The difficulties of interstellar travel and the implausibility of the Extraterrestrial Hypothesis.

Many people, not just believers, are under the impression that given sufficient time we will crack the "science" behind faster-than-light travel and someday in the future we will be whizzing across the galaxy in a way that is not unlike how we fly around in our atmosphere today. Unfortunately, this notion is not grounded in any science but rather delusional fantasy.The following paper published in the 1960s explains why:

The insurmountable difficulties of relativistic space travel

Radio astronomy and Communications Through Space by Edward Purcell (U.S. Atomic Energy Commission Report BNL-658, reprinted in Cameron, A.G.W. (editor), Interstellar Communication. New York: W.A. Benjamin, Inc., 1963). Edward Purcell, a pioneer of radio astronomy and Nobel Laureate of physics, dedicated a section of this paper which was primarily on radio astronomy to space travel. In it, he is quoted:

The performance of a rocket depends almost entirely on the velocity with which the propellant is exhausted,” he notes. Thus, “the elementary laws of mechanics – in this case relativistic mechanics, but still the elementary laws of mechanics – inexorably impose a certain relation between the initial mass and the final mass of the rocket in the ideal case… It follows very simply from conservation of momentum and energy, the mass-energy relation, and nothing else.

He continues

For our vehicle we shall clearly want a propellant with a very high exhaust velocity. Putting all practical questions aside, I propose, in my first design, to use the ideal nuclear fusion propellant… I am going to burn hydrogen to helium with 100 percent efficiency; by means unspecified I shall throw the helium out the back with kinetic energy, as seen from the rocket, equivalent to the entire mass change. You can’t beat that, with fusion. One can easily work out the exhaust velocity; it is about 1/8 the velocity of light. The equation of Figure 13 tells us that to attain a speed 0.99c we need an initial mass which is a little over a billion times the final mass.

The implication here is that for 1 kg of the spacecraft, there would be a required 9 billion kg to propel it to 0.99c. This is the devastation of the exponential relationship in the relativistic Tsiolkovsky rocket equation. So, fusion won't work, neither will fission of course which is even less efficient. How about antimatter?

This is no place for timidity, so let us take the ultimate step and switch to the perfect matter-antimatter propellant…. The resulting energy leaves our rocket with an exhaust velocity of c or thereabouts. This makes the situation very much better. To get up to 99 percent the velocity of light only a ratio of 14 is needed between the initial mass and the final mass.

Only one problem. Even if you could produce sufficient quantities of antimatter, contain it, and then annihilate it with ordinary matter in such a way that could generate thrust effectively (I pity the engineer that would be tasked to design that magnetic field configuration), there is no way to decelerate. Even if you could using the same method, you would require 1:196 mass-to-fuel ratio and thus 98 kg of antimatter of every 1 kg of matter. To put things into perspective, the world's largest particle accelerators would require a 1000 years and 100 trillion dollars to create a miligram of antimatter (0.000001 kg) at the current rate they produce it. Also, Purcell notes in order to achieve this acceleration, the rocket would have to radiate 1 exawatt (10^18 watts) near the beginning of its journey. That's about the entire energy received by Earth from the sun but in gamma rays. You can't exactly hide these signatures, let alone their disastrous effects, no matter how sufficiently advanced you are. But he continues:

Well, this is preposterous, you are saying. That is exactly my point. It is preposterous. And remember, our conclusions are forced on us by the elementary laws of mechanics.

Finally, he concludes:

All this stuff about traveling around the universe in space suits – except for local exploration, which I have not discussed – belongs back where it came from, on the cereal box.

Hence, if ET is here, they are obviously not using relativistic space travel as stated by Stanton Friedman:

a one-way trip of thirty-seven years (the distance to Zeta 1 or 2 Reticuli) at 99.9 percent c would take only twenty months’ crew time; at 99.99 percent c it would take only six months’ crew time. Thus even a trip to a distant galaxy such as Andromeda, two million light-years away, would take under sixty years’ crew time if the intergalactic ship somehow could manage to keep accelerating at one G, using some yet unknown technique.

