
Curious Link Between the Fly-By Anomaly and the “Impossible” EmDrive Thruster - scrumper
https://www.technologyreview.com/s/601299/the-curious-link-between-the-fly-by-anomaly-and-the-impossible-emdrive-thruster/
======
deftnerd
I think what I most enjoy about the possibility of the EmDrive is that it's
similar to how things were often discovered during the "golden age" of
science.

Often, engineers or inventors would create something and then scientists would
have to explain why it happened. In the last few generations, physicists and
mathematicians would come up with theories and engineers would have to build
equipment to test those theories.

The EmDrive is one of the rare modern situations where someone has engineered
a device that shouldn't work according to what we know and the scientists are
having to come up with the explanation.

Personally, solving a mystery is more exciting than purely intellectual
theories and the EmDrive has created a very interesting mystery.

~~~
gus_massa
> _I think what I most enjoy about the possibility of the EmDrive is that it
> 's similar to how things were often discovered during the "golden age" of
> science._

There were also a lot of false discoveries. Someone made a machine that does
something, and after a few iterations it was discovered that it was only a bad
measurement (or a scam). It happens also with theoretical ideas, the most
famous are aether and flogisto. They were good ideas, they explained a lot of
experiments, but after a time it became obvious that they were wrong.

> _The EmDrive is one of the rare modern situations where someone has
> engineered a device that shouldn 't work according to what we know and the
> scientists are having to come up with the explanation._

The obvious explanation is that they have an error in the measurement.
Probably something get very hot and the thermal effect produce a tiny force,
some experiments show that it need some time to build up and it continue a
little after the current is off, like a thermal effect. Another possible
explanation is that the high currents produce a magnetic field that produce a
tiny force. They are putting a lot of electricity and energy in a small
device, and they only measure a tiny force, it's very difficult to rule out
experimental errors. A similar case are the faster than light neutrinos, that
were the product of a bad measurement.

~~~
rosser
Measurement error is a fine, and even necessary hypothesis in attempting to
explain the observed effect. Multiple, independent replications tend to cast
doubt on the ultimate viability of that hypothesis, however. How likely is it
that all of these people at all of these labs are making the same measurement
error?

And then, on top of that, when the observed effect comports with a theory that
also predicts another, well-established observed effect?

It's been said that the most important phrase you will ever hear a scientist
utter isn't, "I've found it!", but rather, "Well, _that 's_ strange."

This is very much in the, "Well, that's strange" class of things. Either way,
we're going to learn something about how the universe works, or about our
ability to measure it, or both. This should be celebrated, not dismissed as
mere "measurement error."

~~~
roywiggins
People noticed an effect every time the Dean Drive was turned on... but it is
just a stiction engine and obviously won't work in space. It could be this
drive is actually generating magnetic forces or moving air around and thus
"creating thrust" by pushing off its surroundings, which won't work in a
vacuum.

~~~
m_mueller
... which was already tested for. vacuum or not seems to make no difference on
the effect.

~~~
ajuc
It could also push off the Earth magnetic field.

~~~
m_mueller
Then it should depend on the orientation (and altitude, geographical
location). According to [1] this was tested for.

[1] [http://emdrive.com/faq.html](http://emdrive.com/faq.html)

------
rimunroe
> Since then, something interesting has happened. Various teams around the
> world have begun to build their own versions of the EmDrive and put them
> through their paces. And to everyone’s surprise, they’ve begun to reproduce
> Shawyer’s results. The EmDrive, it seems, really does produce thrust.

That's a misleading statement. I'm passingly familiar with a few of the
experiments they're referring to, and none of them both produced significant
results and were performed by groups which seemed un-suspect. I'm not aware of
any peer reviewed paper on this stuff, and I don't personally know any non-
laypeople who believe there is anything actually remarkable happening here.

[edit] fixed some grammar

~~~
martinflack
The article mentions NASA tested it. Is that untrue or less true than it
sounds? Genuinely curious.

