Vacuum energy as a power source?

[Sorcerer]

Sorry, I was unsure which subcategory this should go under.

 

I was having a sci-fi discussion recently and talking about means of intersellar propulsion available to possible advanced cultures.

 

Would it be possible to somehow tap vacuum energy to create a force to propel a spacecraft? What would you need to harness it?

 

Could you, for instance, have positive energy created infront of the spacecraft, pulling it forward, and negative energy created behind, making the spacecraft/space expand away from it?

[dr.syntax]

Sorry, I was unsure which subcategory this should go under.

 

I was having a sci-fi discussion recently and talking about means of intersellar propulsion available to possible advanced cultures.

 

Would it be possible to somehow tap vacuum energy to create a force to propel a spacecraft? What would you need to harness it?

 

Could you, for instance, have positive energy created infront of the spacecraft, pulling it forward, and negative energy created behind, making the spacecraft/space expand away from it?

 

 

REPLY:That is a very interesting question. The one thing that immediately popped into my mind was: what is the source of energy for such a system ? Can you think of one ? It requires energy to move things such as a spaceship.I cannot think of any, can you ? The energy required for a vacuum cleaner is of course the electrical energy you plug into when you run a vacuum cleaner. I do not see how a vacuum in and of itself has any energy. I do not see a way for this to work. ...Dr.Syntax

[Sorcerer]

I was refering to vacuum energy, as in particle/antiparticle pair - borrowed energy from the vacuum of space +1 + -1 = 0. If it were possible to somehow, rip-off (for lack of a better word) the universe steal its energy (thus shrinking it) and use it for propulsion.

 

See: A Universe From Nothing http://www.scienceforums.net/forum/showthread.php?t=45226

 

So, if the universe adds up to 0, then wouldn't it be possible to steal some, it still would add up to 0, the conservation of energy law would still apply, spaceship +, universe -

 

Btw, I really hope, for your sake, you're being very sarcastic.

[swansont]

You can't use the vacuum energy in this way. It's not a reservoir you can tap into — if you have kinetic energy that came from the vacuum, the vacuum has less energy, and it has to remain the same.

[Bob_for_short]

Would it be possible to somehow tap vacuum energy to create a force to propel a spacecraft? What would you need to harness it?

 

In an empty space (a classical vacuum) there is nothing.

 

A quantum vacuum is a synonym to the ground state of some compound system. If your spaceship is cold (T=0) it is in its ground state. Thus there is nothing to harness.

 

If your spaceship is hot (T>0) it can emit an electromagnetic radiation. It provides a kind of radiative recoil. It is rather inefficient though. Better "radiate" particles, as in jet engines. This is how the excess of energy (the energy above the ground state in the combustion chamber) is employed.

Edited October 29, 2009 by Bob_for_short

[Sorcerer]

I guess if ur constantly trying to keep imaginary particles in existence you would need to use energy to keep it going anyway, so better off just to use classical propulsion and gravity assists.

 

Maybe an Event Horizon or a particle accelerator making anti matter for an antimatter drive, is similar to what I was getting at. Would be neat if there were an easier way though.

 

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Merged post follows:

Consecutive posts merged

You can't use the vacuum energy in this way. It's not a reservoir you can tap into — if you have kinetic energy that came from the vacuum, the vacuum has less energy, and it has to remain the same.

 

Can I ask, why does it have to? Do you mean, "and it cannot, because it always remains the same."

Edited October 29, 2009 by Sorcerer
Consecutive posts merged.

[Bob_for_short]

I guess if ur constantly trying to keep imaginary particles in existence you would need to use energy to keep it going anyway, so better off just to use classical propulsion and gravity assists.

There is no imaginary or virtual particles, as a matter of fact. It's an awkward way of physicists to name interactions (forces like Coulomb one) in calculations.

 

Accelerators can provide high momentum particles which is an efficient way to create a recoil, but! But the particles are charged and to keep the space-ship neutral you have to eject the equal numbers of positive and negative particles. It is done indeed - in the so called ion-jet engines which in fact eject neutral plasma beams.

[Klaynos]

There is experimental evidence for imaginary and virtual particles.

