Stephen Hawking on time travel, M-theory, and extra terrestrial life | Hacker News Reader

Stephen Hawking on time travel, M-theory, and extra terrestrial life

arstechnica.com

121 pointszoowar80 comments

The odd thing about the universe seems to be that the distances are so vast that it almost doesn't matter if there's other sentient life here or not because it's far too distant to be of any relevance.

Travelling between stars is incredibly expensive (in terms of pure Joules) and time-consuming. I can see the logic in the theory that the most likely outcome for any species reaching sentience is to destroy themselves. either through direct means (eg nuclear or biological war) or indirectly (simply running out of resources)

Calling it irrelevant just because you can't travel there is short-sighted. We could still learn a lot just by watching the broadcasts of another civilization, even if they're already long gone.

And just knowing they exist would be incredibly exciting, even if there was zero chance that we could directly contact them in the span of our entire existence.

The distances are so great that the broadcasts of another civilization would attenuate to undetectable levels before they could reach us.

Out of all infinite amount of different methods to communicate and broadcast themselves they could possibly be using. Including the ones we didn't even discover yet. Assuming they're using the same ones humans just found out in recent history. The ones SETI is measuring. Even then, assuming it's formatted in a way we would decipher and be able to understand its structure (as in Carl Sagan's movie). That just sounds so improbable.

Even if they are broadcasting it, we're probably listening to it with the wrong technology. Even if we happen to be lucky of listening with the "right" technology. We probably wouldn't be able to tell it from random noise.

I find it extremely unlikely humans will ever be able to watch alien broadcasts during our existence in the universe.

"Even if they are broadcasting it, we're probably listening to it with the wrong technology. Even if we happen to be lucky of listening with the "right" technology. We probably wouldn't be able to tell it from random noise." That's why you start by blasting prime numbers on all em frequencies for 5 years.

I don't think there are many different ways to encode meaningful information. We all live in the same universe and I see no reason to believe that intelligent alien life won't be intellectually quite similar to us. While tricky without context, decoding extraterrestrial signals will inevitably produce something of interest (images, audio) even if understanding e.g. the audio itself will be tricky.

That being said, while I suspect that meaningful, structured information will be, by definition, structured and therefore obvious to spot in a broadcast, the real problem is that these transmissions are likely to be (a) compressed and/or (b) encrypted.

While compression formats may reveal a few hints that there is some structured information present, encrypted data will be all but impossible to distinguish from random transmissions. We may be picking up transmissions from alien life but be unaware simply because the data is encrypted.

I have no idea what proportion of our broadcast signals are encrypted today, but I suspect it's a fairly significant and growing proportion (privacy and intellectual property concerns being the primary reasons).

> While tricky without context, decoding extraterrestrial signals will inevitably produce something of interest (images, audio) even if understanding e.g. the audio itself will be tricky.

Serious question: How is it presumably simple to decode images and audio, but difficult to understand the audio? Is it because one can assume image representation would tend towards mathematical efficiency, but spoken languages do not?

>While compression formats may reveal a few hints that there is some structured information present, encrypted data will be all but impossible to distinguish from random transmissions. We may be picking up transmissions from alien life but be unaware simply because the data is encrypted.

I would think that encrypted transmissions would be easily distinguishable from background white noise, no? My thinking is, you have the general random noise of space, and then you would have something obviously different, is that totally not the case?

Yes, I believe that images (encodings of electromagnetic radiation of particular wavelengths) and audio (encodings of mechanical waves of pressure) are universal concepts aliens are also likely to be familiar with, whereas understanding the information encoded within the transmission requires interpretation within a context we are highly unlikely to have here on Earth.

This is just my intuition and speculation but I would guess somebody could formalise some support in terms of Kolmogorov complexity (http://en.wikipedia.org/wiki/Kolmogorov_complexity): there are only so many ways to represent an image or audio, and over time an intelligent race will discover the least complex method and use it. Therefore, alien races of equivalent levels of technical advancement in a given field should be able to decode raw (uncompressed and unencrypted) transmissions of common types of information (images, audio).

Any additional complexity on top of this method will probably be quite structured, e.g. with television signals we have portions of the signal that are blank because during that time the CRT of old televisions would be retracing and not displaying data. (Actually, I believe these "dead" portions of the video signal are sometimes used to send additional structured data, e.g. Teletext, which would make the structure of the signal even more apparent.)

