Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: Herra Tohtori on December 05, 2011, 04:33:27 pm
-
http://www.bbc.co.uk/news/science-environment-16040655 (http://www.bbc.co.uk/news/science-environment-16040655)
AAAAAAAAAAA
-
Sweet. Gonna book myself some tickets.
-
The question is, what is the mass of this planet. I guess that with 2.4 times the diameter of Earth, G on Kepler 22 b has a lot higher value of G.
-
Why hello Goldilocks.... how you doin'?
-
yay! lets go nuke it!
The question is, what is the mass of this planet. I guess that with 2.4 times the diameter of Earth, G on Kepler 22 b has a lot higher value of G.
depends on its density. if it has a large iron core, forget it. we might be able to land but i dont think were going to be getting out of that gravity well, let alone function well. of course if it has a less dense composition, it could just as easily be close to our gravity. large planet of course means more surface area and better access to resources, so provided gravity is not insane it might be valuable.
-
That's why I' concerned about the G value, this planet is 4,5 times as large as Earth. If it's as dense as the Earth, then it's completely uninhabitable (nobody except fighter pilots is exposed to 4.5G too frequently).
I guess it's mass should be measurable somehow, so I'm eagerly awaiting news on that.
-
I guess it's mass should be measurable somehow, so I'm eagerly awaiting news on that.
Nope. I mean, you could estimate it, but that would require knowing what else is floating around in that system, and where it is. And the mass of the sun in that system. And having equipment sensitive enough to detect their orbits. Not really possible with current equipment for a small target like that.
-
is it currently possible to do spectroscopy on exoplanets?
-
Nope. I mean, you could estimate it, but that would require knowing what else is floating around in that system, and where it is. And the mass of the sun in that system. And having equipment sensitive enough to detect their orbits. Not really possible with current equipment for a small target like that.
Well, with current equipment, maybe. But telescopes are getting bigger and more precise. I hope we'll have a rough idea of it's G in the near future.
Anyway, we should have the technology to know it's mass well before somebody thinks of sending a Sleeper Ship onto it. :)
In general, it's an interesting discovery. It could be especially valuable to our search for extraterrestrial life forms. 600LY is relatively close, maybe close enough for detecting possible emissions from them, or for them to detect ours. But we'll see about that in 1200 years, because that's how long we'll wait for any possible answer to our signals.
is it currently possible to do spectroscopy on exoplanets?
It won't do much good here, I don't think you can look inside the planet using it.
-
These things are such cockteases. I mean, it's awesome that we're finding them, but then you think about the fact that we won't be able to get even a closer look at them, much less go to them, for a very long time. :(
-
is it currently possible to do spectroscopy on exoplanets?
It won't do much good here, I don't think you can look inside the planet using it.
granted it would only be a surface scan. but you could tell if the planet had a thick atmosphere, or a solid surface, or water. it wont give you an accurate picture of the planets density though.
-
Space thread, paging FlamingCobra.
(http://farm3.static.flickr.com/2208/5722888296_45a1e3f7c2.jpg)
-
Well.
The only way to determine a planet's mass is to look at the effect it has on the central star. Planet and star both orbit the same centre of gravity, so the heavier the planet, the more the star is displaced from its exact centre.
If the planet is massive enough, and its orbital period short enough, that can give the central star's light a detectable doppler shift variation as the star's radial velocity cyclically changes in conjunction with the planet's orbital period. If - and only if - you have accurate enough spectrometre to detect this shift of spectral lines, then you can determine the mass of the planet (within error bars of course).
If the planet doesn't cause detectable weave in the star's velocity, that gives use a crude upper limit for the planet's mass: Below observation threshold.
The problem here is that the planet is quite far from the star so orbital period is rather long, which reduces the radial velocity changes (and their frequency), and the planet is also likely quite small, which further reduces the amplitude of the velocity change.
I'm afraid we don't have sufficiently accurate means of observation to detect the mass of such a small orbiting body.
Of course, if we simply bruteforce our way through a few generations of telescope sizes, and the planet happens to have a moon of detectable size orbiting it... then it would make determining the mass and therefore surface gravity of the planet much easier and more accurate.
Spectroscopy of the planet itself would be incredibly awesome as it would gives us overall idea of its atmospheric composition, and even possible surface composition if you get lucky.
-
In general, it's an interesting discovery. It could be especially valuable to our search for extraterrestrial life forms. 600LY is relatively close, maybe close enough for detecting possible emissions from them, or for them to detect ours. But we'll see about that in 1200 years, because that's how long we'll wait for any possible answer to our signals.
Wrong. You are suffering from the same misconceptions that the original SETI people suffered from. Let me explain.
When SETI was founded, people thought that we would be pumping out as many radio emmissions or more than we did at the time. Remember, back then, there were lots of very very big radar installations, and TV and radio stations had to broadcast with high energy levels to be receivable.
However, if anything, the amount of RF energy generated by our civilization has dropped off sharply, given that we've laid a lot of cable, and our emmitters and receivers have become smaller, more efficient over time.
There's a corollary to the famous saying "Sufficiently advanced technology is indistinguishable from magic", called "sufficiently advanced technology is indistiniguishable from nature". Meaning that as our technology matures, it will get more eficient, less disturbing, and thus less detectable, especially over distances of several light years. If we take our technological development as an example, there's about a 100 to 200 year window where we put out enough energy to be visible over interstellar distances. Before and after that window, there simply isn't anything you really can detect from space.
This means that the chances of catching a civilization in that developmental stage are astronomically low, and establishing two-way communications is practically impossible.
Oh, and of course that is all predicated on having an alien species that follows the same path of technological discovery we did.
