The Fermi Paradox - Where is Everybody?

[keithisco]

It is impossible to accelerate a pound of mass (or any amount of mass) to the speed of light.

"Closed Loop" thinking based on current theories. "Impossible" is never a good word to use, not where science is concerned anyway.

[questionmark]

It is impossible to accelerate a pound of mass (or any amount of mass) to the speed of light.

I wonder how many planets in the galaxy are inhabited by an intelligent species that is a close neighbor to another star with a planet inhabited by another intelligent species.

Say, close enough that it would be practical to for them to visit each other's planet.

As it was impossible for a train carriage to accelerate beyond 40 Km/h because the passengers would suffocate (Thank god Stephenson did not know that) and later to attain the speed of sound.

There is no point where anything becomes infinite (well excepting human stupidity, of course) and when talking about accelerating just a question of needed energy.

And, depending on what you define "practical", if we put our mind to it we could send people to other civilizations.... if we would know where to find them. Just the people you would send out would not be the same as those who come back... and maybe things could have changed so much that nobody cares if anybody comes back at all.

[StarMountainKid]

"Closed Loop" thinking based on current theories. "Impossible" is never a good word to use, not where science is concerned anyway.

As it was impossible for a train carriage to accelerate beyond 40 Km/h because the passengers would suffocate (Thank god Stephenson did not know that) and later to attain the speed of sound.

There is no point where anything becomes infinite (well excepting human stupidity, of course) and when talking about accelerating just a question of needed energy.

Ok, how much energy is required to accelerate a pound of mass (or any amount of mass) to the speed of light, if it is just a question of needed energy?

[questionmark]

Ok, how much energy is required to accelerate a pound of mass (or any amount of mass) to the speed of light, if it is just a question of needed energy?

We have the formula above, you convert the pound and the speed into SI units (0.45359237) and multiply by 299,792,458² and you will have the value in Kilojoules (if my memory does not fail me). Sorry, my calculator does not really compute that 299,792,458 square... but we come to something like 40,766,849,157,300,671.95 Kilojoule, or 40 Petajoule.

While those are only numbers for most of us: That corresponds to (give or take a few) 1/4 of the energy the sun sends to Earth. Or to put it into context, the total energy generation on the planet in 2008 was 20,261 Terrawatt/h, or less than 5/10000 of that value.

So, abbreviating, all the energy generated on the planet during a few million hours could accelerate 1 pound to the speed of light... given that you accelerate the item away from all friction.

Disclaimer: I am famous for skipping a comma or two, so it could be that the above is 1000 times worse than the reality... or 1000 times better and still be beyond our means.

Edited July 19, 2014 by questionmark

[StarMountainKid]

So, abbreviating, all the energy generated on the planet during a few million hours could accelerate 1 pound to the speed of light... given that you accelerate the item away from all friction.

According to special relativity, the energy of an object with rest mass m and speed v is given by γmc², where γ is the Lorentz factor defined above. When v is zero, γ is equal to one, giving rise to the famous E = mc² formula for mass–energy equivalence. The γ factor approaches infinity as v approaches c, and it would take an infinite amount of energy to accelerate an object with mass to the speed of light. The speed of light is the upper limit for the speeds of objects with positive rest mass. This is experimentally established in many tests of relativistic energy and momentum.

http://en.wikipedia.org/wiki/Speed_of_light#Upper_limit_on_speeds

[questionmark]

http://en.wikipedia....limit_on_speeds

Try e= (1/2)mv² wherein v is the final attained velocity. Acceleration is the constant energy by time.

[StarMountainKid]

Try e= (1/2)mv² wherein v is the final attained velocity. Acceleration is the constant energy by time.

At relativistic speeds mass increases as energy is applied to accelerate that mass.

Before I answer your question, I would like to start by giving a more explicit version of Einstein's famous equation, E = mc². It is commonly written as follows:

where E is the energy of the object in question, m₀ is its rest mass, c is the speed of light, and gamma () is a numerical factor that depends on velocity. The expression for gamma is

where v is the object's velocity. At very small velocities, gamma is approximately equal to one. At velocities near the speed of light, gamma becomes larger and larger (try plugging in some numbers and see). Already you can see why a massive particle can never travel at the speed of light: it would take an infinite amount of energy, and no engine in the universe can provide that sort of power!

