# Negative density balloon! :-)

1. May 29, 2005

### Omegatron

So I know you can make a "negative density" region between two plates due to the Casimir effect. I know there's probably not, but is there any theoretically possible way to create a region of such negative density that the total density of the plates and region would be less than vacuum? I had a dream about little personal vehicles with fist-sized negative density regions that were so much less dense than anything that they floated buoyantly through the sky like little hover-scooters. Like a hot-air balloon, but smaller. :-)

If this is not possible, what kind of magic "negative energy" or "negative mass" or whatever would be needed to make it happen?

Last edited: May 29, 2005
2. May 30, 2005

### topside

I've had this same thought experiment too...

Thought about space being so empty and being pulled apart by massive galaxies enough to strain space to the point of "less than nothingness". Of course, I believe this has been thought of many times as a solution to "dark energy" problem where negative density/mass/energy/space would have a force repulsive to gravity thereby having these vast empty "less than nothing" spaces exerting a "pressure" onto super-huge macro objects like galaxies....a macro force to keep the galaxies from flying apart.

That's the concept, but this ultimatly boils down to "Does negative mass/energy exist? If so, will it have a repulsive effect when exposed to gravitational forces?"

I think these ideas have largely been disbanded by the scientific community for good reason I'm sure - but I really don't know - I think it was disproven or at least shown not to fit with the math. Someone more experienced and knowledgable about this line of thought please exlpain the faults with this idea.

3. May 30, 2005

### Omegatron

Yeah, I'm sure it's impossible, but I'd like to know why. You can learn a lot by considering impossible things.

I know the Casimir effect produces a region which has a lower "energy density" than vacuum, by "restricting the wavelengths of virtual particles" or some nonsense. :-) I wish I knew this stuff better.

Last edited: May 30, 2005
4. May 30, 2005

### Danger

Hang on just a second here! Yet another misunderstanding of spatial expansion. Get thee to the astronomy/astrophysics forum. Space is expanding, and carrying matter with it. Matter is in no way 'pulling space apart'. The only effect that matter has is to try and bring more matter to it in accordance with the laws of gravity.
My apologies if that sounds harsh; I didn't mean it to be. It's a very common error, that seems to be the result of non-scientists teaching science. I'm certainly no expert, but at least I had very good books to teach me.

Last edited: May 30, 2005