
NASA engineer's 'helical engine' may violate the laws of physics - elorant
https://www.newscientist.com/article/2218685-nasa-engineers-helical-engine-may-violate-the-laws-of-physics/
======
knzhou
The description in the article is oversimplified.

Relativistic dynamics is different from Newtonian dynamics in a lot of ways.
Force isn't parallel to acceleration anymore. Acceleration gets harder the
faster an object moves. You can mimic _some_ of these changes by just
pretending that you still have Newtonian dynamics but the mass can change with
velocity, but we don't use this language in physics because it's misleading --
there are many effects this idea _can 't_ capture. (For example, the fact that
force is not parallel to acceleration.) It is a very fragile analogy that
causes a lot of conceptual mistakes.

It's easy to prove that Newtonian mechanics conserves momentum. It's also easy
to prove that relativistic mechanics conserves momentum. A weird hybrid of
Newtonian mechanics plus a magically changing "relativistic mass" does _not_
conserve momentum, but nobody has ever thought this was a correct description
of nature. It's the result of taking a helpful simplifying analogy too far.
Any reactionless drive formulated using this Frankenstein theory doesn't work.

If you just bounce an object back and forth, in either Newtonian mechanics or
relativistic mechanics, you won't get anywhere. If you change the _rest mass_
of the object to be different going right than left, you will go somewhere,
but it will cost momentum to do this, as explained in gus_massa's comments. So
we haven't gotten thrust for free.

~~~
elcomet
How could NASA allow research on such a topic if it is obvious for physicists
that this is impossible ?

~~~
sgift
Even things we think we know very well may be wrong, so having a certain
budget for "fringe" subjects which may yield unexpected results is not a bad
idea. At the same time it's probably a good idea to assume everything they
report is a measurement/test setup error until further proof.

~~~
_0ffh
Yup. As it is said "If a physicist says it's possible, then it's possible. If
a physicist says it's impossible, then it's undecided."

~~~
lonelappde
The actual saying is that everything that an elderly distinguishes scientist
has an opinion about is probably possible.

It's a complicated way if saying almost everything is possible so don't
believe old dogs who have given up on optimism.
[https://www.brainyquote.com/quotes/arthur_c_clarke_100793](https://www.brainyquote.com/quotes/arthur_c_clarke_100793)

~~~
antonvs
Everything _in their field_ , that is. Since some elderly scientists have come
up with some pretty nonsensical ideas about things outside their field.

------
gus_massa
The idea of the article is to use the change of mass in special relativity.
Some particles go faster in one direction (and they have more mass), and then
they return more slowly in the other direction (and has less mass).

In special relativity, when the charged particles accelerate and decelerate
they emit electromagnetic radiation. The whole process conserve the energy and
momentum. The momentum that the device provides is compensated by the momentum
of the electromagnetic radiation, aka photons.

So this device should work. It doesn't break the laws of physics. It produce
some photons in the intended direction and more photons in other random
directions. So it is just a very inefficient photon thruster
[https://en.wikipedia.org/wiki/Photon_rocket](https://en.wikipedia.org/wiki/Photon_rocket).
It's like attaching a laser to the back of your starship, and then adding some
lamp to illuminate in every direction to make it more inefficient.

~~~
aeternum
The claimed power to thrust ratio of 165 MW / N does check out as less
efficient than a photonic rocket at 150 MW / N assuming the beam is reflected
off the craft.

~~~
iamgopal
165 mega watt per Newton ? Is it theoretical or practical number ?

~~~
trhway
Sun radiation is about 1.4KW/m2 at the Earth orbit and the pressure is
0.00001N/m2 - basically the same numbers as GP mentioned for the photonic
drive - can be calculated as 1.5KJ (for roundness of numbers) of photons
divided by c which gives 0.000005kg-m/s of momentum per second, double that
for bounce and thus 0.00001N. As photons are usually the things being thrown
for the thrust in the mass-less thrust schemas, then those photonic thrust
numbers seems to be a theoretical limit .

------
gus_massa
Don't dismiss this article just because of the main image. It's a image of an
EmDrive that is another impossible device that doesn't work but is totally
unrelated to the device in this article.

