UFO sighting in Texas...

[Khamsin]

Or, if they can after all travel at speeds above light, maybe they possess technology to avoid radar and makes cameras to record on shitty quality.

Personally I just hope they don't think like humans.

You don't wish them to possess a capacity for peace, compassion, and humanity?

Well, at least if they don't, we can always just shoot 'em down.

[Woozie]

There's no reason to assume they're traveling faster than light. Due to time dilation, one could traverse the distance between habitable planets in a life time at subluminal velocities, even if the planets are hundreds of light years apart.

[Tajin]

You don't wish them to possess a capacity for peace, compassion, and humanity?

Well, at least if they don't, we can always just shoot 'em down.

well played, but you know damn well what I meant.

There's no reason to assume they're traveling faster than light. Due to time dilation, one could traverse the distance between habitable planets in a life time at subluminal velocities, even if the planets are hundreds of light years apart.

How is this possible in a scenario where you travel inside a ship, well protected of external forces?, you would be protected of the effect of traveling at speeds close to the speed of light.

[Neosutra]

life in the visible universe (as we understand life) might be very rare indeed.

some reference to life being statistically likely was made in this thread, but even the basic inputs to that sort of problem are highly disputed. (for instance, given a finite number of stars (our galaxy), what percentage of those stars have planets in the habitable zone, what is the percentage of those planets that have the necessary chemical makeup to allow for the generation of life, what percentage of those planets remain stable for sufficient time to generate life (and what is that minimum time) and what is the probability that, given the necessary conditions, life is generated. then find the % of such life that becomes sentient/sapient/space-faring.) the answer, of course, is by definition >=1 but there's no reason necessarily to believe (statistically) that the answer must be >1.

on the other hand, if you buy into any of the strong anthropic principles (especially the 'final' anthropic principle) the generation of 'intelligent' information-processing structures in the universe is inevitable, but this does not at all guarantee the existence of other intelligent information-processing structures beyond ourselves; nor does it indeed require that such structures meet the classic definition of life. (beyond of course the fact that most SAP's are really tautologies that basically say: because humanity exists, we must therefore live in a universe in which humanity exists.)


it is important to remember that there are two parts to the likelihood of life in the universe: firstly, the number of 'chances' (this is presumably quite large, based on current estimates of the size of the visible universe and the approximate number of stars and estimated percentage of those stars with planets of any type). and secondly, the probability that any given chance will result in life.

the second number is much harder to estimate, and there isn't any basis to call more conservative estimates (those that place total number of planets supporting life at or near 1) ridiculous any more than there's basis to call more optimistic estimates (those placing total number of planets supporting life as a significant percentage of all planets.) ridiculous. although, thus far, there is more evidence for the former than the latter, at least with respect to intelligent life. (see: fermi paradox).

Almost nothing in this post is correct. So I will just quote the entire thing and say "No".

While there are a finite number of stars, and a finite number of stars that have reformed with a coronal disk of heavy matter that is able to form into planets, and a finite number of those that have planets albe to sustain carbon based life, there would still be millions of planets capable of supporting life in this galaxy. And we all know that life exists where the conditions to support it arise. Life is just chemistry playing the entropy game in packets of biomatter rather then gas clouds. As for the rest, life evolves. All life evolves. All life evolves to be more efficient with it's surroundings, intelligence is a derivitive from this.

I am not sure where you got that crap, or if you're just regurgitating scientific sounding data to attempt to comfirm stuff, while just proving you dont understand it in the process.

[archibaldcrane]

And we all know that life exists where the conditions to support it arise.

Well, we only have one example of that (earth) and we can't even recreate those conditions to success in a lab, so...

[Woozie]

You don't wish them to possess a capacity for peace, compassion, and humanity?

Well, at least if they don't, we can always just shoot 'em down.

well played, but you know damn well what I meant.

There's no reason to assume they're traveling faster than light. Due to time dilation, one could traverse the distance between habitable planets in a life time at subluminal velocities, even if the planets are hundreds of light years apart.

How is this possible in a scenario where you travel inside a ship, well protected of external forces?, you would be protected of the effect of traveling at speeds close to the speed of light.

It has nothing to do with anything external, actually. Time dilation is an effect in which observers in different reference frames appear to travel through time at a different rate.

Let's say we were to have two reference frames, K and K'. K' is moving at velocity v with respect to K (so in our example, the earth would be in the coordinate system described by K and the spaceship would be in K', moving at velocity v). Let's say we have a clock in the frame K. We light a candle and notice here in frame K that the candle takes a time ?t to burn out.

