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Pioneer Anomaly Solved

samzenpus posted more than 2 years ago | from the space-anchor dept.

Space 147

First time accepted submitter gstrickler writes "After years of work recovering and analyzing old mission data and vehicle schematics, a just published analysis(Pdf) provides strong evidence for anisotropic thermal radiation being the source of the slowing of the Pioneer 10 and 11 spacecraft. The theory isn't new, but the recovered data and new analysis provide solid evidence that at least 80% of the deceleration is accounted for by anisotropic thermal radiation. Members of The Planetary Society were instrumental in recovering the data and helping fund the analysis. The lesson is, in space, it matters what direction your heat radiating surfaces point."

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147 comments

Pioneer (0)

Sene (1794986) | more than 2 years ago | (#39740099)

Was just wondering what the company have made an Anomaly out of...

Re:Pioneer (-1)

Anonymous Coward | more than 2 years ago | (#39740227)

http://phys.columbia.edu/~tutorial/

This just in (3, Funny)

jhoegl (638955) | more than 2 years ago | (#39740143)

Heat makes things go fast!

Re:This just in (2)

amRadioHed (463061) | more than 2 years ago | (#39740219)

You mean slower? Cause that's what happened in this case.

Re:This just in (3, Informative)

Fluffeh (1273756) | more than 2 years ago | (#39740303)

Faster, slower - just depends on where the heat is being emitted - either towards where the craft is going (mainly the case here) or back towards where it came from.

Re:This just in (2, Informative)

girlintraining (1395911) | more than 2 years ago | (#39741767)

Faster, slower - just depends on where the heat is being emitted - either towards where the craft is going (mainly the case here) or back towards where it came from.

In space, speed is a meaningless attribute without a point of reference. As well, space is non-euclidean in nature -- you can travel in a straight line and wind up in the same place you started. It's better to speak in terms of vectors and delta...

Re:This just in (4, Insightful)

Iniamyen (2440798) | more than 2 years ago | (#39741807)

The "speed" of the Pioneer craft is usually referenced to the Sun and it's orbit

Re:This just in (3, Interesting)

l0ungeb0y (442022) | more than 2 years ago | (#39740355)

Well actually, if they'd anticipated this and pointed the heat dissipating surfaces to the rear, Pioneer would be going faster.
What the article did not state was how long it would take for these forces to cease forward momentum -- or if that is an issue.

Re:This just in (3, Insightful)

Wraithlyn (133796) | more than 2 years ago | (#39740533)

I'm thinking pointing your heat dissipating surfaces directly towards the sun might decrease the efficiency of said heat dissipation.

(Obviously this becomes less of a concern the farther from the sun you are)

Re:This just in (4, Interesting)

Chris Burke (6130) | more than 2 years ago | (#39740545)

Well actually, if they'd anticipated this and pointed the heat dissipating surfaces to the rear, Pioneer would be going faster.

I'm not sure they'd have done anything... the effect is so small, completely irrelevant for the main part of the missions, and they might have other reasons for orienting the craft a certain way -- maybe to maximize cooling. As a rule the side that emits the most photons would also be absorbing the most from the sun. I realize the situation could be more complicated than this; if it was simple the result would have been calculated a long time ago.

What I'm wondering is how many people will remove this from their "these handful of unexplained results in not fully understood circumstances mean all of physics are wrong (and my pet theory is right)" lists?

Re:This just in (4, Insightful)

X0563511 (793323) | more than 2 years ago | (#39740603)

Could one compromise and put the radiators perpendicular to the direction of the sun (and travel?) eg, not on the front or back, but on the sides? Provided you did so equally, any force resulting in their radiation should cancel itself out.

Re:This just in (5, Insightful)

Anonymous Coward | more than 2 years ago | (#39741005)

[...]and they might have other reasons for orienting the craft a certain way -- maybe to maximize cooling.

One end of the spacecraft is a big-ass radio dish, and the orientation is determined by pointing that dish at the Earth so that we can communicate with it.

