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Space Is Full of Planets, and Most of Them Don't Even Have Stars

forbes.com

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Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#61

Post by simonh »

hamilyon2 wrote: post #47
itronitron wrote: post #26

Interstellar travel now seems a lot more hazardous than it did before. To quote one of my TAs in college, "it's the stuff you can't see that gets you" ...

Actually, one could refuel reactive mass by mining those planet if delta v is favorable. Reactive mass deficit is one of biggest problems with interstellar travel. Suddenly, I think interstellar travel is a bit less impossible.

The trouble is you'd need to stop, mine the mass, then accelerate back up again. If you have the fuel to stop to refuel in the first place, you don't need to stop refuel, unless there's something else you need as well.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#62

Post by ben_w »

boznz wrote: post #59
mrarjen wrote: post #53

Earlier quoted context omitted.

Exactly, and I saw that when the Andromeda Galaxy collides with ours, it's unlikely many planets/systems will be colliding with one another.

Never really understood how galaxies can collide if space has been expanding since the big bang and everything is moving apart

It goes both ways depending on distance. Expansion is exponential (ish), gravity is inverse-square [1]. Only the few that happened to be close enough that gravity is more significant than expansion can collide.

[1] at least in Newtownian physics. The argument is geometry, so I suspect but am not qualified to say it isn’t exactly inverse square in GR.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#63

Post by lebrad »

ianai wrote: post #34
afterburner wrote: post #29

New 4x games should now include plenty of planets between star systems. Cold and still, but potential mining boons and refueling bases.

And I demand Star Trek TNG be reran with scientifically appropriate visits to rogue planets. /s

The Founder's homeworld on Deep Space Nine was a rogue planet

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#64

Post by mickronome »

boznz wrote: post #59
mrarjen wrote: post #53

Earlier quoted context omitted.

Exactly, and I saw that when the Andromeda Galaxy collides with ours, it's unlikely many planets/systems will be colliding with one another.

Never really understood how galaxies can collide if space has been expanding since the big bang and everything is moving apart

Same reason I can collide with someone on the sidewalk while the universe is expanding at tremendous speed. Over short distances, the expansion can easily be overcome by others forces like gravity or my muscles excerting force through friction against the ground. However, given enough time, there will be less and less objects that are close enough to be able to collide at all. Lots of time though, and there are already now lots of things over galaxy could never ever collide with.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#65

Post by kamaal »

zaarn wrote: post #57
lev99 wrote: post #32

Earlier quoted context omitted.

The article states that planets may outnumber stars 100,000 to 1. The Milky Way has 4E^11 stars. It has an upper estimate of 4E^16 planets. It has a lowest estimate diameter of 100kly. It has an estimated thickness of 2kly. It's lower estimate volume is 63,000 kly^2. ----------------------------- If planets are uniformly disrupted (they surely aren't), there are ~17 planets in every cubic light year. Sure, that's a h…

People tend to forget how big a cubic light year is. The earth itself is only 0.02 light seconds in diameter, yielding a cube of 8000 cubic lightmilliseconds. Compared to the 2.9 10^31 cubic light milliseconds in a cubic lightyear... It's a rounding error inside a rounding error. For light seconds, you're looking at 2.9 10^22 (if my math isn't wrong). That's the amount of cubes fitting between earth and moon to fill…

If something doesn't shine already. The only way to detect its existence is to send radio waves and see if something bounces off(Like Radar).

I guess the point people are trying to make here. If you can't see light coming off an object, then while traveling at interstellar speeds means it will be harder to spot objects until they get too close.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#66

Post by ben_w »

everdev wrote: post #46
nabla9 wrote: post #38

Earlier quoted context omitted.

Planets can be detected by their gravity field. Collision with planet sized object in space would be extremely rare. Even if you would travel blind it would be very unlikely that you would hit star or plant while traveling trough galaxy.

Well, if there's not much around it, it might be hard to detect it's gravitational effects. I'd imagine you could detect it blocking a circular patch of sky more easily and from farther off than you could detect the gravitational pull on your spacecraft. Just don't steer twords the black disc and you'll be fine.

Four ships (or a ship and three probes) arranged in a tetrahedron, where the distance between each pair is precisely measured with a laser or similar. Changes to the edge lengths of the formation show a nearby gravity gradient.

What’s one wavelength per minute if the formation is 1000km?

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#67

Post by kamaal »

This sort of space real estate is the biggest hindrance to developing long term interstellar traveling tech.

With so many asteroids and planets lying around. There is no real motivation to travel very far distances for resources. Once you start mining the first set of asteroids and settling your race in space. You could grow organically, and at some point mine a terrestrial planet. At that point you have so many resources at your disposal it doesn't really make much sense to move out to very large distances unless for science or your population is just multiplying beyond control.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#68

Post by zaarn »

kamaal wrote: post #65
zaarn wrote: post #57

Earlier quoted context omitted.

People tend to forget how big a cubic light year is. The earth itself is only 0.02 light seconds in diameter, yielding a cube of 8000 cubic lightmilliseconds. Compared to the 2.9 10^31 cubic light milliseconds in a cubic lightyear... It's a rounding error inside a rounding error. For light seconds, you're looking at 2.9 10^22 (if my math isn't wrong). That's the amount of cubes fitting between earth and moon to fill…

If something doesn't shine already. The only way to detect its existence is to send radio waves and see if something bounces off(Like Radar). I guess the point people are trying to make here. If you can't see light coming off an object, then while traveling at interstellar speeds means it will be harder to spot objects until they get too close.

Not all black objects reflect radar, black holes don't reflect at all.

I think if you were to encounter a black hole, esp an inactive one, in interstellar space, you'd probably just get sucked in if you didn't notice the black disk...

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#69

Post by ben_w »

cobbzilla wrote: post #60
ChuckMcM wrote: post #20

Earlier quoted context omitted.

Napkin math (aka pure speculation) suggests that unless the rogue planet hit the star directly and at an angle that could send ejecta our way, the results would be more observational than catastrophic. The Earth is roughly 333,000 times less massive than the Sun. Think of it this way, If an asteroid hit the Earth that was, in relative terms, the size of the earth relative to the sun, it would be about 1/3 the size of…

Let's say the rogue planet is a massive, super-cold planet. How big and how cold would it have to be to lower the Sun's energy output just enough to trigger a "Snowball Earth" scenario? Assume a direct hit.

The extra mass of the planet would increase the rate of fusion.

https://what-if.xkcd.com/14/

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#70

Post by King-Aaron »

akvadrako wrote: post #54
King-Aaron wrote: post #51

Earlier quoted context omitted.

The title doesn't seem to embellish the article, and others are noting that the author is credible. Sorry to hear that you were blocked from being able to read it.

The author is not credible - he posts almost every day and he doesn't understand half of it. It's just fluff.

¯\_(ツ)_/¯ I'm just going off what others with a deeper understanding of theoretical astrophysics than me are saying.
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