# Could we move a gas giant by venting its gas?

Could humanity move a planet such as Jupiter by forcing it to vent its gas?

Assuming we have the technology to do huge mining operations and use these to make some of Jupiter's moons into a huge tube going deep into Jupiter. This tube would carry the gas from the mid area of the planet to space. could this gas tube move gas with just the vacuum, or would it require something else to propel it?

If not how could we move Jupiter or a similar gas giant?

edit: if you think of the vacuum of space as your mouth, the tube as a straw, and Jupiter as the drink then you get the idea. straws work because we create a lower pressure place at one end of the straw. edit 2: was wrong, you need to fuse the gas coming out of the end of the straw.

• Try a simple experiment. Take a glass of water (= gas giant) and a drinking straw. Stick the drinking straw in the water (= tube connecting the inner part of the gas giant with the vaccum of space). Will the water move up on its own and flow through the upper end of the straw? Why not? Won't the same force which is keeping the water in the glass also keep the gas in the gas giant? – AlexP Oct 24 '19 at 0:08
• More importantly your straw is much shorter than the gas giant is wide. What is stopping your straw from falling into the gas giant? Your straw will need two engines, one engine is firing gas out into space through the straw. The other is stopping the straw from falling into the gas giant. – Kain0_0 Oct 24 '19 at 0:14
• the straw analogy is wrong since there is no vacuum the water out. the Jupiter thing is more like having a vacuum, such as the one created by your mouth, at the other end. kain has point. – meaninglessname Oct 24 '19 at 0:32
• "The straw analogy is wrong": assuming that the tube was initially empty, the gas would raise in the tube to the level where the pressure of the gas at the bottom of the tube would be equal to the pressure of the surrounding gas; which is exactly the level to which the atmosphere of Jupiter extends. Just as when placing a straw in water, the water will rise in the straw until its level equals the level of the surrounding water. (Think of it: if there was a net force pushing gas out of Jupiter, there would be no need for the tube. The tube does nothing, it does not push the gas upwards.) – AlexP Oct 24 '19 at 0:46
• The answer is no it is not possible to move Jupiter unless you take on god like powers and magic. Jupiter is currently moved by nearby astronomic objects such as stars and large planets and this will remain true in future. – Slarty Oct 24 '19 at 1:16

# Yes, if the tube is a candle.

While a giant tube or straw would not do anything for you on its own (as others have noted, gravity has the same pull inside the tube as outside), we can take it a step further into something that works.

An older question on getting Earth to Jupiter mentions the proposed physics of a gas giant-scale fusion torch drive that you can use to ride around on. The explanation there is quite well done, but the short of it is:

1. Your tube feeds materials (at great expense, but given the scale of construction here energy is the least of our concerns) to a large fusion torch on the outer end.

2. The inner end contains another fusion torch to keep our planetary drive afloat, instead of ramming itself into Jupiter's depths at the first opportunity.

3. Maneuvering is accomplished via lateral thrusters (or still more, smaller, fusion torches) that move the whole tube around Jupiter as needed.

• Interesting take, but when I think of the end inside the giant I only see it heating up the gas, causing it to displace itself, but not necessarily pushing the center of mass in the direction that we want. The opposite end is actually used to keep the tube in place so it can blast the core on the inner end, but there isn't even a guarantee that a core exists, or that enough energy will be able to reach it instead of the dense gas surrounding it, which would expand in all directions causing no change in the planet's orbit. This does effectively reduce its mass though, potentially terraforming? – V. Sim Oct 24 '19 at 1:39
• @V.Sim Valid points! I'm somewhat sentimentally attached to the concept thanks to finding A World Out of Time on a bookshelf one rainy day many years ago, but as with much of Niven there's a fair bit of optimism in even the harder science portions. – Pottermost Oct 24 '19 at 3:02
• The basic idea is good, in principle. But it's less of a candle and more of a rocket exhaust. – a4android Oct 24 '19 at 3:57

If you use the tube idea the gas would just fall back out into Jupiter, also you'd definitely have propel the gas out somehow. Secondly, Jupiter is the second most massive thing in our solar system. It is so big it makes the sun itself wobble.

Momentum is mass x velocity

You want to change its trajectory you will need either a huge amount of mass or a huge amount of velocity. Huge amount of mass is silly because if you could move huge masses on a whim you wouldn't have this issue. What's left is velocity. If you can shoot some asteroids at relativistic speeds you can knock even Jupiter into a new trajectory. That's probably the easiest way to do it.