Now let's assume a person in reference frame K' (i.e. in the spaceship moving at velocity v) observes the exact same event. He would measure that the event took a different amount of time, ?t'. The relationship between ?t and ?t' is

?t'=?t/sqrt(1-v^2/c^2), where c is the speed of light.

This means that if any two observers are moving at a different velocity, the rate at which they travel through time are different.

If I were to get into a spaceship, travel four light years away from earth, then four light years back at 47% of the speed of light, I'd be 16 years older when I arrive back on Earth, whereas everyone else on earth would be 17.9 years older. If I were to go 99.9% of the speed of light and travel the same route, I'd be four months older when I get back, whereas everyone else on earth would be 8 years older.

There will always be some speed lower than that of light that will allow one to travel any distance in a human life time.

If one were to go above the speed of light, they would actually go backwards in time. There is another unfortunate effect of traveling faster than light, and that's the fact that only tachyons can do it. I'd assume any alien race couldn't go faster than light due to the fact that they would have to be made of tachyons to do so (tachyons always travel faster than light. I find it hard to believe that there's a race out there somewhere that always travels faster than light through their whole lives). Protons, neutrons, and electrons aren't tachyons because they have real mass (as opposed to imaginary mass). If there was some way to cause them to go faster than light, that would lead to another effect. Charged particles traveling faster than light always emit cherenkov radiation. This causes the particle to lose energy. Tachyons actually move faster when their energy is lowered, and move slower when their energy is higher (the exact opposite of normal matter). A charged tachyon would emit cherenkov radiation even in free space. This would cause it to lose energy and move even faster. This would then cause it to emit even more cherenkov radiation, etc etc. This would lead to tachyons moving at arbitrarily high speeds (and moving backwards in time at arbitrarily high rates) as well as emiting arbitrarily high amounts of energy, violating conservation of energy. If these kind of events occurred, we would have most likely noticed by now, so it's safe to assume the aliens aren't traveling faster than light.

[Tajin]

Does not compute (I do understand most of the explanation). However how do you stop (slow) the body from aging?

[archibaldcrane]

By distorting time, which isn't fixed. It's all relative, hence, you know, the theory of relativity.

[Woozie]

By distorting time, which isn't fixed. It's all relative, hence, you know, the theory of relativity.

What he said.

In your own reference frame, you'll see yourself aging as normal. If you were to keep a clock and calender with you, you'd see yourself age and die at what you perceive to be a normal rate. People in other reference frames also see themselves aging and dying at normal rates. The discrepancy shows up when you compare yourself to those in other reference frames.

http://en.wikipedia.org/wiki/Time_dilation

Time dilation would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed retards the rate of passage of onboard time. That is, the ship's clock (and according to relativity, any human travelling with it) shows less elapsed time than the clocks of observers on Earth. For sufficiently high speeds the effect is dramatic. For example, one year of travel might correspond to ten years at home. Indeed, a constant 1 g acceleration would permit humans to travel as far as light has been able to since the big bang (some 13.7 billion light years) in one human lifetime. The space travellers could return to Earth billions of years in the future (provided the universe had not collapsed and our solar system were still around, of course). A scenario based on this idea was presented in the novel Planet of the Apes by Pierre Boulle.

A more likely use of this effect would be to enable humans to travel to nearby stars without spending their entire lives aboard the ship.

(Then it goes on to explain the technical problems of building and using such a ship)

[Tajin]

Well, indeed, but the scenario I picture is one of somebody inside a ship, competely shielded from speed (othewise human body could not sustain the forces of course).

So again, inside the ship, you are not really moving.

Edit: beaten by woozie. Already read that article.

[Kaylia]

Oh shi-...I actually agree with most of what was said in a sciences thread. That's rare

You guys act as if every single "world" (I guess that is what you would call it) follows our rules of physics. Now I'm not physics major, but maybe they have technology far different from ours that doesn't produce such byproducts as sonic booms.

They lives in the same universe, and because of this, they are bound to the same physics laws we observes. Technology can do nice thing, but it can only do them within the limit imposed by those laws.

Now, there could be technical way to reduce sonic boom, but does it worth the effort if anyone could see your ship? Maybe everyone is blind on their planet and they only care about sound? >_>

The whole UFO concept makes very little sense to begin with. If that aliens race is magical enough to breaks physics laws and travel freely through space, I'm certain their technologies is good enough to avoid being seen.

