Space is not 100% vacuum, true. Sound waves, very technically, are travelling compression/rarefications of the transport medium. This means that the properties of these waves depend intimately on the medium : that's why the same exciting source will generate different sounds inside water and outside it.
In space, the medium is so rarefied that our ears and our best instruments will not be able to pick up these waves (they will have very very long wavelengths, so you need very very big ears to hear them, and also you have to wait very very long time for a single wave to pass over you).
So, if you want to be pedantic, yes, any none-true vacuum is capable of tranporting sound waves. But they will be in frequencies that are so low that the human ears can hear as "sound" (or, as the Original poster alluded to, high enough energy to imping upon starships and generate sound waves on the body of the starship, unless of coruse the starship is (a) very very big so it acts as an antenna to soundwaves (b) very very springy so it can respond to such weak excitation).
The number of constants in the Standard Model of Particles varies depending on what you count as a constant, but is around 20+, so that may be where our friend got his number. That's the closest I can think about where he got that number. We also know that the SM is not the complete theory so there. So yes, you are right that he may be alluding to that.
66 is something I have no idea where he got that from...
One can argue about where those "constants" come from. Remember that "constants" of nature are very model-dependent things : change the model, you change the number/value of the constants etc.
Roughly speaking, science is the pursue of trying to explain the universe with as few constants as possible. The ultimate goal is to only have *one* constant in your theory. Then you can claim that the we can always rescale this number,by choosing different reference points for example, and thus the universe can be explained without any use of "arbitrary" constants.This is the so-called "bottoms up" approach to science, and is the path pursued by string theorists etc.
Of course, one can imagine that the ultimate theory of the universe really have more than one constant : there is no guarantee that the ultimate "single-constant" theory of everything exist. Or one could subscribe to Hawking's "Top down" approach....(too long to say here...)
With that preamble : here are the responses to your points.
(1) yes, that's right
(2) This is a fine point in the so-called Anthropic Principle. The AP, is as its name implies, a Principle which must *predict* results. TO say that things are they way they are because if not we won't be here to see it is not applying the AP correctly. ONe must say, ok, what are the conditions that are required for life as we know it to exist, and then use them to derive quantities that then can be measured. Now, the usual argument against the AP (similar to the one you stated) : one cannot imagine what are the "conditions for life" due to lack of experience, is *not* correct. Not knowing the conditions for life does not mean those conditions don't exist. The AP must ultimately pass or fail, as a theory, when one knows all the conditions, and then apply it to predict measurable quantities that can be tested against experiment.
Sadly, a lot of people, even in the science community, often mistook this point. (One particularly galling example is a recent paper by M.Rees, the astronomer Royal no less....)
(3) This argument is often used as an attempt to "quantify" the statistics of why we live in the universe with such constants. Recently, it has received a lot of attention, thanks to some half-hand wavy arguments from string theory. (The old form is the many-world intepretation of Quantum Mechanics, but that's a bit out of date though never disprove : you can't prove or disprove things you can't observe.) It's fine, but there is always the caveat that statistics can only tell you so much...
(4) This is new physics, since we still have no complete, testatble theory that can resolve singularities. So to make the claim that each singularity is a new universe is a matter of conjecture. Having said that, yes, people do have models that do things like that...T.Jacobson is one of those proponent who use such "birth of universes" in BH to bypass the information paradox...
(5) ID. Like I said, ID is just a bunch of mumbo jumbo. Here's how it failed the slippery slope argument : You can always ask who design the designer...for starters.
So, for me, (3) is actually a meaningful question to ask. It won't be satisfying as an answer, like you said, it won't be completely testable. But a lot of things are described statistically (thermodynamics), so what is wrong to say that the universe is just a realization from an ensemble of possibilities? You can "test", statistically speaking, by doing a bayesian analysis and have some sort of answer (like "The probability of us living in this universe, given the model is such as such, is 70% etc..."). (5) is just baloney. (2) is not giving up, but often cast as such, though I still think it is hokey and its results often overstated.