Re:This just in (1)

Chris Burke (6130) | more than 2 years ago | (#39741085)

That's what I was going to say at first but I wanted to lead into the cooling thing -- anticipating the follow-on that they craft could have been designed differently to both radiate heat and radio in the same direction. Somehow.

Re:This just in (1)

jrumney (197329) | more than 2 years ago | (#39741179)

Even better. The radio dish provides shade from the sun's rays for the cooling surface behind.

Re:This just in (1)

mug funky (910186) | more than 2 years ago | (#39742319)

and acts as a solar sail...

Re:This just in (1)

v1 (525388) | more than 2 years ago | (#39741037)

The lesson is, in space, it matters what direction your heat radiating surfaces point

Am I arrogant for saying "wasn't this obvious?" Isn't that newton's first law at work? This looks like a job for Captain Obvious.

Re:This just in (5, Informative)

Chris Burke (6130) | more than 2 years ago | (#39741251)

Am I arrogant for saying "wasn't this obvious?"

Not really as long as you realize that some things seem obvious once you know they're true... Or as long as you just mean "obvious possibility".

It's not like they didn't know that if there was a favored direction for the emission of radiation that this would affect the velocity of an object. The concept of a photon drive existed for decades before the Voyagers were launched. It's just that it was though that whatever net force there was would be essentially zero. Assume a uniform, spherical Voyager craft...

This has been a long-standing possible, and then probable, explanation for the anomaly. Seems to have taken quite a bit of effort to figure out what the actual value of the force would be with sufficient precision. I remember what seems like a long time ago an article posted to /. about someone calculating the effect of heat radiation using Phong shading, the 3D graphics technique, as an approximation and got pretty good agreement.

Going all the way to a complete finite element analysis, using multiple methods to come up with the coefficients for the model, and getting a result that leaves only a noise-level signal is pretty impressive. And not what I'd call obvious.

So despite maybe feeling like it, it's not exactly a case of research by the Maximegalon Institute of Slowly and Painfully Working Out the Surprisingly Obvious.

Re:This just in (2)

jrumney (197329) | more than 2 years ago | (#39741165)

What the article did not state was how long it would take for these forces to cease forward momentum -- or if that is an issue.

I'm more worried about how long it will take before it plunges back to Earth. But on a more serious note, I think the energy source that is causing the heat will run out before either of those events happen, and if not, hopefully Earth will be in a different place in its orbit than it was when Pioneer was launched when it flies past on its way back.

Re:This just in (0)

Anonymous Coward | more than 2 years ago | (#39740511)

You mean because? 'Cause you need an apostrophe in this case.

Re:This just in (1)

jrumney (197329) | more than 2 years ago | (#39741117)

You mean slower? Cause that's what happened in this case.

If it keeps it up, eventually it will be going fast in the other direction.

Re:This just in (0)

Anonymous Coward | more than 2 years ago | (#39741763)

> You mean slower? Cause that's what happened in this case.

That depends on your choice of reference.

Slowing? (1)

countach (534280) | more than 2 years ago | (#39740147)

Err... is it the slowing of the craft, or the accelerating? Because the analysis refers to the "acceleration" of the spacecraft.

Re:Slowing? (3, Informative)

Overzeetop (214511) | more than 2 years ago | (#39740161)

Acceleration can be positive or negative.

Oops. More specifically... (4, Informative)

Overzeetop (214511) | more than 2 years ago | (#39740181)

Sorry to self-correct - acceleration is a vector, it has both magnitude and direction. By summing all of the acceleration vectors, you get a resultant which determines the rate of change of your velocity.

Re:Oops. More specifically... (0)

Anonymous Coward | more than 2 years ago | (#39740255)

Sorry to self-correct - acceleration is a vector, it has both magnitude and direction. By summing all of the acceleration vectors, you get a resultant which determines the rate of change of your velocity.

technically, I also took high-school physics

Re:Oops. More specifically... (0)

Anonymous Coward | more than 2 years ago | (#39740405)

There's only the one acceleration vector, which is the result of all the FORCE vectors which are acting on the object.