-
The surface gravity of a planet is given by g=GM/r2. For Earth, that's (6.67x10-8erg*cm*g-2(5.97x1027g)/(6.37x108cm), which gives us 981cm/s2.
We don't know the mass of Kepler 22 b, though we could find out by using the Radial Velocity method (http://en.wikipedia.org/wiki/Radial_velocity). However, if we assume that the planet is composed of roughly the same materials as Earth, and thus has a similar average mass density ρ as Earth (5.51g/cm3), then its mass is just ρ*4/3*п*(2.4RE)3 = 8.25x1028g, or about 13.8x more massive than Earth.
Then the surface gravity of Kepler 22 b would be (G*ρ*4/3*п*(2.4RE)3)/(2.4RE)2. The (2.4RE)2 downstairs cancels two of the same upstairs, and we get a result of ~2353cm/s2, or about 2.4 Earth gravity. Wait, holy ****, was that a coincidence that it scaled exactly with the planet radius? Let's see... duh, of course! Replace ME with volume times density, and everything but the 2.4 cancels out. So it turns out the surface gravity of a planet scales exactly with the planet radius, if the average mass density is held constant. You learn something new every day. :)
-
Then the surface gravity of Kepler 22 b would be (G*ρ*4/3*п*(2.4RE)3)/(2.4RE)2. The (2.4RE)2 downstairs cancels two of the same upstairs, and we get a result of ~2353cm/s2, or about 2.4 Earth gravity. Wait, holy ****, was that a coincidence that it scaled exactly with the planet radius? Let's see... duh, of course! Replace ME with volume times density, and everything but the 2.4 cancels out. So it turns out the surface gravity of a planet scales exactly with the planet radius, if the average mass density is held constant. You learn something new every day. :)
The gravitational effects of a sphere, outside the sphere's surface radius, are identical to that of a singularity positioned at the sphere's centre.
So, yes, if you increase radius by a factor of k, mass increases by a factor of k3, and effect of gravity is inversely proportional to square of radius... you end up with
g1 = GM / r2
g2 = G k3M / (kr)2 = G k3M / k2 r2 = k3/k2 * GM / r2
g2 = k * g1
QED.
Of course, if density is not the same as Earth's, we get deviation from this equation. Which is what needs to be determined.
I just have to say, I'm incredibly thankful this thing is not orbiting a gas giant. Would be too close to Pandora for comfort.
I would not be opposed to finding out the planet is inhabited by blue aliens, though. I'd be ok with that.
-
In general, it's an interesting discovery. It could be especially valuable to our search for extraterrestrial life forms. 600LY is relatively close, maybe close enough for detecting possible emissions from them, or for them to detect ours. But we'll see about that in 1200 years, because that's how long we'll wait for any possible answer to our signals.
Wrong. You are suffering from the same misconceptions that the original SETI people suffered from. Let me explain.
When SETI was founded, people thought that we would be pumping out as many radio emmissions or more than we did at the time. Remember, back then, there were lots of very very big radar installations, and TV and radio stations had to broadcast with high energy levels to be receivable.
However, if anything, the amount of RF energy generated by our civilization has dropped off sharply, given that we've laid a lot of cable, and our emmitters and receivers have become smaller, more efficient over time.
There's a corollary to the famous saying "Sufficiently advanced technology is indistinguishable from magic", called "sufficiently advanced technology is indistiniguishable from nature". Meaning that as our technology matures, it will get more eficient, less disturbing, and thus less detectable, especially over distances of several light years. If we take our technological development as an example, there's about a 100 to 200 year window where we put out enough energy to be visible over interstellar distances. Before and after that window, there simply isn't anything you really can detect from space.
This means that the chances of catching a civilization in that developmental stage are astronomically low, and establishing two-way communications is practically impossible.
Oh, and of course that is all predicated on having an alien species that follows the same path of technological discovery we did.
Correct insofar as the odds of both of us detecting one another's stray emissions are insignificant. However, if they're past the point where they're putting out stray emissions, they could still detect ours in another 600 years--and then they could choose to respond with a powerful radio signal* if they wanted to.
*or relativistic weapon
-
Gah! Its 600 Light Years away! But I'm renaming it Alpha Pacifica.
It almost seems that Gliese 581 disappeared from the headlines that system seemed the most promising since it was only 20 light years away. It had four to six planets around a Red Dwarf Star.
-
981cm
Why?
I'm also proud to say I understand what you did there. Thank you physics course. :)
-
Because **** decimals.
-
981cm
Why?
I'm also proud to say I understand what you did there. Thank you physics course. :)
Sorry, astrophysics prefers CGS units for some reason. It's terrible. D:
-
Because **** decimals.
behold the glory of integer maths!!! need more precision? use a smaller unit of measure!
-
....or, you know, exponents of ten tend to do the job too.
Like SI-prefixes.
-
Space thread, paging FlamingCobra.
-snip-
sorry. couldn't stay away.
Gah! Its 600 Light Years away! But I'm renaming it Alpha Pacifica.
It almost seems that Gliese 581 disappeared from the headlines. That system seemed the most promising since it was only 20 light years away. It had four to six planets around a Red Dwarf Star.
I've heard about that star. Not only that, but some of the "predicted planets" could have fallen in the goldilocks zone. I think the problem is we can't be sure whether or not all of the predicted planets exist.
On the subject of Keppler 22b, the NASA article doesn't actually say there is water on the planet. It merely says water could exist. I find this odd, as we have detected water vapor in the atmosphere of extrasolar planets before.
-
Right now, we don't even know whether that planet has an atmosphere. In order to find out, we need get spectogram of the thing, which as of right now we don't have.
