negative mass sounds just as imaginary (no pun intended) as negative numbers. So how does matter have negative mass and still actually exists?

Wait. Imaginary numbers are just as real as real numbers (no pun intended either ), there's really nothing special about imaginary numbers that makes them any less "existent" than 'regular' numbers like 42.
[edit]Oh, I read that as "just as imaginary as imaginary numbers" -- replace "imaginary" with "negative" in my reply -- 42 and -42 are both just as logical a concept[/edit]

Particles with positive or negative charge exert a certain pull or push on other particles, via the electromagnetic field.
Likewise, particles with positive mass exert a certain pull on other particles, via the gravitational field. Although we've never observed a particle with negative mass, all the math behind the gravitational field still works if you plug in negative numbers (like it does for charge). So if we take the hypothesis that such a particle might exist, we can make a prediction what it's effects would be, even though we've never seen one.
It may be that such a thing doesn't exist, or that our predictions are wrong -- but that's still a current research topic with no definitive answers yet.

Everything theoretical is imaginary. Otherwise it becomes actual.

In science, "theory" means fact, and "hypothesis" means speculation. All we have are theoretical models. Which means nothing is actual and everything is imaginary!

It can be argued that there is no objective 'actual' reality and there is only pictures of reality as drawn by models.

[quote name='Alpha_ProgDes' timestamp='1348162714' post='4982097']negative mass sounds just as imaginary (no pun intended) as negative numbers. So how does matter have negative mass and still actually exists?

Wait. Imaginary numbers are just as real as real numbers (no pun intended either ), there's really nothing special about imaginary numbers that makes them any less "existent" than 'regular' numbers like 42.
[edit]Oh, I read that as "just as imaginary as imaginary numbers" -- replace "imaginary" with "negative" in my reply -- 42 and -42 are both just as logical a concept[/edit][/quote]
As a concept, yes I agree. But in reality, if I have 5 apples, you can only take 5 apples. Not six and therefore leave me with -1 apple. See what I mean?

Particles with positive or negative charge exert a certain pull or push on other particles, via the electromagnetic field.
Likewise, particles with positive mass exert a certain pull on other particles, via the gravitational field. Although we've never observed a particle with negative mass, all the math behind the gravitational field still works if you plug in negative numbers (like it does for charge). So if we take the hypothesis that such a particle might exist, we can make a prediction what it's effects would be, even though we've never seen one.[/quote]
Maybe it's my dealing with positive mass, but the idea of matter with negative mass actually existing is just weird to me.

Everything theoretical is imaginary. Otherwise it becomes actual.

In science, "theory" means fact, and "hypothesis" means speculation. All we have are theoretical models. Which means nothing is actual and everything is imaginary![/quote]
I thought "theory" means given a set of conditions this is shown to be true. Or until you prove this wrong, it's right.

I thought "theory" means given a set of conditions this is shown to be true. Or until you prove this wrong, it's right.

In general language, I would say "theory" agrees with your definition, but in science it is more strictly defined. A theory by definition can never be proved because there are no known physically based axioms to build proofs with - it can only be disproved (and then adjusted to account for exceptions, if applicable). So a theory is "a hypothesis that is heavily supported by experimental evidence, and assumed to be true, until shown otherwise". Also, there are other requirements, such as, a theory must be observable (you must be able to verify it through experiments), and you certainly need a significant amount of various experiments to support your hypothesis before you can call it a theory.

But in reality, if I have 5 apples, you can only take 5 apples. Not six and therefore leave me with -1 apple. See what I mean

Yeah, but this is just an application of numbers, it's not where the numbers themselves come from.
Yes, we started out by physical counting with examples like that, but then we realised that we didn't just invent a counting system, we'd discovered a deep system of logic, and we now call your "non-imagined" set of numbers the "natural numbers".

Also, the fact that you count the apples in multiples of "1" is just a convention. If we used a strange convention where we do everything the opposite way around, we can still count. I can say each apple is worth "-1" (and -1 + -1 + -1 + -1 + -1 == -5, so) you've got "-5" apples in this bizarro convention, and I take 4 of them (and taking an apple is worth "+1"), then "-5 + 4" leaves you with "-1" apple, which equates to 1 apple in the regular convention.