Now I will answer your question. Einstein interpreted the combination gamma * m₀ to be the mass of an object in motion. This is why the equation is usually quoted simply as E = mc². The equation relating mass to velocity is

Mass, like gamma, grows with velocity. As the object approaches the speed of light, the mass approaches infinity!

I should give a word of caution: many physicists simply call m₀ the mass, dropping the distinction between the rest mass and Einstein's velocity-dependent mass. So be careful to note which definition is being used!

This relationship can probably be found in most introductory college physics texts. A good book for more details, at a slightly more technical level, is Ray D'Inverno's book Introducing Einstein's Relativity.

http://www.physlink.com/education/askexperts/ae388.cfm

[questionmark]

At relativistic speeds mass increases as energy is applied to accelerate that mass.

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http://www.physlink....perts/ae388.cfm

To double the speed you have to quadruple the energy input. That is known since the Renaissance.

You observed it correctly in another thread: relativity is applicable from the viewpoint of an observer, from there the name. I doubt very much that relativity applies to anything from a non-observer viewpoint. And there you are perfectly right: you cannot observe anything that is faster than light. But that does not mean that it cannot exist.

[StarMountainKid]

To double the speed you have to quadruple the energy input. That is known since the Renaissance.

This only applies to non-relevatistic speeds. As on nears c the energy required increases exponentially.

You observed it correctly in another thread: relativity is applicable from the viewpoint of an observer, from there the name. I doubt very much that relativity applies to anything from a non-observer viewpoint. And there you are perfectly right: you cannot observe anything that is faster than light. But that does not mean that it cannot exist.

Assuming a "non-observer viewpoint" means within the frame of reference of the accelerated mass. Within the frame of reference of the accelerating mass, to increase its velocity you must add energy, and since e=mc^2, the more energy you add the more mass you are adding within that frame of reference.

So, even from a non-observer frame of reference, as the speed of the mass increases, it's mass will increase.

This is how I would explain it.

[questionmark]

This only applies to non-relevatistic speeds. As on nears c the energy required increases exponentially.

Assuming a "non-observer viewpoint" means within the frame of reference of the accelerated mass. Within the frame of reference of the accelerating mass, to increase its velocity you must add energy, and since e=mc^2, the more energy you add the more mass you are adding within that frame of reference.

So, even from a non-observer frame of reference, as the speed of the mass increases, it's mass will increase.

This is how I would explain it.

Well, mass does not come from nowhere, nor does energy. So from a non-observer standpoint you would have to explain where the mass comes from. certainly not from the energy, as that is translated into speed.

[StarMountainKid]

Well, mass does not come from nowhere, nor does energy. So from a non-observer standpoint you would have to explain where the mass comes from. certainly not from the energy, as that is translated into speed.

When you accelerate mass, the faster it goes the more kenetic energy it has, and as energy = mass, its mass increases. At relativistic speeds the ratio of energy/mass increases exponentially.

[questionmark]

When you accelerate mass, the faster it goes the more kenetic energy it has, and as energy = mass, its mass increases. At relativistic speeds the ratio of energy/mass increases exponentially.

quite, quite, but it did not create any mass. If you see that as an observer it might be true, but the accelerated mass remains what it was. Because the mass is not relative, the observer and the mass are to each other. And that is the point you have to understand to understand relativity.

[StarMountainKid]

quite, quite, but it did not create any mass. If you see that as an observer it might be true, but the accelerated mass remains what it was. Because the mass is not relative, the observer and the mass are to each other. And that is the point you have to understand to understand relativity.

I understand what you're saying. Nevertheless, and any which way you look at it, to accelerate mass you must add energy, and since energy = mass, you are adding mass. In my understaning, the relativistic mass is what increases and the rest or invariant mass remains the same.

If a stationary box contains many particles, it weighs more in its rest frame, the faster the particles are moving. Any energy in the box (including the kinetic energy of the particles) adds to the mass, so that the relative motion of the particles contributes to the mass of the box. But if the box itself is moving (its center of mass is moving), there remains the question of whether the kinetic energy of the overall motion should be included in the mass of the system. The invariant mass is calculated excluding the kinetic energy of the system as a whole (calculated using the single velocity of the box, which is to say the velocity of the box's center of mass), while the relativistic mass is calculated including invariant mass PLUS the kinetic energy of the system which is calculated from the velocity of the center of mass.