~~~
rybosome
Here is a good summary of the state of EmDrive testing (as of a year ago):
[https://www.reddit.com/comments/34cq1b/](https://www.reddit.com/comments/34cq1b/)

TL;DR - a small, experimental division within NASA called Eagleworks tested
the device. They are a very small group with very limited funding tasked with
exploring unconventional theories around advanced propulsion. Their results
were not published in a peer-reviewed journal, and there is considerable
disagreement as to the validity of their experiment. They are continuing to
refine their experiments, and the last update provided is that they intend to
publish a peer-reviewed paper describing an experiment that successfully
breached 100uN of thrust, which was the target needed for JPL and others to
attempt to replicate their results.

~~~
HCIdivision17
Thanks for the link - that comment is great.

I gotta quote one line that is just cool, though:

    
    
      4. A test at 50 W of power during which an 
      interferometer (a modified Michelson device) 
      was used to measure the stretching and compressing 
      of spacetime within the device, which produced 
      initial results that were consistent with an 
      Alcubierre drive fluctuation.
    

Which is just really cool. The followup sums up my fascination with the whole
thing niceley:

    
    
      Test #4 was performed, essentially, on a whim 
      by the research team as they were bouncing ideas 
      off each other, and was entirely unexpected. They 
      are extremely hesitant to draw any conclusions based 
      on test #4, although they certainly found it interesting.
    

That right there is science in progress: a hint of something interesting, a
test leading to another test leading to another, each interesting in their own
right. It's still not clear if something spectacular is going on, but I think
it's undeniably interesting. Careful reexamination can yeild all manner of
useful insights!

(Off topic, but along the lines of closer examination, see
[https://news.ycombinator.com/item?id=9020065](https://news.ycombinator.com/item?id=9020065)
for how some careful (and extensive!) experimentation helped illuminate
sodium's reaction with water. Not just how much work was needed to tease out
the details!)

~~~
noir_lord
> The most exciting phrase to hear in science, the one that heralds new
> discoveries, is not 'Eureka!' but 'That's funny...' \- Isaac Asimov.

This could be complete bunkum but it's fun watching anyway as an interested
bystander.

------
apsec112
I don't think there's anything real here. McCulloch's papers on arXiv seem
very confused. Eg., this paragraph:

"In this scheme there is a minimum allowed acceleration which depends on a
Hubble scale Θ, so, if Θ has increased in cosmic time, there should be a
positive correlation between the anomalous centripetal acceleration seen in
equivalent galaxies, and their distance from us, since the more distant ones
are seen further back in time when, if the universe has indeed been expanding,
Θ was smaller. The mass to light ratio (M/L) does seem to increase as we look
further away. The M/L ratio of the Sun is 1 by definition, for nearby stars it
is 2, for galaxies’ it is 50, for galaxy pairs it is 100 and for clusters it
is 300. As an aside: equation (11) could be used to model inflation, since
when Θ was small in the early universe the minimum acceleration is predicted
to be larger." ([http://arxiv.org/pdf/astro-
ph/0612599v1.pdf](http://arxiv.org/pdf/astro-ph/0612599v1.pdf))

If an effect was stronger in the early universe, you'd expect to see a big
correlation between the effect size in a galaxy, and that galaxy's redshift z.
It wouldn't make any sense to say that "galaxies" have a ratio of 50, since
there are galaxies at every redshift; many are nearby and have redshifts of
almost zero, while the Ultra Deep Field galaxies have very large redshifts of
up to ~10. If the number is really the same for "galaxies" in general, that
means there's no distance dependence, but McCulloch doesn't seem to realize
this. He seems to imply that nearby stars have a higher mass/luminosity ratio
because of their distance compared to the Sun (?!), but the time-delay effect
for anything in the Milky Way is negligible (< 0.0005% of the universe's age).
In reality, nearby areas of space will have higher ratios than the Sun just
because they contain many objects which, unlike the Sun, don't emit much light
(red/brown/white dwarfs, gas and dust, etc.). Likewise, he seems to imply that
"galaxy clusters" are farther away than "galaxies", but most galaxies are part
of clusters, and we can observe both galaxies and galaxy clusters at both
small and large redshifts.

~~~
anentropic
Isn't he saying the 'standard' M/L ratio for galaxies is 50... and that by
looking at a lot of galaxies at different distances you see a trend that the
more distant ones are more >50 ?

------
adekok
The hard part for physicists to accept is that the theory requires the speed
of light to change.

It would be interesting to see how the theory behind the Unruh radiation works
with "The quantum vacuum as the origin of the speed of light"
([http://arxiv.org/abs/1302.6165#](http://arxiv.org/abs/1302.6165#))

Or also MOND
([https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics](https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics))
Which also has predictions based on very low accelerations.

It seems like the theories could be related.

(says an ex Nuclear physicist who's now doing computers).

