Oumuamua may be a hydrogen iceberg • Hacker News Board

Re: Oumuamua may be a hydrogen iceberg

#21

Post by sq_ » Wed, Jun 03, 2020, 5:49 PM UTC

phkahler wrote: post #18

sq_ wrote: post #9

Earlier quoted context omitted.

That's really cool. Definitely helpful in order to drop deceleration fuel requirements if we ever manage to put together a relativistic interstellar spacecraft.

In a bit over 1M years another star is expected to pass around 1000 AU from the sun. Chemical rockets should be able to get there in a decade or two. It's a huge stretch, but we have a million years to prepare.

Oh wow. Had never heard about that. Wouldn't that pass within the range of the Oort Cloud? Seems like we might have some issues from the gravitational effects if so (although that's assuming humans manage to keep ourselves going for another million years).

Re: Oumuamua may be a hydrogen iceberg

#22

Post by radioactivist » Wed, Jun 03, 2020, 5:51 PM UTC

crimsonalucard1 wrote: post #4

Is there an element or compound in the universe that will remain a gas at 0K? Does everything become solid at that temp?

Helium does not solidify down to the lowest temperatures that have been achieved (at standard pressure). Though it does become a superfluid, which is a distinct phase of matter from a gas/liquid.

Re: Oumuamua may be a hydrogen iceberg

#23

Post by dmitrygr » Wed, Jun 03, 2020, 5:54 PM UTC

whatshisface wrote: post #15

dmitrygr wrote: post #10

Earlier quoted context omitted.

Complete lack of motion would violate Heisenberg uncertainty principle ("no motion" == "I know both momentum and location with zero uncertainty" and that's not allowed)

No, you can have zero momentum. However it comes along with having a position wavefunction that fills the whole universe.

Precisely. But that doesn't work for OP's question since the whole universe isn't at 0K.

Re: Oumuamua may be a hydrogen iceberg

#24

Post by troymc » Wed, Jun 03, 2020, 5:56 PM UTC

monadic2 wrote: post #2

Makes me wonder if you could slingshot around the sun towards relativistic speeds with thermal power. At the very least it could save fuel on the egress, if not the second half. Can you aerobrake around a star?

Brown dwarf stars can be relatively cool and can have atmospheres, so you could aerobrake around those.

Re: Oumuamua may be a hydrogen iceberg

#25

Post by NikolaeVarius » Wed, Jun 03, 2020, 5:58 PM UTC

rrmm wrote: post #19

whatshisface wrote: post #15

Earlier quoted context omitted.

No, you can have zero momentum. However it comes along with having a position wavefunction that fills the whole universe.

Hey let's probe the boundary conditions of the universe.

The boundary condition is that at some arbitrary point god smacks you and tells you to knock it off

Re: Oumuamua may be a hydrogen iceberg

#26

Post by crimsonalucard1 » Wed, Jun 03, 2020, 6:12 PM UTC

radioactivist wrote: post #20

caymanjim wrote: post #16

Earlier quoted context omitted.

To be pedantic, it's impossible to get to 0K due to quantum fluctuations. Even empty deep space is over 2K. In laboratory settings, we've gotten way below 1K. I don't think anything qualifies as a gas at that temperature. It'd be a solid or a BEC.

This is true, but doesn't have anything to do with quantum mechanics -- the third law of thermodynamics is basically a statement that you can't cool things to absolute zero.

Your input caused me to google a video about this:

https://www.youtube.com/watch?v=kswiDQ2aAKA

Very intereting!

Re: Oumuamua may be a hydrogen iceberg

#27

Post by btilly » Wed, Jun 03, 2020, 6:17 PM UTC

fenwick67 wrote: post #3

This is great sci-fi fodder, imagine if you could land a tiny craft on that thing and then use the hydrogen as fuel without having to haul all that fuel into deep space (very unlikely to be practical but the idea is exciting).

Matching speeds with it for this operation would take much better rockets than we have available.

Re: Oumuamua may be a hydrogen iceberg

#28

Post by throwaway2048 » Wed, Jun 03, 2020, 6:23 PM UTC

ISL wrote: post #13

diroussel wrote: post #11

Earlier quoted context omitted.

Then the problem becomes getting oxygen. As a hydrogen won't burn in a vacuum.

Unless you can fuse it into helium.

If you have the tech to fuse hydrogen the amount of fuel you would need for a nearly unlimited amount of energy is tiny, you would save very little by harvesting it off a comet/asteroid.

Re: Oumuamua may be a hydrogen iceberg

#29

Post by interestica » Wed, Jun 03, 2020, 6:38 PM UTC

whatshisface wrote: post #15

dmitrygr wrote: post #10

Earlier quoted context omitted.

Complete lack of motion would violate Heisenberg uncertainty principle ("no motion" == "I know both momentum and location with zero uncertainty" and that's not allowed)

No, you can have zero momentum. However it comes along with having a position wavefunction that fills the whole universe.

> However it comes along with having a position wavefunction that fills the whole universe.

I love that this sentence exists. Because it's absurd and enlightening at the same time.

Re: Oumuamua may be a hydrogen iceberg

#30

Post by koheripbal » Wed, Jun 03, 2020, 6:42 PM UTC

fenwick67 wrote: post #3

This is great sci-fi fodder, imagine if you could land a tiny craft on that thing and then use the hydrogen as fuel without having to haul all that fuel into deep space (very unlikely to be practical but the idea is exciting).

I think the theories of it being an artificial alien probe were definitely more sci-fi fodder.

I'd always imagined that an alien intelligence might have seeded every solar system in the galaxy with a probe to monitor for evolving intelligence - but after Oumuamua, I realized it would be far more efficient and reliable to have swarms of them coasting through systems periodically to check on them. ...or maybe both.