The main part is:

> _This mass changing isn’t prohibited by physics. Einstein’s theory of
> special relativity says that objects gain mass as they are driven towards
> the speed of light, an effect that must be accounted for in particle
> accelerators._

In special relativity, when the charged particles accelerate and decelerate
they emit electromagnetic radiation. The whole process conserve the energy and
momentum. The momentum that the device provides is compensated by the momentum
of the electromagnetic radiation, aka photons.

So this device should work. It doesn't break the laws of physics. It produce
some photons in the intended direction and more photons in other random
directions. So it is just a very inefficient photon thruster
[https://en.wikipedia.org/wiki/Photon_rocket](https://en.wikipedia.org/wiki/Photon_rocket).
It's like attaching a laser to the back of your starship, and then adding some
lamp to illuminate in every direction to make it more inefficient. So you can
dismiss this article after all.

EDIT: I copied most of this comment to other comment in
[https://news.ycombinator.com/item?id=21253796](https://news.ycombinator.com/item?id=21253796)
, but the other comment was later moved here, so there is a lot of overlap.
The other article at least don't use a big photo of an EmDrive.

~~~
rurounijones
> Don't dismiss this article just because of the main image. It's a image of
> an EmDrive that is another impossible device that doesn't work

Do you have a link for that? I haven't been following the EM Drive but a quick
google now suggests that a team in Germany believe that they found the reason
for the anomolous readings but I cannot find anything definitive.

~~~
knzhou
The problem with EM drive testing in general is that you're looking for a
signal (thrust) which should be zero, while pumping an enormous amount of
energy into a system, and declaring _any_ nonzero reading as success.
Physicists know from experience that this is a recipe for fooling yourself.
There are a million things that could imitate the purported signal.

In the last EM drive test I looked at, the "thrust" was pointing in the wrong
direction, and moreover it perfectly matched the temperature curve of the
apparatus, even though no theories of the EM drive say it should. That is a
dead giveaway that the temperature is causing a fake signal, which e.g. could
happen by thermal expansion messing up the meters. In general, the EM drive
seems like a playground for sloppy experimentalists, because what anybody else
would call a failure can be reported as a success.

~~~
taneq
> declaring any nonzero reading as success

And as anyone who's worked with sensors should know, if your sensor is reading
_exactly_ zero, that means your sensor is broken.

------
milchek
The animation comparing the helical engine with same mass vs with relativistic
masses was super helpful, I wish more articles that went into physics had
these kinds of simple illustrations.

>“I know that it risks being right up there with the EM drive and cold
fusion,” he says. “But you have to be prepared to be embarrassed. It is very
difficult to invent something that is new under the sun and actually works.”

This was actually my favourite part of the article and a beautiful reminder
that it's OK to fail.

~~~
pmoleri
The animations sure help, but I find the second one misleading because the
ring bounces instantly and it has only 2 discrete sizes.

Instead of a discrete bounce, picture a slow motion elastic bounce where the
ring gets heavier as it's being accelerated. It seems to me that when the box
pushes the ring (left side), the ring would be gaining mass as it accelerates,
thus cancelling the harvested movement, right?

~~~
pontifier
I think the mass increase is not supposed to come from the forward/backward
motion. Rather, the mass increase comes from rotating the ring.

Imagine the ring at the front of the ship spinning up to relativistic speed,
then you push hard on it to get your ship moving a bit. Then you slow the ring
down again before it hits the back, so it's much easier to bring back to the
front.

~~~
pmoleri
Interesting, maybe that's why they chose a ring, although the article is not
clear in that aspect.

------
lallysingh
"But you have to be prepared to be embarrassed. It is very difficult to invent
something that is new under the sun and actually works."

I appreciate the courage of this.

~~~
mellosouls
Yes, that stood out for me too. The guy doesn't come across as the
stereotypical blinkered crank.

------
mdorazio
Here's the actual paper [1]. The article was super confusing because it
implied the box itself would need to be traveling near the speed of light for
the theorized effect to work, which is pretty useless if you're at 0c to start
with. I don't fully understand the paper, but it suggests using magnetically
contained ions in a rotating ring arrangement. If nothing else, this will be a
fun thought experiment for other physicists to break down.

[1]
[https://ntrs.nasa.gov/search.jsp?R=20190029657](https://ntrs.nasa.gov/search.jsp?R=20190029657)

~~~
AnIdiotOnTheNet
> The article was super confusing because it implied the box itself would need
> to be traveling near the speed of light for the theorized effect to work,
> which is pretty useless if you're at 0c to start with

Even more useless when you consider that in your own frame of reference you're
always at 0c.

