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I don't think the Drake equation is garbage, but it is certainly incomplete. I'm reasonably satisfied that its terms are sufficient for calculating the number of planets that host life in the galaxy, once the values of those terms can be discovered. What it doesn't cover is the kinds of environments that can be colonized by living species once they've developed technology to leave their home planets. That kind of expansion could increase the ubiquity of life in the galaxy by several orders of magnitude.

But keep in mind that if living beings do colonize extra-planetary space (see Shadowalker's thread about O'Neil-type space habitats) eventually they will respond to these new environments by adapting to them, and optimizing their biology to efficiently live in those places. At that point, they will find that asteroids and even more especially comets in the outer reaches of star systems are much, much easier to reach and exploit than massive star-hugging planets such as Earth. Life just might be common throughout the galaxy, but it would be living off Oort Cloud bodies, not watery planets. We may not be visited for very long periods, simply because our planet has nothing to offer interstellar E.T.'s that they could not get far more easily elsewhere, and if they're evolved for elsewhere, Earth is not going to look very inviting to them.

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I think Star Trek got this right. My guess is, if we havent already discovered them before hand, we will be contacted by any intelligent ETs aware of us when we achieve interstellar flight. Reason being, right now as a civilization that is basiclly stuck on its home planet we are of no consequence to any intelligence out there.

However, the day we achieve interstellar flight that changes. I suspect we may be contacted at that point, and basiclly told (paraphrasing of course) "Hey, welcome to the big leagues, but before you go out playing around the stars, be aware there are others out here, and what you do can have consequences on yourself, or others".

Thats what I hypothesize will happen.

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Or, they just might say: "This territory is already taken. It's OUR Oort Cloud. Go home, you aren't welcome here!"

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Well, at the end of the day, there are only 3 possible answers to the question "Why aliens have never visited Earth":

1 - They don't exist.
2 - They exist, but are too far away to reach us.
3 - They exist and can reach us but choose not to reveal themselves.

Number 1 seems unlikely to me, simply due to the vast size of the universe. Even selecting the extreme low probabilities for every term in the Drake equation, I find it hard to believe that we are the only ones in the universe. The only ones in our galaxy I could buy, but not in the universe.

Number 2 seems quite likely to me, again due to the vast size of the universe. For anything but the highest probabilities in the Drake equation, there could easily be hundreds, thousands, or millions of light years separating intelligent species. So unless there is some unknown way to bypass the speed of light, we may never cross paths.

Number 3 seems pretty unlikely again, although I can't rule it out. It would pretty much require either extremely high probabilities to most of the terms of the Drake equation for intelligent life to be nearby enough to reach us, or some form of FTL travel.

Jarad

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Well, at the end of the day, there are only 3 possible answers to the question "Why aliens have never visited Earth":

1 - They don't exist.
2 - They exist, but are too far away to reach us.
3 - They exist and can reach us but choose not to reveal themselves.

Number 1 seems unlikely to me, simply due to the vast size of the universe. Even selecting the extreme low probabilities for every term in the Drake equation, I find it hard to believe that we are the only ones in the universe. The only ones in our galaxy I could buy, but not in the universe.

Number 2 seems quite likely to me, again due to the vast size of the universe. For anything but the highest probabilities in the Drake equation, there could easily be hundreds, thousands, or millions of light years separating intelligent species. So unless there is some unknown way to bypass the speed of light, we may never cross paths.

Number 3 seems pretty unlikely again, although I can't rule it out. It would pretty much require either extremely high probabilities to most of the terms of the Drake equation for intelligent life to be nearby enough to reach us, or some form of FTL travel.

Jarad

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There's also the little problem of navigation. When going near the SOL (what a fortunate accident is this acronym almost the entire sky is 1) crowded into the area directly ahead of you 2) vastly shrunken in angular size 3) intensely blue-shifted and 4) greatly intensified. So you literally would have no idea where you were going, except "that way", in the direction of the only thing visible in the entire sky - a very very intense, very very blue, very very tiny patch of light in an otherwise featureless, pitch black sky.

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Indeed.

Also, near max speed all the cosmic junk, even hydrogen atoms, becomes hard radiation. Hitting a speck of dust is equivalent to a giant nuclear explosion.

Actually... is it? The assumption is that all the kinetic energy of the dust mote is converted to heat. But this is a very very fast dust mote. I wonder if it wouldn't simply punch a needle hole through the ship, with a loud commotion no doubt, but not much else.

