Extrasolar Planet Discussion - Now Discussing: KEPLER announces hundreds of candidates

Lowie, in order to cross the vast distances in space to even realistically explore planets, how feasible do you think alternate propulsion systems are?

I remember when fusion rockets were being examined, the benefits of fusion power being high thrust ability. "Project Daedalus" was one such study, which was the subject of A LOT of hard science fiction, but then it never really went anywhere.

The other is the Hydrogen scoop ship. As I understand it, free hydrogen can be scooped up by using an electomagnetic net. The more hydrogen the ships captures, the faster it can go, which starts a near endless cycle. The drawbacks here are the size of the "net" which is needed.

Of course there are the purely fantastical examples like warp drives and hyperspace, but the two above were supposed to be feasible with technology available even back in the 1980's. Now nothing to be heard from in this regard.

 

Everything from Starwisp to antimatter are feasable, it's just the cost of such advanced propulsion is beyond us.

HERE'S a better bang for your buck than antimatter, totally undeveloped however.

 

Well, on one hand, I'm sure there will be some form of technology that'll work to get to some of the closest planets that will be developed. It won't be terribly fast, but it will happen.

However, I don't view that as a priority of yet both because it'll be a little while yet until we get an idea of where it is we'd want to go, and because I think before we start heading for other systems, we need to start with the exploration of our own solar system. We've not yet really done that, and I think that'll help in large part as it'll mean developing the technology for supporting humans living off the earth and that way we'll know what sort of payload any alternative technology is going to have to be able to move.

 

I thought I'd bring up an interesting open question (there's no proper scientific answer on this since it's decently subjective) but just would toss out the question of what, exactly, constitutes being an 'earth-like' planet?

 

Personally, the definition of an earth-like planet is a rocky planet in the 'habitable zone' of its star, with liquid water and an oxygen rich atmosphere.

Of course, that's really only important for life as we know it. There's every possibility that we have a myriad of other types of life forms in the universe (silicon instead of carbon based for example).

 

Personally, the definition of an earth-like planet is a rocky planet in the 'habitable zone' of its star, with liquid water and an oxygen rich atmosphere.

Ah, the Hertzsprung-Russell diagram. On the H-R plot, stars that would theoretically sustain Earth-like planets sit in the "G" and "K" band. Capella is such a star. Betelgeuse is close as well, although I think it's actually a "class M" star.

Besides physical characteristics, NASA also conducted a study to determine what psychological needs have to be fulfilled by Earth-like planets as well. I don't remember the planet's name, but a hypothetical Earth-like planet was found, but its rotation caused it to have an 83 hour day. How would such aspects impact those people who initially had to colonize it?

Could planets that are close be made to be "Earth like?"

One of Carl Sagan's proposals, well theories really, was to send dozens of rockets full of blue-green algae into the atmosphere of Venus. Venus suffers from basically the greenhouse effect on steroids. I understand that blue-green algae proliferate in a carbon-dioxide rich environment, and transform the C02 into oxygen.

The blue/green algae process still takes a couple of hundred of years to transform the atmosphere, but this is still much faster than the millions of years that it took on Earth. The exciting thing to think about that if this was actually undertaken back in 1976, we'd actually be able to see the beginnings of a breathable atmosphere on Venus by now. (assuming it worked.)

 

Disturbing the Habitable Zone

 

Can you imagine working those Mondays?

 

I'm against colonizing any planet found to have an oxygen-rich atmosphere, as that indicates that the body already supports its own indigenous life, and that inevitably leads to violations of the prime directive and fatal transporter accidents.

 

So, while not dealing specifically with extrasolar planets, I have a question for the theoretical physicists out there that relates back to travelling throughout the vast distances of space.

We know that time is relative, and the speed of light is constant. It's what accounts for the famous "twin dilemma" theory, which states that if one twin stays on Earth, while the other files away at near the speed of light, the Earth-twin will have aged and died, while the light-twin will have only aged by a minor factor from their own perspective. (depending on the speed and distance travelled) For example, if an explorer speeds off to Alpha Centauri at 93,000 miles/sec, about 9 years will pass on Earth, while the astronaut will have only physically aged 2 years or so.

I don't think there's any way to bypass the effects of the time displacement. It's not logical to think that time would somehow "undue" itself on the astronaut's return trip, like Superman flying backwards around the Earth.

Does the theory of relativity hold if one goes through a black hole, or other wormhole? Since travelling in hyperspace is a theoretical possibility, is there an equation that calculates how much time passes if one uses hyperspace to travel vast distances?

 

In other words is there time dilation for FTL. I think the time dilation effects are muted in things like wormholes and warp drives, since locally you are moving at whatever slower than light speed but non-locally you are moving along with your FTL system.

And your time dilation example is way off. HERE

Dilation effects don't really start to factor heavily until you get above 80% lightspeed.