Re:Oops. More specifically... (1)

X0563511 (793323) | more than 2 years ago | (#39740613)

I thought force vectors WERE acceleration vectors?

Re:Oops. More specifically... (0)

Anonymous Coward | more than 2 years ago | (#39740697)

A force vector is a force vector. If you're Newtonian,

F = ma

So to figure out the acceleration vector, you sum all of the force vectors and divide by the object's mass.

Re:Oops. More specifically... (1)

Anonymous Coward | more than 2 years ago | (#39741141)

Technically the Newtonian way of putting it would be F = dp/dt.

Re:Oops. More specifically... (5, Informative)

Chris Burke (6130) | more than 2 years ago | (#39740715)

There's an acceleration vector for every force vector and a net acceleration and a net force vector. They're mathematically equivalent. You could also look at it as a sum of momentum delta vectors. How is the electromagnetic force conveyed? By a photon exchanging momentum. So is force something that only exists as an effect of adding up all the changes in momentum, or vice versa? Neither, both are correct viewpoints. Have a nice day.

Re:Oops. More specifically... (0)

Anonymous Coward | more than 2 years ago | (#39741821)

Not really. Acceleration is a property of the mass being acted upon by many forces. The acceleration of that mass cannot happen in multiple directions (unless the mass is not a rigid body). Thus there is only one acceleration vector for any one rigid mass. While you may mathematically view it as many accelerations, it isn't physically correct at all. Forces cannot be determined by "adding up" all the changes in momentum, as there is only one directional change in momentum at any given time. The forces cannot be inferred by the acceleration, thus disproving your point. As I am an AC, however, I will be ignored.

Re:Oops. More specifically... (2)

Chris Burke (6130) | more than 2 years ago | (#39742003)

The forces cannot be inferred by the acceleration, thus disproving your point.

You can't infer the forces from the net acceleration, you can't infer the accelerations from the net force, what is your point? Physically, the "force" keeping you from falling through your chair is being transmitted via discreet transfers of momentum and the 'force' field is just a consequence. But you can still talk about forces. You're not wrong about that, you're just wrong that it's wrong to talk about accelerations or changes in momentum adding to produce a net force. F = dp/dt. It's not a one-way thing. It's an equivalence.

Re:Oops. More specifically... (1)

ThreeKelvin (2024342) | more than 2 years ago | (#39742481)

It's rather easy to infer the acceleration from the resulting force (and mass). But why do you keep talking about "accelerations" (plural)? A ridgid body can only have one acceleration. (As the grandparent previously correctly stated.)

Re:Oops. More specifically... (4, Funny)

FrootLoops (1817694) | more than 2 years ago | (#39742587)

Your post and its high moderation made me feel overeducated, so I wrote a poem in archaic style to reinforce the feeling.

      Today I chanced to Look Down from my Ivory Tower;
            the Vision horrified me.
      I saw the Peasants Clamoring blindly
            for the Simplest Certain Knowledge
            of the Calculus and of Physicks.
      I saw the Depth of Divide betwixt us thus:
            One Man's Hidden Knowledge is Offal to th' Other.

P.S. To be fair, the stuff you mentioned is somewhere around the programming equivalent level of "objects can have properties".
P.P.S. Also, note the pun on "offal"/"awful" in the last line. It's the only good line of the poem. It's true in at least 4 ways.
P.P.P.S. Sorry for such a weird post. Maybe it'll amuse someone.

Re:Slowing? (-1)

Anonymous Coward | more than 2 years ago | (#39740209)

Which I learnt at school in 11th grade - proof of me living in one of those god-forsaken commie socialist leftie countries, where they value knowledge over important things like conformity and praying to the flag every day.

Re:Slowing? (1)

tibit (1762298) | more than 2 years ago | (#39741435)

That's some lame ass commie country, in my commie country we knew laws of dynamics in grade 8 at the latest ;)

but it always means... (0)

Anonymous Coward | more than 2 years ago | (#39740221)

...you are going faster than before, eh?