------
leni536
If your starting point is a well understood theory that is known to conserve
momentum (as a mathematical theorem), you design a complicated device using
this theory and then within this specific design you find that momentum is not
conservered then you should double check your calculations.

It first happened with classical electrodynamics (the EM drive) and now it
happens with special relativity it seems.

To be fair, I am not arguing that conservation of momentum is 100% true. But
starting from well established theories where conservation of momentum is a
mathematical consequence seems to be a flawed approach.

~~~
Enginerrrd
I can't believe this is so far down. This is exactly why I don't need to pay
attention to someone's weird magnet arrangement or marble track geometry to
create a proportioal motion machine, I know they're playing with conservative
fields and it isn't going to work.

However in this case, there is some significant acceleration which implies GR
which is not in general conservative. I suspect it is though if you restrict
yourself to the special case of accelerations with no significant gravity.

In general, however, this is still the correct approach to thinking about such
problems. If you can find a no-go theorem, then you needn't concern yourself
with the complex details. That said, if you can find a weird place where it
looks like momentum isn't being conserved, it probably is because you are
inadvertently predicting an effect of the theory that will take care of that
problem.

------
semajian
Mass is a Lorentz scalar and thus is invariant; the mass of relativistic
particles does not increase as velocity increases. One can say the force
necessary to keep a constant acceleration increases as velocity increase. This
is a common misconception, and it appears even NASA engineers don't understand
this. This is not science.

~~~
bufferoverflow
> _the mass of relativistic particles does not increase as velocity increases_

What are you talking about? This stuff was taught in high school to me:

    
    
        m = m0/√(1 − v²/c²)

~~~
gus_massa
Your teacher lied to you :).

The problem is that you have a different "mass" when you try to accelerate the
particle in the direction it is traveling and a different "mass" when you try
to accelerate the mass in a perpendicular direction. (If the acceleration is
not parallel or perpendicular, it's more complicated.)

Your formula is the correct one for the acceleration in the perpendicular
direction, like in the magnetic field of a cyclotron, that is the typical
example.

For an acceleration in the parallel direction you must add a ^3 to the
correction.

    
    
      m = m0/√(1 − v²/c²)³
    

Most modern books of advanced electromagnetism/relativity try to avoid the
change in the "mass" an use only the rest mass m0. The other "mass" is
sometimes handy and sometimes misleading.

~~~
bufferoverflow
I doubt my teacher lied to me. This stuff is in the text books, in wikipedia.

~~~
antonvs
"Lie" might be a bit strong, but the concept of relativistic mass is
misleading and technically incorrect in various ways.

As a result, in the last few decades or so the concept of relativistic mass
has gone out of favor in physics and its teaching.

The wikipedia section for relativistic mass[1] includes the following quote
from the textbook "Spacetime Physics," by Taylor and Wheeler:

> "The concept of "relativistic mass" is subject to misunderstanding. That's
> why we don't use it. First, it applies the name mass – belonging to the
> magnitude of a 4-vector – to a very different concept, the time component of
> a 4-vector. Second, it makes increase of energy of an object with velocity
> or momentum appear to be connected with some change in internal structure of
> the object. In reality, the increase of energy with velocity originates not
> in the object but in the geometric properties of spacetime itself."

In short, relativistic mass is not a good way to understand what's actually
happening in these scenarios.

Essentially, the relativistic kinetic energy of the object is being counted as
mass, following E=mc^2. However, that only works because E=mc^2 is a special-
case simplification that is designed to apply when momentum is zero, i.e. in
an object's rest frame, to its rest mass.

If you look at the full mass-energy equivalence equation[2]:

E^2 = (pc)^2 + (m0 c^2)^2

...you can see the separate momentum component p. It's possibly to "cheat" and
eliminate the (pc)^2 term and bundle it into a revised value for m, but this
loses information and leads to various issues of the kind described by Taylor
and Wheeler.

[1]
[https://en.wikipedia.org/wiki/Mass_in_special_relativity#Rel...](https://en.wikipedia.org/wiki/Mass_in_special_relativity#Relativistic_mass)

[2]
[https://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalenc...](https://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence#Applicability_of_the_strict_formula)

------
keyle
The designer, David Burns, has the most ironic name for someone who doesn't
want to use propellant.