[Woozie]

Now, there could be technical way to reduce sonic boom, but does it worth the effort if anyone could see your ship?

It wouldn't be worth it when they spend most of their time in space anyways, would it?

[Blarg]

You don't wish them to possess a capacity for peace, compassion, and humanity?

Well, at least if they don't, we can always just shoot 'em down.

well played, but you know damn well what I meant.

Woozie's science going over our heads was here, also something about tachyons

Are tachyons a theory or have they actually been 'seen'. Does anyone know how exactly they move faster than light, do they even have a mass?

[Kuya]

If they're moving faster than the speed of light, then they can't possibly have mass.

[Woozie]

Tachyons have never been observed and aren't believed to really exist. Their mass will always be equal to an imaginary number instead of a real number. I don't know exactly what you mean when you ask "how" they move faster than light. Any particle with imaginary mass travels faster than light at all times. Any particle with real mass travels slower than light at all times. Any particle with no mass travels at exactly the speed of light at all times. These are required by relativistic energy formulas.

[Neosutra]

And we all know that life exists where the conditions to support it arise.

Well, we only have one example of that (earth) and we can't even recreate those conditions to success in a lab, so...

Um.. yes we can.

What the fuck are you talking about.

If you dont fucking understand science, please stop posting. So many god damned debates on this forum started from people that just dont know what the hell they are talking about.

[Blarg]

Tachyons have never been observed and aren't believed to really exist. Their mass will always be equal to an imaginary number instead of a real number. I don't know exactly what you mean when you ask "how" they move faster than light. Any particle with imaginary mass travels faster than light at all times. Any particle with real mass travels slower than light at all times. Any particle with no mass travels at exactly the speed of light at all times. These are required by relativistic energy formulas.

What do you mean by imaginary, can there be negative mass? Wouldn't any mass 'imagined' be above no mass/0 mass and hence not be able to surpass the speed of light, if you can have negative mass how does that even work. Where did the idea of Tachyons come from, is their existence required to explain a theory/something else.

[Woozie]

Tachyons have never been observed and aren't believed to really exist. Their mass will always be equal to an imaginary number instead of a real number. I don't know exactly what you mean when you ask "how" they move faster than light. Any particle with imaginary mass travels faster than light at all times. Any particle with real mass travels slower than light at all times. Any particle with no mass travels at exactly the speed of light at all times. These are required by relativistic energy formulas.

What do you mean by imaginary, can there be negative mass? Wouldn't any mass 'imagined' be above no mass/0 mass and hence not be able to surpass the speed of light, if you can have negative mass how does that even work. Where did the idea of Tachyons come from, is their existence required to explain a theory/something else.

By imaginary, I mean it's proportional to the square root of negative 1. A number that is the square root of a negative number is imaginary. Like in algebra when you learned sqrt(-4)=2i, where i=sqrt(-1). Any number of the form a*i, where a is a real, non-zero number, and i is sqrt(-1) is imaginary. This is what I mean when I say tachyons have imaginary mass.


Edit:
The idea of tachyons comes directly from the relativistic equations. By definition, a tachyon is simply any particle moving faster than light (in free space). If you ask yourself "What properties would a particle have to have in order to be in order to move that fast?", the equations immediately tell you something about its mass.

E=mc/sqrt(1-v^2/c^2). Since v>c, then 1-v^2/c^2<0, and therefore, sqrt(1-v^2/c^2)=k*i, for some real number, k. Then the energy can be written, E=-mci/k. If the particle is to exist (energy to be real), then m=i*p, for some real number, p.

[Septimus]

Tachyons have never been observed and aren't believed to really exist. Their mass will always be equal to an imaginary number instead of a real number. I don't know exactly what you mean when you ask "how" they move faster than light. Any particle with imaginary mass travels faster than light at all times. Any particle with real mass travels slower than light at all times. Any particle with no mass travels at exactly the speed of light at all times. These are required by relativistic energy formulas.

How many people actually believed in Black Holes when they were only mathematical?

[Tajin]

So, we have a ship that can reach 90% of the speed of light, and we travel to the closest star, that is not the Sun (Proxima Centauri)

9,460,730,472,580.8 km * 4.2 = Too lazy to load calc.exe

We can't make the distance any less, and the ship can't reach the speed of light, are you telling me a passenger of that ship will not be 4.2~ years older? No cryogenic stuff.

I don't get it :/