This post is so reflective of the circuitous arguments that are often used to justify Intelligent Design.
There is no respect to ID given by the scientific community. I don't know where you get those numbers 26 and 66 on the number of variables needed for "our existence".
You 3rd paragraph is a bunch of nonsense strewned with enough difficult words to make it sound important but actually contain no information.
Not everybody wants to be a scientist, especially when you get low pay, poor advancement and lousy job opportunities. And that's after you have spent 5-7 years slogging away as a slave in grad school....
On the other hand, doing science is the most rewarding experience I've ever had*.
Btw, Geoffery Landis is himself a scientist...
* Other than hot, steamy sex.
Re:Software Design != Rocket Design OR does it?
on
X Prize and John Carmack
·
· Score: 3, Insightful
If you can afford to test your hardware as often as you can, do it. A test is worth a million analysis plots.
Making mistakes in a test environment is the best way to learn about your design and your own limitations.
I don't think it works that way. There are some subtlety involving the many meanings of the word "temperature".
It depends on the body and its emissivity properties. To be in equilibrium with the Sun, a body must emit as much flux as it is receiving from that sun. FOr an object near EArth's orbit with the Sun, it is 1.4kW/m^2. Earth's emissitivity ensures that its effective temperature is about 300k ( i.e. Flux = stefan-boltzman constant * T_eff^4). Remember the Blackbody temperature is only a definition, not something you can measure with a mercury thermometer for example.
The Flux emitted by the object is dependent on the properties of the object, including its body temperature (i.e. the temperature you measure with a thermometer), and emmisivity properties of its surface. THe latter is important, because a body with the same effective temperature but wildly different emmisivity will have wildly varying body temperatures. Thus an object can have whatever temperature from 3k to 6000k.
So the an object can have wildly different equilibirum body temperatures even if they see the "same amount of sun". I add in the "body" here to clear up the confusion in my previous posts : my bad.
I suppose we have different opinions (which is fine) about his rebuttal. Personally I think Friedmann tried very hard to be respectful, and I applaud him for that. But I do think that it does come out to sound like false praise. Well, just my completely unsubstantiated opinion.:).
The "equilibrium temperature" of any object in space, where the only dominant source of heat transfer is radiation, depends completely on the thermal surfaces of this object.
Earth's "equilibrium" temperature is about 300k, that's true. But for other spacecraft, its equilibrium tempreature depends on what kind of thermal surfaces the engineer stick on it. Most spacecraft aims for 300k, since the spacecraft's instruments are from Earth, and most "normal" components have their optimum operating temperature at 300k.
However, this does nto have to be so. You can put a big black box in space, with zero emissitivity, and it will reach a temperature between 6000k and 3k as an equilibrium.
IN fact for the solar sail, if it is a perfect mirror, it will actually reach equilibrium near 3k, since it does not absorb any energy from the Sun. THus it will radiate away as a blackbody until it equililbriates with the rest of the Universe, i.e. 3k.
But equally true is the statement that no scientific position ought to be elevated merely because some proponents once did good work, in a different subdiscipline.
I agree. But I was onnly using hoyle as an illustration why the OP is not right to attack Gold based purely on his association with a discredited theory. One can read GOld and judge him then. On his "proof of the invalidity of solar sailing", I've read it and thinks it's bunk.
I am not sure what you mean by "intermediate temperature".
The rays of the sun is hitting the sail, and since the sun can be assumed to be a point source, the rays are hitting it in parallel. The distribution of the energy of the photons follow the planck spectrum at 6000k.
You are making a personal attack, not attacking his ideas.
Here are two cases:
(a) Another BIG proponent of the Steady State universe is Fred Hoyle.(While we are at it, let's throw in that Hoyle also supported life from space rocks theory). Is he a quack? No. He has good arguments. In fact, Fred Hoyle is sadly forgotten for his VERY seminal work on figuring out how the Sun nuclear engine works. Sadly the Nobel committee only awarded Willie Fowler the Nobel though Hoyle arguably did as much to solve the problem : an scandalous injustice that many astrophysicists now rued.