~~~
hinkley
“I am the only Burns allowed in this facility.”

------
todd8
Many times now, friends have introduced me to friends of their's that need
help on some kind of engineering or are seeking investors for some new kind of
technology. I heard about magnetic bubble memories, new logic gate designs for
digital ICs, and improvements to starting batteries for internal combustion
automotive applications. These seemed possible but quite risky.

However, some of the most interesting presentations were different. They
seemed to be simply impossible inventions thought up by well-meaning,
passionate people.

For example, two high schools kids swore that they had invented a video
compression algorithm that worked better than existing ones such as H.264,
while at the same time being lossless. They were trying to obtain investors
and their parents had already contacted a public relations firm to promote
their work. All they needed were some outside investors so that they could
work out the kinks.

I was quite skeptical about their claim since: (1) they wouldn't reveal their
methods nor any example of the algorithm in action, (2) they were completely
unfamiliar with any literature on video compression, (3) didn't know how to
program, and (4) couldn't understand the notation used for a mathematical
discussion of the issues. Here's a quote: "What do the big E symbols all over
the page mean?" (they were capital sigmas). The P.R. firm arranged for me to
do a couple fo days of consulting with them to untangle what was going on.
Unsurprisingly, the check I received for consulting with them later bounced.

Another time, a likable young guy claimed to have invented a purely
mechanical, reactionless propulsion engine. It was a memorable experience. I
listened and watched the "inventor" describe the weights, arms, and rotating
parts. Forces were going in all kinds of directions and were quite dynamic. I
explained that conservation of momentum meant that it wouldn't work and his
reply was "Okay, but just explain why this part wouldn't push the whole thing
forward when it swung around, [etc. etc.]" He simple didn't believe that
conservation of momentum would keep his device from flying though space, on
its own without expending any mass. Because I refused to calculate every force
and integrate them over time as the parts revolved and slid back and forth he
felt like I hadn't refuted his intuition about the mechanism. He had no
understanding of vectors or calculus or physics. Every so often after our
initial meeting I would hear from him again. He was a earnest, nice guy.

Every time I see an article like this I think briefly that I should send him a
link to it, but it's probably better that I don't.

------
fao_

       """It would also need to be big – some 200 metres long and
          12 metres in diameter – and powerful, requiring 165
          megawatts of power to generate just 1 newton of thrust, 
          which is about the same force you use to type on a 
          keyboard. For that reason, the engine would only be 
          able to reach meaningful speeds in the frictionless 
          environment of space. “The engine itself would be able 
          to get to 99 per cent the speed of light if you had 
          enough time and power,” says Burns."""
    

So it falls into the same "impractical except at very high speeds for long,
long, long journeys" category with "we can explode nuclear bombs on one end of
the ship and use the explosion against a giant shield, to speed us up".

In other words, it's no Alcubierre drive.

~~~
thelazydogsback
> requiring 165 megawatts of power to generate just 1 newton of thrust

Not my field, but with that power, wouldn't an old-fashioned ion drive give
you a lot more thrust than that??

[after some searching]

With 165MW is looks like you could run hundreds of existing ion engines to get
you to about 1/2C speed with a thrust measured in 1000's of newton's.

[https://en.wikipedia.org/wiki/Ion_thruster](https://en.wikipedia.org/wiki/Ion_thruster)

~~~
skykooler
With ion engines, you need fuel to be ionized - usually xenon. The faster you
want to go, the more of your energy just goes toward accelerating the fuel in
your tank. The upper limit for speeds you can reach approaches the speed of
the exhaust - which tops out around 50 km/s for current ion drives, about
.0002C.

~~~
adwn
> _The upper limit for speeds you can reach approaches the speed of the
> exhaust - which tops out around 50 km /s for current ion drives, about
> .0002C._

That is not correct. The delta-v of a rocket (i.e., the maximum speed it can
reach) depends on the effective exhaust velocity _and_ on the mass fraction of
its propellant; see [1]. For example, a rocket which is initially 90%
propellant, can reach a velocity ~2.3 times its effective exhaust velocity.

[1]
[https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation)

~~~
skykooler
Fair enough. Either way, the fuel requirement makes it pretty much impossible
to reach a significant fraction of the speed of light with ion engines.

