Is it worth colonizing a planet that travels near the speed of light?

Question

There is a planet that is orbiting around not a single star, but the core of a galaxy. It is independent of the other solar systems in the galaxy, but is affected by the center of mass of the core. It is orbiting very near the speed of light. It does have a clean orbit, meaning, it does not collide with any other planets or stars in the galaxy while it’s orbiting around the core.

It is very difficult to land a spacecraft on this planet as only a few civilizations in the galaxy can approach a significant fraction of the speed of light, therefore only the most advanced ones can come close to the planet and land on it.

The question is: would it be worth it to colonize this planet for any reason? Politically, economically or from a military standpoint? Or use it as a treasury, or anything? Would we have any use for it? Would it be worth any investment?

(The technology to live in very cold places, far from stars is already developed and established, so even if this planet does not have an atmosphere and very cold, cities could be build on it which can support life with existing technology)

Answer 1

My gut instinct is "no: don't colonize." The biggest problem I see with this planet isn't the cold: it's time dilation.

Politically, most civilizations can't even send diplomats there - and with time dilation, I can't imagine it would be a "key player" in intergalactic politics.

Economically relies a lot on how the economy in the rest of the galaxy works. With that said, even if there are a lot of key resources on the planet itself, exporting them would have to outweigh the costs of the ships required to get there in the first place. Furthermore, that time dilation rears its ugly head again: time is money! (Setting up an interest-earning account, going to this fast planet, then returning to collect your earnings may or may not be a viable solution, depending on banks.)

Militarily is a little more interesting. It's moving fast enough that I don't think it would be a key defensive or offensive position. It'd be hard to invade due to its speed... but all someone has to do is move something massive into its orbit and wait to effectively eliminate it. (Launching a kinetic weapon from it might be useful, if you just so happen to be going by someplace interesting at just the right time.)

The only positive feature I can see would be to someone wishing to "time travel to the future" - and even then, it only works if they'll end up close to where they want to be when they want to leave.

Once all that is said and done, however, it might be of interest to scientists who wish to perform experiments - either observing very long-term experiments off-world, or perhaps some relativistic experiments on-world.

Answer 2

Well, not colonization, but certainly a research station. There is exactly one location in the galaxy which fits your description - close orbit around the super black hole (~4 million solar mass) which inhabits the center of the galaxy. For a Schwarzchild geometry, there exists an unstable orbit at twice the Schwarzchild radius, with an orbital velocity of 0.7 c. The closest stable orbit occurs at about 3 times the radius, but the orbital velocity is a good deal less.

Of course, construction will be a problem, since tidal forces will run several thousand g's per meter of radial distance, so some sort of gravitic control on the part of the advanced races will be a must.

And let's not forget the radiation problem. This close to the black hole, infalling radiation and matter will have achieved very respectable energies.

Answer 3

While the amount of time dilation isn't as extreme as something going at .9 c, it is still enough to make some significant difference between the planet and objects in the rest of the galaxy.

Since time is money, this could be exploited for various economic effects. The simple example of a person collecting compound interest in the outside galaxy while residing on the planet shows some of what is possible, and eventually many more subtle and complex financial instruments could be devised based on the time differential between the planet and the remainder of the galaxy.

The other effect which comes to mind is the use of the planet for long term storage. Items which have limited lifespans but command a high value could be stored on the planet and have their lifespans artificially extended due to the time dilation effect. Of course, don't expect this to allow you to store a bottle of wine for millennia, the time dilation effect is not all that great at .6 c

Realistically, if there is a desire to use time dilation for political, economic, social or military ends, it would make more sense to either build some sort of construct near the event horizon of a black hole or travel at relativistic speeds in order to take advantage of the Lorentz factor.

Answer 4

You're going to need to give it handwavium shields.

lets assume 0.9 c as it's speed. Lets assume that it's path is as clean as interstellar space without any gravel or asteroids. The only thing it hits is the fine mist of atoms between the stars.

Lets treat the planet as about the size of earth.

Volume: 1.08321×10^12 km3

mass: 5.972 × 10^24 kg

Surface area: 510.1 trillion m²

Approximate circumference: 40075 km

approximate cross section: 1.28×10^8 km²

using the figures for a cold neutral interstellar medium from wikipedia: 20—50 atoms/cm3

So let's go with 25 atoms/cm3

25000000 atoms per cubic meter.

We can treat the volume of space that the planet passes through as a cylinder with a cross section of 1.28×10^8 km²

Now lets look at how much it hits while traveling, say, 10 light years from an outside reference frame (I think about 4 years planet-time).

I'm going to ignore time dilation because it's hard and I need to maintain my sanity.

Treat it as a cylinder 10 light years long with the diameter of the planet.

