T.R | Title | User | Personal Name | Date | Lines |
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347.1 | | ENGINE::BUEHLER | Don't mess with my planet. | Sat Jun 21 1986 23:06 | 4 |
| It's been verified that stopping a photon dead in it's tracks produces
a particle known as a Hostess Twinkie. :-)
John
|
347.2 | Twinkie, twinkie, little star... | 3784::ROGERS | | Sun Jun 22 1986 10:14 | 5 |
| That explains why they are so `light' and bright yellow! But, I'm
confused as to where the extra mass comes from. Potential energy?
mike.
|
347.3 | a little einstein here | CACHE::MARSHALL | | Mon Jun 23 1986 15:34 | 12 |
| matter of positive-real mass cannot be accelerated to the speed
of light and "become" a photon. matter of imaginary mass can only
go faster than light and can never be accelerated down to the speed
of light. technically, it is not possible to speak of the rest-mass
of a photon, a photon is created already moving at light-speed.
the extra mass indeed comes from the energy being used to try to
accelerate the mass, which is exactly where the expression e=mc^2
came from; to account for the Lorentz contraction:
m = m0/sqr(1-v^2/c^2)
|
347.4 | c squared? | CACHE::MARSHALL | | Mon Jun 23 1986 15:54 | 3 |
| >> from 0 to c^2 matter undergoes some dramatic changes...
don't you mean from 0 to c ?
|
347.5 | Fruit Pie of Theoretically Infinite Mass | SOFBAS::JOHNSON | It's Only a State of Mind | Tue Jun 24 1986 13:19 | 3 |
| But isn't it true that the Tachyon Ring Ding is a pastry snack that
cannot travel slower than the speed of light?
|
347.6 | confection currents | PROSE::WAJENBERG | | Tue Jun 24 1986 16:00 | 21 |
| I don't know what the pies have to do with it, but the Lorenz
transformations are very strict about what kinds of mass may travel
at what kinds of speed:
If the object has zero rest-mass (and still exists) it must travel
at the speed of light, exactly.
If the object has real rest-mass, it must travel slower than light.
Only positive real masses have been observed, but negative ones
are compatible with the mathematics. A real rest-mass traveling
faster than light would have an imaginary observed mass. That is
presumably impossible.
If the object as imaginary rest-mass, it must travel faster than
light. No such object has ever been observed. An imaginary rest-mass
traveling slower than light would have an imaginary observed mass.
That is presumably impossible. This raises the interesting problem
that an imaginary rest-mass is impossible in its own rest-frame.
But then so is a zero rest-mass, and people BELIEVE in those....
Earl Wajenberg
|
347.7 | Now *THAT* would be interesting | ACADYA::RUSH | | Fri Jun 27 1986 17:02 | 85 |
|
According to the Lorenz formulae, certain aspects of matter
change due to change in velocity.
These are:
MASS - Which increases relative to an outside observer
as velocity approaches c.
{ Mo
{ M = ------------------
{ sqr[1-(v^2/c^2)]
LENGTH - (In direction of travel) Which decreases
relative to an outside observer as velocity
approaches c.
{ L = Lo * sqr[1-(v^2/c^2)]
TIME - Which decreases relative to an outside observer
as velocity approaches c.
{ T = To * sqr[1-(v^2/c^2)]
From these, it is postulated that an object cannot obtain the
velocity c because:
a) Time rate would be zero
b) The object would have no length in direction of
travel ( Therefore it would be two dimensional )
c) The object would have an infinite mass
Seeing as no non-infinite force could overcome the inertia of
an object moving infinitely close to the speed of light, and as most scientists
doubt the existence of an infinite force, reaching c is considered an
unobtainable goal.
But if the reasons stated above are the only objections to the
attainability of c, then the speed of light would appear to be a very
obtainable goal.
How? ... Simply by using a nuclear reaction located
ON THE OBJECT as the means for acceleration.
