Hello, I am new here and still do not understand all the features of this site. To many buttons to click. It kind of makes me want to go back to SDC. Which I can, but I was told about this site and had a very important question that I thought this forum might be able to answer.

I am why06 at Space.com and I have a thread called Dark Energy and Tachyons

Anyway 9 pages into the thread I realized there were some amazing inconsitancies going on with the information used to back up certain physics of Tachyons. All the brain power combined was not able to answer this question on SDC. So here is my question to you....
Question:

Do a few searches on the internet you will see my dilemna and lack of information. I come to this site to see if this question may fare better. If you have any questions about my dilemna. Post on this site or feel free to register at SDC. I am sure there are a few SDC members here.

Thank you, and goodluck

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The Union Why06

Your help is appreciated...

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The Union Why06

Tachyons (if they existed) would have imaginary rest mass, but we would never "see" that rest mass because the tachyon is constrained to move faster than the speed of light. Under those circumstances, two imaginary numbers cancel, and the final result is the appearance of a particle with real mass.

Grant Hutchison

Okay so they have "real" mass. Now is this mass negative or positive?

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The Union Why06

Imaginary mass means that tachyons behave in unexpected ways. Here's a thread with many links which may interest you.

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"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire

Look:
from:http://www.faqs.org/faqs/astronomy/f...ection-12.html

from:http://www.ibiblio.org/lunar/school/.../tachyons.html





This is my problem. I have looked at many of these sites before. The data is inconsistent.

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The Union Why06

That'd depend on the type of imaginary mass they were assumed to have.
A positive mass is something that already exists in the real world, so it seems like it might be a good idea to end up with that; but IIRC there is also a hypothesis that calls for a negative mass, whatever that is.

Grant Hutchison

Here, he's assuming that m is real and nonnegative. That would make E imaginary.

Then he switches to assuming that m is imaginary, which would make E real, but negative.

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"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire

Dark energy?

Or is that so "not right" that it isn't even wrong. (to paraphrase someone famous).

Note that I'm not positing that I've come up with a great idea, I am wondering if the hypothesis that calls for a negative mass is in any way an attempt to explain what dark energy is.

Grant,

Cross your fingers with me for the existence of negative mass-energy. That will make the so-called Alcubeirre (sp? whatever) warp drive possible.

Now, negative mass must mean negative inertia (that's GR's required equivalence principle view). So negative mass repels everything, including other negative masses. This is very different from EM. But positive mass attracts negative mass.

Put a positive mass and negative mass of equal magnitude some distance apart. The positive mass pulls the negative toward it, like anything else, put the negative mass pushes the positive mass away at the same time. The distance between the two masses remains constant, but the whole shebang accelerates off! Now, put a small test particle right in between. It's dragged along with it, accelerated along with it, feeling no force the whole time. And note the external field off to the side -- stuff alongside gets dragged as well, but it doesn't ride with it like the test particle in the center.

That's Newton. And you'll note that kinetic energy and momentum is conserved there, even though both are accelerating off in the same direction. That's what negative inertia does, makes a reactionless drive possible.

Do that with GR and it gets very, very interesting. Warp Drive interesting. In the GR view, that test particle in the center is "riding a wave" in space-time, continously "falling" foward as the "wave" moves foward.

Now, note that in GR, coordinate speeds are not constrained like they are in SR......yes, Virginia, you can make that wave travel faster than 'c' relative to an asymptocially flat observer. [This is just the same thing as an observer down deep in gravity well seeing the coordinate speed of light much greater than c high up. No problem at all.] Well, on paper solving GR equations you can have such a wave travelling faster than c. Actually doing the engineering to make such a thing is, well, another matter entirely.

So, keep your fingers crossed that negative mass-energy exists.

-Richard

Not sure if it helps or not, but I think that the use of Imaginary is to do with Imaginary Numbers (i.e. i the Sqare Root of -1) rather than Fictional or made-up. As far as I understand, Imaginary Numbers, just as with the subset Real Numbers, can be either positive or negitive.

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Howling from the Shadows

It must be fun to lead a life completely unburdened by reality. --- JayUtah

You can't reason an irrational person out of an irrational belief. --- Noclevername

Apollo: The History and the Hoax
Enter the World of Athran

The Non-Imaginary "REAL" answer to all of this is...

Truely understanding WHAT Planck length Non-Baryonic Dark MATTER is!!!

>
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AND, the one place NO ONE from mainstream OR especially anyone from the other side wants to go...Where it is made and how it gets here!!!

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RussT
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Everything is, as it should be, otherwise, it wouldn't be!

EXACTLY!!!!


Now Tachyons have imaginary mass so which is it. Do they show up as positive or negative? I beleive part of the problem is the inability to put complew numbers in to any real form.....Normally though the only way to get imaginary numbers into real form is to square the "i".......This makes one end up with wahtever number times -1. It is for this reason that I believe Imaginary mass could be negative, but this same effect could also make you end up with a negative answer.

I am watching closely to see if you find an answer. I will post this link at SDC

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The Union Why06

In some way it does. Check out the thread at SDC in Phenomenom and you will see why I need this question answered....

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The Union Why06

So have we found a difinitive answer. Does anybody know for sure weather tachyons are hypothesized to have negative mass.


If not I will take this to be the case...

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The Union Why06

There is no definitive answer, since these are hypothetical particles: it depends on your hypothesis.

Grant Hutchison

I actually I went to the library and found a difinitive answer.


So it turns out Tachyons have imaginary rest mass, but negative real mass. I will explain this later if you want me to, but not right now Im very busy.

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The Union Why06

Thanks why. I needed a good laugh today.

I thought tachyons were only an idea therefore a definitive answer is unlikely. Now it's possible that one theory about tachyons gives them imaginary rest mass (i.e. it's imaginary since they can only move faster than the speed of light) and negative real mass but what does that mean. Until their existence is proved or their existince is a necessary condition for some other observations, there is no definitive answer.

Can anyone provide an up-to-date view. Is there any proof or need for tachyons? Can their effects be observed, even theoretically?

It's a cool idea but AFAIK still science fiction.

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Spike
:)

Actually currently I don't want or need or comfirmative data. I simply wanted to know what they were theorized to be.


FYI: They are hypothetical particles. They are as good science fiction as reality is itself. BTW Tachyons can be detected if they were charged moving through a vacuum. They would emit Cherenvok radiation. But this is ONLY hypothesized!

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The Union Why06