This lets us estimate the total number of (almost all hydrogen) atoms in the path of the planet, lets assume they all hit and there's no shockwave effects:

37984965888934182667500000000000/pi m^3 (cubic meters)

so over the course of 10 light years it will impact with 505924000 metric tons of gas atoms.

How much energy will they be carrying?

505924000 metric tons at .9c carry 5.885×10^28 J (joules)

This energy will need to be radiated away by the surface. To do it accurately I would have to take into account time dilation but to err in favor of the planet and to keep myself sane I'm going to ignore it.

Surface area is 510.1 trillion m²

The planet needs to radiate away 6.7180365296 × 10^23 Joules per hour.

Dividing by the surface area each square meter needs to radiate

365.8 kW per meter square

For comparison the sun radiates ~17.53 kW per square meter of it's (approximate) surface

The surface of this planet is going to be glowing hotter than the surface of the sun

You don't need to survive the cold, you need to survive the heat.

Answer 5

As a few of the others have said, due to time dilation, this planet wouldn't be very useful as a colony. Between the speed and the proximity to the SMBH, it would probably be one of those situations where every hour that you spend on the planet, a hundred years go by in the rest of the galaxy*.

But there is one thing that it could be used for, and that's long term storage, especially of data.

Scientists have looked into all kinds of long term data storage methods, trying to find something that could last 1000 years or longer.
But by using the time dilation you no longer have to worry about that at all. Send a library probe to the planet, and 20,000 years is only a few days on the planet.

Updating and retrieving information would be slow, but possible. You simply fly your ship near by and use a laser to make your data request. The library receives the request, the super computers do the lookup and 3 ms later it uses its own communication laser to send the information back.
Back on the ship it's been 3 months, and the reply comes back with the recipe for how to make yum yum sauce that had been lost in the last galactic collapse.

* This is only an example.

Answer 6

It occurs to me to wonder how large the radius of the orbit is, and what the centripetal force would have to be to remain in orbit, and what the mass of the primary would have to be to keep an object in orbit at such a speed.

If the radius of the orbit is the same as Earth's distance from the sun and the orbital velocity is 0.8c, then using classical mechanics -- ignoring any relativistic effects --, v^2=GM/r, I calculate the mass of the primary at 1.3e38 kg, or like 100 million times the mass of our sun. The centripetal acceleration, v^2/r, would be 384,000 m/sec^2. Earth's centripetal acceleration is about 6.3 m/sec^2. The force to keep this planet in such an orbit would be huge. I seriously question if it wouldn't be torn apart.

But for the sake of the story let's assume it's possible.

What would be the advantages of colonizing such a planet? Assuming near-light-speed travel is not routine in this society, it might be difficult and expensive to reach. That could make it a good place to store something valuable, the secret plans to the Death Star or whatever. But if you have the technology to reach the planet, presumably you have the technology to launch a spaceship travelling at near-c, in which case you don't need the planet for your high-speed storage. That is, any benefit gained by the planet travelling at such high speed, to get there you have to have a spaceship that can travel that speed. Why not just do whatever on the spaceship, and why do you need the planet? Unless it's something on such a huge scale that you need a planet for it.

Time dilation would mean that time on this planet would pass very slowly relative to the rest of the galaxy. Good if you want to see the future or leave some message for posterity. Maybe a place to keep an archive that will survive for thousands of years of outside time. (But again, why not just put it on a ship?) Not so good if you're worried about keeping up with technological advances. A military base on this planet would be obsolete very quickly. It would also be difficult to keep up with news from outside, as it's happening so fast relative to you. So as a military or political center, it would be a terrible choice.

Might be nice for research on relativity.

Besides that, I'm hard pressed to come up with any advantage.

I suppose the planet might have some valuable resource that has nothing to do with its unusual orbital speed. But that begs the question.

Answer 7

Assuming that such a planet is stable, and assuming you're limited to relativistic travel in your universe, this planet might be extremely valuable as a way station.

To get from one planet to another quickly you have to expend a huge amount of energy getting up to near lightspeed, then expend that same amount of energy again to slow down to synchronize with your destination's orbit.

But this planet is already moving at near lightspeed. So with careful planning to meet up with the planet as it matches the direction of your travel, you could make a pit stop for refuelling, trading, etc. without incurring the energy cost of slowing down.

[EDIT] ...except that I didn't consider that the gravitational attraction of the black hole is going to be accelerating the ship as it comes in. That could be enough to invalidate my whole answer.

Answer 8

That planet could be the galactic Panama Channel. If you want to go from one side of the galaxy to the other, and you either don't want nor can't use shortcus (wormholes), then you have two options: hop from arm to arm, or go through the core. The planet could then also harbor a transportation hub, where ships can ressuply, or where you could unboard one shuttle and board another one.