Re:but it always means... (1)

sribe (304414) | more than 2 years ago | (#39740261)

No.

Re:but it always means... (1)

Forty Two Tenfold (1134125) | more than 2 years ago | (#39740381)

Your statement is relatively wrong.

Re:Slowing? (0)

Anonymous Coward | more than 2 years ago | (#39740183)

Well, it's now going so fast that time seems to have slowed down.

Re:Slowing? (0)

Anonymous Coward | more than 2 years ago | (#39740475)

Doesn't moving at any velocity whatsoever relative to a stationary body result in time slowing down for the moving object?

Re:Slowing? (1)

tomhath (637240) | more than 2 years ago | (#39740579)

Which is stationary and which is moving? It's all relative. Both think their own clocks are right and the other one is slow.

Re:Slowing? (4, Informative)

gbjbaanb (229885) | more than 2 years ago | (#39740265)

its accelerating backwards... ie, it's effectively got its "engine" (ie the heat radiating surface) pointing in the direction its heading, and this is slowing it down. I guess its still got a lot of velocity, but this is being reduced by the lack of anything pushing it in the right direction.

In other words, in space, your hot arse is a form of propulsion!

Re:Slowing? (2, Informative)

geekoid (135745) | more than 2 years ago | (#39740313)

Usually my hot arse propels people away from ME~

Re:Slowing? (1)

Wraithlyn (133796) | more than 2 years ago | (#39740555)

I believe this was the cornerstone of Einstein's Theory of Relativity.

Re:Slowing? (1)

X0563511 (793323) | more than 2 years ago | (#39740627)

For every action there is an equal and opposite reaction.

Your ass propels you with as much force as it propels others.

Re:Slowing? (1)

smellotron (1039250) | more than 2 years ago | (#39741447)

Your ass propels you with as much force as it propels others.

But that's only force, and we all know F==m*a. So his ass must propel his mass, while the gas from his ass must propel the mass of the masses behind his ass.

Re:Slowing? (0)

Anonymous Coward | more than 2 years ago | (#39740855)

You'd be amazed how many people end up inside of my hot arse.

Well (0)

Anonymous Coward | more than 2 years ago | (#39740157)

That's that, I guess.

Y'all wanna do somethin?

Re:Well (0)

Anonymous Coward | more than 2 years ago | (#39740213)

Hookers and Blow?

Re:Well (1)

rikkitikki (91982) | more than 2 years ago | (#39740531)

In fact, forget the Blow...
-Bender

Re:Well (0)

Anonymous Coward | more than 2 years ago | (#39740791)

Ah, screw the whole thing.

Re:Well (1)

AngryDeuce (2205124) | more than 2 years ago | (#39740495)

I call player one!

I wanna get skit on my nose. (-1)

Anonymous Coward | more than 2 years ago | (#39741669)

LET'S DANCE!

Inadvertant proof of concept? (4, Interesting)

Banichi (1255242) | more than 2 years ago | (#39740289)

Does this discovery have a relationship (however distant or inefficient) to Nuclear Lightbulb or Nuclear Photonic propulsion? https://en.wikipedia.org/wiki/Nuclear_lightbulb [wikipedia.org]

Second rate story (-1, Offtopic)

lucm (889690) | more than 2 years ago | (#39740317)

"First time accepted submitter gstrickler" == "at least once rejected submitter gstrickler".

I don't want no stories from a stinkin' do-over deadbeat.

it's like the Dems bringing back Kerry.

Re:Second rate story (1)

gstrickler (920733) | more than 2 years ago | (#39740367)

"First time accepted submitter gstrickler" != "at least once rejected submitter gstrickler".

FTFY

Re:Second rate story (1)

smellotron (1039250) | more than 2 years ago | (#39741483)

(strcmp("First time accepted submitter gstrickler", "at least once rejected submitter gstrickler") != 0)

FTFY

Re:Second rate story (0)

Anonymous Coward | more than 2 years ago | (#39740439)

... or the Repugs bringing back Romney.

voyager twitter feed (0)

Anonymous Coward | more than 2 years ago | (#39740321)

The Voyager probes are getting closer to Earth! They have twitter feeds, and report the light-travel time to the Earth. If you look at the history of their tweets, you'll see they have been getting closer to Earth recently.