Either ET is getting here by using some method that effectively circumvents the speed of light limit imposed by the fundamental laws of physics, or the ETH is flawed and should be discarded.

The absurdity of faster-than-light travel

The Alcubierre Drive

Miguel Alcubierre published a paper in 1994 that demonstrated by using the field equations of general relativity that a bubble of flat spacetime can move at an effective speed faster than the speed of light.



Unfortunately, there are numerous problems that appear to be show-stoppers to the Alcubierre Drive. For one, the paper only states how to keep the bubble moving once it has already formed, but does not show at all how to generate the bubble. Secondly, part of the warp bubble wall is causally disconnected from the interior of the bubble since we have an effective velocity faster than the speed of light. This means it is impossible for someone inside the ship to send signals to control the bubble. Thirdly, according to a paper published by cosmologist Stefano Finazzi, temperatures would soar to 10^32 kelvin inside the bubble. That's 26 orders of magnitude hotter than the core of the sun.

Even if a sufficiently advanced civilization could solve all of these engineering problems, the major hurdle is the energy requirements. The early calculations showed it required an amount of energy that was greater than all that existed in the known universe. This number was brought down by subsequent calculations to the mass-energy equivalence of Jupiter, and finally recently, the mass-energy equivalence of the voyaegeur space probe. Only problem is that this is not ordinary energy that gravitates as we would expect. Rather, it is negative energy. Other than negligible effects such as the Casimir effect and the energy responsible for the accelerated expansion of the universe, there is no evidence of a macroscopic instance of this phenomena that can be engineered. The most advanced and accepted examples of quantum field theory, which is by far the most successful model of nature devised by mankind, does not include the existence of negative mass. Thus, the warp drive is looking like it will always remain in science fiction.

Wormholes

What about wormholes, you might retort? Another golden staple of science-fiction that does seem to be a theoretically sound concept. The idea originated in the 1930s with Albert Einstein and Nathan Rosen. It was a theoretical curiosity and it wasn't until almost 60 years later that Kip Thorne and his graduate student Mike Morris revived the idea as a method of space travel. Like the warp-drive, it is riddled with problems that seem to be insurmountable. Firstly, papers based on the model used by Kip Thorne show it to be inherently unstable and would collapse as soon as it was opened. The only way to stabilize the wormhole is through the constant supply of the wormhole, which brings us back to the warp-drive. Secondly, the mouths of the wormhole must be transported to the destination in order to be accessed and thus requires at least 1 trip via subluminal travel to the destination. So, ET must have at least been to our system once using subluminal methods and avoided complete detection. Thirdly, there is as of now no evidence that wormholes exist in nature and has so far never been observed. Fourthly, as Einstein showed in general relativity that space and time are intricately connected, distorting space in such a way would also simultaneously distort time as well. This means when you enter the hypothetical wormhole, there is no guarantee you won't emerge 300 billion years into the future or 10 million years into the past. Effective faster than light travel means you can also create time-travel, which brings with it the problem of all the time-travel paradoxes that are yet to be resolved. There is no known way to divorce space and time in such a way that you would obey causality as you pass through.

Lastly, both methods require the existence of anti-gravity and if it can be utilized for practical purposes. This doesn't seem controversial, but it is in direct opposition to one of the two greatest models of nature to date: general relativity.

Einstein Speaks

Albert Einstein published the formidable general theory of relativity in 1916, which replaced classical Newtonian gravity as the supreme model for gravity. It was a triumph for general relativity that it predicted the nature of the bending of light in the 1919 eclipse, a phenomena that could not be explained via Newtonian gravity. Almost all of its predictions have been verified to many decimal places. In this model of nature, gravity is not considered a force, but rather the byproduct of the bending of spacetime by mass-energy.

In general relativity, seeing as gravity is the positive geometry of the curving of spacetime, anti-gravity requires "negative geometry". Seeing as such a thing is absurd under this model, general relativity therefore prohibits the existence of anti-gravity. Now, in all fairness, there are some models beyond the standard model of particle physics that require the gravitational force to be mediated by some particle known as a "graviton". This is in direct contradiction of the classical interpretations of gravity as a byproduct of the curving of spacetime in general relativity. It is unknown whether anti-gravity can be ruled out completely under such models, but seeing as such effects would effectively be on microscopic scales that could never be used for any practical application such as space travel and that these models must reduce to the predictions of general relativity for macroscopic gravity, anti-gravity is therefore completely impractical at best and outright impossible at worst.