I suspect it'll be much easier to look at alien video transmissions and figure out what they're about than trying to listen do the same with audio transmissions because video would provide objective context (assuming it's not just a video of talking alien heads, or whatever the equivalent of a "head" for them would be).

With respect to encrypted transmissions, if the entire protocol is encrypted from start to finish, and you're using the right cipher* then no, you can't distinguish encrypted data from random noise. This is the principle behind TrueCrypt's hidden volumes (http://www.truecrypt.org/docs/?s=hidden-volume).

* What's the right cipher? So far no nobody has found a distinguisher for AES, and that's in common use, so that's probably good enough to make an alien race blind to us; i.e. we could be picking up signals from a race as sophisticated as c. 1998 humans (http://en.wikipedia.org/wiki/Advanced_Encryption_Standard) without realising it.

> then no, you can't distinguish encrypted data from random noise.

But, would there not be a noticeable difference between random noise in space, and that same space PLUS someone broadcasting random noise? (And would it depend on whether or not they cared about being heard, even if they still wished their transmission to be encrypted).

It just seems to me that if there is a particular point that is continuously broadcasting randomness, would it not be noticeable? Or is what you are saying that that is essentially what stars are doing is broadcasting randomness, across a broad spectrum, and we can't distinguish between a star and an intelligent race....they are literally indistinguishable.

Yes, as I understand it (I'm no expert though), we can't distinguish between the background noise of the universe and an encrypted alien signal. I believe the main problem has to do with all the various possible sources of background noise constantly moving and interfering with each other through the galaxy.

That being said, from a physics perspective perhaps there's some way to say "these bits of random noise are unusually powerful, and based on our multiple noise detectors over a large area we've managed to estimate the path these signals travelled and there's only a planet on the other end with nothing else appearing in in the way (over the course of time it took for the signal to arrive) to explain them as mere background noise."

Note that encrypted traffic, indistinguishable from noise, is almost always then encoded for transmission in a format that contains redundancy (frequently, there are more than one such layer).

For example if you electrically sniff an ethernet cable over which only SSL traffic using AES is being sent, the first thing you will notice is a concentration of energy near 200Mhz. Then you may see bursts of a Manchester-encoded signal; further study reveals the regular structure of Ethernet headers and trailers, along with IP, TCP and SSL headers. Only within that will you hit a brick wall at the AES data itself.

Even if the payload is encrypted it should be possible in most cases to detect a modulated transmission.

That's a good point. In effect, if we look at this from the perspective of the OSI model, you're saying that whereas the application layer may contain encrypted data the lower layers may contain structured data. So the logical question that follows: is there any reason to believe aliens might use encryption all the way down to the data link layer? Maybe our neighbours are all at war and need to disguise and protect signals from each other?

Have you read ithkuil's comment? http://news.ycombinator.com/item?id=4188160

Yes, but spread spectrum modulations are very much a minority among all our transmissions, so I see no reason to expect any different from other civilizations.

Today yes. But imagine that our technology gets refined in the following 10k years, even assuming no more technological breakthroughs, but only incremental improvements.

Even today we use some technology which is not really necessary to solve a given problem, just because it uses off the shelf components which are cheaper even if more complicated (e.g. a embedded cpu instead of dedicated and simpler electronics)

some encodings are virtually indistinguishable from background noise,. e.g. spread spectrum like CDMA used in GPS. It's already difficult to decode them here on earth if you don't know the sequence key, let alone picking faint signals from distant civilizations.

I was not aware of that. This is an interesting counter-point to caf's observation: http://news.ycombinator.com/item?id=4188432

Mandatory XKCD reference: http://xkcd.com/638/

Woa, I had never seen that one before. It puts together every criticism I have about SETI in much more clear and obvious language. I could never be so eloquent. Randall Munroe is an absolute genius.

What lessons are to be learned from the alien version of "I Love Lucy"?

The super intelligent life will live forever so distance/time might not be relavant to them as it is to us.

Also, it seems like at this stage of our intelligence we can communicate and find only intelligent life which is at similar stage (which is maybe span of 100K +/- 10K years). That is nothing.

It's kind of like an old joke from Penny Arcade, once something gets too expensive to be practical it may as well cost infinity.

http://www.penny-arcade.com/2008/12/1/

Mathematically inaccurate but can be a short and simple way of summarizing costs and complexity.

Could we travel by moving the entire solar system with us?