What now? (0)

Anonymous Coward | more than 2 years ago | (#39740325)

Well that's been solved. What now?

Re:What now? (1)

RightwingNutjob (1302813) | more than 2 years ago | (#39740359)

make up conspiracy theories?

Can they fix the problem? (1)

rossdee (243626) | more than 2 years ago | (#39740395)

So now they know why its slowing down, can they fix the problem?

I think they should reconfigure the main deflector to emit a tachyon pulse. That usually works.

Re:Can they fix the problem? (1)

zAPPzAPP (1207370) | more than 2 years ago | (#39740459)

Shoot it with a laser from over here, heat up the other side too.

Re:Can they fix the problem? (0)

Anonymous Coward | more than 2 years ago | (#39740479)

Better reverse the polarity first.

Just in space? (4, Funny)

fahrbot-bot (874524) | more than 2 years ago | (#39740423)

The lesson is, in space, it matters what direction your heat radiating surfaces point.

It matters in bed too.

Re:Just in space? (1)

qu33ksilver (2567983) | more than 2 years ago | (#39742621)

You don't say !! .. :o

This was already solved by a portuguese in 2009 (4, Informative)

GreatBunzinni (642500) | more than 2 years ago | (#39740519)

A portuguese aeronautics engineering student from Instituto Superior Técnico [ist.utl.pt] already figured this out way back in 2009 in his masters thesis, available here [ist.utl.pt] .

Re:This was already solved by a portuguese in 2009 (1)

geekoid (135745) | more than 2 years ago | (#39740605)

and now they have confirmed it.

Re:This was already solved by a portuguese in 2009 (2)

DerekLyons (302214) | more than 2 years ago | (#39740641)

So, how does his evidence and analysis stack up against the current one? (Especially in light of how little data was available until recently.)

I.E. lots of people have theorized the effect, some have made (relatively crude) calculations supporting this as a cause - but this is the first using the whole dataset.

Re:This was already solved by a portuguese in 2009 (5, Interesting)

careysub (976506) | more than 2 years ago | (#39740873)

Not exactly.

Numerous investigators have been strengthening the case for thermal radiation as the cause for nearly a decade. The work of Bertolami, Francisco, et al in Portugal in 2008-2009 accounted for 67% of the acceleration, a then-new high point in this reckoning. This was a notable result, but they didn't "figure it out" or "solve" it, they strengthened the case that was by then widely believed to be correct. For an account of the whole story up through 2010 see: http://arxiv.org/pdf/1001.3686v2.pdf [arxiv.org] .

The new study raises the level of confirmation to 80%, using data that they newly recovered, and further shows that the remaining 20% is not statistically significant. It is this study that deserves to be regarded as having "solved" the problem: accounting essentially for the full anomalous acceleration, and leaving no residual anomaly.

Re:This was already solved by a portuguese in 2009 (1)

Jorgensen (313325) | more than 2 years ago | (#39740965)

Yep. These guys are coming to the same conclusion. Too bad that the title in slashdot claims it to be "solved" - the new paper does not claim to have it solved - merely to have reached the same conclusion with (what appears to be) a higher confidence level.

Don't be misled by the title in Slashdot... :-)

Re:This was already solved by a portuguese in 2009 (1)

Chris Burke (6130) | more than 2 years ago | (#39741545)

A portuguese aeronautics engineering student from Instituto Superior Técnico already figured this out way back in 2009 in his masters thesis, available here.

Ah, that was the Phong shading one! Only in 2009? Seemed like longer ago...

At the time people were saying "Oh, why Phong shading? What's so perfect about that?" and, well, the answer is it isn't, it's an approximation. Not a bad one, either, but still. So's the finite element analysis these folk did. Just a much better one.