The result would be quite interesting.- As the mass of the ship
increased, so would the mass of the nuclear fuel. The increased fuel mass
would result in increased energy output by E = mc^2. Therefore, the increase
in ship mass and the increase in fuel mass would counter-ballence each other
so that acceleration would remain constant right up to the velocity c.
( Whereas, with any other type of accelerator, the force produced would have
less effect on the growing mass and inertia of the object, and acceleration
would slow. This is a great problem with nuclear accelerators these days.-
As we get closer and closer to bringing particles up to light speed, the gains
achieved by increasing accelerator energy are becoming smaller and smaller.)
At the speed of light, however, you have a problem:
At this point, the mass of the object is infinite.
At this point, the force provided by the nuclear fuel
is infinite.
This makes things interesting.
To an observer outside the object, it unmovable from the course that
it is now on.
To the same observer, the force provided by the nuclear reaction is
irresistible - infinite and unstoppable.
To the same observer, time will have stopped in the system of the
object and the force.
So, what happens when an irresistible force acts on an
unmovable object in an infinite period of time?
I don't know, but I'd sure like to be there to see it.
______
/-/ JASON
-----
|
347.8 | regretful cold water | PROSE::WAJENBERG | | Fri Jun 27 1986 17:32 | 39 |
| Very clever. Your proposal should be enshrined among the problems
at the back of the chapter in a college physics text. But it should
be there to make the students figure out why it DOESN'T work, I'm
afraid.
First, a side-issue. You don't need to postulate a nuclear reactor
powering the rocket. The mass increase amplifies any other source
of thrust in the same way. Suppose it was a chemical rocket. By
your reasoning, as the speed increases, each molecule of fuel becomes
more massive and so stores more chemical energy, which can be released
to make the rocket go faster, which increases the mass and chemical
energy of the remaining fuel, in the same feedback loop you postulated
for a nuclear reactor.
To see why it doesn't work, ask yourself where the extra mass of
the fuel comes from. It has to come from somewhere -- you can make
a general analysis of Newton's Laws together with the Lorenz
transformations to show that mass/energy and momentum are conserved
under them. We started out with a fueled ship of finite mass.
We ended up with an infinite mass. We did NOT conserve mass/energy.
Something went wrong.
When an object gains mass as it gains velocity, that mass is a form
of energy supplied by agent moving the object. With a particle
in an accelerator, the energy is supplied by the magnetic fields
of the magnets doing the accelerating. The magnets can pump in
energy forever; some of it shows up as increased velocty, some of
it as increased mass. The closer you get to the speed of light,
the more energy gets pumped into mass and the less gets pumped into
velocity increment.
With a ship, you can't pump energy in forever; it starts with all
the energy it's going to have. Imagine an ideal ship that turns
every bit of fuel energy into kinetic energy. That's still a finite
quantity of energy. It won't get you up to light-speed.
Nice try, though.
Earl Wajenberg
|
347.9 | Clever, And Already Used | INK::KALLIS | | Fri Jun 27 1986 17:38 | 8 |
| re .7, .8:
For everybody's information, the reaction/power-mass-aboard-the-ship
concept was used in the 1940s by Edmund Hamilton in his book, _The
Star Kings_.
Steve Kallis, Jr.
|
347.10 | MASS confusion! | RT101A::ROGERS | D'em atoms don't cost nothin'... | Sat Jun 28 1986 11:12 | 18 |
|
re: .4
>> From 0 to c^2 matter undergoes some dramatic changes...
> Don't you mean from 0 to c.
No, I mean from 0 velocity, total matter, to c^2, `pure' energy.
re: .7
> Length - (in direction of travel) which decreases relative to
an observer as velocity approaches c.
> b) The object would have no length in the direction of travel
(therefore it would be two dimensional).
