# Five G Planet **URL:** \ **Category:** Factual Questions\ **Created:** [September 30, 2010, 1:14pm UTC](https://boards.straightdope.com/t/five-g-planet/555593 "2010-09-30T13:14:13Z")\ **Posts on this page:** 15\ **Page:** 5
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [October 1, 2010, 11:28pm UTC](https://boards.straightdope.com/t/five-g-planet/555593/81 "2010-10-01T23:28:34Z")
> [@Whack-a-Mole](#): > > > [@Der\_Trihs](#): > > > > Actually, no, there’s another time that matters: how long will it take to invent a better probe? There’s not much point in building a probe that takes 1000 years to get somewhere if 50 years from now we can build one that’ll get there in 100. In other words, we shouldn’t bother to build probes that will simply get passed by more advanced ones built later. > > Near as I can tell things like warp drive are not even theoretically possible. > > So, there is no likely chemical rocket that will be invented between now and whenever that will produce a far superior rocket. They know that stuff pretty darn well now. > > Other methods such as laser or ion propulsion are also well understood and new tech will not improve their limitations. > > In short I am not seeing some super tech for propulsion that we don’t already understand coming along that would change how fast we can get to another star Improved versions of a nuclear drive. Launch systems that require a large infrastructure in space. Lighter materials to build the probe out of. > [@Chronos](#): > > Quoth **Iggins** : > > > [@](#): > > > > What are the odds of imaging this planet, in say the next 50 years? Is there any possibility of technology that could provide even a blurry look? > > If you just want to see the planet distinct from its parent star, there are NASA missions for which the technology is pretty much already there and they’re just awaiting funding which could do the trick. For being able to make even a map of the surface, though, it’d probably be easier (though slower) to send a probe there than to build a telescope here that could do the trick. I read quite a few years ago about a possible technique where if you get a probe way out from Sol, past Uranus, at the right distance you can use the gravitational lensing effect of the Sun’s gravity as an enormous telescope. Supposedly good enough to easily resolve land masses on a planet of another star. I expect that nothing has been done about it because you’d only be able to use that trick to study a single spot in the sky; the only way to change where the “telescope” is pointed would be to move the probe, and it would eventually run out of fuel if you kept doing that. But, assuming I am remembering correctly (and that it hasn’t been proven impossible in the years since then), that sounds like it would work fine for getting a closer look as a specific extrasolar planet you were willing to spend that much on studying, and it would certainly be cheaper and faster than an interstellar probe. ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [October 2, 2010, 12:12am UTC](https://boards.straightdope.com/t/five-g-planet/555593/82 "2010-10-02T00:12:16Z")
> [@Der\_Trihs](#): > > I read quite a few years ago about a possible technique where if you get a probe way out from Sol, past Uranus, at the right distance you can use the gravitational lensing effect of the Sun’s gravity as an enormous telescope. Beginning at around 550AU ( which is about 30X further than Uranus). > **[SETIsail: a space mission to 550 AU to exploit the gravitational lens of the...](https://ui.adsabs.harvard.edu/abs/1994JBIS...47....3M/abstract)** > > Near-term solar sail technology can project small payloads from the solar system into interstellar space. A sailing mission is proposed whereby a 5-10 kg payload attached to a current technology solar sail is flown on a trajectory to 550 Astronomical... > **[The Gravitational Lens and Communications | Centauri Dreams](https://www.centauri-dreams.org/2009/11/06/the-gravitational-lens-and-communications/)** ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 2, 2010, 2:44am UTC](https://boards.straightdope.com/t/five-g-planet/555593/83 "2010-10-02T02:44:24Z")
> [@Ximenean](#): > > > [@TriPolar](#): > > > > Well, what Stranger said. > > > > And yesterday I was sure planets like this one existed. Today’s news hasn’t changed that. > > But the thing is, science is based on observations, not on what you happen to think. Previous observations showed that there were planets and stars in all sorts of sizes and shapes and other variations that made it a certainty that such a planet existed. This is just confirmation of something predicted by science, and wasn’t really in question. Science is more about prediction based on past observation than new observations. The observation part is important, but once enough observations have been made, the predictions become more important than each additional observation. If the observation of this planet revealed something new and unknown, it would have greater importance, but it didn’t. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 2, 2010, 4:11am UTC](https://boards.straightdope.com/t/five-g-planet/555593/84 "2010-10-02T04:11:42Z")