Re:This was already solved by a portuguese in 2009 (0)

bdabautcb (1040566) | more than 2 years ago | (#39742303)

It's not real science if it comes from Instituto Superior Taquito, although they do make some great snacks.

next questions... (5, Funny)

countach (534280) | more than 2 years ago | (#39740591)

Will this effect be powerful enough to ever cause it to stop, turn around and come home? And when it does so, how much strife will it cause to Spock and Kirk?

It depends... (2)

Grog6 (85859) | more than 2 years ago | (#39741185)

It depends on the particular machine race the spacecraft runs into; If it's Beserkers, they aren't going to care about the cute bald chick. :)

The Borg on the other hand; If they look like 7of9, they can assimilate me anytime.

.

Mass?? (1)

wisnoskij (1206448) | more than 2 years ago | (#39740599)

But if heat radiation does not have mass then why should it effect it?
Does it have mass?

Re:Mass?? (1)

countach (534280) | more than 2 years ago | (#39740689)

Alpha and Beta radiation has mass. They are particles.

Re:Mass?? (0)

Anonymous Coward | more than 2 years ago | (#39740831)

Isn't heat radiated in the form of infra-red?

This would seem to work by the same idea as a solar sail

Re:Mass?? (0)

Anonymous Coward | more than 2 years ago | (#39740865)

Photons don't have mass, but they have momentum, which is what was being conserved by the deceleration.

Re:Mass?? (1)

MiG82au (2594721) | more than 2 years ago | (#39740899)

It has momentum. C'mon, this is high school physics.

Re:Mass?? (4, Informative)

Chris Burke (6130) | more than 2 years ago | (#39741069)

Does it have mass?

In a sense yes. Radiation and all other forms of energy have relativistic mass, as in the m in E=mc^2, as in things that have more energy (moving objects, high-energy states of atoms and molecules, systems in general) have more mass as it applies to inertia and gravity.

Heat radiation as in (mostly infrared) photons don't have rest mass. That's the m0 in E = root(pc^2 + m0^2*c^4). So they don't have mass in the sense of matter as you usually think of it. But it turns out the way you usually think of mass is not equivalent to matter. Even though the usual way you think about it is that they are.

Hope that clears things up. :)

Re:Mass?? (1)

wisnoskij (1206448) | more than 2 years ago | (#39741395)

I thought that E=mc^2 meant that E could me converted to M not that all it was both energy and mass at the same time.
And that massless photons when shot in one direction actually push back in the other.

Re:Mass?? (4, Informative)

Chris Burke (6130) | more than 2 years ago | (#39741583)

I thought that E=mc^2 meant that E could me converted to M not that all it was both energy and mass at the same time.

So did I! But it's not a conversion, it's an equivalence! Energy and mass -- relativistic mass, the quantity that informs our notions of gravity, weight, and inertia -- are really, always, the same thing just in different units. If there's more energy in a system, then it weighs more on a scale. Water weighs less than two hydrogen and one oxygen because it's at a lower energy state. This of course includes the energy that is in the form of rest mass.

Rest mass is a form of energy. It can be converted into other forms of energy at a rate equal to m0*c^2. Energy and relativistic mass are always related by the equation E=mc^2.

Stress energy tensor (-1)

Anonymous Coward | more than 2 years ago | (#39740679)

Isnt it convinent shit can have no "mass" but still have "momentum". I wonder if people just make this shit up just to keep their equations from turning into goblygook.

We have neutrinos that are supposed to have mass and travel slower than light..of course because they change as they travel except after more than a hundred thousand years in flight they arrive sequenced with photons from 1987A within the margin of error of the calculated photon delay...their mass is just small..really really small...just small enough that we don't all end up looking like idiots.

I'm just venting after all these years the simple solution seems to have won out over all the exotic gyberish.

Re:Stress energy tensor (0)

Anonymous Coward | more than 2 years ago | (#39740953)

"goblygook" "gyberish"

Umm, speaking of which...

Re:Stress energy tensor (1)

tibit (1762298) | more than 2 years ago | (#39741505)

Isnt it convinent shit can have no "mass" but still have "momentum".