See also: http://blogs.discovermagazine.com/badastronomy/2011/12/05/kepler-confirms-first-planet-found-in-the-habitable-zone-of-a-sun-like-star/#more-41652
-
I've heard about that star. Not only that, but some of the "predicted planets" could have fallen in the goldilocks zone. I think the problem is we can't be sure whether or not all of the predicted planets exist.
Predicted planets?
-
Damn, and I thought we were finally making good headway in finding an Earth-like planet that we can live on.
-
An Earth-like planet that we can live on. Yeah, right. First of all, we are getting better at finding exoplanets. Second, "Earth-like planet" covers a range from Venus to Mars in our solar system alone, neither of which are habitable.
Third, even if we find them, we can't get to them. The closest exoplanet we've found, Gliese 581c, is 22 light years from us, and we have no way at all to build a colony vessel that could get a group of canned monkeys there safely.
-
And 100 years ago we had no way at all to build a vessel to get a group of monkeys to the moon safety. Your pessimism is uncharacteristic and (while injecting some measure of realism into the discussion) ultimately non-constructive. Hardly like your normal posts at all.
-
An Earth-like planet that we can live on. Yeah, right. First of all, we are getting better at finding exoplanets. Second, "Earth-like planet" covers a range from Venus to Mars in our solar system alone, neither of which are habitable.
Third, even if we find them, we can't get to them. The closest exoplanet we've found, Gliese 581c, is 22 light years from us, and we have no way at all to build a colony vessel that could get a group of canned monkeys there safely.
Pretty much. Right now a manned mission to Mars is deemed a too risky and expensive endeavor, and with the lack of political will / reason to do so we're not even doing that. Going outside our system? Forget about it. Also, let's not forget that the methods of detecting exoplanets most often rely on detecting small footprints these planets leave behind rather than observing them directly. I'm guessing most of the space obsessed forumites know all these, but I'm going to go over the extrasolar planet detection methods just for the sake of argument.
RV (Radial Velocity) method relies on a doppler shift cause by a gravitational effect the orbiting planets have on the host star. This is why this method usually detects hot Jupiters - a big gas giant close to a star will have a larger effect on it's host star.
Gravitational microlensing depends on a target star being exactly in line with us and another star behind it. The star behind the target emits light, which the target star in front of it bends like a lens. Planets in orbit of the target star can have a measurable effect on it.
There's the best known transit method, that just measures the slight variations in magnitudes caused by a planet doing a transit and blocking some if it's star's light.
We even found some planets with direct imaging, but that method works best on huge planets with a very high orbital period. So nothing Earth-like.
There's also the pulsar timing method which was the one that discovered first exoplanets. The theory behind it is simple - you measure the timings of a pulsar and see if there are slight variations that can only be explained by the presence of an exoplanet. Given that this only works with pulsars, it's not in wide use anymore.
At any rate, yes with some methods it is possible to measure a "chemical footprint" a planet or it's atmosphere might have, but since most of the methods rely more on analyzing very subtle tell-tale signatures these planets leave behind rather than directly observing them, we really have no known way of confirming, for sure, that a detected planet would be habitable for us. In most cases, but not all, we can determine the orbital period, size, and whether or not it's in the goldilocks area. But it would kind of suck to send a multi-generational colony ship to a "new home" that turns out to be something like Venus.. Oh well, let's put it in reverse and go home now.
And 100 years ago we had no way at all to build a vessel to get a group of monkeys to the moon safety. Your pessimism is uncharacteristic and (while injecting some measure of realism into the discussion) ultimately non-constructive. Hardly like your normal posts at all.
You're making two mistakes here. The first is assuming that the challenge of colonizing an extrasolar planet is something even comparable to sending a few astronauts to the Moon to collect rocks. It's not. The task is exponentially more difficult by a margin large enough to make it completely non-feasible now or in any near foreseeable future. Unless we discover something that causes a sudden boom in technological development the likes of which we've never seen before, you can forget this happening any time soon. If you see man on Mars in your lifetime, consider yourself lucky.
The second mistake is confusing this with pessimism. If I understood E correctly, he's not saying it will never be possible. He just acknowledged it's very far away. Pretending it's not wouldn't be optimism, it would be having completely unrealistic expectations induced by not really understanding just how exponentially more difficult said task is compared to the Moon landing, or any endeavor mankind has made so far. To colonize an extrasolar planet, you need two things at the very least. One is detecting with any degree of certainty that a planet is indeed colonisable. The other is getting there. You can't do either yet.
Now, our extrasolar detection methods are advancing all the time and I wouldn't be surprised we'll be able to tell an incredible amount of things about a planet 20 years from now. But that still leaves you with two problems. One is, the statistical chances of finding a planet with atmo close enough to ours so we can breathe on it are rather slim. Meaning either learning how to terraform, or living in pressurized, sealed environments. Something I'd be reluctant to commiting on a life long basis to, myself. The other is, you still can't get there. And won't be able to for a long time. How long is long, I'd prefer not to speculate. But expecting manned extrasolar travel in this century is something I'd call unrealistic at best.
-
And 100 years ago we had no way at all to build a vessel to get a group of monkeys to the moon safety. Your pessimism is uncharacteristic and (while injecting some measure of realism into the discussion) ultimately non-constructive. Hardly like your normal posts at all.
going to the moon was merely a cold war penis measuring contest. cold wars are good for space exploration. we need another one. we need to go glass those damn gliesians, and now we got keplernians to deal with too. we better get our **** together and nuke them or they will be invading us.
im curious of how feasable it would be to (eventually) construct a large railgun out in the outer solar system (like on pluto) with the sole purpose of firing small probes at near relativistic speeds at exoplanets and then have them send back telemetry about the solar systems it passes through. if you know enough about the target solar system you could probably get that probe to fly fairly close to the potentially habitable exoplanet. the biggest problem with this would actually be transmitting the data back to earth (maybe a quantum entanglement transmitter) where radio signals and lasers would attenuate greatly after a couple of light years. we know how to build railguns and we know how to get to pluto. this is one of those maybe in the next several hundred years kinda ideas.