------
kscomb
Re: the Sun article on the helical NASA engine, there is a correction on why
this will not work. Please see: [https://www.universetoday.com/143741/nasa-
engineer-has-a-gre...](https://www.universetoday.com/143741/nasa-engineer-has-
a-great-idea-for-a-high-speed-spacedrive-too-bad-it-violates-the-laws-of-
physics/) But relativity still obeys Newton’s third law, so the idea doesn’t
work in the real world. Burns is right that there’s an error in his paper, but
it’s a subtle one.

His design only accelerates the circular motion of the particles, so he
assumes their speed forward and backward along the axis of the rocket should
remain constant. But in relativity, as the mass of the particles increase,
their speed along the axis would slow down. This is due to the relativistic
effects of time dilation and length contraction. As a result, the particles
give the rocket an equal push at both ends. Einstein’s theories don’t let you
get around Newton.

In fairness, Burns knew his idea was a long shot, which is why he put it out
there for others to review. That’s what science is all about. That’s also why
it’s worth getting just a little excited when ideas like this are put forward.
Most of them will fail, but someday one just might work. We could get to the
stars after all, but only if we’re willing to keep testing new ideas.

~~~
phayes
Koberlein's explanation is okay but I read Burns's "Keep velocity constant on
z-axis" as an instruction rather than an assumption. In that light the error
doesn't appear so subtle (it manifests as a simple error of "conservation
arithmetic").

------
davebryand
The laws of physics can't be violated. The human definition of "the laws of
physics" is what has been violated, and this will continue for as long as
human's exist and evolve our understanding of reality.

~~~
onefuncman
You can certainly create a simulation in which the laws of physics are
mutable, or have different immutable values than in our perceived reality.

------
zonidjan
> But, Burns asks, what if the ring’s mass is much greater when it slides in
> one direction than the other? ... In fact, a simplistic implementation of
> Burns’s concept would be to replace the ring with a circular particle
> accelerator, in which ions are swiftly accelerated to relativistic speed
> during one stroke, and decelerated during the other.

OK... that's great, but how do you plan to quickly accelerate particles
without expending lots of energy (and without receiving a 'reaction')?

~~~
jamisteven
Exactly what I was thinking, kinda baffled that this guy is an engineer at
NASA.

------
program_whiz
I think the guy has the diagram backwards. As the ring moves counter to the
boxes motion, it has higher relative velocity (in terms of the box frame), and
therefore higher mass. As it moves in the direction of motion of the box, it
will be moving more slowly (almost sitting still), so it will have less mass /
momentum in that direction. The result is that after a few iterations, it will
balance out.

He's drawn the diagram relative to the outside observer (where the ring seems
to go more slowly on the backstroke), but not relative to the box (where the
ring has much higher relative velocity on the backstroke, and lower relative
velocity on the forward stroke).

Another issue here is that the ring uses the box itself to pull itself forward
with the spring, and if the mass is increasing, then its pulling ever more on
the spring as it "gets faster", thereby slowing the box down by that much on
the way back.

------
pontifier
I was thinking about the propellant problem a couple of days ago. Is there a
reason we can't use electrons? It's relatively easy to accelerate them to high
percentages of the speed of light, and it's almost a certainty that your ship
would start collecting stray electrons to replace the ones you lost.

~~~
gus_massa
It is essentially a Ion thrusters.
[https://en.wikipedia.org/wiki/Ion_thruster](https://en.wikipedia.org/wiki/Ion_thruster)

It's better to accelerate the nuclei, because you get more momentum for the
same energy. You need to send the electron in the same general direction. From
the Wikipedia page:

> _Ion thrusters emit a beam of positively charged xenon ions. To keep the
> spacecraft from accumulating a charge, another cathode is placed near the
> engine to emit electrons into the ion beam, leaving the propellant
> electrically neutral. This prevents the beam of ions from being attracted
> (and returning) to the spacecraft, which would cancel the thrust._

Most device use Xenon, but other devices use Hydrogen instead. Perhaps you can
try to collect the Hydrogen from the almost vacuum (there are a few Hydrogen
atoms per cubic feet), but I don't know if it will work in real life.

------
Beltiras
I hate that title. Nothing violates laws of physics. It just means we need new
laws.

~~~
TulliusCicero
This comment just seems pedantic, like when people complain that a 'free
[thing]' is never actually free because taxes or some other product paid for
it. Everyone knows that free in that context actually means 'no charge for the
user at the time of transaction' but some people feign being obtuse so that
they can nitpick.

Obviously it means that it violates _the laws as we currently understand
them_. I know it means that, you know it means that, so what's the actual
problem?