~~~
daeken
> The hard part for physicists to accept is that the theory requires the speed
> of light to change.

I'm a complete layman here, so I don't understand how the link you shared says
that the speed of light is changing; it seems more like a change in the way we
_define_ the speed of light. Is that right?

If the actual speed of light is to change, how is that possible? We've
experimentally verified it up one side and down the other, so this seems like
a huuuuuge discovery.

~~~
empath75
So there's c, which is essentially a conversion factor between space and time,
and also happens to be the speed at which massless particles move. If photons
happen to not be massless, the speed of light might change, though 'c'
wouldn't have to.

------
th0ma5
The sentiment I hear in this thread is like those that dismiss cold fusion.
Sure, we can all make statements like "obviously, someone screwed up" but it
is another thing entirely to have to the patience to simply cite the
experiments that disprove the proposed effect. I don't know what to make of
cold fusion, but I also know for a fact that neither do physicists, and
instead of studying it, they're just simply saying because there is no theory
it must not work. Same with this stuff.

The one YouTube guy discovered the beaded-chain lifting effect, and _then_ it
had to be studied to find out what was going on. Obviously that was an easily
reproduced experiment.

So with this thing, we must find conclusively the unmeasured heat or ions or
whatever and show a repeatable method for such mistakes. That is my opinion
about science, of course I probably lost most scientists with my first
sentence.

~~~
greglindahl
Extraordinary claims require extraordinary proof, and the history of physics
is littered with intentional fraudsters and sloppy experimentalists.
Disproving every perpetual motion machine via experiment would take a lot of
effort from scientists who don't want to do it. If you think those experiments
should be done, then by all means do them.

~~~
th0ma5
Fair enough, but the problem with perpetual motion stuff is that no energy can
be extracted or the time until the device stops is very long, not that they
don't do what people claim that they do, which is work more or less
perpetually.

We need to find that kind of explanation for this supposed propulsion.

~~~
taneq
These devices work "more or less perpetually" the same way 1000.0f is "more or
less infinite".

~~~
th0ma5
I upvoted you because you're right, but maybe you and I should take a few
months off and time some of the better ones! Worthless machines but I've heard
of some lasting a great deal of time.

------
scrumper
I'm curious to what degree Unruh radiation (and the resulting consequences
this idea relies on) 'established physics'?

By extension, I think this is the most interesting article I've seen to date
on the EmDrive: it seems to have a basis in a fairly non-controversial result
of GR, which in turn is something which nicely explains an otherwise bizarre
physical phenomenon. And, to top it off, there are a number of falsifiable
predictions which are within our ability to test. I'm interested in whether
any of my assumptions are wrong.

~~~
gaur
> I'm curious to what degree Unruh radiation (and the resulting consequences
> this idea relies on) 'established physics'?

Most theorists think Hawking–Unruh radiation has to exist, I guess because the
calculation is relatively straightforward. You just need special relativity
and some basic field theory.

Hawking–Unruh radiation has never been observed in a gravitational system, and
doing so would be very difficult because it requires a truly enormous
acceleration in order to produce a horizon with a temperature that is an
appreciable fraction of 1 K.

There are certain regimes in fluid mechanics where the mathematics governing
the fluid looks like the mathematics governing relativity. Some people have
produced phenomena in those systems that look like Hawking–Unruh radiation.
Some people further claim that this demonstrates the existence of
Hawking–Unruh radiation for gravitational systems, but I find that reasoning
to be specious.

------
spottedquoll
Extraordinary claims require extraordinary yada yada.

A working reactionless drive isn't just extraordinary. It's utterly mind-
boggling. The least interesting thing is that it's a free-energy device.

It requires breaking spatial symmetry. If it works, it's not some edge-case
theoretical law that's being broken. It's the geometry of space.

[https://en.wikipedia.org/wiki/Noether%27s_theorem](https://en.wikipedia.org/wiki/Noether%27s_theorem)

~~~
api
Even if this works, _reactionless_ drive would be my last hypothesis after
exhausting all possible things it might be interacting with via some as-yet-
unknown means: dark matter, nearby gravitational bodies, etc.

The infinite energy device claim is easy enough to test. Since a working
infinite energy device would be perverse, I'd predict that an EmDrive rigged
up so as to produce infinite energy would fail to do so. Exactly _how_ it
fails to do so might tell us what's going on. Do the energy requirements rise
with momentum (as they should in a sane universe), or do you pass a point at
which the effect ceases, or does something truly wacky occur like space-time
distortion in such a way as to cancel the effect?

My reading of the McCullough hypothesis is that it's pushing against all
matter in the universe at once, or some such thing, but that could be way off.
I'm not a physicist.

------
jimmcslim
This is probably incredibly naive... but couldn't this all be put to bed by
someone putting such a drive on a cubesat, lifting it into orbit, and seeing
if it works under practical conditions?

Maybe Hawking and Milner should be considering this for Starshot?