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

In other words, within the refrence frame of a space ship, for instance, mass increase due to speed is unnoticed, but the relativistic mass of the space ship has increased.

This is my explanation.

[questionmark]

I understand what you're saying. Nevertheless, and any which way you look at it, to accelerate mass you must add energy, and since energy = mass, you are adding mass. In my understaning, the relativistic mass is what increases and the rest or invariant mass remains the same.

http://en.wikipedia....cial_relativity

In other words, within the refrence frame of a space ship, for instance, mass increase due to speed is unnoticed, but the relativistic mass of the space ship has increased.

This is my explanation.

The reference frame is always relative to the observer. The space ship is independent of the observer.

What you are trying to tell me is that because you move at a higher speed you have more mass, well not quite you have more energy as in energy equal mass by speed. If what you say were true most of our conventional physics could be thrown straight out of the window.

Einstein is not conventional physics, it is physics based on the external observation. Seeing something from the outside is not quite the same as the object itself.

Now, what the actions of the object does to the reality continuum of the observer is something different, but does not affect the object.

Best example, it has been shown that time gets slower through the time dilation: for those observing it. The object actually lived/existed less time than the observer.

[StarMountainKid]

What you are trying to tell me is that because you move at a higher speed you have more mass, well not quite you have more energy as in energy equal mass by speed. If what you say were true most of our conventional physics could be thrown straight out of the window.

The c^2 is not a measure of speed, it is a constant of proportionality, the energy of mass is proportional to c^2.

It seems to me what you're trying to say is E does not = mc^2, that energy and mass are not equivalent, that adding energy to mass does not increase that mass.

[questionmark]

The c^2 is not a measure of speed, it is a constant of proportionality, the energy of mass is proportional to c^2.

It seems to me what you're trying to say is E does not = mc^2, that energy and mass are not equivalent, that adding energy to mass does not increase that mass.

ehm, yes... but I fail to see how that makes your point that the mass of the object increases with increasing speed.

In classic physics v² is used because it has been established that you don't increase speed linear in relation to the energy (in fact to double the speed you have to quadruple the energy, hence v².) Now, if you have a constant speed (or a speed limit) and increase that energy then the mass has to increase. But that is formal math, not reality.

[StarMountainKid]

ehm, yes... but I fail to see how that makes your point that the mass of the object increases with increasing speed.

Mass of the object increases because you have to add energy to the object to increase its speed, and energy = mass. It's that simple.

In classic physics v² is used because it has been established that you don't increase speed linear in relation to the energy (in fact to double the speed you have to quadruple the energy, hence v².) Now, if you have a constant speed (or a speed limit) and increase that energy then the mass has to increase. But that is formal math, not reality.

At relatavistic speeds classical physics falters and you have to use special relativity, which gives you counterintuitive results. It seems by experimental evidence that this is reality.

[questionmark]

Mass of the object increases because you have to add energy to the object to increase its speed, and energy = mass. It's that simple.

At relatavistic speeds classical physics falters and you have to use special relativity, which gives you counterintuitive results. It seems by experimental evidence that this is reality.

Sorry, but energy not equal mass else acceleration would be impossible.

There are no relativistic speed for an object, unless that object is observing another object or its existence is relative to the existence of another object.

[StarMountainKid]

I've run out of ideas.

[questionmark]

I've run out of ideas.

Oh well, we can try again some time...

[Waspie_Dwarf]

This discussion about FTL is all very interesting, but it is a massive red herring in terms of the subject of the thread. StarMountainKid ois quite correct about his assertion of the problems of accelerating mass to light speed, he is quite wrong in asserting that this has any relevance on the Fermi Paradox.

Fermi did not rely on FTL travel when he pointed out his "paradox". In fact you don not need FTL to have colonise the galaxy. There are half a dozen stars within 10 light years of Earth. If we could attain just 20% of the speed of light then we could reach all of these stars within 50 years.

If the colonists arriving at these stars were then to build new ships and then venture out further then 100 stars can be reached within a century. Growth by this method is exponential, a civilisation can spread to many thousands of stars in a few millennia. There has been billions of years for this kind of colonisation to occur. The galaxy SHOULD be entirely colonised by now.