 

Well, the cause of time dilation comes from differences in gravity or differences in velocity. So really with something like wormholes where you're effectively jumping from one spot to the next, I think that would actually mean you wouldn't have any time dilation effect because it's more that space-time is being warped than it is traveling at high speed. You may get there faster than light, but not by GOING faster than the speed of light, so it won't properly apply to the best of my knowledge. There may be a gravitational effect, though.

And I'd agree with VLM in that the time dilation there is off. Traveling to Alpha Centauri and back at half the speed of light in that example would be 9 years of time in the rest frame, but on the ship it would be, I believe, 15% off. So I think it's about 7.8 years doing the calculation off the cuff. Still significant, but not as extreme as the example stated it'd be.


On my earlier 'earth-like' question... few comments, notes, etc...
some interesting stances on what constituted earth-like, Kyptastic hits about what I'd define as earth-like, although I'm not sure if I'd have oxygen-atmosphere as a requirement, although liquid water definitely would be. Since I'd point out that life as we know it needs water, but not necessarily oxygen.

Mr44, really, before you look at the star types needed, what you mean by earth-like needs definition. A red dwarf could well have an earth-sized planet with liquid water orbiting it, it just wouldn't be getting the same wavelengths of light we do, and similarly, further out planets could be around on the other side of it, hotter stars could hypothetically have earthlike planets further out, although these ones do carry the trouble of shorter lives. I'd also say that the stars you mentioned are both probably not good picks (though I could be proven wrong) in that Betelgeuse is a red giant, which has destroyed or baked any planets that were orbiting it closer in to where a habitable zone might've been for most of it's life, and I'm hesitant with Capella as well, since Capella contains two giant stars. So the spectral type range is right, I think it'd be better to keep it to the main sequence, which is where a star spends most of it's life. Once you get to giants, I think those are stars that are too dynamic at that point to have stable systems for life to really develop much.

I do find it interesting that you put a lot more constraints on earth-like, looking for a much closer match by including things like rotational characteristics, which is a much narrower application of the term.


I'll also throw in this fun possibility... while we don't know of any earth-sized planets, we do know of large gas giants, some of which are in the habitable zones of their stars, and that does open up the possibility of them having large enough moons to possibly hold an atmosphere, so we may be looking at habitable moons in some systems rather than habitable planets.

 

Ah, so time dilation doesn't really become noticeable until 80% of the speed of light. I guess it won't ever be that big of an issue then. Do you think any spacecraft will be able to reach such velocities? Estimates put 50% the speed of light as obtainable, but even that speed will take a long time to get beyond the galaxy.

I suppose bending space is more desirable from the standpoint of human limitation, but isn't the problem with a real "warp drive" that it also takes a huge amount of energy to bring about? I know that on his radio show, the physicist Michio Kaku estimated that to create a warp field for even a modest spacecraft, it would need to produce the energy that's equivalent to the planet Jupiter. Because of mass?energy equivalence, I'd say it's possible, we just need to develop some sort of super-fusion, or other exotic energy generation system.

 

Right now, as scientists understand the Universe, to make a real working warp drive or wormhole would require approx 10^22 aircraft carriers of anti-matter combined with the same mass of matter. The good news is that it is not infinite, just.....ALOT. (Mr Vivec did the math for me).

Other than that, getting closer to lightspeed depends on the mass of fuel to vehicle ratio. Off the cuff as I did not look it up, but something like 2/3 of the mass of the vehicle at start equals the exhaust velocity. Most antimatter designs say something like 50% lightspeed is plausable. The only problem is dust. Asmimov said that the safest speed for a ship made of diamond would be 30% lightspeed. Too much beyond that makes dust particles into atomic weapons.

 

The latest Symphony of Science video is out on Youtube, and it features "The Case for Mars." I'd say it one of the better ones, but with so many out now, there's something for everyone. As Zubrin points out in the video, Mars has everything to look forward to.

HERE

 

I'd view warp drive type things more likely as it may well work, it just requires concepts we've not yet understood. Whereas, trying to just accelerate to near the speed of light simply requires energy, and we know how much of a limitation that is.

 

Aren't most of the planets categorised as "Earth-Like" those found within the so called "Goldilocks Ring". That being far enough away from a star so as not to be too hot but close enough so as not to be too cold.

These planets are rare, but it seems like they'd have the best likelihood of having life.

After all, the planet just after Earth (Mars) is too cold and the planet just before Earth (Venus) is too hot. Earth itself is just right.

I'm sure there are other factors that are neccessary for a planet to be classed as possibly having life, but the Goldilocks Ring seems to be one that is looked for a lot.

 

Well, therein is why I think it becomes an interesting question. There's varying reasons one would USE the term Earth-like. And it's why I always say what quality I'm looking at when I say that something is earth-like. However, to just say a planet is earth-like, there's a lot of things that matter. For example, we still don't have planets that are earth-like in size, really, so the location of the orbit isn't even a factor yet when we have very few planets that aren't gas giants.