~~~
losteric
Sure, the tricky part is finding funding

~~~
mabbo
How much funding?

A Falcon 9 can lift 10,000 kg to LOE (or more). Let's say we could get a
simple Em-drive and basic satellite and solar panel in for under 100kg. (We
can do better, but let's start there). That's 1/100 of the load, so (in
theory) we could maybe pay 1/100 of the $60m cost for a Falcon 9 lift, or
$600,000.

Half a million bucks plus some change, let's say.

Edit: Less if we can get on board a previously-enjoyed rocket!

~~~
daeken
You also have to add in the payload integration fees, testing (very, very
expensive), the actual payload development, insurance, and also be in a launch
configuration such that you can piggyback behind a payload taking up most of
the F9 capacity.

I'd be astonished if the cost of this was less than $2-3M.

------
est
refuted by reddit

[https://www.reddit.com/r/EmDrive/comments/4fm2ac/the_curious...](https://www.reddit.com/r/EmDrive/comments/4fm2ac/the_curious_link_between_the_flyby_anomaly_and/)

> ... (McCulloch) proposes a constant term that modifies the acceleration
> corresponding to the inertial mass. He says torsion balance experiments
> can't detect it because torsion balance experiments measure differences in
> acceleration. But he's wrong because since it's a constant term he
> "predicts", it should manifest in the Eotvos parameter. Torsion balance
> experiments have gone well beyond the limit to detect this. But it's
> irrelevant because he completely misunderstands all the theory he bases this
> on.

------
mcnamaratw
The article leaves out all the numbers and so skips over one little problem.
The momentum some people think they might have observed (if it's not
experimental error) is compatible with what you'd get by using a microwave
antenna as a thruster. Just ordinary radiation pressure, with the puzzle of
how the radiation could be escaping the cavity.

But the minimal measurement results I've seen are not compatible with the
radiation pressure multiplied by some large factor for the Q of the cavity,
which seems to be the claim from some. That really would violate our
understanding of conservation of momentum, rather than violating our
assumptions about where the momentum goes in this experiment. And that seems
to be ruled out experimentally so far.

------
wmeredith
> At very small accelerations, the wavelengths become so large they can no
> longer fit in the observable universe. When this happens, inertia can take
> only certain whole-wavelength values and so jumps from one value to the
> next.

So the EmDrive glitches the universe size? This is hilarious.

~~~
tremon
This was also my first reaction. I don't see how energy could be quantized
with the inverse of the diameter of the observable universe.

Could someone explain the current thinking around how energy quanta relate to
the size of the universe, or rather why wavelengths larger than the universe
are impossible?

If the latter were true, I'd expect that an energy quantum corresponding to
0.99 * universe would be equally impossible as 1.01 * universe, and that only
integer multiples of the corresponding frequency would be allowed (i.e. a
harmonic series across the universe).

~~~
TheOtherHobbes
The corollary is that you'd be able to measure the size of the universe by
observing quantisation effects.

This seems unlikely, because - unless I've missed something obvious - you'd
have to be able to set up a wave with a phase velocity > c.

------
phkahler
Photons must behave as if they have mass. From TFA:

McCulloch’s theory could help to change that, although it is hardly a
mainstream idea. It makes two challenging assumptions. The first is that
photons have inertial mass.

When I was taking college physics, there was a question on the exam about
radiation pressure. I missed that day, so had no idea how to solve it. "a 5mW
laser is reflected off a mirror (perpendicular) what is the force exerted on
the mirror"? Later looking it up in the book there was a page on this and a
derivation using electromagnetic theory. In the exam however, I decided to
convert 1 second of laser energy to mass, bounce it off the mirror at speed=c,
compute the force and change in momentum (over change in time which was 1s). I
got the right answer of course.