All this is achievable without breaking any of the currently understood laws of physics.

So it returns to the paradox... if it is possible then where are they?

[questionmark]

This discussion about FTL is all very interesting, but it is a massive red herring in terms of the subject of the thread. StarMountainKid ois quite correct about his assertion of the problems of accelerating mass to light speed, he is quite wrong in asserting that this has any relevance on the Fermi Paradox.

Fermi did not rely on FTL travel when he pointed out his "paradox". In fact you don not need FTL to have colonise the galaxy. There are half a dozen stars within 10 light years of Earth. If we could attain just 20% of the speed of light then we could reach all of these stars within 50 years.

If the colonists arriving at these stars were then to build new ships and then venture out further then 100 stars can be reached within a century. Growth by this method is exponential, a civilisation can spread to many thousands of stars in a few millennia. There has been billions of years for this kind of colonisation to occur. The galaxy SHOULD be entirely colonised by now.

All this is achievable without breaking any of the currently understood laws of physics.

So it returns to the paradox... if it is possible then where are they?

Somewhere battling the same problems we are and, even if science capability doubles every ten years, we will not solve for another long, long time.

Additionally, to this day all we know for certain is that there is a dead satellite and a dead planet that don't show much signs of life (if any at all). So we can hardly claim that we know that the entire galaxy is not settled where settlement is possible (which is where humans, if ever possible, will also try to settle, because things like a Moon or Mars colony will be dead on delivery (for humans) and never will go much beyond our current space station status. Settling the deep sea will be more likely).

As far as biology , I doubt we would recognize all biological possibilities for life as such (see the latest biobacter research in the science forum). This planet could be inhabited by other intelligent lifeforms and that neither they no we are aware of each other because our forms are so different from each other. So could other planets be and we would never notice, even in our solar system. Which leads us to Fermis first logical fallacy which implies that we should be able to identify all life as such.

Lastly, given that all the universe started more or less at the same time and the time it took us to from harnessing a few kilowatts of non animal energy to the few Terrawatts we are capable of harnessing today it will take at lest another 1000 years (without major civilization collapses) until we are capable of creating energy in wast enough quantities to make non-kamikaze outer space travel possible*. Whatever civilization capable of finding us therefore must be at least 1000 years ahead of our development and be in our immediate vicinity. The further away the larger the technological advancement ahead of us. And there we would end up with the usual biological impossibilities of a intelligent life form recognizable by us as such (not only physics has its laws, but also evolution) and to recognize us.

And permit me to doubt that there is any limit to anything in the universe as long as you can harness enough power to make it possible. But given the amounts of power required, even for making a multi-generation expedition to a system only a light year away, and that we are still incapable of stemming it with a minimum guarantee of success (never mind the next suitable planet we know of this far, 13 light years away), also makes the Fermi paradox less a paradox than a postulate in which not enough variables were considered.

* not to mention that it would be quite hazardous to hit a single atom in space at a high enough velocity, which then would require us to develop materials much more durable than those we have.

[StarMountainKid]

Fermi did not rely on FTL travel when he pointed out his "paradox". In fact you don not need FTL to have colonise the galaxy. There are half a dozen stars within 10 light years of Earth. If we could attain just 20% of the speed of light then we could reach all of these stars within 50 years.

If the colonists arriving at these stars were then to build new ships and then venture out further then 100 stars can be reached within a century. Growth by this method is exponential, a civilisation can spread to many thousands of stars in a few millennia. There has been billions of years for this kind of colonisation to occur. The galaxy SHOULD be entirely colonised by now.

I agree in principle, but how would we build new ships on arrival to these "stars"?

My original intent on commenting on the impossibility of reaching light speed or some kind of FTL travel was to remind those who consider this kind of inter-stellar travel possible by thinking advanced civilizations would automatically have this kind of technology is speculative and not necessarily a foregone conclusion.

I would speculate that colonizing the galaxy by any method is someow not as easy as we imagine it to be. I think the Great Filter in some form may prevent this from happening. Either that or colonization exists in several or many locations in the galaxy, but remain local due to the scarcity of inhabitable planets at reasonable distances from each other.