(b) You can also attack Friedman's comment about the "obscure british "preprint physics archives".
A number of colleagues have contacted me since the web posting (on a rather obscure British web site of "e-print physics archives", http://uk.arXiv.org.)
The arXiv is the main distribution of physics and maths papers nowadays. Everybody in the field reads the archives. In fact the uk.arXiv.org is just one of the many mirrors of the main site arXiv.org hosted, ironically by Cornell.
So Friedmann did a "personal attack" on Gold (implying that Gold only published his findings in some no-name website). THat's not a good thing. A good scientist names his source without judgement : the reader can decide for himself whetehre it is good or not by its contents.
The two temperatures are NOT the same. They are slightly different. The mirror is not infinitely massive, so in the mirror's own reference frame the photons reflecting from the mirror have a lower energy / longer wavelength after their elastic collision with it- the mirror receives a small bit of momentum from each photon in the collision. And in the sun's frame, the mirror is receding and the reflected photons are doppler shifted. He can't assume that the incident and reflected energy are the same and run off making derivations from that. They are extremely close, but the difference between them is not zero like he assumes.
This is true, but not the reason why the Carnot analogy fails.
The main point is that the mirror is not receiving "heat energy" (a scalar quantity), but a constant radiation directed radiation pressure ( I hate the term "pressure", because pressure to me seems to be a local scalar quantity but such is jargon.), a directed constant force (i.e. a vector quantity.) So the MIrror is NOT a heat engine. A battle analogy is that the Sun is the engine powering the "mirror".
The sail temperature will rise to some intermediate temperature between 3 and 300K and reach thermal equilibrium with all available radiation.
Not 300k. The Sun is approximately a Blackbody at 6000k, so the mirror sees a Planck spectrum of radiation at 6000k in one side, and cosmic microwave 3K on the other. THe rest your explanation is spot on.
Slashdot Mirror
Male/Female marriage is OK as long as the parties agree.
Gay marriage is OK as long as the parties agree.
Polygamy is OK as long as the parties agree.
Monogamy is OK as long as the parties agree.
Only when a any party is FORCED to do anything they want, is there a problem.
The link you have is broken.
Space is not 100% vacuum, true. Sound waves, very technically, are travelling compression/rarefications of the transport medium. This means that the properties of these waves depend intimately on the medium : that's why the same exciting source will generate different sounds inside water and outside it.
In space, the medium is so rarefied that our ears and our best instruments will not be able to pick up these waves (they will have very very long wavelengths, so you need very very big ears to hear them, and also you have to wait very very long time for a single wave to pass over you).
So, if you want to be pedantic, yes, any none-true vacuum is capable of tranporting sound waves. But they will be in frequencies that are so low that the human ears can hear as "sound" (or, as the Original poster alluded to, high enough energy to imping upon starships and generate sound waves on the body of the starship, unless of coruse the starship is (a) very very big so it acts as an antenna to soundwaves (b) very very springy so it can respond to such weak excitation).
No.
The number of constants in the Standard Model of Particles varies depending on what you count as a constant, but is around 20+, so that may be where our friend got his number. That's the closest I can think about where he got that number. We also know that the SM is not the complete theory so there. So yes, you are right that he may be alluding to that.
66 is something I have no idea where he got that from...
One can argue about where those "constants" come from. Remember that "constants" of nature are very model-dependent things : change the model, you change the number/value of the constants etc.
Roughly speaking, science is the pursue of trying to explain the universe with as few constants as possible. The ultimate goal is to only have *one* constant in your theory. Then you can claim that the we can always rescale this number,by choosing different reference points for example, and thus the universe can be explained without any use of "arbitrary" constants.This is the so-called "bottoms up" approach to science, and is the path pursued by string theorists etc.
Of course, one can imagine that the ultimate theory of the universe really have more than one constant : there is no guarantee that the ultimate "single-constant" theory of everything exist. Or one could subscribe to Hawking's "Top down" approach....(too long to say here...)