Build a dyson sphere around the sun and harness part of the energy to ever so slowly move our planet and sun towards a nearby suitable star system. Then settle our planet in orbit around the other star.

This way we should have at least some way of sustaining human life past the end of our sun.

The distances are indeed vast, but the time periods involved are yet more vast. A Von Neumann probe travelling at quite modest speeds should be able to spread over our entire galaxy in mere millions of years; the universe is billions of years old.

So while direct visitation by aliens seems highly improbable, such a probe making contact seems at least a theoretically plausible possibility.

I've been watching his "Into the Universe" series, and honestly I have been a bit disappointed. I was hoping for more science -- details about subatomic particles, a discussion of the various interpretations of quantum mechanics, an introduction to M-theory (that doesn't involve violins and floating colors). Instead, one whole episode was devoted to ragging on religion -- a bunch of speculation that doesn't teach any of the interesting science to the show's viewers.

How about an introduction to Hawking radiation, the holographic principle, superpartners? At least an overview of the standard model? Nope. Just reasons "God isn't necessary". I'm not sure why he takes this route for the show. Maybe it gets more viewers and more controversy. It's sadly reminiscient of the history channel. It used to be full of a lot of interesting, objective content about -- believe it or not -- history, but now it's just full of alien speculation and religious prophecies.

It's not a show about science; it's a show about ratings. Popular science gets ratings, which are still less than non-popular-related shows, and which are far higher than any hard-science-related shows could ever get. You'll have to scratch that itch somewhere else... though I totally agree with you!!!

I used to watch the History Channel all the time. I'd keep it on throughout the day while I worked, always enjoying war documentaries or historical pieces. Now it's all reality TV and "Who would win in a fight: Navy SEAL vs. Samurai" nonsense. I guess the "watching television to be informed" target audience is dwindling faster than I thought.

I love Hawking. But unfortunately, this interview is too short, simple and obvious to be interesting. Reminds me of:

http://xkcd.com/799/

I don't really see how this is news.

Don't get me wrong, I think Stephen Hawking is a very smart man, and he has definitely done his fair share of work to help people understand science - not to mention that his scientific accomplishments aren't bad, either. That being said, there's just nothing new in this Q&A that he hasn't already said or wasn't already widely known to anyone who bothered to do a quick search on Google (except perhaps the part about his quality of life, but let's face it, that's not important).

I don't think the part about his quality of life is not important.

Lots of people have disabilities, only accounting for spina bifida which is physically less disabling that ALS, or muscle atrophy which leaves cognitive capacity intact, already puts them in the thousands. Someone needs to show them they can achieve many of what they dream about, because most of society only gives them pity and consent. We have Olympic Games for disabled people whose dreams are of being athletes, and we need people like Stephen Hawking to show disabled wannabe scientists and hackers (many of whom I believe read HN and ars) that they can also triumph in their geeky endeavours.

You raise a valid point. If that were the case, though, then I would argue the article should've been posted under a different title. The current title suggests that I'm going to see mr. Hawking say something profoud about time travel, M-theory and extraterrestials.

Thats just it though. There are many who WONT go back and re-read what he has said. Some people think that by virtue of him having something to say that he's presenting something new.

You have to remember that in knowing and being familiar with the content being presented that you're in the minority of people who will EVER grasp this knowledge, even on a basic level.

Its important for more people to learn about the frontier in as many ways as possible, as often as they can.

I'm surprised to hear someone of his intellectual caliber resort to ridicule when someone brings up UFOs. UFOs "appearing" to "cranks and weirdos" doesn't really describe the phenomena, as anyone who spent more than 30 minutes on the subject would know.

I'd would have loved to have heard him debate the late John Mack (Harvard Medical School, won a Pulitzer) on the subject. It's incredibly arrogant for him to think that he can ignore the research of other academics (or remain in ignorance of it) and still speak authoritatively on the subject.

I don't expect him to champion the field but since he's asked so frequently about extraterrestrial life and/or UFOs it would be nice if his canned response was a bit more intelligent.

It's incredible to dismiss so much theoretical/speculative physics in the interview and at the same time say that maybe M-Theory will tie up the loose ends in the Standard Model, but then again, maybe it won't and we'll be back to the drawing board. Even though we admittedly don't understand the universe with any degrees of completeness, obviously these popular ideas are false based on our understanding of the universe?

  > doesn't really describe the phenomena, as anyone who
  > spent more than 30 minutes on the subject would know.

It actually does.