~~~
Beltiras
Then the headline should read something like "Breakthrough points to new
physics". This is just a clickbait title. When you read the article it becomes
clear that there's a lot of wishful thinking involved. Others have pointed out
that this is not likely to work.

~~~
wickedsickeune
This is not clickbait. This is just a catchy title. Clickbait is when you
write a title, to infer something, and that something is not part of the
content.

------
nautilus12
Of the options proposed the most promising propellantless thrust mechanism for
space travel? As of now, which one has been tested the most and is most likely
to become our first choice. Could it enable interstellar travel?

~~~
larkeith
Unless I've missed anything, the only known, proven to actually work,
propellantless thrust system are solar sails (and various beam-powered
equivalents). Even nuclear photonic rockets slowly use up reaction mass.

However, ion drives are already fairly mature and perfectly viable for
interstellar travel, if you're willing to wait.

Sails aren't yet feasible outside the solar system (and are still in their
infancy even within), but with enough power production they might be another
option in the future.

------
karlh
Would there be issues with decelerating?

~~~
yellowapple
No more than there would be with accelerating, I suspect. "Decelerating" in
space is just accelerating in the opposite direction.

~~~
jiofih
Which makes the prospect of engines failing halfway through a lot more scary.

~~~
gpderetta
Lithobreaking is always an option.

------
DarkmSparks
surely this is pretty easy to debunk? So it gains mass while you accelerate
it. But the reaction force required to accelerate it as it gains mass
increases at exactly the same time in the opposite direction. f=ma holds just
the same if you change the mass as when you change the force.

------
hsnewman
Or, it may not!

------
aaron695
> NASA engineer's 'helical engine' may violate the laws of physics

So it's magic?

Except as the article says there absolutely nothing that violates the laws of
physics.

Especially given it's theoretical so I'm not sure how using a simulation it
may violate even the current laws of physics.

Why is a magazine like New Scientist pushing magic?

~~~
xamuel
Things absolutely can violate the laws of physics, in which case the laws of
physics have to be rewritten. In fact, that's the holy grail in physics, is to
find an experiment which reliably breaks the currently existing laws of
physics. That is how progress is made. If it were like you say, then there
would be no need for physics research, everything would already be known.

~~~
zucker42
Considering that "the laws of physics" means by definition "the things that
are observed to happen in the natural world" I don't think observable
phenomenon can break the laws of physics. They can change our understanding of
the laws of physics, but the laws themselves remain the same. It's a bit of a
definitional issue though.

~~~
jamesrcole
I think that they actually mean "our _description_ of how reality works". As
in, the laws are part of the map, not the territory. "Breaking" those laws
just means finding out they're an inaccurate description.

~~~
zucker42
Considering I believe that we discover physical laws, rather than invent them,
that definition makes less sense to me.

~~~
jamesrcole
We make maps of new lands that we discover. And, those maps may be inaccurate.
They often are.

------
ummonk
Does violate the laws of physics, not may. No need to give quack ideas
unmerited deference.

~~~
kscomb
Re: the Sun article on the helical NASA engine, there is a correction on why
this will not work. Please see: [https://www.universetoday.com/143741/nasa-
engineer-has-a-gre...](https://www.universetoday.com/143741/nasa-engineer-has-
a-great-idea-for-a-high-speed-spacedrive-too-bad-it-violates-the-laws-of-
physics/) But relativity still obeys Newton’s third law, so the idea doesn’t
work in the real world. Burns is right that there’s an error in his paper, but
it’s a subtle one.

His design only accelerates the circular motion of the particles, so he
assumes their speed forward and backward along the axis of the rocket should
remain constant. But in relativity, as the mass of the particles increase,
their speed along the axis would slow down. This is due to the relativistic
effects of time dilation and length contraction. As a result, the particles
give the rocket an equal push at both ends. Einstein’s theories don’t let you
get around Newton.

In fairness, Burns knew his idea was a long shot, which is why he put it out
there for others to review. That’s what science is all about. That’s also why
it’s worth getting just a little excited when ideas like this are put forward.
Most of them will fail, but someday one just might work. We could get to the
stars after all, but only if we’re willing to keep testing new ideas.