For example, a larger Mars would have higher gravity and be able to hold onto more atmosphere which would allow for maintaining warmer temperatures. Not the best, but better, and it would really depend on just how much of a greenhouse effect there was. So in that sense, the Goldilocks ring really can vary a lot, and it's tough to say just where it is. Atmosphere is a huge part of planet temperature.

 

It's not like that at all. When you accelerate closer to the speed of light, matter becomes heavier. At least that's what happens when they attempted to fire atomic particles faster than light in a particle accelerator. So the concept of warp drive is really just science fiction. Although it would be nice, I just don't have much faith in Star Trek for our future.

 

I would define a planet as "Earth-like" if it had within .5 and 5 times the Earth's mass, was in its star's habitable zone, and its star weren't too close to other stars and didn't make the planet uninhabitable (e.g. a pulsar). And of course it has to have water. Earth-like doesn't mean Earth per se, but what is Earth's most defining characteristic?

 

Yuthura, you're talking about 2 almost completely different things here, which is why Lowie made the distinction.

A warp drive operates by creating an energy field which actually distorts local space, which pulls/pushes the spacecraft along. In essence, it eliminates the vast physical distances one has to travel across the universe. Imagine if you threaded a string through a bead, and then looped the string to where the bead was. The bead itself wouldn't have to travel the entire distance of the string to get from point to point, even though the string itself is still there. There's no separate acceleration involved, so there's no mass/energy conversion.

What you're thinking of is Faster-than-light- (FTL) or "nearly light speed" travel. A nearly light speed ship would use some sort of propulsion system, like a fusion drive, to accelerate itself as close to the speed of light as possible. It's closer to what we think of as a conventional rocket, just with much, much, more velocity. This is where special relativity applies because you're attempting to accelerate the ship as fast as possible to the speed of light.

(There's also a more theoretical concept of a drive which basically uses energy to "ring the doorbell" of wormholes- in order to enter other dimensions and emerge back out in ours in a different place, but that requires the mapping of possibly millions of such holes, and currently, no one actually knows what the effects would be beyond speculation)

The energy required for a warp drive, while a large amount, is certainly obtainable. Warp drives are actually theoretically possible right now, assuming the technology catches up, and probably represent the best chances for people to explore the universe. These are the basic differences. Maybe VLM or Lowie can go into more detail, or correct any errors in my post here.

 

Mr44 largely hit what I was going after. Warp drive in a tech sense refers to forms of travel that warp space-time rather than rely on the relative velocity of the spacecraft. Basically, you create some sort of disturbance to provide you with a short cut from one place to another. That's something that is a question of HOW to do that, but would, theoretically, work. I wouldn't say the energy needed is 'certainly obtainable' but it COULD be. Whereas actually accelerating something to the speed of light is purely about just increasing an object's energy, which, for the speed of light, requires infinite energy and therefore is limited such that I don't think it could ever be done. I do think Mr44 is overly generous in saying that it's theoretically possible now, as from what I've read of it, there's a lot to address still, but I do think it's the more promising route.



And, I'm giving points to DarthIktomi for being the first person to highlight the danger of other stars towards the chances of a planet having life. Good point that hadn't come up yet.

See, this is why I like this question, so many different possible interpretations.

 

Size of the planet, distance to the sun of the solar system the star lives in; oxygen; water; temperature...these could be some obvious features that may constitute "earth-like". However, I think that first, and foremost, the one and only feature (to me anyway) that constitutes a true "earth-like" feature is LIFE. If the planet is absent of life, then there are only similarities that misses to larger and greater extent the most unique and abundant feature of all. And maybe to some extent, that is "earth-like". But seeing as life is so abdundant on earth, under every rock, in every corner, in every nut and cranny...I'm going to say that life, and this is only in a simple form (be it bacteria, or a microbe) would constitute "earth-like". All other features are just sketching the surface of Earth features.

 

I'd actually point out that chemically speaking, without a cycle to generate it, you wouldn't have oxygen in the atmosphere. Offhand, I'm not aware of any such cycle that would generate oxygen OTHER than life and so it would seem that life is a requirement for oxygen in the atmosphere, not the other way round.


I would disagree on defining an earth-like planet as being just one with life, as that, to me, is describing another car as being like mine if it has someone in it. Compared to all properties of the earth, I think life isn't the most distinct feature, it just happens to be what we care about. On that definition, though, the space station would fit as earth-like, which I think represents a bit of a misguided definition, in that sense, if we focus on that too much. It does also seem to flip the order, at least conventionally, since we use the term earth-like planet as what to look for as a step towards finding life elsewhere, but defining earth-like planet as a planet with life skips to the end and doesn't give anything about the direction to get TO planets with life. Sort of like if I was looking for a car that suits my needs, but my definition of what that car is were the car I get, because I'd get the car that suits my needs.

 

Planets, planets, everywhere