-
just make sure the probe moving at near relativistic speeds doesn't hit the target planet, we don't want to start an interstellar war.
-
And 100 years ago we had no way at all to build a vessel to get a group of monkeys to the moon safety. Your pessimism is uncharacteristic and (while injecting some measure of realism into the discussion) ultimately non-constructive. Hardly like your normal posts at all.
Okay, let's see. Let us assume that we find a habitable planet (habitable in this case being defined as a planet within the habitable zone of a stable star, with a confirmed nitrogen-oxygen atmosphere, and a surface gravity around that of Earth) in a system 100 light years away.
Let us further assume that c remains as the absolute speed limit, and that the laws of thermodynamics will remain valid.
Finally, we will assume a willingness to launch a colonization effort on behalf of humanity.
Here are the challenges we need to overcome:
1. Build a vessel sturdy and fast enough to get to our target.
2. This vessel needs to carry a crew complement large enough to give birth to a new variant of human civilization.
3. The crew needs to have a sampling of skills available to cover all eventualities.
4. The vessel needs to be able to essentially provide all the technological capabilities humanity possesses at that point, an agricultural/industrial complex in a box, if you will.
5. The vessel needs to be capable of ensuring the survival of the entire colony seed while in transit.
Let us tackle these points in random order. Starting off with 2 and 3, what would be an appropriate size for our colony seed? Personally, I believe we would be looking at a population figure north of several hundred thousand people. Why? Because, in order to be as disaster-proof as we can make this whole thing, we need to have enough people on board with a diverse enough skillset to, if needed, bootstrap the colony to a tech level where it can flourish on this new world without the toys we brought with us on our vessel. Note that it isn't enough to send along people who can operate the machinery, we want people who can design these things. Then we need people who can teach these skills to others. And people who can run the societal support structure all of the above implies.
Now, we need to look at number 4. Our vessel needs to be equipped with enough tools to do any form of terraforming our newfound planet may require, including having a feedstock of pioneer species to, if necessary, bootstrap a compatible biosphere from scratch. This necessitates advances in biology (especially gene manipulation and cloning) we do not have at the moment. The problem here is that we cannot be certain that there's going to be anything usable at the other end of our trip, so we best pack everything we can to make our new home usable for our purposes.
On to point 5. Obviously, this whole endeavour is pointless if there's a risk that a percentage of our colonists dies en route. Given that we're looking at a transit time of several hundred years, there are two possible approaches. Cryogenic sleep or a generation ship. The first one is as of now an unknown quantity. We do not know how, or even if, we can freeze a human being for a long period of time and wake him or her up again. However, given the other constraints, this is likely to be the most attractive option.
Generation ships run into a different set of problems. One, they require full self-sufficiency in order to feed all our canned monkeys. Two, the society needs to be set up in a way that guarantees that we do not lose essential skills in transit. Three, the society needs to be kept from blowing itself up over some stupid squabble. Four, this society needs to be able to make the transition from shipboard life to planet colonization. All of these require a degree of social engineering we do not have available at the moment.
Now, all of the above has implications on point 1. We need a vessel capable of transporting all of the above, fast enough, and safe enough to do some useful things at the other end. There are a lot of numbers involved here that are appropriately astronomical.
So yes. I am heavily skeptical of extrasolar colonization efforts. Barring the discovery of several magic wands to sidestep these issues, I am firmly convinced that we are not going to see the launch of such an effort in our lifetime. That does not mean it is impossible; just highly unlikely.
-
im curious of how feasable it would be to (eventually) construct a large railgun out in the outer solar system (like on pluto) with the sole purpose of firing small probes at near relativistic speeds at exoplanets and then have them send back telemetry about the solar systems it passes through. if you know enough about the target solar system you could probably get that probe to fly fairly close to the potentially habitable exoplanet. the biggest problem with this would actually be transmitting the data back to earth (maybe a quantum entanglement transmitter) where radio signals and lasers would attenuate greatly after a couple of light years. we know how to build railguns and we know how to get to pluto. this is one of those maybe in the next several hundred years kinda ideas.
Don't see much of a reason behind doing this on Pluto. It's a classic case of using Earth-based spacial and distance awareness in space. Which doesn't work. Why? To move from one point to another on Earth, you need to apply constant force to move in most cases, because gravity, friction and drag will do their best to stop you. If you constantly have to transport something to the United States, then Mexico or Canada make for better departure points than Europe. Because they're closer and you need to spend less energy/resources to get there. Yes.
In space, things work differently. You don't need to constantly apply thrust to keep moving. Furthermore, you can use other gravitational sources to augment your speed without spending a drop of additional fuel - if you calculate your trajectory well enough.
Two of the most difficult things to overcome in launching a probe are getting the thing in orbit in the first place, and financing the whole infrastructure needed to do it. Pluto would work great with the first thing, as it has a relatively low surface gravity. It would be pretty horrible with the other since the costs and technical challenges of setting up and maintaining the needed infrastructure would be prohibitively high. And there would be no reason. If you don't want to deal with all that pesky atmo and gravity to achieve orbit in the first place, then a Lunar base would serve much better. You don't need much fuel to achieve orbit, and you can use Earth, the Sun and possibly Jupiter/Saturn as gravitational slingshots for such probes. There's no need for a Pluto base just because Pluto is further away from Earth. Once you get going, you set up your transfer orbits and eventually reach solar escape velocity, it's going. A departure point far away from Earth just needlessly complicates matters. You'd probably end up firing probes back inside the solar system that way so you can use the Sun for gravity assist maneuvers to pick up more speed.