Of course, we have no real solution to the paradox. Intelligent species capable of such colonization may be much rarer than we think. The natural evolution of human beings depended on multiple random chance occurrences on our planet. Remove one essential event and we may not be here, and may never have evolved.

Edited July 21, 2014 by StarMountainKid

[Waspie_Dwarf]

Somewhere battling the same problems we are and, even if science capability doubles every ten years, we will not solve for another long, long time.

How far WE are from such technology is totally irrelevant, it is not US colonising the galaxy that we are talking about.

Additionally, to this day all we know for certain is that there is a dead satellite and a dead planet that don't show much signs of life (if any at all). So we can hardly claim that we know that the entire galaxy is not settled where settlement is possible (which is where humans, if ever possible, will also try to settle, because things like a Moon or Mars colony will be dead on delivery (for humans) and never will go much beyond our current space station status. Settling the deep sea will be more likely).

Again most of this is irreverent at best and quite possibly fallacious.

We are not talking about what human are capable of now, we are talking about a galaxy which has been able to sustain life for billions of years.

As for saying what worlds we will or won't colonise in the future, unless you have a time machine you can not possibly know what technological capabilities we will have a century from now, never mind millennia from now.

As far as biology , I doubt we would recognize all biological possibilities for life as such (see the latest biobacter research in the science forum). This planet could be inhabited by other intelligent lifeforms and that neither they no we are aware of each other because our forms are so different from each other. So could other planets be and we would never notice, even in our solar system. Which leads us to Fermis first logical fallacy which implies that we should be able to identify all life as such.

Once again irrelevant, we don't have to recognise the biology, we have to recognise the technology and communications of an alien race. It is I adamit, highly possible that we can't recognise alien technology because it is too advanced.

Lastly, given that all the universe started more or less at the same time and the time it took us to from harnessing a few kilowatts of non animal energy to the few Terrawatts we are capable of harnessing today it will take at lest another 1000 years (without major civilization collapses) until we are capable of creating energy in wast enough quantities to make non-kamikaze outer space travel possible*. Whatever civilization capable of finding us therefore must be at least 1000 years ahead of our development and be in our immediate vicinity. The further away the larger the technological advancement ahead of us. And there we would end up with the usual biological impossibilities of a intelligent life form recognizable by us as such (not only physics has its laws, but also evolution) and to recognize us.

I don't get your point here. Why would you assume that all technological species would emerge at roughly the same time, especially as there are stars (and therefore planets) that are considerably older than ours.

And permit me to doubt that there is any limit to anything in the universe as long as you can harness enough power to make it possible. But given the amounts of power required, even for making a multi-generation expedition to a system only a light year away, and that we are still incapable of stemming it with a minimum guarantee of success (never mind the next suitable planet we know of this far, 13 light years away), also makes the Fermi paradox less a paradox than a postulate in which not enough variables were considered.

You can doubt what ever you like, me I'd rather base my doubtsw on the evidence.

* not to mention that it would be quite hazardous to hit a single atom in space at a high enough velocity, which then would require us to develop materials much more durable than those we have.

More irrelevance. What we are capable of has nothing to do with this.

[Waspie_Dwarf]

I agree in principle, but how would we build new ships on arrival to these "stars"?

The same way we would build them here.

My scenario was deliberately simplified, however if only a few percent of such missions were successful there would still be time for a star-faring race to have colonised millions of stars.

My original intent on commenting on the impossibility of reaching light speed or some kind of FTL travel was to remind those who consider this kind of inter-stellar travel possible by thinking advanced civilizations would automatically have this kind of technology is speculative and not necessarily a foregone conclusion.

That's as may be, but it is still irrelevant to Fermi's argument.

I would speculate that colonizing the galaxy by any method is someow not as easy as we imagine it to be. I think the Great Filter in some form may prevent this from happening. Either that or colonization exists in several or many locations in the galaxy, but remain local due to the scarcity of inhabitable planets at reasonable distances from each other.

It doesn't have to be easy, it only has to be achievable and there is no scientific show stopper that makes it impossible.

Of course, we have no real solution to the paradox. Intelligent species capable of such colonization may be much rarer than we think. The natural evolution of human beings depended on multiple random chance occurrences on our planet. Remove one essential event and we may not be here, and may never have evolved.

I agree. And when in doubt quote Arthur C. Clarke:

Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.