[Bob_for_short]

These are experimental evidence of real particle interactions. Think of the Coulomb potential. In QED it is a "photon propagator" called also a "virtual photon". But in fact, it is mainly a usual Coulomb potential (solution of the field equation with a charge as a source). Some minor quantum corrections to it do not invalidate the physics - it is an inter-particle interaction of real particles.

 

It is quite incorrect to think that a usual empty space (classical vacuum) is filled with virtual particles.

[swansont]

Virtual particles are a valid model in physics. You really need to stop saying, in effect, that it is incorrect to use that model. You don't have to use it if you don't want to, and some other valid explanation works for you and your understanding.

[Bob_for_short]

I am only against a vulgarization of science. Those questions about harnessing the "vacuum energy" are provoked by this vulgarization. And I give an explanation what is meant by the virtual particles.

[Sorcerer]

This is where ideas come from, where'd science be without ideas?

[Bob_for_short]

This is where ideas come from, where'd science be without ideas?

You had a good idea. It is not your problem that it failed but of those who are responsible for speaking of "vacuum energy" in empty space.

Edited October 29, 2009 by Bob_for_short

[toastywombel]

You had a good idea. It is not your problem that it failed but of those who are responsible for speaking of "vacuum energy" in empty space.

 

These particles do exist as said previously in the post. This is how black holes give off thermal radiation. Have you ever read any Hawking?

[Bob_for_short]

These particles do exist as said previously in the post. This is how black holes give off thermal radiation. Have you ever read any Hawking?

 

Yes, I did. I attract your attention to the fact that it is the blackhole that radiates, as any material system out of thermal equilibrium with its environment.

[insane_alien]

but the mechanism for radiation is that virtual particle pairs are separated at the event horizon and become real with the virtual particle that entered the blackhole turning a particle inside the black hole into a virtual particle and anihilating.

 

which kind of indicates that they do exist.

[Bob_for_short]

Let us consider a long-wave radiation with a short antenna. Is the EM wave separated from antenna?

 

You see, any radiation needs a source somewhere. It does not appear in a fully empty space.

 

Let us consider a thermoelectric emission of electrons from radio-lamp cathods. It is a transfer from the ground to highly excited states of cathod atoms.

 

Any radiation - photons and pairs is a transition from the ground state (=quantum vacuum) to an excited state of the original, real system rather than of empty space (classical vacuum). Thus the "virtual particles" belong to real particles/systems and not to the empty space. It is a real particle feature. Without it there is no virtual particles.

 

The pairs are created from the quantum vacuum, not from empty space (=classical vacuum).

[dr.syntax]

I was refering to vacuum energy, as in particle/antiparticle pair - borrowed energy from the vacuum of space +1 + -1 = 0. If it were possible to somehow, rip-off (for lack of a better word) the universe steal its energy (thus shrinking it) and use it for propulsion.

 

See: A Universe From Nothing http://www.scienceforums.net/forum/showthread.php?t=45226

 

So, if the universe adds up to 0, then wouldn't it be possible to steal some, it still would add up to 0, the conservation of energy law would still apply, spaceship +, universe -

 

Btw, I really hope, for your sake, you're being very sarcastic.

 

 

I was not being sarcastic. WHY, FOR MY SAKE ,WOULD YOU REALLY HOPE I WAS BEING VERY SARCASTIC ? Why would you WANT ME, to be very sarcastic ? That makes no sense to me at all. ...DS

[swansont]

I was not being sarcastic. WHY, FOR MY SAKE ,WOULD YOU REALLY HOPE I WAS BEING VERY SARCASTIC ? Why would you WANT ME, to be very sarcastic ? That makes no sense to me at all. ...DS

 

I'm guessing it's because you spoke of vacuum cleaners, meaning that if you were serious you didn't come close to understanding the question. One might wonder why you would choose to attempt an answer under that circumstance. But I could be wrong about this.

[Moontanman]

see these links for info on vacuum energy

 

http://en.wikipedia.org/wiki/Vacuum_energy

 

http://en.wikipedia.org/wiki/Zero-point_energy

[dr.syntax]

I'm guessing it's because you spoke of vacuum cleaners, meaning that if you were serious you didn't come close to understanding the question. One might wonder why you would choose to attempt an answer under that circumstance. But I could be wrong about this.