Due to this fundamental reason alone, it seems both wormholes and warp drives are out of the question.

What do the modern-day experts make of this

A recent survey of physicists, physics graduate students, and physics undergraduate students was conducted by UC sandiego professor of physics Tom Murphy. The results can be found here. The results? 96% of physics professors surveyed think wormhole travel will never possible, 92% think we will never have warp drives, and 64% think we will never essentially leave our solar system. So, to those posting and saying that Purcell was stuck with a "60s mindset", well it seems a majority of physicists are also stuck living in the 60s.

Well sure if we take the "Brute Force" Approach to moving through space it indeed will be near impossible to move faster than the speed of light. So how do we edit the mass of an object through electromagnetic fields. That would be one way. Thinking outside the box as opposed to 1960's in the box thinking.

reply to post by Diablos


I agree with this post.

When my friends ask me if i believe we have been visited by aliens i tell them the amount of energy it would take them to reach us and the lengths of time involved and i watch their eyes glaze over. Then i answer No i dont believe they are visiting us and then the argument ensues.

reply to post by Diablos

Either ET is getting here by using some method that effectively circumvents the speed of light limit imposed by the fundamental laws of physics, or the ETH is flawed and should be discarded.

That is a very limited view in regards to what we would classify as ET. The best chance for an advanced race evolving that would at least address the multiple reports would be right here on Earth, as we know life is possible here, the only reason to object is that we should have at least found artifacts so the next place is in our solar system, then in a rogue planet or a as we are now proposing artificial life (genetic or mechanical) or a multi-generational craft. The FTL issue should be relegated to the last possibility even further than time travel or multi-verse (extra-dimentional) visitations. Of course all those by our own perspective and that itself is an issue since our human perspective by default does not apply...

If they exist, I doubt they are using rockets to travel through space.

Of course I don't pat myself on the back too much for my insight. After all - it has been fairly obvious for 50 years now that rockets are a poor choice if one wishes to travel the stars.

On the other hand: what I don't know I can't know, so I don't automatically discount that we have been or are being visited. Perhaps our aliens are from the earth and live in caves, or under the sea? Or maybe they are time travelers from our distant future?

Or maybe the perceived distances between stars is part of our experience of isolation, and we only perceive these distances as insurmountable because our corner of the simulation is programmed to keep us boxed in until our sentence is lifted?

There are lots of possibilities.

reply to post by 0zzymand0s


If we look at ET reports and mythology only a very few of the ancient ones would suggest the use of rocket engines. That alone is interesting as the use of rockets would signify close proximity. Note that even if we had lunched a multi-generation ship to Alpha-Century (4.37 light years) after "getting to the moon" we would had to use rocket engines to land at the destination.

As long as you believe something is impossible, you don't look for how to make it possible.

200 hundred year's ago it was implausable to bend metal and fly around the world,200 hundred years ago it was implausable to communicate with somebody on the otherside of the world in under 24 hrs.200 years ago it was implausable to flick on a switch to light a room.200 hundred year's ago gorrila's did not exist. 200 hundred years ago you couldn't even communicate your hypothisis to all of us .What you talking bout willis?

reply to post by Panic2k11


No doubt. Frankly - I have always suspected that IF earth has indeed been visited by ET's in the past, they are very local. No further than Saturn, and possibly a lot closer.

The reasons why they would choose to appear as if they were from a completely different star are almost as interesting as the question of their existence in the first place, IMO,

I'm not understanding how we can take what a paper says that was published in the early 60s, and apply that to 2013, we are talking about 50 years later, we have come a long ways since then.

I think there was a thread or two on ATS that talked about different methods of propulsion, like Plasma engines and Solar sails to name a couple, I'm sure NASA and some other space agencies are already testing these things.

I always like to think outside the BOX, and I don't pay much attention to people who say things are impossible, because they always seem to be proven wrong, in time.