The second problem is that rail guns accelerate mass while it's being fired. Once the mass being fired has cleared the railgun, unless it has it's own propulsion unit, acceleration under it's own power is over and it's at the mercy of gravity. This means that to achieve speeds needed for a suggested space probe system you'd need to fire it at incredible accelerations. The G-forces would probably destroy the probe, or at least it's scientific and comm equipment. Rail guns are a "accelerate stuff very quickly to their max speed" kind of systems. For space probes you really want a slow-burning, fuel efficient system that is capable of producing a large delta-v over longer periods of time. You could, I suppose, have a rail gun assisted launch system on a low grav environment such as the Moon, fire a probe to give it initial speed (at an acceleration rate that doesn't tear it apart), and then do delta V with some sort of an ion drive or something, and using gravitational sources to gain more speed. Whether or not we'll ever do that will depend on how the tech advances and whether or not the cost/benefit ratio will go in it's favor.
-
just make sure the probe moving at near relativistic speeds doesn't hit the target planet, we don't want to start an interstellar war.
Um...
Its Nuke.
-
I keep thinking of Voyager 1. Thirty or so years on, it's still inside the Solar System, and it still needs another 14 millennia to do a single light year...
Yeah, we'll still be stuck here for a very, very long time. :blah:
-
Perhaps that's why the Fermi's paradox exists - members of any existing extraterrestial species know how impossible colonizing the space is, so they simply don't bother.
-
Maybe. But I prefer not to speculate on extraterrestrials that may or may not exist, may or may not have evolved in a way remotely similar to ours, and may or may not have concluded this or that :P
-
just make sure the probe moving at near relativistic speeds doesn't hit the target planet, we don't want to start an interstellar war.
This is actually one of the big problems of first contact with other species--it's impossible to tell whether an incoming relativistic object has hostile intentions or not until it's far too late to do anything about it. And if you guess no and you're wrong, you can say goodbye to every inhabited surface in your solar system.
-
just make sure the probe moving at near relativistic speeds doesn't hit the target planet, we don't want to start an interstellar war.
Just make sure the probe moving at near relativistic speeds DOES hit the target planet, hard enough to wipe out all life. We want to WIN the interstellar war. :arrrr:
-
Ummmmm...... generation ships.
problems:
1. retarded
2. extremely hard to do (self sufficient)
3. won't get there any time soon.
but still possible.
-
im curious of how feasable it would be to (eventually) construct a large railgun out in the outer solar system (like on pluto) with the sole purpose of firing small probes at near relativistic speeds at exoplanets and then have them send back telemetry about the solar systems it passes through. if you know enough about the target solar system you could probably get that probe to fly fairly close to the potentially habitable exoplanet. the biggest problem with this would actually be transmitting the data back to earth (maybe a quantum entanglement transmitter) where radio signals and lasers would attenuate greatly after a couple of light years. we know how to build railguns and we know how to get to pluto. this is one of those maybe in the next several hundred years kinda ideas.
Don't see much of a reason behind doing this on Pluto. It's a classic case of using Earth-based spacial and distance awareness in space. Which doesn't work. Why? To move from one point to another on Earth, you need to apply constant force to move in most cases, because gravity, friction and drag will do their best to stop you. If you constantly have to transport something to the United States, then Mexico or Canada make for better departure points than Europe. Because they're closer and you need to spend less energy/resources to get there. Yes.
In space, things work differently. You don't need to constantly apply thrust to keep moving. Furthermore, you can use other gravitational sources to augment your speed without spending a drop of additional fuel - if you calculate your trajectory well enough.
Two of the most difficult things to overcome in launching a probe are getting the thing in orbit in the first place, and financing the whole infrastructure needed to do it. Pluto would work great with the first thing, as it has a relatively low surface gravity. It would be pretty horrible with the other since the costs and technical challenges of setting up and maintaining the needed infrastructure would be prohibitively high. And there would be no reason. If you don't want to deal with all that pesky atmo and gravity to achieve orbit in the first place, then a Lunar base would serve much better. You don't need much fuel to achieve orbit, and you can use Earth, the Sun and possibly Jupiter/Saturn as gravitational slingshots for such probes. There's no need for a Pluto base just because Pluto is further away from Earth. Once you get going, you set up your transfer orbits and eventually reach solar escape velocity, it's going. A departure point far away from Earth just needlessly complicates matters. You'd probably end up firing probes back inside the solar system that way so you can use the Sun for gravity assist maneuvers to pick up more speed.
The second problem is that rail guns accelerate mass while it's being fired. Once the mass being fired has cleared the railgun, unless it has it's own propulsion unit, acceleration under it's own power is over and it's at the mercy of gravity. This means that to achieve speeds needed for a suggested space probe system you'd need to fire it at incredible accelerations. The G-forces would probably destroy the probe, or at least it's scientific and comm equipment. Rail guns are a "accelerate stuff very quickly to their max speed" kind of systems. For space probes you really want a slow-burning, fuel efficient system that is capable of producing a large delta-v over longer periods of time. You could, I suppose, have a rail gun assisted launch system on a low grav environment such as the Moon, fire a probe to give it initial speed (at an acceleration rate that doesn't tear it apart), and then do delta V with some sort of an ion drive or something, and using gravitational sources to gain more speed. Whether or not we'll ever do that will depend on how the tech advances and whether or not the cost/benefit ratio will go in it's favor.