With that preamble : here are the responses to your points.
(1) yes, that's right
(2) This is a fine point in the so-called Anthropic Principle. The AP, is as its name implies, a Principle which must *predict* results. TO say that things are they way they are because if not we won't be here to see it is not applying the AP correctly. ONe must say, ok, what are the conditions that are required for life as we know it to exist, and then use them to derive quantities that then can be measured. Now, the usual argument against the AP (similar to the one you stated) : one cannot imagine what are the "conditions for life" due to lack of experience, is *not* correct. Not knowing the conditions for life does not mean those conditions don't exist. The AP must ultimately pass or fail, as a theory, when one knows all the conditions, and then apply it to predict measurable quantities that can be tested against experiment.
Sadly, a lot of people, even in the science community, often mistook this point. (One particularly galling example is a recent paper by M.Rees, the astronomer Royal no less....)
(3) This argument is often used as an attempt to "quantify" the statistics of why we live in the universe with such constants. Recently, it has received a lot of attention, thanks to some half-hand wavy arguments from string theory. (The old form is the many-world intepretation of Quantum Mechanics, but that's a bit out of date though never disprove : you can't prove or disprove things you can't observe.) It's fine, but there is always the caveat that statistics can only tell you so much...
(4) This is new physics, since we still have no complete, testatble theory that can resolve singularities. So to make the claim that each singularity is a new universe is a matter of conjecture. Having said that, yes, people do have models that do things like that...T.Jacobson is one of those proponent who use such "birth of universes" in BH to bypass the information paradox...
(5) ID. Like I said, ID is just a bunch of mumbo jumbo. Here's how it failed the slippery slope argument : You can always ask who design the designer...for starters.
So, for me, (3) is actually a meaningful question to ask. It won't be satisfying as an answer, like you said, it won't be completely testable. But a lot of things are described statistically (thermodynamics), so what is wrong to say that the universe is just a realization from an ensemble of possibilities? You can "test", statistically speaking, by doing a bayesian analysis and have some sort of answer (like "The probability of us living in this universe, given the model is such as such, is 70% etc..."). (5) is just baloney. (2) is not giving up, but often cast as such, though I still think it is hokey and its results often overstated.
This post is so reflective of the circuitous arguments that are often used to justify Intelligent Design.
There is no respect to ID given by the scientific community. I don't know where you get those numbers 26 and 66 on the number of variables needed for "our existence".
You 3rd paragraph is a bunch of nonsense strewned with enough difficult words to make it sound important but actually contain no information.
Finally, I think I've just fed a Troll.
to be Malaysian!
*sniff*
*sniff*
My name is Boba Fett. I do thy bidding....
just don't forget to let me use those damn cool carbonite freezer to chill 'em virus writers.
Not everybody wants to be a scientist, especially when you get low pay, poor advancement and lousy job opportunities. And that's after you have spent 5-7 years slogging away as a slave in grad school....
On the other hand, doing science is the most rewarding experience I've ever had*.
Btw, Geoffery Landis is himself a scientist...
* Other than hot, steamy sex.
If you can afford to test your hardware as often as you can, do it. A test is worth a million analysis plots.
Making mistakes in a test environment is the best way to learn about your design and your own limitations.
Come on, he has a knife and a bow, is dressed in leather armor, so he must be a RANGER!
this equation :
G_{\mu\nu}=T_{\mu\nu} ?
thanks.
Trying to get a girlfriend to read /. is the most complicated endeavour undertaken by mankind.
Not really, just a Euclidean one :P.
oh it's pork. POOOORRRKKKK!!
ah, but if you think about it, at infinite distance from the point source, even a mathematician will agree :).
I don't think it works that way. There are some subtlety involving the many meanings of the word "temperature".