There are plenty of credible witnesses to UFO sightings. The problem is people getting their knickers in a twist over the acronym 'UFO' - a product of societal conditioning.

Here's an idea that's been kicking around in my mind for a while: what if it's not that it takes such a tremendous amount of time to travel anywhere interesting in the universe, but that our perception of time is just too fast? Perhaps to an alien race a thousand (or million) years seems like a second. Wikipedia suggests that our perception of time does get (slightly) slower as we age [1], so maybe living significantly longer could do this to us as well. Finally, it seems that our perception of time is largely shaped by the Circadian rhythm; if life evolved somewhere with a much slower "cosmic clock" could that also cause a much slower time perception?

[1]: http://en.wikipedia.org/wiki/Time_perception#Long-term

While our perception of time night be subjective, as you suggest, the distances involved are not. Even if it only feels like a few moments, the universe doesn't much care how we feel, or what we perceive.

Well, yes, obviously, but it would certainly affect how we (read: aliens) approach space travel psychologically, and thus to a certain extent its feasibility - a trip across the solar system could seem like a trip across the street.

Everyone interested in the possibility of alien intelligence should read about the Fermi Paradox: http://en.wikipedia.org/wiki/Fermi_paradox

It is a collection of theories that try to explain why we haven't been contacted yet by aliens.

There is also a very good book on the subject that elaborates further on the theories of the Fermi paradox. In total there are 50 different theories, from life been too young on the universe and thus we're rather alone, to not be able to communicate because they're using superior technology. http://www.amazon.com/Universe-Aliens-Everybody-Solutions-Ex...

> I have experimental evidence that time travel is not possible. I gave a party for time-travelers, but I didn't send out the invitations until after the party. I sat there a long time, but no one came.

Why would one need to send invitations if the outcome is already known once the party is over? It seems that merely giving a party for time-travelers is a plenty sufficient evidence.

> Another frightening possibility is intelligent life is not only common, but that it destroys itself when it reaches a stage of advanced technology.

Or that it transcends beyond physical 3D realm (as corny as it sounds) and so it's no longer detectable from within it.

> Why would one need to send invitations if the outcome is already known once the party is over?

Well, if you didn't invite anyone, maybe the reason no time-travellers came is that they weren't invited?

Is it possible that in another universe, time travel is possible and Steven Hawking had the most awesome party imaginable?

Lets be honest, there's obviously other intelligent life in the universe. There's probably tons of it, I don't think it's ever visited earth before, and we'll likely never shake its hand, but its out there. One day we can hopefully communicate with one, it would have to be done with radio signals over generations, but it would be amazing to see it happen.

I've always thought it more likely than the fact that intelligent civilizations destroy themselves is the fact that intelligent civilizations are out there and the really smart ones actually know the Earth exists. Interstellar distance is likely a problem that no one has truly solved but I like to think there's civilization out there that knows the Earth exists and is ripe for life, just they're too far away to do anything about it.

Obviously? Like I go outside and there it is— obvious non-terrestrial intelligent life? For me it obviously does not exist. It may exist somewhere in the galaxy far away. It might not. We don't know. We will never (by never I mean ~1 billion years) know. I am amazed to see so much wishful thinking and ignorance regarding physics and astrophysics.

This comment seriously made me laugh out loud:

Maybe they like a higher CO2 level and warmer temperatures, and are masquerading as energy company executives. Alienforming a planet is easy if you can get the natives to do it for you.

We will NEVER be visited by extra terrestrial life. The amount of luck required is too great. It's extremely unrealistic and foolish.

1) We need to come to the realization that it is and always will be impossible to travel at the speed of light or anywhere near the speed of light. Doing so would cause radiation particles, micro particles, space dust, and other little things floating around to hit the the crew and ship at extreme speeds and rip the ship apart. A bullet fired from a high powered rifle is only going 1,200 mph and can rip through metal. So imaging your space ship getting pummeled by particles at 670,616,629 mph and the faster you go the more particles you got bombarded with. There are no metals or materials that can sustain this type of damage because these radiation particles are SMALLER than x-ray particles so they'll pass through absolutely everything. And nothing can filter out or block this astronomical amount of radiation that will pummel the crew. We can wish and hope but it's a problem that is out of our control.