The logic is simple. If we can convert back and forth between matter and
energy, any experimental setup must obey conservation of momentum and it's CG
must not move. So a laser inside a closed spaceship would actually be
tranfering mass (as energy) from one end to the other. The net effect must be
the same as if that mass was moved any other way.

I derived a general expression for radiation pressure after the exam and it's
identical to the EM one from the book. Photons behave - and must behave - as
if they have mass with a velocity of c. By the same reasoning, gravity must
bend light rays, though I have not compared this prediction to that of
relativity.

------
askvictor
I can't help but look at things like this as hacks in/of the simulation we are
probably living in.

~~~
josephagoss
Interestingly, that would imply we are possibly living in an imperfect
simulation, one that hypothetically does not replicate the physics of a real
non-simulated universe.

If that is true, why? I can think of four possible reasons:

1) Is it because the simulation was designed in such a way that it leaves its
inhabitants clues that reveal the true nature of the universe? This lets them
figure out the truth once their society and knowledge become sufficiently
advanced.

2) That it's impossible to simulate a real universe? This would imply any
sufficiently advanced society will be able to detect that they do in fact live
within a simulation.

3) That the creators made a mistake and it's not a fundamental limitation.
It's simply an error made by whatever civilisation created this simulation,
they messed something up.

4) That it's possible to create a perfect simulation, but for some reason they
decided to make a simulation that used less resources and this brings errors
or the need of hacks to get it working. Now we might be exploring these hacks.

------
drudru11
This is fascinating stuff. It is also good to see more and more respectable
names looking at this. Good things will come from that regardless of the
overall outcome of the emdrive.

------
api
"Yes, they're still using warp drives to heat food..." \- alien observers

------
baltcode
So is there any microwave radiation escaping the cone? If more of it escapes
from one side than the other, won't the momentum of the escaping photons
(radiation) be the reaction of the thrust produced? Why does it need special
physics? I am probably missing something here, but what is it?

------
russdill
One of the main issues I see with the EmDrive in general is time invariance.
And especially with the theory Mike McCulloch put forward. If photons cause
this process for a positive change in momentum, the same process should happen
in reverse with a negative change in momentum.

------
PaulHoule
People have been doing "research" into reactionless propulsion for a long
time, such as this science fiction writer:

[http://rexresearch.com/dean/stine.htm](http://rexresearch.com/dean/stine.htm)

------
trhway
> inertia must quantized at small accelerations.

as everything does :) I think it is quantized at all levels, it just becomes
noticeable at low levels as usually.

~~~
outworlder
Everything seems to be limited by the precision our simulation is running on
:)

------
aalexgabi
Humans have learned a lot of things. However they still have to learn about
the universe because there are non-naturally-observable physical phenomena and
we have no evidence that we discovered them all.

Edit: These so called "laws" are laws in our minds and things like EmDrive
show us that our minds can expand forming new "laws".

------
ridgeguy
For anybody who's interested, there's a NASA forum devoted to the EmDrive:

[http://forum.nasaspaceflight.com/index.php?topic=39772.1440](http://forum.nasaspaceflight.com/index.php?topic=39772.1440)

------
Joof
Inertia is quantized? Do we actually live inside a computer, because that's
really weird. Physicists, help explain this outside of the universe uses a
lookup table to approximate inertia.

------
323454
Supposing this theory is true, how big an emdrive does it predict is needed to
lift a reasonable payload, say 100kg?

~~~
codeduck
The EmDrive would never be powerful enough to be a lifting engine; but what it
would be is an incredibly useful engine once your mass is in orbit.

------
dnautics
wonder if this inertial/acceleration effect is what is responsible for "dark
matter" in the universe, i.e. galaxy-scale gravitational anomalies that don't
agree with existing newtonian and GR models.

------
kempe
Would be very interesting to see an actual implementation.

------
alfiedotwtf
Meta: Wow that drop down menu at the top is really annoying

------
lunchTime42
Is there a thing that allows for Science Annonymous?

------
jaekwon
How does this relate to the spinning black/white thing?

~~~
gerbilly
The Black White thing is a Crookes Radiometer[1] and it rotates because of
differential heating of the black and white sides of the plates interacting
with air molecules to create a tiny air flow from the light side to the dark
side of the plate.

The device is under _partial_ vacuum. Under total vacuum, no rotation will
occur, if the air pressure is too high, drag forces outpace the tiny thrust.

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

------
33a
Man, this is the perfect news story for 4:20.