> [@Der\_Trihs](#): > > Improved versions of a nuclear drive. Launch systems that require a large infrastructure in space. Lighter materials to build the probe out of. Even building the probe out of Styrofoam or AeroGel will not net you much. Most of the weight will be in the propellant and as noted already you get a serious case of diminishing returns as more fuel = more weight = more fuel needed to push more weight (look at the Saturn V that sent people to the moon…it was mostly fuel and it was huge just to push that relatively tiny capsule from here to the moon). Assembling in space would be required because we are near our limits in how much weight we can get off the ground on earth with chemical propellants. As for nukes the Orion thing might do it but it is a long way from the concept to a workable ship assuming it is even feasible given sufficient will to build the thing. After Orion not sure what could do better that in theory would work and is not sci-fi. And by work I mean as a practical matter. A gazillion jigawatt laser pushing a solar sail and stationed one per AU out from earth might in theory be possible but absurd as a practical matter. Anti matter is the only thing I can see seriously changing the landscape on this. If we could find a way to mass produce it then a lot of new avenues open up. However, cool as antimatter is as an energy source it’d probably doom the human race to extinction (imagine a city buster nuke equivalent you could comfortably fit in a purse). ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [October 2, 2010, 4:46am UTC](https://boards.straightdope.com/t/five-g-planet/555593/85 "2010-10-02T04:46:59Z")
> [@Whack-a-Mole](#): > > Assembling in space would be required because we are near our limits in how much weight we can get off the ground on earth with chemical propellants. Not simply assembling in space. There’s a variety of ideas for launchers to accelerate spacecraft without the craft needing to use fuel. Spinning tethers, extended space elevators, large linear accelerators, launching lasers or masers. > [@Whack-a-Mole](#): > > As for nukes the Orion thing might do it but it is a long way from the concept to a workable ship assuming it is even feasible given sufficient will to build the thing. > > After Orion not sure what could do better that in theory would work and is not sci-fi. There’s actually a fairly wide variety of ideas for nuclear drives as I understand it. > [@Whack-a-Mole](#): > > And by work I mean as a practical matter. A gazillion jigawatt laser pushing a solar sail and stationed one per AU out from earth might in theory be possible but absurd as a practical matter. Why? Your problem seems to be that you’ve decided that we are at pretty much the apex of possible technology, and we aren’t even close. > [@Whack-a-Mole](#): > > Anti matter is the only thing I can see seriously changing the landscape on this. If we could find a way to mass produce it then a lot of new avenues open up. > > However, cool as antimatter is as an energy source it’d probably doom the human race to extinction (imagine a city buster nuke equivalent you could comfortably fit in a purse). By the time we or our posthuman descendants can do that with antimatter (assuming that is even possible) we’ll be all over the solar system. If we have that kind of energy to play with zipping around the system will be fairly easy. Destroying life on Earth would only be a setback not an extinction event. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [October 2, 2010, 6:13am UTC](https://boards.straightdope.com/t/five-g-planet/555593/86 "2010-10-02T06:13:16Z")
In theory, all stars have a goldilocks zone. In practice, not all do. A double star system may have the two stars close enough together that the varying light from the two stars means that there is no orbit where the temperature is always in the desired range. It’s likely that in such cases, any hypothetical goldilocks zone will not have a stable orbit anyway. As for stars coming near the solar system, [Gliese 710](http://en.wikipedia.org/wiki/Gliese_710) is due to pass by some 1.4 million years from now. It probably won’t come closer than about a light year, but could come as close as 1000 AUs. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 2, 2010, 6:17am UTC](https://boards.straightdope.com/t/five-g-planet/555593/87 "2010-10-02T06:17:26Z")