In other words, if you're a multi-story structure and you're hit on the roof by a relativistic speck of dust, how much kinetic energy is transformed into heat?

Would the speck and the vaporized material spread out in a deadly wide jet, or would it stay collimated and punch a needle hole?

I don't think the usual scattering from the Rutherford experiment applies here, because that experiment assumes the crystal lattice remains intact, whereas here the lattice is blown to kingdom come.

Perhaps the rocket is no different from a cloud of plasma, from the p.o.v. of the relativistic dust mote.

I'd be very curious to learn the answer.

Too bad we can't accelerate dust motes at CERN.

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Would the speck and the vaporized material spread out in a deadly wide jet, or would it stay collimated and punch a needle hole?

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There's also the little problem of navigation. When going near the SOL (what a fortunate accident is this acronym almost the entire sky is 1) crowded into the area directly ahead of you 2) vastly shrunken in angular size 3) intensely blue-shifted and 4) greatly intensified. So you literally would have no idea where you were going, except "that way", in the direction of the only thing visible in the entire sky - a very very intense, very very blue, very very tiny patch of light in an otherwise featureless, pitch black sky.

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Indeed.

Also, near max speed all the cosmic junk, even hydrogen atoms, becomes hard radiation. Hitting a speck of dust is equivalent to a giant nuclear explosion.

Actually... is it? The assumption is that all the kinetic energy of the dust mote is converted to heat. But this is a very very fast dust mote. I wonder if it wouldn't simply punch a needle hole through the ship, with a loud commotion no doubt, but not much else.

In other words, if you're a multi-story structure and you're hit on the roof by a relativistic speck of dust, how much kinetic energy is transformed into heat?

Would the speck and the vaporized material spread out in a deadly wide jet, or would it stay collimated and punch a needle hole?

I don't think the usual scattering from the Rutherford experiment applies here, because that experiment assumes the crystal lattice remains intact, whereas here the lattice is blown to kingdom come.

Perhaps the rocket is no different from a cloud of plasma, from the p.o.v. of the relativistic dust mote.

I'd be very curious to learn the answer.

Too bad we can't accelerate dust motes at CERN.

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The alcubierre drive would not have this problem. Any particles it encountered would be stretched out over the space time of the warp bubble. The only side effect being that it may sap some energy from the warp bubble.

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As I look outward with my telescope it is certainly legitimate to wonder is some other frustrated individual out there looking back. I too am overwhelmed by the size and scope of the universe and conclude while they may be out there it is unlikely that they have the ability to travel here.

Spectral analysis of our star compared to analysis of those in far off galaxies suggest that one consistent set of physical laws are enforce as far away as we can observe. It is reasonable to assume that while they may have advanced technology they remain trapped by the same physical laws as we are. I was impressed by your solar energy source in a shoebox however you neglected to include the mass of that box. This mass is key to the accelerations available to them. As stated above, the universe, as described by Special Relativity, does not prohibit us from travel over vast distances within a human lifetime. This is a common misunderstanding about SR.

I too find the ET behavior described of UFO reports unconvincing.

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While I agree that UFO/Alien abduction reports are phooey, I think there are likely aliens out there.

However, I don't think there not visiting us is due to lack of technology, but for the same reason we prohibit people from interferring with uncontacted tribes here on Earth.

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However, I don't think there not visiting us is due to lack of technology, but for the same reason we prohibit people from interferring with uncontacted tribes here on Earth.

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However, I don't think there not visiting us is due to lack of technology, but for the same reason we prohibit people from interferring with uncontacted tribes here on Earth.

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Huh ??

Have you read any history ?

History is littered with examples of explorers heading out over the world in sailing ships, and when they arrived somewhere, usually the first thing was to make contact with the locals. Often, they wanted to re-supply with food and water, and, in return, they provided the locals with a few things, like syphilis, smallpox, etc etc.

If you think space-faring visitors will not make contact because of some 'prime directive', then I suggest you've been listening to a lot of star-trek nostalgia, and, not paying attention. Heck, even in the star trek episodes, the only time the subject of 'prime directive' ever came up, was because it was being broken, yet again. Even those with a directive to NOT make contact, did exactly that, each and every time they found something / someone to contact.

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Yeah, explorers did that before. Our society has come along way since then. For example, Ill mention again, the way we treat uncontacted tribes here on Earth. We leave them be.

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Our society has come along way since then. For example, Ill mention again, the way we treat uncontacted tribes here on Earth. We leave them be.

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