2) We need to stop falsely and foolishing assuming that there are aliens far out in the universe that can see us (2012) through a telescope. If you look at the earth right now (2012) from 65 million light years away, to the extra terrestrial, they are just now seeing light from 65 million years ago reach them. So to them there is no intelligent life on earth yet. It won't be another 65 million years until they are finally able to see us humans. By that time WE or THEY will be extinct. Because WE have the same problems THEY have. The vast majority of planets or uninhabitable and we can't travel fast enough to reach a planet, nor evolve or adapt to the bacteria on that planet fast enough to actually live on it.

3) We will most certainly never be able to "move homes" to another planet because the bacteria and organisms on it would be hostile to the point where we can't even safely evolve around it. We can live on Earth because for millions of years our ancesters have built up immunities to all the nasty viruses and plagues and flus that have come and gone. If an extra terrestrial landed here on earth they would not be able to interact with us in ANY way without wearing a bio-suit. They can't breathe our air or drink our water. And you think they're going to travel millions of years to get to a planet they can't even vacation on or enjoy or interact with in any way.

4) Extra terrestrial life that is more advanced than us has no reason to go on a suicide mission to come see us (a bunch of war-mongering primitive hairless baboons)

To any potential aliens who are living millions of years away, we haven't even evolved yet. By the time they see us, we will be gone. By the time they travel millions of light years to finally reach us, both of our species will be dead. Us from extinction and them from getting blasted by radiation. Also, if they are more advanced than us why the hell would they want to come all this way to see us?! That would be like us traveling millions of years on a suicide mission to go see a planet of lemurs.

Most of your points are sound, but I think you are too pessimistic about them being interested in us. Mightn't they be just as desperate as we are to not be alone?

exactly.

> Extra terrestrial life that is more advanced than us has no reason to go on a suicide mission to come see us (a bunch of war-mongering primitive hairless baboons)

Just as advanced western scientists have no interest in going on biology field trips to remote parts of the world to study lesser species.

Traveling on your own planet (which is easy and cheap) and traveling to an unknown planet in space which costs trillions of dollars and takes a minimum of 20,000 years are two very different things. Lets keep things in perspective now.

Traveling a few hundred miles to see a creature you can stand a few feet away from, touch, and study /AND/ traveling for millions of years, never seeing the fruit of your labor so that your great X 1,000 grandchildren might be able to reach a planet they can walk around on in an air tight suit for the rest of their lives, then send a signal back to earth which will take 20 years to reach. That's a whole new "field trip".

Where are you getting this stupid 20,000 year figure from? Even with current tech, we can travel at 0.1c easily, that is without any extra effort made in actually travelling outside our solar system. Near-by candidates are within 20ly, so at min it would take just 200 year, or 3 human generations.

And if it might give you some peace, there are thing called machines that can be built to contact other civilization without sacrificing your hypothetical children.

  > we can travel at 0.1c easily

Can we? I mean as humans, not just some spacecraft. We can also sustain closed ecosystem for three generations? Last I heard an attempt to do that on Earth failed.

> We can also sustain closed ecosystem for three generations? Last I heard an attempt to do that on Earth failed.

Most things fail before they succeed.

I'd love to know how we can "easily" get a spaceship up to 0.1c using "existing" technology.

[NB I wouldn't consider the Project Orion approach "existing" technology, it hardly got off the drawing board and was never tested with anything other than chemical explosives on a very small scale].

If you felt alone, would you risk your life savings, and life to go visit a chimpanzee in a war torn, unstable, volatile 3rd world country whose jungle contains malaria carrying mosquitoes, has a life expectancy of 23 years, and gives you a high chance of being raped, killed, or infected with incurable disease?

Maybe. Depends on what kind of protection my life savings can get me, and whether I have anything else to do. :)

We have found planets that may support life 20 light years away. Recent evidence suggests that most stars around us have planets and a significant percentage of those stars have planets that may support life. It's just that resolving a planet at those distances is hard, let alone radio traffic. So while we have little chance of contacting life 1 million light years from us there is a chance intelligent life with technological civilizations could be within as little as 50 light years of us. And even if they exist we would probably have not noticed them yet.

We might never have physical contact with civilizations a 100 light years from us we could have meaningful if high latency conversations with them at reasonable costs.

PS: It's hard to talk with Voyager 1 a mere (1.8x10^10 km) from us at 50 light years the signal would be 1/700,000,000th the strength. So, the only way your talking out to that distance is with a dish that's pointed in the right direction and even then if the signal was not 1 million times as strong there is no way in hell we would notice it.