first off you dont need to tell me how space works. dont worry about launching it (this will require existing in-space infrastructure), that would be impossible because it would need to be a very large railgun to get a massive object to near relativistic speeds and would probably need a 10th generation nuke reactor to power it. theres math to figure out how big the railgun would need to be and how much power it would need, but i dont want to look it up and do it. i figure to hit such a distant target would need to have very accurate aim, and that entails launching from an area of low gravitational influence, where orbital velocities are about as fast as grandma's driving, and losses from the solar system gravity could be minimized. i used pluto as an example but im sure a further out kuiper belt object would be even better. think of it as the sniper shot from hell, you definitely want to control your breathing.
after some thought i very much doubt an object at relativistic speed would stay in anythings gravity well long enough to adversely effect its trajectory. a launch from a railgun on the moon is likely possible and also doesn't preclude the possibility of a gravity assist from jupiter (though that limits potential trajectories somewhat). you still need to compensate for massive objects (stars, large gas giants) in our solar system as well as the target's. also it would be a flyby, save possible aerobreaking/aerocapture manuvers, and the probe's delta-v capabilities would be rather low, making these difficult or impossible.
probe itself would need to be fairly lightweight. things like an engine or some kind of rcs system (using a 2x2 grid of hall effect thrusters pointing down the z axis with them angled outward from the center about either the x or y axis by a few degrees would provide thrust and 3 axis rotational control, by firing the thrusters in pairs) would be for vernier control only, minor course corrections, and orientation control (to align sensors/antennea), it would not need to be powerful or large. probe needs a sensor device, and some kind of transmitter, a computer to run the show, and needs to be powered/heated for most of the trip. im curious if collisions with particles in the interstellar medium would cause significant heating at relativistic speeds to power some kind of heat differential device. like a stirling engine or thermoelectric cell that you might be able to draw power from/keep the spacecraft alive, or perhaps a small rtg with a decent life span. now fit all this into a package the size of a football (american of course), load it in the railgun, and fire at your target. oh and it needs to survive launch too :P
let me reiterate that this would be a very long term plan and has many prerequisites that we haven't even got started on yet, and even then only works for nearby solar systems, at half the speed of light 44 years to gleise and another 22 for return telemetry (baring entanglement transmitter), something doable in a human life span. there is also the slow burn mentality where you send out a large probe and have electric engines, reactors, propellant, though it does have the potential to bring more sensor equipment to bear. but a single massive probe sent to a single target i dont think is a very good idea. instead mass produce those tiny football probes, give em all the velocity they would ever need, have em take a photo and a spectagraph and send back the results, then you will know what planets are ripe for sending the larger probes too (or perhaps warships).
-
Ummmmm...... generation ships.
problems:
1. retarded
2. extremely hard to do (self sufficient)
3. won't get there any time soon.
but still possible.
go rent cosmos, watch it all, watch it again, and then come back.
according to carl sagan a ship at .9c would experience so much time dilation that time experienced on ship would be within the range of a human life span dispute being able to cross large distances. catch is by the time you made it home thousands and thousands of years would have passed and your planet might not be there any more. of course, thats not a generation ship.
a more plausable way to make a generation ship is go to the kuiper belt, find an ice dwarf, and build massive nuclear-water rockets pointing skyward, around which you build ice mining camps to produce propellant for them. you can then hollow out the interior and build habitats there. several meters of ice will provide awesome radiation shielding. power reactors could also be built outside so as not to contaminate the interior. one of these days il do actual maths to figure out how much delta-v you can get out of an ice dwarf.
-
Wrong. You are suffering from the same misconceptions that the original SETI people suffered from. Let me explain.
[snip]
This means that the chances of catching a civilization in that developmental stage are astronomically low, and establishing two-way communications is practically impossible.
Oh, and of course that is all predicated on having an alien species that follows the same path of technological discovery we did.
I did take that into account.
While technology-based emissions are indeed reduced, scientists are sending signals into space exactly for the purpose of looking for aliens. Assuming the aliens do that too, and noticed Earth as a possible place for life to exist, chances of establishing some sort of contact increase greatly. My post was extremally optimistic, as it assumed many other things would not go wrong. (like aliens having a vastly different definition of life than us or never using EM emissions in first place.) I also assumed that the alien civilization is on the similar (or slightly higher) tech level as humanity and that they also wanted to look for other life forms. In other words, I was considering the best possible scenario.
go rent cosmos, watch it all, watch it again, and then come back.
according to carl sagan a ship at .9c would experience so much time dilation that time experienced on ship would be within the range of a human life span dispute being able to cross large distances. catch is by the time you made it home thousands and thousands of years would have passed and your planet might not be there any more.
This could be calculated, time dilation would indeed make the journey seem much shorter for the crew. I doubt a planet would go anywhere in about 1000 years, so this sounds quite reasonable. People on Earth, on the other hand, would have to wait a bit for any news from the colony.
Accelerating to such speeds is the main problem, as at these velocities, most of kinetic energy goes into mass. And after getting to the target, you need to decelerate without breaking the ship apart.
-
If it can handle the acceleration, it can handle the deceleration.
(Just flip it around)
-
The obvious answer to all of this is warp drive/hyperspace/subspace. Get on it, someone!
-
The obvious answer to all of this is warp drive/hyperspace/subspace. Get on it, someone!
To provide a semi-serious response, somebody already has (http://members.shaw.ca/mike.anderton/WarpDrive.pdf) (warning, pdf).
Background: current estimates put the age of the universe at about 14 billion years, while the radius of the observable universe is about 45 billion light-years. Since the universe began at a single point, you'll probably notice a contradiction here.
The gist of the explanation is this: while relativity prevents any particle, wave, or the like from equaling or exceeding the speed of light, the rate at which space itself can expand and contract is under no such restriction.