> [@](#): > > Even building the probe out of Styrofoam or AeroGel will not net you much. Most of the weight will be in the propellant and as noted already you get a serious case of diminishing returns as more fuel = more weight = more fuel needed to push more weight (look at the Saturn V that sent people to the moon…it was mostly fuel and it was huge just to push that relatively tiny capsule from here to the moon). No, the payload mass does absolutely matter. For any given desired speed and any given rocket technology, you can solve for the ratio of propellant needed to payload. Halve the mass of your payload, and you can halve the mass of your propellant. And a lighter payload need not necessarily be less dense, either: It could just plain be smaller. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [October 2, 2010, 1:07pm UTC](https://boards.straightdope.com/t/five-g-planet/555593/88 "2010-10-02T13:07:46Z")
> [@Der\_Trihs](#): > > > [@Mr.Excellent](#): > > > > The only time that matters is the time it takes to build and launch the probe - after that, whether it takes 200 or 400 years to get to its destination, it’s still going to be long after we’re all dead. > > Actually, no, there’s another time that matters: how long will it take to invent a better probe? There’s not much point in building a probe that takes 1000 years to get somewhere if 50 years from now we can build one that’ll get there in 100. In other words, we shouldn’t bother to build probes that will simply get passed by more advanced ones built later. This is a red herring. Not only is that a big _if_, but one of the prime ways of learning is by doing, so we build the first probe and from it learn how to build the next, better, probe. > [@Whack-a-Mole](#): > > So, there is no likely chemical rocket that will be invented between now and whenever that will produce a far superior rocket. They know that stuff pretty darn well now. > > Other methods such as laser or ion propulsion are also well understood and new tech will not improve their limitations. All very true, but there can be workarounds. The second-biggest problem (after time) in space exploration is Earth’s gravity well, which limits the size of the probe and the amount of fuel. So, for example, perhaps we might make a probe that is assembled in orbit or stops off at Pluto or Sedna or wherever to harvest tholins or xenon or whatever which the probe then uses to speed its way. So, may as well get on with it now. If something better comes along then great! I’d love to see it. As far as we know though (and not because someone hasn’t thought of it yet but because of the very limits of physics itself) that stuff will remain sci-fi. [/QUOTE] ---
**Author:** ![CutterJohn](https://avatars.discourse-cdn.com/v4/letter/c/91b2a8/32.png) [@CutterJohn](https://boards.straightdope.com/u/CutterJohn)\ **Post date:** [October 2, 2010, 2:46pm UTC](https://boards.straightdope.com/t/five-g-planet/555593/89 "2010-10-02T14:46:38Z")
> [@Quartz](#): > > This is a red herring. Not only is that a big _if_, but one of the prime ways of learning is by doing, so we build the first probe and from it learn how to build the next, better, probe. Learning by doing only helps you learn how to do what you are doing better. Chemical rockets are quite inadequate for crossing the gulf between planets, much the empty space between stars. All we would do by sending a probe without the proper tech is learn how to make a slightly faster probe that still has inadequate tech. If you want to put money towards something that will get us(or at least a probe) to another star faster, you’ll want to pump money into fundamental research, so we can figure out completely new drive systems that would actually be capable of this feat. Even if we had gave an unlimited budget, built a mammoth ship in orbit instead of an earth launch, launched at a star along the ecliptic to take advantage of earths orbital speed, i can’t see how any modern tech can get you past 500,000 kph, and thats still something like 9000 years just to proxima, making it a completely pointless endeavor. Develop a drive with 100x the specific impulse of ions, and sure.. We might be in the 100 year business using that fancy drive tech and plain old fission reactors. ---
**Author:** ![Locrian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/locrian/32/14146_2.png) [@Locrian](https://boards.straightdope.com/u/Locrian)\ **Post date:** [October 2, 2010, 9:25pm UTC](https://boards.straightdope.com/t/five-g-planet/555593/90 "2010-10-02T21:25:34Z")
> [@MrDibble](#): > > 37-day orbit? Christmas every month! Sign me up… HA! That’d be nice, but you’d also have 9.9 Earth birth years. (?) If you live there, you could live to be 500! 😃 ---