No rest mass, but they do have relativistic mass, m_r = h*f/c^2, where h is Planck's constant, f is photon's frequency, and c is speed of light. And they are affected by gravity, a photon emitted from a flashlight held horizontal will fall on Earth a bit. That's why gravitational lensing works.

Chalk up another win for the known laws of physics (1)

ganv (881057) | more than 2 years ago | (#39740769)

It is very nice to see this analysis come to a clear conclusion. There are many reasons for physicists and those who feel constrained by the laws of physics to wish for violations of known laws that have significant effects in our corner of the galaxy. But time after time mundane explanations based on known laws turn out to be right. At some point more people are going to catch that we are not going to continuously overturn accepted science. Eventually the philosophers and sociologists of science might catch on too. But maybe that is wishful thinking.

Solved means %100 certainty (0)

Anonymous Coward | more than 2 years ago | (#39740811)

So, the reason accounting for %20 of the unknown deceleration is still a mystery? If so drop the term "solved".

Re:Solved means %100 certainty (3, Insightful)

careysub (976506) | more than 2 years ago | (#39740893)

100% certainty exists only in a fictional version of science.

They showed that the residual 20% is not statistically significant. This is a showing that there is no additional anomaly to be accounted for. This is what is called "solving a problem" in real science.

Prior art? (0)

Anonymous Coward | more than 2 years ago | (#39740903)

I had a Crookes radiometer (http://en.wikipedia.org/wiki/Crookes_radiometer) as a kid, which demonstrated this very thing.

Re:Prior art? (2)

careysub (976506) | more than 2 years ago | (#39740941)

Nah. Crookes radiometer is not due to thermal radiation pressure in a vacuum. It is a ballistic effect of air molecules in a very thin atmosphere bouncing off a hot surface with more velocity than they had when the collided with.

Re:Prior art? (0)

Anonymous Coward | more than 2 years ago | (#39740971)

No, it didn't.

And the other 20%? (0)

Anonymous Coward | more than 2 years ago | (#39741095)

Dark Matter. It's always Dark Matter. Except when it's Cosmic Strings. Or Quantum Boogaloos. Or Electron Roulette.

But at least it's not the Phlogiston.

interesting for ion engines (3, Interesting)

slashmydots (2189826) | more than 2 years ago | (#39741279)

If I understand ion thrusters correctly (that's a big if), a big tank of neutral atoms are bombarded by electrons to knock other electrons out of orbit around those atoms, creating positive particles, which are electrostatically accelerated out a big metal screen thing and the motion of them going the opposite way makes your spaceship go the correct way.
I believe thermal radiation in this article's context means heat being turned into infrared light, that means photons going the opposite direction can have a noticeable impact on an existing spaceship in a real world text over a relatively short distance in space. I would think a gigantic atom nucleus has thousands of times more mass than a photon so ion thrusters would be pretty effective over time. Now of course the opposite "kick back" reaction is proportionate to the amount of energy you're putting into the ions and their speed is ohhhhh just a hair slower than a photon (lol) but at least we can say the theory should work in real space based on this experience.

Re:interesting for ion engines (1)

Roachie (2180772) | more than 2 years ago | (#39742133)

Yea, I was wondering about this as well. What kind of specific impulse this would represent?

But I thought it was You-Know-Who? (1)

JoshuaZ (1134087) | more than 2 years ago | (#39741319)

This means it wasn't Voldemort making a Horcrux out of the Pioneer Plaque!

As Always On /. (0)

Mana Mana (16072) | more than 2 years ago | (#39741425)

A> Solved

B> evidence for

brash pronouncements of a _solution_ (A) sound a lot like a hard MAYBE (B). *sigh*

Can this explain the Universe acceleration? (0)

Anonymous Coward | more than 2 years ago | (#39741607)

All gases expand if they are released in a lower pressure environment. I wander what happens when you release a gas under pressure at high temperature in the space outside the solar system. I would guess that it accelerates as it cools down. What about the matter released by the Big Bang. Do we really need dark matter?

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