Would it not also appear to have no mass to an observer in three
dimensional space? Or, can two dimensional objects displace three
dimensional space?
|
347.11 | It's all relative, anyway. | FRSBEE::FARRINGTON | a Nuclear wonderland ! | Mon Jun 30 1986 09:11 | 20 |
| re .7 (I think)
Sounds like a description of "life" on the event horizon,
just over ole Schwartzchild's Limit, of a handily placed
black hole.
re .10
c^2 is not "pure" energy; last time _I_ checked, it was still
a mathematical concept. I could be wrong; corrections are ALWAYS
appreciated (but with this one, I would like a little math rigor).
The confusion on 0 length, infinite mass, et al, may be handily
addressed by remembering we're talking 'relativity'; inertial
reference frames. Rest mass for the observer ---> infinity for
an accelerated body does not mean the body's mass is actually
increasing, to the body in its frame of reference. Similarly with
its length.
Dwight
|
347.12 | units | PROSE::WAJENBERG | | Mon Jun 30 1986 11:20 | 20 |
| c^2 (which has units of meters-sq / second-sq ) is just a conversion
factor, describing how much emergy you can extract from a given
quantity of mass. c^2 is not a velocity, but the square of a velocity,
so you cannot meaningfully speak of anything "moving at c^2."
In special relativity, it is very convenient to take c, the speed
of light, as a conversion factor between space and time, amounting
to about 30 cm to the nanosecond. It is then convenient to measure
time in meters rather than seconds. E=mc^2 then becomes E=m, because
c itself is 1, tautologically. E=m shows even more clearly that
energy in any form has the effects of mass (i.e. inertial and
gravitational effects), and that all mass is "good for" a certain
amount of energy if only you know how to get at it.
If you accelerate something to the speed of light, it does not "turn
into energy," first because you CAN'T accelerate it to c, at least
not if specialy relativity is correct, and second because the cargo
already IS energy.
Earl Wajenberg
|
347.13 | I'm a little photon,... | MINAR::BISHOP | | Tue May 31 1988 15:15 | 9 |
| What is the experience of a photon? By the equations, no time
passes for it, so it is everywhere in its entire history at
once. This is not so suprising when the fact that it "sees"
the universe (or rather, the photon's path through the universe)
as having a length of zero.
How photons can "know" how to interact if they have no time is
what confuses me.
-John Bishop
|
347.14 | You Have To Start Somewhere | ATSE::WAJENBERG | Make each day a bit surreal. | Wed Jun 01 1988 10:55 | 25 |
| Re .13
How a photon "knows" what to do is part of a larger question of how
any particle "knows" what to do. The photon has no time for internal
processes to take place inside it, but then neither does any other
particle, really. An electron, for instance, may last longer, but
when it interacts with another particle, it does not, so far as
we know, have time to "process" the incoming cause before it has
to produce the outgoing effect.
Really, this situation almost has to arise in any physics. If
elementary particles processes each interaction over time, this
would imply interior mechanisms to do the processing, so that the
particles wouldn't really be elementary. (This is what happened
with atoms, which used to be thought elementary, but turned out
to have parts. Then protons and neutrons were thought elementary
but now seem to have parts, probably quarks. And quarks? Who knows?)
At some point, you have to posit elementary interactions that take
no processing time. Either that, or you have to postulate an infinite
regress of interactions composed of other interactions, down and
down forever. No one has come up with a way to make a testable
scientific theory out of such a regress.
Earl Wajenberg
|
347.15 | I hope this is right. | ARTMIS::MILLSH | Is there any Tea on this spaceship? | Wed Aug 02 1989 05:20 | 17 |
| re: .7 & .10
> Length - (in direction of travel) which decreases relative to
an observer as velocity approaches c.
> b) The object would have no length in the direction of travel
(therefore it would be two dimensional).
> Would it not also appear to have no mass to an observer in three
>dimensional space? Or, can two dimensional objects displace three
>dimensional space?
What actually happens to the length of the object observed is that
it appears to become foreshortened. Given two points on its surface
which are a known distance apart (e.g. 1 metre), the object will always
measure the same length, *using the mark on its side as a base length*
HRM
|