**Author:** ![Locrian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/locrian/32/14146_2.png) [@Locrian](https://boards.straightdope.com/u/Locrian)\ **Post date:** [October 2, 2010, 9:28pm UTC](https://boards.straightdope.com/t/five-g-planet/555593/91 "2010-10-02T21:28:57Z")
Also, I thought it was only 17 light years away. Astronomer Vogt said if we have a vehicle that can reach near-light speed, 20 years to get there. Hooo, boy. 20 years on a spacecraft?? Most of those years you’d be in darkness it seems. We’d have to bring lots of DVDs, beer, weed, and at least one deck of cards! 😃 ---
**Author:** ![digs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/digs/32/14889_2.png) [@digs](https://boards.straightdope.com/u/digs)\ **Post date:** [October 3, 2010, 3:03am UTC](https://boards.straightdope.com/t/five-g-planet/555593/92 "2010-10-03T03:03:08Z")
Okay, I’d agree that the inhabitants of Gliese 581g (_“The Gleasons”_?) are too far away. But… It’d speed things up if we meet them halfway. (Come on, am I the first person to think of that?) ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 3, 2010, 11:33am UTC](https://boards.straightdope.com/t/five-g-planet/555593/93 "2010-10-03T11:33:49Z")
> [@Locrian](#): > > Also, I thought it was only 17 light years away. Astronomer Vogt said if we have a vehicle that can reach near-light speed, 20 years to get there. > > Hooo, boy. 20 years on a spacecraft?? Most of those years you’d be in darkness it seems. > We’d have to bring lots of DVDs, beer, weed, and at least one deck of cards! 😃 Nah…for those on the spaceship (if they were going near lightspeed) the trip would take considerably less time due to the time dilation they’d experience. For us on earth it’d take them 20(ish) years. I do not know how to do the math but an example is below on just how little time it’d take them. Note for time dilation to be notable they have to get (IIRC) over 90% lightspeed at least (it is not a linear relationship where 10% lightspeed gets you a 10% decrease in time…the effect grows faster the closer to C you get). > [@](#): > > v = 0.9999999999999999999999951 c > > \ > > ```auto > > Object Light Years Perceived Travel Time > Alpha Centauri 4.36 0.43 milliseconds > Galactic nucleus 32,000 3.2 seconds > Andromeda galaxy 2,180,000 3.5 minutes > Virgo cluster 42,000,000 1.15 hours > Quasar 3C273 2,500,000,000 3 days > Edge of universe 17,000,000,000 19 days > > ``` > > SOURCE: [The Oh-My-God Particle](http://www.fourmilab.ch/documents/OhMyGodParticle/) ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [October 3, 2010, 5:57pm UTC](https://boards.straightdope.com/t/five-g-planet/555593/94 "2010-10-03T17:57:23Z")
The factor that time is dilated (and lengths are contracted) between two inertial frames of reference is just 1/(1 - v[sup]2[/sup]/c[sup]2[/sup])[sup]1/2[/sup], where v is the relative velocity of the two frames along the axis one is moving with respect to the other. So if v = 0.5\*c, v[sup]2[/sup]/c[sup]2[/sup] = 0.5[sup]2[/sup] = 0.25, (1 - 0.25)[sup]1/2[/sup] = 0.75[sup]1/2[/sup] = 0.87, and finally 1/0.87 = 1.15, so in a ship moving at half the speed of light, time is slowed by a factor of 1.15 – not terribly much, but definitely noticeable. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 4, 2010, 2:05am UTC](https://boards.straightdope.com/t/five-g-planet/555593/95 "2010-10-04T02:05:41Z")
> [@Half\_Man\_Half\_Wit](#): > > The factor that time is dilated (and lengths are contracted) between two inertial frames of reference is just 1/(1 - v[sup]2[/sup]/c[sup]2[/sup])[sup]1/2[/sup], where v is the relative velocity of the two frames along the axis one is moving with respect to the other. So if v = 0.5\*c, v[sup]2[/sup]/c[sup]2[/sup] = 0.5[sup]2[/sup] = 0.25, (1 - 0.25)[sup]1/2[/sup] = 0.75[sup]1/2[/sup] = 0.87, and finally 1/0.87 = 1.15, so in a ship moving at half the speed of light, time is slowed by a factor of 1.15 – not terribly much, but definitely noticeable. Noticeable sure…especially on a trip that long. Hell, they calculated the guys on the Mir spacestation were about 3 seconds off with earthlings upon their return (6 months or so in space). Not something they could notice really but easily calculated. On a trip that far it’d add up. If I am following your math at 0.5c instead of 40 years of travel (what we on earth would see them take to Gliese) it’d feel to them like 34.7 years. Definitely a noticeable difference but not an overly big one in the scheme of things. [Previous page](https://boards.straightdope.com/t/five-g-planet/555593.md?page=4)