What Alcubierre describes in the paper I linked is the metric by which space might be collapsed in front of a ship and expanded behind it to give the effects of FTL travel without actually exceeding the speed of light. His work has been extensively peer-reviewed, and nobody has been able to find any disagreement with established physical laws or theories.
There are only three problems:
1. Alcubierre himself fully expects that some future discovery will probably invalidate his theory.
2. Even if the theory is sound, nobody has any idea how we would actually generate such a field.
3. Even if we knew how to generate such a field, doing so would require more energy than the total output of the sun over its entire lifetime.
-
I was actually thinking of the joke Stephen Hawking made when he guest-starred on Star Trek: TNG. He was taking a tour of the sets, and when they came to Engineering/the warp core, he stopped and said, "I'm working on that." :D
-
after some thought i very much doubt an object at relativistic speed would stay in anythings gravity well long enough to adversely effect its trajectory.
I think the change in velocity while escaping the planetary or solar gravitational well is negligible for an object traveling at a significant fraction of c. (Still have tiny corrects for the curvature of spacetime though -- even photons will be deflected to some degree.) And if it's not negligible, then no big deal... it's a predictable effect and thus no more difficult than calculating the gravitational slingshot trajectories for space probes like Voyager or Cassini.
Come to think of it, though without doing the math to demonstrate it, I'm under the impression that the more significant factor for "aiming" a relativistic interstellar probe are the heliocentric velocity of the object it was launched from, and the relative velocities of the sun and the target star, AND the orbit of the target planet. (How embarrassing would it be to shoot off your probe only to have it arrive when the target planet is on the other side of its orbit!)
So even if we can neglect gravitational perturbations, the relative orbital motions still make it a fairly complex problem, though of course not unsolvable. :)
-
The one thing that does make me laugh about the reporting of this is that most news reporters seem to think that the artists impression of the world is an accurate depiction of it. Science is good, but it's not that good, at least not yet :D
-
Heh, reminds me of what one of the guys working at the Smithsonian Astrophysical Society said in a lecture.
"I had to teach myself how to make celestial artwork on my computer, because the reporters kept telling me they couldn't write about my research if it didn't have any pretty pictures."
-
My friend and I talk about the sort of generation ship where everyone's consciousness is basically stored on a computer, and they share a general reality that runs at a much slower clock cycle than the rest of the universe; making the entire trip seem like days to them. Once they arrive their bodies are reconstructed using nanobots, which may or may not be included on the ship.
It's really far out there but once you start looking at the mathematics to support human life in space, especially for long durations, the ship starts to become exceedingly heavy, complex, and gigantic.
-
-snip-
2. Even if the theory is sound, nobody has any idea how we would actually generate such a field.
3. Even if we knew how to generate such a field, doing so would require more energy than the total output of the sun over its entire lifetime.
How about using a black hole (http://en.wikipedia.org/wiki/Black_hole_starship) to power the starship? All the gravity you would ever need! And it is better then antimatter for several reasons, such as being not quite as dangerous as antimatter, and not requiring any new physics.
We really need to see one of these get blown up in a sci-fi show, as a change of pace from exploding reactor cores.
-
Burrow deep into the planet.
Attach big thrusters on equator, 100 km+ tall structures that dump propellant (matter from the planet in significant quantities) into space at really high speeds. The higher the speed, the better the impulse, of course.
First, adjust planetary velocity as required to keep at suitable distance from the Sun while it expands. This should extend the useable life time of our planet some, but we'll need to conserve quite a bit of propellant for the Big Trip, too - the one that we'll have to make once the Sun shrinks into a black dwarf that only radiates residual heat.
Once that time comes, we'll have to see if there are any other possible means of survival available.
Geothermal heat should provide sufficient energy reserves for a viable human population living underground. There'll be a temperature gradient between deeper and higher, which can be used to power thermal cycle, and that's really all you need to run a turbine.
Obviously, a planet will travel quite slowly, but it WILL be able to support life long after the Sun dies, provided there's not catastrophic impact event of some sort. The biggest problem, really, is propulsion even at slightest scale, since the energy and propellant requirements are, frankly, quite insane. However, if we can avoid getting swallowed by the expanding Sun, then humanity will be able to survive within Earth for quite a while. If the propulsion problem is solved, then it's just a matter of time to float to another suitable star, which will ideally melt all the frozen water, nitrogen, oxygen and other stuff that basically rains down when the atmosphere cools down sufficiently, and the atmosphere will form again.
Of course, seeds of aquatic and other life would need to be maintained underwater, which might provide unique challenges, but hey, if we can ever figure out how to move an entire planet through space, I'd say that's the least of our worries.
Needless to say, this kind of space travel would take long, long, long time to get anywhere.
But, if you consider the viability of life underground, it's not that far-fetched after all.
In fact, now that I think of it, there may be countless wandering burrowing civilizations... making them, quite literally, planetary in the original meaning of the word.
The idea does hold some appeal. Technically, we could even convert the planet into some kind of megaengineered space station - some could argue that this happens as soon as the propulsion system is constructed. Some sort of relativistic matter ejectors would probably do the trick... problem would be energy to drive them, and matter to eject.
Coincidentally, these propulsion systems would double as extremely formidable weaponry.
-
My friend and I talk about the sort of generation ship where everyone's consciousness is basically stored on a computer, and they share a general reality that runs at a much slower clock cycle than the rest of the universe; making the entire trip seem like days to them. Once they arrive their bodies are reconstructed using nanobots, which may or may not be included on the ship.