If you think of mass as just being another "named attribute" that a point can have, and charge is another "named attribute", then it's not so weird -- electricity is a flow of particles with negative charges. But we could just as well have called them "positive charges" or "up charges" or "strange charges", if different people had done the naming.
Or if you think of positive mass as something that sucks space-time in towards it (like a vacuum cleaner's nozzle against a bed-sheet), then 'negative mass' would be something that pushes space-time outwards (like a leaf-blower).

Or until you prove this wrong, it's right.

Yep, which makes it 'accepted fact'. There's no such thing as absolute fact (unless you're religious), so I'd just call it 'fact'. The theory that if you jump out a window, you will fall down, is a fact -- it could be disproved at any time, but it's pretty well accepted for the time being.

Or if you think of positive mass as something that sucks space-time in towards it (like a vacuum cleaner's nozzle against a bed-sheet), then 'negative mass' would be something that pushes space-time outwards (like a leaf-blower).

So I guess Dark Matter has negative mass. Since in theory, it's pushing the universe outward.

[quote name='Hodgman' timestamp='1348239008' post='4982394']
Or if you think of positive mass as something that sucks space-time in towards it (like a vacuum cleaner's nozzle against a bed-sheet), then 'negative mass' would be something that pushes space-time outwards (like a leaf-blower).

So I guess Dark Matter has negative mass. Since in theory, it's pushing the universe outward.
[/quote]
That would be Dark Energy - Dark Matter - as the name implies - exerts the same gravitational effects on fabric of space time as ordinary matter. The only difference is that it seems to only interact with the rest of universe via gravitation.

Yep, which makes it 'accepted fact'.

Scientific laws are closer to fact than theory. A theory is just a verified hypothesis. The level of it's verification does not make it any more or less of a theory. String theory is a good example of a non-accepted fact that is still a theory.

There's no such thing as absolute fact (unless you're religious)
[/quote]
1. As a moderately religious catholic, I don't think there are very many facts in my faith. There are things I believe to be true, but I would not call them facts.
2. There are nobel prize winning scientists who are religious. I don't see why bringing up religion at all was necessary, but looking down on religious people by virtue of them being religious doesn't make you correct, it makes you an asshole; as it would with looking down on any group of people.

I don't see why bringing up religion at all was necessary, but looking down on religious people by virtue of them being religious doesn't make you correct, it makes you an asshole; as it would with looking down on any group of people.

I am having a hard time assuming you aren't intentionally flame-baiting with that statement. If not, then you are completely missing the point:

- Science doesn't allow for the very concept of absolute truth. It's at best a philosophical ideal towards which we may strive.
- Faith, on the other hand, is founded on the concept that there is some absolute truth, and that even though it can never be scientifically validated, it is still 'truth'.

Hodgman's statement was in no way derogatory towards religion of religious individuals.

I am having a hard time assuming you aren't intentionally flame-baiting with that statement. If not, then you are completely missing the point:

- Science doesn't allow for the very concept of absolute truth. It's at best a philosophical ideal towards which we may strive.
- Faith, on the other hand, is founded on the concept that there is some absolute truth, and that even though it can never be scientifically validated, it is still 'truth'.

I'm not flame baiting. I just don't find faith based truths to be facts because they are subjective/personal truths. Facts are objective truths.

For example, as a person of faith, I believe fully that there is a god, but I would not consider that god's existence a fact. If that makes sense?

The way it read to me was that religious people have different standards for what they would consider factual than scientists. Considering that there are many accomplished religious scientists, and that there are many religious people that hold science in a very high regard, I found it unnecessary to bring religion into contrast with science in that measure at all.

"There's no such thing as absolute fact (unless you're religious)," would be grossly offensive if you replace the word "religious" with any other identifier. I don't see why it being religion instead of sexuality, race, nationality, etc makes it less offensive.

I'm a theist, and for the life of me, I cannot figure out how or why religion wound up in this discussion! Why does this always have to happen? It doesn't matter which side of the religious argument you're on, someone is bound to throw a in jab. This time it was by a moderator! Hodgman, intent aside, it was not necessary to mention.

I hate it when threads like this get closed because people cannot keep their religious opinions to themselves. This is about warp drive, not religion. Let's get back on topic. Please!