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BAMAPHIN 22
06-27-2007, 03:42 PM
An ocean on Mars. An Earth-like planet light years away. The evidence is mounting, but are astronomers ready to say we're not alone?

http://www.netscape.com/viewstory/2007/06/27/life-beyond-earth/?url=http%3A%2F%2Fwww.smithsonianmag.com%2Fissues%2F2007%2Fjuly%2Flifebeyond.php&frame=true

Pagan
06-27-2007, 04:10 PM
To think we're the only life that exists when we're just one planet in one solar system in one galaxie is ridiculous.

There's other life out there somewhere. We just haven't found it yet.

Sponge
06-28-2007, 12:57 PM
To think we're the only life that exists when we're just one planet in one solar system in one galaxie is ridiculous.

There's other life out there somewhere. We just haven't found it yet.

Or they're watching us act like idiots and have decided not to interact with us. :wink:

Megatron
06-28-2007, 01:06 PM
Or they're watching us act like idiots and have decided not to interact with us. :wink: I think it may be light speed travel is an impossibility. That would be a weird one wouldn't it, that there may be life throughout the universe but that life has no way to interact.

ABrownLamp
06-28-2007, 01:14 PM
I think it may be light speed travel is an impossibility. That would be a weird one wouldn't it, that there may be life throughout the universe but that life has no way to interact.

Even if light speed travel was possible, the next closest star in this galaxy is 6 light years away. Our galaxy alone, in diameter, is over 100,000 light years across. So really, the only conceivable way to travel would be through wormholes.

Sponge
06-28-2007, 01:15 PM
Unless of course there are methods of travel we haven't conceived of.

Pagan
06-28-2007, 01:24 PM
Unless of course there are methods of travel we haven't conceived of.
Exactly.

Hard for alot of people to accept, but we may not be the brightest bulbs in the universe's Xmas tree, ya know? :wink:

Sponge
06-28-2007, 01:44 PM
Exactly.

Hard for alot of people to accept, but we may not be the brightest bulbs in the universe's Xmas tree, ya know? :wink:

I've always had a lot of difficulty with the concept that we are consistently on the leading edge of science.

At one time, the best scientists in the world believed the earth was flat (not saying it isn't by the way). Early last century, someone claimed to have proved scientifically that it was impossible for a human to run a mile in under 4 minutes. Then someone did it. There are many more examples, bumblebees are aeronomic impossibilities etc.

The point is for me at least, that it's a lot safer to believe you don't know something than it is to believe you do.

Megatron
06-28-2007, 01:56 PM
Exactly.

Hard for alot of people to accept, but we may not be the brightest bulbs in the universe's Xmas tree, ya know? :wink: Oh I don't discount that at all, but there is still a likelyhood that that kind of travel is impossible. That would be the weirdest thing if we know there's life elsewhere but have no way to interact.

ckb2001
06-28-2007, 03:01 PM
I think it may be light speed travel is an impossibility. That would be a weird one wouldn't it, that there may be life throughout the universe but that life has no way to interact.

The PRIMARY difference between General Relativity (and thus all deterministic theories in science) and Quantum Mechanics is that all deterministic theories in science have to abide by the rule that nothing can travel faster than the speed of light.

In Quantum Mechanics however, instantaneous information transfer is possible. For example, quantum entanglement allows one to show that as soon as one of two entangled particles is observed, the other instantaneously has a certain property.

Specifically, suppose you have one particle that is observed as spin-up at time t=1. At THAT moment, another particle entangled with it will have spin-down (at time t=1), NO MATTER where it is in the universe.

And quantum mechanics is the single most accurate theory in science, so it's actually likely that information can be transferred instantaneously from one part of the universe to another. What isn't likely is that something made of matter could actually travel faster than the speed of light.

Complicated, yes, but it's at the heart of the present conflict in physics (dating 70 years) in trying to unify QM and GR.

ckb2001
06-28-2007, 03:15 PM
I've always had a lot of difficulty with the concept that we are consistently on the leading edge of science.

At one time, the best scientists in the world believed the earth was flat (not saying it isn't by the way). Early last century, someone claimed to have proved scientifically that it was impossible for a human to run a mile in under 4 minutes. Then someone did it. There are many more examples, bumblebees are aeronomic impossibilities etc.

The point is for me at least, that it's a lot safer to believe you don't know something than it is to believe you do.

You have to be very careful with what is claimed to be proven or not. In mathematics, a proof must work ALL the time, NO exceptions. So, when mathematics says they "know" a theorem is proven, it means there is supposed to be NO possibility it is wrong (occasionally it does happen a future mathematician shows a "proof" of the past was flawed, but that is VERY rare). So, in mathematics, it's safer to assume what they claim to know is true really IS true than assuming they don't really know what they claim to know is true is true.

In most other sciences however (those that make statements about how Nature works), the word "proof" means something completely different. It doesn't mean the claim is correct, it means the probability it's correct is high enough that we can for the most part assume it to be true and continue on to the next step in research. So, you shouldn't take claims of "X was proven" in sciences other than the abstract sciences to mean anything other than "it's our best guess given the information we have at that moment".

So, the question is really wrong. You shouldn't be asking whether it's safer to say "we KNOW" or "we don't KNOW", since obviously the answer is we don't (that's why there's a probability of being accurate involved).

No, the question should be "is it safer to assume this claim is true or not?" That's a different question. It's a question that asks IF you had to make a decision, which decision affords you the greatest likelihood of being correct. And it's there that science is so powerful. There, it IS better to assume what is "proven" is correct, even if you KNOW that statement is correct with only a certain probability.

Hope that's clear.


Oh, and for historical accuracy, it's a bit misleading to say leading scientists once thought the Earth was flat. Science as we know it developed mostly after 1600 in Europe (with very few exceptions). By that time, it was mostly accepted the Earth wasn't flat.