20 light years is still 20,000 years of traveling in space even after taking into account that technology and speed will improve over time by about 90%-100%.

Who and what government would go on a suicidal safari to another planet which "MIGHT" support life which will take trillions and trillions of dollars, and 20,000 years to reach? First it may not be possible to have children in space even with artificial gravity. Second, the radiation would kill the child before he can even speak his first word.

Even if through a magical genie we solved these problems and avoided cancer... Would you feel comfortable living on a space ship for the rest of your life? Bringing children into this world knowing they'll never have a normal life like back on earth. Sacrificing not only your life but the lives of thousands of your 1,000+ generation grandchildren so you can go explore a planet that you think "might" have life.

Assuming we end-up with reasonably efficient fusion power and an even mildly space based economy we are eventually going to start mining the ort cloud. Which set's up a natural path to vary slowly expand into the stars.

Basically, if it's profitable you get exponential growth till it's not and even slow exponential growth ends up with ridiculous growth numbers fairly quickly on a geological timescale let alone a galactic one.

Just remember that "normal life like back on earth" sucks balls for most of the people on earth. If there was a ship on the pad, there would be a line around the block that made "American Idol" auditions look like a small, intimate gathering.

All your points are based on limitations particular to human understanding of physics and technology.

Just as a microwave oven is practically magic to a caveman, it is reasonable to assume that our tech is caveman-tech to an advanced alien race.

Why travel at the speed of light, for example? Maybe wormholes or teleportation is possible?

Magical concepts from science fiction, sorry theoretical concepts from educated guesses based on current (incomplete, unproven, un-seen) understandings of the universe. If such things existed intelligent life would have used them to reach us.

Maybe they wouldn't be interested in us. Certainly there are some people here on this Earth that I wouldn't want to meet (for instance some of my relatives).

"If such things existed intelligent life would have used them to reach us."

For what reason would we be a magnet for everything out there to have to come visit us (the assumption being that if they don't visit us it can't be possible because we are somehow too important to ignore)? It's a rather flawed basis for an argument.

Our communications out don't speed up getting to them because their ability to get to us has. There is no reason to assume anyone knows we exist yet.

The assumption is if you have a FTL civilization you vary quickly grow to the point where you go just abut everywhere you can reach with FTL travel, unless something else was already there to defend it. Extinction becomes really hard when individuals are being sent out faster than just about anything that could catch them.

I fail to distinguish your magical concepts from sufficiently advanced technology.

They have may be a very correct prediction that we are a parasite-like race in terms of spiritual advancement and do not live in harmony with our provided environment, and thus, it is best to not touch us till we learn to not kill everything we touch for our own pleasure.

There may be many reasons why an alien race does not automatically make contact, some of which are actually unknown to us. If you have difficulty swallowing the "some things can be unknown to us" thought, believe it or not, you have an ego problem.

> these radiation particles are SMALLER than x-ray particles

This indicates you might not understand enough physics to be able to back up your assertions. Firstly, X-rays are in the same category as "radiation particles" (I assume you are referring to electromagnetic radiation). Secondly, radiation "particles" are photons and they don't strictly have a size; they do, however, have a wavelength, which might be what you are alluding to?

(And lastly, if particles "pass through absolutely everything", they do no damage and so aren't problematic.)

> If an extra terrestrial landed here on earth they would not be able to interact with us in ANY way without wearing a bio-suit. They can't breathe our air or drink our water. And you think they're going to travel millions of years to get to a planet they can't even vacation on or enjoy or interact with in any way.

They can vacation on it and enjoy it by wearing a biosuit. And this isn't unreasonable: humans can't breathe water, but we still can enjoy it using a biosuit (SCUBA equipment).

they do, however, have a wavelength, which might be what you are alluding to

Yes, thank you for correcting me. Cosmic radiation comes in all sorts of varieties from the very powerful (that passes through nearly everything to the less powerful. From my very basic knowledge of x-rays, they can pass through or stay in the body. Then can also affect tissue they pass through which is why too many x-rays are bad.

"humans can't breathe water, but we still can enjoy it using a biosuit (SCUBA equipment)"

True. But how would you like for you and your entire family and ALL subsequent generations had to live either indoors or in a scuba suit for the rest of your lives?

Also while in space, as cosmic radiation passes through an astronauts eyes and brain they see flashes of light. Even with their eyes closed. Going at light speed would mean an almost constant white out. This is despite shielding space shuttles from radiation as much as possible.