It's really far out there but once you start looking at the mathematics to support human life in space, especially for long durations, the ship starts to become exceedingly heavy, complex, and gigantic.
i thought about a cloner ship that would transfer frozen embryos or gamete cells transported on an ai ship. when the ship found a planet that was habitable, it would then use the stored genetic material to grow humans in an artificial womb of sorts. these children would be raised by robots and trained to start a colony. the ship would also come with a number of tools, building materials, farming machines, seed stock, perhaps also genetic material for livestock, everything the would need to start a colony. the ship would land automatically before producing the colonists. such a ship would need a pretty beefy propulsion system to be able to survey multiple star systems that it would take to find a habitable location. it would also take some pretty advanced ai systems to be able to raise children without a lord of the flies thing going on. given the state of genetics it might actually be possible to have the ai tweak human physiology to adapt it to the colony planet's environment.
-
Burrow deep into the planet.
Attach big thrusters on equator, 100 km+ tall structures that dump propellant (matter from the planet in significant quantities) into space at really high speeds. The higher the speed, the better the impulse, of course.
First, adjust planetary velocity as required to keep at suitable distance from the Sun while it expands. This should extend the useable life time of our planet some, but we'll need to conserve quite a bit of propellant for the Big Trip, too - the one that we'll have to make once the Sun shrinks into a black dwarf that only radiates residual heat.
Once that time comes, we'll have to see if there are any other possible means of survival available.
Geothermal heat should provide sufficient energy reserves for a viable human population living underground. There'll be a temperature gradient between deeper and higher, which can be used to power thermal cycle, and that's really all you need to run a turbine.
Obviously, a planet will travel quite slowly, but it WILL be able to support life long after the Sun dies, provided there's not catastrophic impact event of some sort. The biggest problem, really, is propulsion even at slightest scale, since the energy and propellant requirements are, frankly, quite insane. However, if we can avoid getting swallowed by the expanding Sun, then humanity will be able to survive within Earth for quite a while. If the propulsion problem is solved, then it's just a matter of time to float to another suitable star, which will ideally melt all the frozen water, nitrogen, oxygen and other stuff that basically rains down when the atmosphere cools down sufficiently, and the atmosphere will form again.
Of course, seeds of aquatic and other life would need to be maintained underwater, which might provide unique challenges, but hey, if we can ever figure out how to move an entire planet through space, I'd say that's the least of our worries.
Needless to say, this kind of space travel would take long, long, long time to get anywhere.
But, if you consider the viability of life underground, it's not that far-fetched after all.
In fact, now that I think of it, there may be countless wandering burrowing civilizations... making them, quite literally, planetary in the original meaning of the word.
The idea does hold some appeal. Technically, we could even convert the planet into some kind of megaengineered space station - some could argue that this happens as soon as the propulsion system is constructed. Some sort of relativistic matter ejectors would probably do the trick... problem would be energy to drive them, and matter to eject.
Coincidentally, these propulsion systems would double as extremely formidable weaponry.
your thrust velocity needs to be greater than escape velocity or you create a situation where reaction mass turns around and falls back to earth, giving you no net velocity change. once you leave the habitable zone you have a limited time to reach your destination before your planet looses its heat. on the plus side all you need is to find a new place to park and you already have everything needed to restart the ecosystem (which you will likely destroy in the process).
im less concerned with the sun increasing its output because it might provide enough energy to re-heat mars before it melts the earth, and that we may planet hop all the way to ceres as the sun heats up further. ceres could be heated up by slamming asteroids into it as a precursor to transforming. especially ice bearing bodies like comets and stuff from the kuiper belt.
-
I'm gonna go out on a limb and say that a ship full of frozen embryos destined to be flung onto some alien planet and raised by AI to survive there brings up some massive ethical issues. Not that that's something you'd concern yourself with, of course. :p
-
Because **** decimals.
Long live significant figures!
-
I'm gonna go out on a limb and say that a ship full of frozen embryos destined to be flung onto some alien planet and raised by AI to survive there brings up some massive ethical issues. Not that that's something you'd concern yourself with, of course. :p
the idea is you let them get a planet going so later on you can send in the warships and invade them, horke their stuff, bang their women, and enslave them.
-
We should abandon planets and instead live on comets. Life originally came from comets anyways, so it's only fitting we return to them. Then where the cometary halos of other solar systems overlap, we can jump over to new comets and (very very slowly) expand throughout the galaxy.
-
I'm gonna go out on a limb and say that a ship full of frozen embryos destined to be flung onto some alien planet and raised by AI to survive there brings up some massive ethical issues. Not that that's something you'd concern yourself with, of course. :p
the idea is you let them get a planet going so later on you can send in the warships and invade them, horke their stuff, bang their women, and enslave them.
Oh, okay. That's better.
-
We should abandon planets and instead live on comets. Life originally came from comets anyways, so it's only fitting we return to them. Then where the cometary halos of other solar systems overlap, we can jump over to new comets and (very very slowly) expand throughout the galaxy.
wut?
Life originally came from comets anyways, so it's only fitting we return to them.
Life originally came from comets
sauce?
-
Life originally came from comets
sauce?
*coff* (http://www.hard-light.net/wiki/index.php/Gaian_Effort)
-
And on this planet we're gonna find remnants of an ancient civilization that flourished 8000 years ago. Find a data storage device that shows us how to disable a shielded alien ship.... :warp:
-
We should abandon planets and instead live on comets. Life originally came from comets anyways, so it's only fitting we return to them. Then where the cometary halos of other solar systems overlap, we can jump over to new comets and (very very slowly) expand throughout the galaxy.
wut?
Life originally came from comets anyways, so it's only fitting we return to them.
Life originally came from comets
sauce?
Er, I don't think there is or ever was actual 'life' on comets, though it is true that comets contain water and some of the ingredients for building life, and thus are generally thought to have delivered that material to the early Earth.
-
I believe that's what he meant.