Sponge
06-28-2007, 06:35 PM
So, the question is really wrong. You shouldn't be asking whether it's safer to say "we KNOW" or "we don't KNOW", since obviously the answer is we don't (that's why there's a probability of being accurate involved).

No, the question should be "is it safer to assume this claim is true or not?" That's a different question. It's a question that asks IF you had to make a decision, which decision affords you the greatest likelihood of being correct. And it's there that science is so powerful. There, it IS better to assume what is "proven" is correct, even if you KNOW that statement is correct with only a certain probability.

Hope that's clear.


Oh, and for historical accuracy, it's a bit misleading to say leading scientists once thought the Earth was flat. Science as we know it developed mostly after 1600 in Europe (with very few exceptions). By that time, it was mostly accepted the Earth wasn't flat.

I hate to disagree with such a well articulated post, however I must, at least semantically. My point is that there is no such thing as being correct, even if it is based on the sum of knowledge currently available. For example if you asked 28 out of 29 people in a room what their favorite color was, and they all said blue, does that imply that the 29th person's favorite color is blue? Or even that the majority of humans' favorite color is blue? It certainly suggests these things, but to claim it "proves" them is stretching it.

As for science being developed after 1600, I suppose it depends on how you define science.

Nicely explained though.

ckb2001
06-28-2007, 08:19 PM
I hate to disagree with such a well articulated post, however I must, at least semantically. My point is that there is no such thing as being correct, even if it is based on the sum of knowledge currently available. For example if you asked 28 out of 29 people in a room what their favorite color was, and they all said blue, does that imply that the 29th person's favorite color is blue? Or even that the majority of humans' favorite color is blue? It certainly suggests these things, but to claim it "proves" them is stretching it.

As for science being developed after 1600, I suppose it depends on how you define science.

Nicely explained though.

Concepts of "correct" and "incorrect" obviously have meaning. I mean the abstract sciences are a good place to find examples of this (either a theorem is proved and is correct or not - no inbetween). And even when making statements about the state of Nature, the concept of "correct" obviously has meaning. For example, if I make a prediction about a measurement I'll make, that prediction could be wrong (I could say the next time I measure how hot it is, the value I get will be greater than 55 degrees F. That's either true or false).

So, obviously there are correct and incorrect statements, even when they are statements about the state of Nature.


Having said all that, let me return to what I was trying to explain (don't think you understood). In the natural sciences, you're always dealing with probabilities of how Nature is, even when the theory itself is deterministic. For example, say Newton's F = ma is to be tested and one finds the prediction doesn't fit exactly with measurement (it should actually never fit exactly). Well, you might have systematic errors (practically all experiments do) or simply noise in the signal/measurement you're making.

So, to determine whether to claim the prediction of that theory was accurate or not, you essentially have to revert to statistics, saying that X percent of the time, the measured value was within Z of the predicted value. This way you can quantify the probability that theory will make correct predictions. That allows you to quantify the uncertainty one should have in the theory!

And if you can quantify the uncertainty one should have in the theory, then there's nothing more to argue. You just choose the theory with the greatest accuracy and you can prove (mathematically) the choice you made gives you the highest probability of predicting future measurements accurately.

See, what you're not understanding is that whenever you deal with making predictions about Nature, science attempts to quantify how uncertain one is in that theory. So, pointing out that the theory might not make accurate predictions in the future is useless, since that was already quantified!!

Make sense?


Oh, and specifically in the example you gave, you can calculate the probability that all 29 people think blue is their favorite color. Just think this way: suppose you have 29 balls, and either all 29 are blue or exactly 28 are blue (with the 29th a different color). Now, if you have NO information about which possibility is more likely, then your prior probabilities for the true state being 29 blue or exactly 28 blue is 1/2 each (if you have extra information, the priors would be different of course).

So, IF the true state is 29 blue, then the probability of choosing 28 blue from a random sample of 28 out of that 29 is 1 (100%). Of course, you have to multiply this "1" by the prior probability all 29 are blue, which is 1/2. Thus, so far you have 1/2.

Now, you have to add that 1/2 to the probability of choosing 28 blue balls from a set of 29 when exactly 28 are blue (and the 29th is a different color). Well, doing this the hard way (let's just assume you ask one person at a time to avoid confusion), you have [(28/29)*(27/28)*...*(2/3)*(1/2)]*(1/2), where the last 1/2 is the prior that you have exactly 28 "blue". (to explain the stuff in brackets, the first person you ask has a 28/29 probability of saying "blue", the second has a 27/28 probability of saying "blue", etc..)

That comes out to 1/58. So, the probability all 29 are "blue" (all 29 people say their favorite color is blue) is 1/2 + 1/58 = 15/29. And thus, the probability the 29th person says their favorite color is NOT blue is 14/29, assuming you have NO other information at hand. Of course, if you have more information about the people you are asking, that could change the priors.

As you see, the predictions are in probabilistic form, and whether they are correct or not isn't determined by what the 29th person says. No, it's determined by the math that allowed you to make that prediction. Thus, the prediction in probabilistic form is a "correct" statement.

Oh, and the "safest bet" is that the 29th person says their favorite color is blue, and you can calculate how much you should wager on that by the probabilities calculated.

Den54
06-29-2007, 05:41 PM
All your talk of star travel and other cavemen from sky
frighten me. But then I'm just a lowly caveman that your scientist unfroze.
http://www.finheaven.com/images/imported/2007/06/2229-1.jpg

George Beauchem
07-03-2007, 07:36 AM
500 years ago the world was flat ( ok maybe not exactly 500) 150 years ago man would never fly like the birds, 50 years ago man would never walk on the moon. If man wants he eventuly will find a way.