (as yet unknown) probability distributions.

I don’t know on what basis you can appear so sure as to the rarity of large moons like the earth’s. If there’s a study or paper you can point me to that discusses this I would happily read it. As I said it’s not my expertise. But I do know from my experience that dealing with have call “small number statistics” can lead one to erroneous conclusions. And I can give a specific example from my research if you’re interested.

Correct me if I'm wrong, but it is my understanding that tides are caused by the Moon's gravity, and gravity is a function of mass and the square of the distance. Thus a much smaller moon closer to Earth could exert the same gravitational effect of our Moon. For instance a moon that has a mass 1/4 of our Moon and it is half its distance from earth. So there is no need for a large moon, unless there are some restraints on the distance. Of course I'm no expert so maybe I just wrote a load of BS

A moon 1/4 of the size of the one we have would still be pretty big by comparison to the two tiddly little things Mars has. The Moon is in the order of a million times the size of Phobos, Mars's largest moon.

Our moon is already pretty close, as moons go. But it certainly could be closer, and it used to be.

The absolute closest it could orbit is about 19,000km, the Roche Limit, closer than which distance tidal forces would pull it apart. Phobos would disintegrate before it got close enough to Earth to replicate our Moon's tidal effects. (Phobos is probably also not as structurally strong as our Moon, and would have a larger Roche Limit).

The Moon is slowly moving away from the Earth (also due to tidal forces); The Moon is about 380 million kilometres away today, but 2.5 bilion years ago it was only about 320 million km from Earth.

 

[Shadowy Man]

And tides are driven by the gravitational differences so the tidal force goes as 1/r^3, dropping off faster than just simple gravitational forces.

 

[Loren Pechtel]

Correct me if I'm wrong, but it is my understanding that tides are caused by the Moon's gravity, and gravity is a function of mass and the square of the distance. Thus a much smaller moon closer to Earth could exert the same gravitational effect of our Moon. For instance a moon that has a mass 1/4 of our Moon and it is half its distance from earth. So there is no need for a large moon, unless there are some restraints on the distance. Of course I'm no expert so maybe I just wrote a load of BS

Gravity goes at the square of the distance, but tide is the differential of gravity and thus goes at the cube. That's why the piddly moon has a tide in the ballpark with the mighty sun.

 

[Spacetime Inhabitant]

The idea that large tides may be *necessary* for the development of intelligent/technological life, seems even more of a stretch based on extremely little information.

That's true, but unavoidable; By necessity all of our thoughts on the subject are highly speculative and woolly, and are more likely than not to be contradicted by future observations and data. It's hard to imagine a scenario in which moons like ours are common, though, however they may arise.

Personally, I don’t think there’s enough information to make a statement like “hard to imagine a scenario in which moons like ours are common”. My expertise is not in planetary system formation but my understanding is that in the early days of a protoplanetary disk, many objects may form. Some may collide, some may be ejected.l due to the developing gravitational dynamics at play.

The current idea for the moon’s formation was the collision between earth and a mars-sized object. We know for sure that earth sized and mars sized objects can form (because of the existence of earth and mars in the solar system) so for me it isn’t “hard to imagine” a scenario in which two of these objects collide.

There just isn’t a large enough sample size to tease out the underlying probabilities. Let’s say there was a 50% chance of a large moon forming, then the fact that of the three major rocky planets only one has a large moon is eminently consistent with such a probability. It is consistent with a wide variety of (as yet unknown) probability distributions.

I don’t know on what basis you can appear so sure as to the rarity of large moons like the earth’s. If there’s a study or paper you can point me to that discusses this I would happily read it. As I said it’s not my expertise. But I do know from my experience that dealing with have call “small number statistics” can lead one to erroneous conclusions. And I can give a specific example from my research if you’re interested.

Correct me if I'm wrong, but it is my understanding that tides are caused by the Moon's gravity, and gravity is a function of mass and the square of the distance. Thus a much smaller moon closer to Earth could exert the same gravitational effect of our Moon. For instance a moon that has a mass 1/4 of our Moon and it is half its distance from earth. So there is no need for a large moon, unless there are some restraints on the distance. Of course I'm no expert so maybe I just wrote a load of BS

A moon 1/4 of the size of the one we have would still be pretty big by comparison to the two tiddly little things Mars has. The Moon is in the order of a million times the size of Phobos, Mars's largest moon.

Our moon is already pretty close, as moons go. But it certainly could be closer, and it used to be.

The absolute closest it could orbit is about 19,000km, the Roche Limit, closer than which distance tidal forces would pull it apart. Phobos would disintegrate before it got close enough to Earth to replicate our Moon's tidal effects. (Phobos is probably also not as structurally strong as our Moon, and would have a larger Roche Limit).

The Moon is slowly moving away from the Earth (also due to tidal forces); The Moon is about 380 million kilometres away today, but 2.5 bilion years ago it was only about 320 million km from Earth.

Your Earth-Moon distances need an adjustment. Metres not kilometres.