It could be neutral ground for negotiations. If it's hard to get there due to the delta-V you need to get there (due to its orbital speed), then it should be very costly, probably prohibitively costly to send a large military fleet there. Only relatively "light" crafts may be able to get there, so even if space fighter craft can get there, the carriers, motherships, frigates, destroyers or whatever you'd like to call the bigger ones can't get close.

It could thrive on tourism. Think of the Everest in our own world: people want to reach it its top just because it is hard and it is there, and this keeps an economy going at the base of the mountain. The top of the galactic everest is the very core of the galaxy, with your planet being the place where the galactic sherpas live.

It could be a tax haven. If it's hard to get there, it is implied that it's hard for auditors to get there.

It could be a pirate hideout, just like some islands in the caribbean during the 1700's. Okay, this is not proper colonization, but the pirate population could grow enough to become a society on their own.

And since not everyone has the technology to get there, then some race or civilization who can get there may monopolize transportation to and from that planet, and make a hell lot of money.

Answer 9

Your advanced race could colonize it because of prestige ("the coolness factor" / "because it's there" / "because we can"). Prestige in the difficulty of not only getting onto the planet, but hardening the colony against the radiation, tidal forces, and all the other cons mentioned in other answers. Sort of a galactic "my tech capability is bigger than your tech capability" contest. Similar to the Cold War era "space race" here on earth.

Not sure if that would be very advanced, or very immature, though... but hey, you might just have the need for such an antagonistic race in your story.

Answer 10

A better military option. Storage of troops. Assuming a great enough time dilation, you can land 1 million troops and 1 million support personnel every year. Spend a fraction to support them (only a short time has passed for them) and in a hundred years launch a 100 million person armada. You would need to refit with modern tech, or hope technology did not drastically change.

Answer 11

Your orbit doesn't correspond to any known theory of gravity.

If it's travelling extremely fast, but isn't orbiting any particular object (like a supermassive blackhole), then it will very quickly exit the galactic core.

Source: https://en.wikipedia.org/wiki/Escape_velocity

Answer 12

I'm pretty sure that matter going that fast is extremely unstable. This planet might be glowing hot just from its own movement. I also think it would be shaped like a bent spear just from pure force, being slung around in very small orbits very VERY fast.

Landing would indeed be difficult, because contact with matter going this fast is going to give a hell of a recoil. Your ship needs to be able to take a punch, because this planet has an enormous mass (because it's a planet) and an even bigger force (due to going near the speed of light). If you can't keep up it would be the equivalent of an unstoppable force hitting a fly.

Then there's part three, the difference in time. Time, gravity and speed are very closely related forces, as far as more sciencey people tell me. Even if the landing succeeds and the colonizing mission only takes one day on that planet, when the crew returns home they might discover that two centuries have passed at a safe distance from this black hole.

Is this colonizing mission worth it? I dunno. But something on that superfast planet should be worth a lot if it requires this much effort, because it sort of stretches the "doing it because it can be done" mentality.

Answer 13

The reasons why to not to do it mention radiation, time dilatation, nonexistence of such planet etc.

Even if such stable planet exists and our civilisation can deal with the radiation and forces in such system there is one point - you have to catch the planet to land on it.

Using Newton's law $F=\frac{dp}{dt}=\dot p$ and relativistic definition $p=\frac{m_0v}{\sqrt{1-\frac{v^2}{c^2}}}$ we can estimate the thrust of the spacecraft to accelerate to the desired speed.

$$F=\dot p=\frac{m_0+\sqrt{1-\frac{v^2}{c^2}}}{1-\frac{v^2}{c^2}}\cdot\dot v$$

It's easy to see that for constant acceleration $\dot v$ the thrust force $F$ diverges to $+\infty$ and for given thrust force the acceleration goes to $0$ when $v\rightarrow c$.

For $v=0.9c$: $F=\dot v\left(5.26m_0+2.3\right)$
for $v=0.99c$: $F=\dot v\left(50.25m_0+7.08\right)$

Answer 14

Assuming there are no in-universe technological reasons to not colonize it, I see the Time Dilation factor as highly useful from an archival standpoint. As humans with only one colonized planet, we have already seen the need to preserve history and things like seeds in vaults that are to be used in the case of disaster, why would a highly intelligent race not do the same things with their history, seeds, and other vital records? Throw those items onto a planet where time is passing more slowly, and you have a preserved, living record. This helps avoid the "Dark Age of Technology" problem in failing civilizations.

Answer 15

Militarily, I could see one use for such a planet. Assuming that your civilization is advanced enough to land on it, they are advanced enough to move a galactic body close enough to gravitationally nudge the planet out of orbit. With nothing to slow it down, the planet would be a near light speed rocket which would destroy most anything it hit. Such a civilization would likely be able to make the calculations necessary to direct it to where they want it to go.