I love absolutist comments like this. Never is a very very long time. Its possible we already were visited and they've moved on. What most folks don't conceptualize well is that the width of the timeline which constitutes "humans are here" is so damn small on a 4 billion year timeline as to be hard to spot with the naked eye :-).

But lets look at your points: 1) You don't have a good grasp of physics but that's ok. One of the things that happens as you accelerate is that you gp through something called time dilation. Travelling a significant fractions of the speed of light will have time passing much much more slowly on the ship than on Earth. You'll want to work it out so that you approach 'c' at the halfway point, then flip over and decelerate. If you do it that way your crew will easily survive the entire trip. There is the question of energy and reaction mass, real problems and as yet unsolved, but not insoluble. We can and do regularly manufacture anti-matter these days, its a pretty good fuel.

2) You make a number of interesting assumptions here. One is that aliens are 65 million miles away. Consider that we already know that our planet is a death trap, its killed off everything several times already, so we figure out how to leave. Better we create our own environments where all we need do is scoop up interstellar hydrogen for fuel, or perhaps harvest a bit of space junk. The Earth is a spaceship that is gravity locked to the Sun. There is certainly enough material in our solar system to build something that could wander amongst the stars. And if we've figured out cellular biology, and can thus 'fix' any issues that come up, it means we can 'live' in our bodies forever via mechanical repair. If we can do it, so can other species. Imagine a flotilla of 'units' moving in parallel, carrying our alien visitors, from star system to star system. Perhaps seeing a new system every 100 years or so.

3) We can certainly create habitats that don't kill us and that keep things that might kill us out. Further there is a really really interesting change coming when pieces of how people work comes together in a provable way. One good thing, the health care crisis for 'rich' people will be gone. Once we've got the source code, all bets are off.

4) This is just projection ;-) We would go visit a society that was in its early stages of development just to see how they do it. We've been doing that with indigenous island people on the planet, I would be surprised if we had interplanetary capability and we didn't do that.

Upvoted for your futile human attempts :P. I still disagree with your rebuttal. Yes, I did use an absolution word like "NEVER". But only because we have a limited time on earth before another massive extinction event occurs and realistically solving all the problems with space travel at light speed have such a tiny percentage of being solved that you might as well say its impossible for the sake of being realistic.

Lets look at your rebuttal:

1) Time dilation doesn't solve ANY of the impossibilities of traveling at light speed. Even the Earth, with its massive atmospheric force field and magnetic field only travels at 67,000 mph and still gets pummeled with meteors, natural space debris, and massive amounts of radiation that, despite being filtered out by a magnetic field thousands of miles thick, still delivers radiation. A tiny particle the size of a ballpoint from a ballpoint pen is nothing to fear, but when that particle is hits anything at light speed it is deadly. If there is 1 piece of space debris every 1 mile in space and you're traveling at light speed, the ship, no matter what it's made of is going to disintegrate when it gets hit with 11.1 million pieces of debris every minute. At that speed nothing can be deflected by shields all objects will disintegrate and rip the ship and crew apart.

Back to radiation: With 2 hydrogen atoms per cubic centimeter in space, at light speed the radiation exposure increases 100,000% PAST THE LETHAL LIMIT for humans. We would die of radiation exposure immediately. It would also destroy electronics on board. And NO, building an artificial force field is not going to work either. At light speed it will be useless. Also no force field of any kind will work or be able to work at such a high speed.

2) Still doesn't solve the unfilterable radiation problem, space debris problem, emotional toll, and cost. Granted things WILL improve in the future. They usually do. The problem is, we're both assuming that we will still be around long enough to figure this stuff out. Yes, we humans are smart and resilient but we live in an opportunist world where the longer any species stays alive (humans) the more counter-species (viruses/plague/bacteria) evolve to feed off of and kill the former species. We've extended our stay for quiet a while and are just now starting to feel our eventual fate with the rise of super viruses, antibiotic resistant bacteria, and super flus. And it will only get worse. As we evolve our microsized enemies do too. Lets not forget we're also self destructive.

3) Agreed, we could create habitats that don't kill us but this is assuming we actually reach another planet. Which just isn't going to happen.

4) We would go visit a society that was in its early stages of development just to see how they do it. At the cost of trillions of dollars and the lives of thousands, possibly millions of people over the course of thousands or millions of years. I don't think so.

I fully agree with you. While all of this is possible in theory, there are so many things that could go wrong, and one single mission would cost trillions.