 

 

REPLY: Do you, SWANSONT. think I was I was being sarcastic? I was thinking through the concept as I typed my answer. I was thinking of how a vacuum engine might work, like when a vacuum of any sort is created here on Earth there is this suction that is a sort of force. Then realized it took energy to create that difference in air pressure and thought of a vacuum cleaner and came to the realization,as far as I could figure that it could not be done. GEEZ some of my most innocent remarks get twisted into some supposed malicious intent. I REALLY DO NOT UNDERSTAND WHY. And why would they hope for my sake I WAS being very sarcastic ? That makes no sense at all to me. ...Dr.Syntax

[swansont]

No, I do not think you were being sarcastic.

[Severian]

Contrary to what a lot of people have said in this thread, yes, I do think that the vacuum energy is a potential energy source. The thing is, we simply don't know enough about the vacuum yet to be sure.

 

For example, imagine a vacuum structure where there were multiple, nearly degenerate vacua, separated by a potential barrier. The true vacuum is the one which is lower in energy, but it could be that the universe is sitting in the meta-stable vacuum, at slightly higher energy. Then, if you could locally move your local vacuum to the true minimum you would gain energy.

 

The barrier would have to be pretty huge (otherwise the lifetime of our meta-stable vacuum would be too short, and we need it to be longer than the age of the universe) but you could imagine some sort of catalyst providing an alternate route around or through the barrier. Then you would have a massive energy release, and a domain wall forming around the region of space that you flipped to the true vacuum. At this point you have to be fairly careful, because you don't want it to spread (and risk destroying the universe) so you would need some mechanism for slowing its growth down. You also want to do this so that the energy release is manageable and can be properly used. I have no idea how you would do this, but I wouldn't rule it out.

 

Interestingly, some models have vacua just like this. The next-to-minimal supersymmetric standard model, for example has 3 vacua which are perfectly degenerate. But various extra higher-energy effects (which I won't go into here) mean that these cannot be properly degenerate but one is lower in energy than the others (the true vacuum).

 

This would also drive the environmentalists nuts of course since you would be 'using up' space. The energy you got out would be incredibly difficult to put back in again, and the region of space in the new vacuum may even have different physics.

 

But I think my point is, we simply don't know, so never say never (in fact, I can think of dozens of other scenarios off the top of my head where vacuum energy could be used as an energy source).

Edited October 30, 2009 by Severian

[Bob_for_short]

As soon as we (you) replace the word "vacuum" with the right term "the ground state of the system", no paradoxes will arise. You have a system in the minimal possible energetic state. Nothing to harness. As simple as that.

[CaptainPanic]

Would it be possible to somehow tap vacuum energy to create a force to propel a spacecraft? What would you need to harness it?

 

Could you, for instance, have positive energy created infront of the spacecraft, pulling it forward, and negative energy created behind, making the spacecraft/space expand away from it?

 

Yes. Sort of.

 

What you need is a pressure difference. A vacuum is a good start, because almost certainly you will have a place somewhere else in space with a higher gas pressure. And then automatically the gas will flow from the high pressure area to the low pressure area. And you can move along with this flow of gas. This principle was already used by people thousands of years ago. In modern English, the craft that moves because of this principle is called a "sail boat".

 

More recently, a new invention was made that created its own high pressure behind the craft. This is called the "rocket engine". Essentially, it creates a very high pressure gas (much higher than our own atmosphere). This gas wants to expand, and will therefore blend with the atmosphere. The action causes a reaction, moving the craft forward.

 

You can also create a vacuum on the front of the craft, and sort of "suck" yourself forward. So far, scientists and engineers found that conventional rocket engines are more efficient, or at least are more cost-efficient.

 

so, essentially it's the pressure difference that gives you power. The keyword here is "driving force", which is always a difference between somewhere and somewhere else. Potential, voltage, height, temperature, pressure, concentration - all these can have differences between two places - and can therefore create a driving force. A vacuum on itself it quite useless. But a vacuum and a high pressure gas next to each other will certainly cause some action.

 

Did that answer the question?

Edited October 30, 2009 by CaptainPanic