I am sure that within the next 10 to 20 years we will see some huge breakthroughs, and then you can say I told you so.



S&F for you




Peace

Classic debate...

Here's a video that should be included in the OP.



Awesome huh?

Also, there are some awesome links provided in the video details on the youtube page for this video.

I find it amusing to realize that there are people who spend time and energy trying to prove something is impossible instead of working towards making that thing possible. Particularly I prefer to face the Universe with a sense of wonder and a feeling that anything is possible, and even if I'm wrong, life is a lot more fun this way

Originally posted by Deny777
I find it amusing to realize that there are people who spend time and energy trying to prove something is impossible instead of working towards making that thing possible. Particularly I prefer to face the Universe with a sense of wonder and a feeling that anything is possible, and even if I'm wrong, life is a lot more fun this way

Sure, anything is possible. Just don't try flying in your birthday suit at Burning Man.

It's kinda hard to remove the importance of regarding something as impossible. Also, what about all the time that people spend pursuing impossible feats or developing theories? Like phlogiston...

"Classic" debate and entirely stupid.

It's like postulating about the (im-)possibility of interstellar space travel from the perspective of someone from 200 years back, saying it will be impossible because there is not enough hay to feed the many horses that are required to pull a carriage towards the stars.

I think most of the more advanced thinkers are LONG beyond proposing interstellar space travel with conventional rockets, rocket fuel etc.etc.

I also don't see the point of this OP, unless as a humorous example of closed minded "scientific" thinking.

Well put Diab... It's a scientific "atheaestic" approach. (In a science type of way.) - not sure if "atheaestic" is a word ..I made that ^%% up..but yeah..I agree,

However.. With this "folding of time and space" type stuff they've been feeding us(You can achieve that in your kitchen sink) -, ..another few hundred years who knows?

Well, this is something I think about alot.

1. FTL travel by brute force is probably never going to happen.
2. Traveling AT the speed of light may happen.
3. Using a unknown method to "teleport" (wormhole, or whatever) may happen, leading to FTL travel


Agreed though, that once you get going it will be hard it slow down. Other things to consider, that I rarely hear, is that the large distances traveled at the speed of light or FTL will have a "time travel" effect for the people going at that speed. It won't matter much if people were going to be locked in the a spacecraft for 100 years if it only felt like 2 weeks for them.

And I always wonder about mass. If there is no gravity in space, and no atmosphere, no friction, why does mass matter?? Would a anti-gravity device (I know there is no such thing) work to "remove" the mass?
I.E. if we had less mass could we need less fuel??

It seems to me that alot of the topics discussed here on ATS are interconnected. Free energy, antigravity, time travel, FTL travel, quantum entanglement, teleportation, perpetual motion..... It does appear as though if we unlock just one of these, we will get them all.

Lol, no offence to you OP, but I just find it funny how people can postulate about space travel when their minds are still stuck in the 70's. This when we still dont properly understand magnetism or found a way to block it.

Worlds like magnetism, magnetic fields, forces, etc, are all just place marks. Words thought up by a scientist to give a description to something he really did not fully understand. You cant move forward unless you give a certain thing/reaction/force a name.

Sometimes you have to wonder whether they were the right names or the correct discription.


All of this postulation and speculation all relies on basic laws of Physics and Mechanics. Who thought up those laws? A person, just like you, just like me. Now are we going to live our lives only by that person's theories or are we going to tweak it, bend it, or just wipe it all out and start from scratch.

My point is, we wont progress untill we hit reverse and start over. It's called revision. And it starts with gravity.

Just my 2 cents.


Posted Via ATS Mobile: m.abovetopsecret.com

I remember reading several years ago that scientists in the 1700's said that the human body would never be able to take the stress of traveling faster than 60 mph. Of course, that was based on wooden wheels and cobblestone roads.

I think it's pretty clear that an action/reaction propulsion system isn't practical for interstellar travel. I think the key will be when we find a way to alter an object's mass. If we can change mass, we can change space. I think a civilization with less than 1000 years of technological progress at the rate we are progressing could do this.