Only if there is some extraordinary law(s) of physics that would open up entirely new methods of travel (and so many other things) would any of this be possible.

I still would like to spend a big chunk of my tax dollars on NASA, etc, but the idea that there is intelligent life out there, and it is likely that we are going to contact it, seems like nonsense to me.

I'd love it if we did, but I just don't think it's going to happen. And that's ok. Some people really seem to have an emotional horse in this game, I'm not sure why.

"Some people really seem to have an emotional horse in this game, I'm not sure why."

I think it's because no one likes being told what their limits are. And when faced with certain inevitable death humans will fantasize their way out of it to make themselves feel better. Even if it's illogical or obviously impossible. (ex: "When I die, I'm going to go to a magical place in the sky where there is no suffering, no pain, no death, no bad things, and I will have everything I want, and I will be happy and live there with all my friends and family forever." - Human fantasizing about "heaven"). And there's nothing wrong with that. We're only alive for so long, might as well spend that time being happy. It just sucks when people bring fantasy desires into scientific reality.

A MAJOR point I forgot to mention in my original post. If planets and suns existed forever then yes we might be able to work something out, even if we're not traveling at light speed. But the delays, distances, and time limits involved are what make all of this near impossible. We only have a few billion years before our sun starts entering into its red giant phase and burns away our home. A few thousand before another extinction event, and possibly few thousand before getting hit by a massive meteor. Whatever planet we find looking through a telescope will have its own time limits, it's own problems that we won't know about until its delayed and outdated light finally hits us. It's the delays, it's the distance, it's the time limits. Everything has to fall into place so well. And with no planet known 100% to sustain life, everything is a gamble with insanely impossible chances to win.

The distances are so massive in space, the time delay between sending a message just light years away and getting it back makes the gamble worse. Imagine starting a voyage and midway finding out the planet has been destroyed or has entered a massive extinction phase that will escalate when we get there. Or finding out the planet is no longer inhabitable. Lets not forget our own Earth has entered periods where it was one massive boiling ocean, one big icicle, a bunch of lava. Granted we've moved away from those periods towards stability. But what if the planet we're heading towards destabilizes while we're on our way there?

Most people are visualizing space by what they've seen in star trek or star wars. With percentages of failure and death completely missing from their mental image of what it truly means to travel in space. People see it as a game of patience. When it's really a game of 'ALL of the odds are stacked against you and continue to stack against you the longer you stay out there'.

The more I think about this the more I realize how really lucky we are being on Earth. Really really lucky.

Perhaps you lack imagination. The first argument has been addressed by many, and in an interesting way by Alastair Reynolds in his Revelation Universe.

Ships apply 1G of acceleration for many years and thus slowly reach speeds close to that of light. The ships are both "aerodynamic" and encased in a thick layer of ice, so that small, rare impacts are survivable. This becomes a plot mechanism in a few of his stories.

"Perhaps you lack imagination."

Possible, but I doubt it. http://www.chrisnorstrom.com

Ice won't do anything about the radiation. At that speed aerodynamic doesn't matter either. Nice try human ;P

I didn't imply you lack imagination in general, just imagination on this particular subject.

Radiation is a separate matter. That speed is precisely where aerodynamics start to matter again, as you hit stray particles. You want your profile to be as narrow as possible, so you're hitting as few particles as possible.

Ice helps absorb the impact of such particles.

Note that Alastair Reynolds is an astronomer, so he did think this bit through somewhat.

While radiation is a serious problem at relativistic velocities, you're a bit too pessimistic:

The most immediate problem is the interstellar gas, which becomes hard radiation at relativistic velocities. However, ~2cm of aluminium shielding are enough to reach 0.3c, and with 1m of water, you can reach 0.5c.

For higher velocities, magnetic shielding coupled with a metallic electron stripper is probably a more pragmatic solution.

My favorite part: And you think they're going to travel millions of years to get to a planet they can't even vacation on or enjoy...

I'd say that the chances of us ever coming into contact with intelligent life are worryingly low until well (as in, billions of years) into the future. If we say that "ultimate maturity" of a civilization is to have a technological singularity of some sort, resources wouldn't really be an issue. SETI hasn't picked up anything. Assuming that the universe is infinite in extent, as it currently is hypothesized to be, the only real solution is that life is so spread out as to be almost irrelevantly far away.

We don't have billions of years. We maybe have one billion.

Pithy.

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