It depends on the body and its emissivity properties. To be in equilibrium with the Sun, a body must emit as much flux as it is receiving from that sun. FOr an object near EArth's orbit with the Sun, it is 1.4kW/m^2. Earth's emissitivity ensures that its effective temperature is about 300k ( i.e. Flux = stefan-boltzman constant * T_eff^4). Remember the Blackbody temperature is only a definition, not something you can measure with a mercury thermometer for example.
The Flux emitted by the object is dependent on the properties of the object, including its body temperature (i.e. the temperature you measure with a thermometer), and emmisivity properties of its surface. THe latter is important, because a body with the same effective temperature but wildly different emmisivity will have wildly varying body temperatures. Thus an object can have whatever temperature from 3k to 6000k.
So the an object can have wildly different equilibirum body temperatures even if they see the "same amount of sun". I add in the "body" here to clear up the confusion in my previous posts : my bad.
There, I did my little exercise.
Ah but this is true.
:p.
The untrue things, we tend to use more jargon than that
I suppose we have different opinions (which is fine) about his rebuttal. Personally I think Friedmann tried very hard to be respectful, and I applaud him for that. But I do think that it does come out to sound like false praise. Well, just my completely unsubstantiated opinion. :).
OK.
The "equilibrium temperature" of any object in space, where the only dominant source of heat transfer is radiation, depends completely on the thermal surfaces of this object.
Earth's "equilibrium" temperature is about 300k, that's true. But for other spacecraft, its equilibrium tempreature depends on what kind of thermal surfaces the engineer stick on it. Most spacecraft aims for 300k, since the spacecraft's instruments are from Earth, and most "normal" components have their optimum operating temperature at 300k.
However, this does nto have to be so. You can put a big black box in space, with zero emissitivity, and it will reach a temperature between 6000k and 3k as an equilibrium.
IN fact for the solar sail, if it is a perfect mirror, it will actually reach equilibrium near 3k, since it does not absorb any energy from the Sun. THus it will radiate away as a blackbody until it equililbriates with the rest of the Universe, i.e. 3k.
hope this helps.
But equally true is the statement that no scientific position ought to be elevated merely because some proponents once did good work, in a different subdiscipline.
I agree. But I was onnly using hoyle as an illustration why the OP is not right to attack Gold based purely on his association with a discredited theory. One can read GOld and judge him then. On his "proof of the invalidity of solar sailing", I've read it and thinks it's bunk.
That does not give him the right to make personal attacks, which is a fallacy in logic in general, and not just among the "cult of scientism".
Making his invention work means he has to be objective. The line between engineering and science is quite vague.
I am not sure what you mean by "intermediate temperature".
The rays of the sun is hitting the sail, and since the sun can be assumed to be a point source, the rays are hitting it in parallel. The distribution of the energy of the photons follow the planck spectrum at 6000k.
You are making a personal attack, not attacking his ideas.
:
Here are two cases
(a) Another BIG proponent of the Steady State universe is Fred Hoyle.(While we are at it, let's throw in that Hoyle also supported life from space rocks theory). Is he a quack? No. He has good arguments. In fact, Fred Hoyle is sadly forgotten for his VERY seminal work on figuring out how the Sun nuclear engine works. Sadly the Nobel committee only awarded Willie Fowler the Nobel though Hoyle arguably did as much to solve the problem : an scandalous injustice that many astrophysicists now rued.
(b) You can also attack Friedman's comment about the "obscure british "preprint physics archives".
A number of colleagues have contacted me since the web posting (on a rather obscure British web site of "e-print physics archives", http://uk.arXiv.org.)
The arXiv is the main distribution of physics and maths papers nowadays. Everybody in the field reads the archives. In fact the uk.arXiv.org is just one of the many mirrors of the main site arXiv.org hosted, ironically by Cornell.
So Friedmann did a "personal attack" on Gold (implying that Gold only published his findings in some no-name website). THat's not a good thing. A good scientist names his source without judgement : the reader can decide for himself whetehre it is good or not by its contents.
The two temperatures are NOT the same. They are slightly different. The mirror is not infinitely massive, so in the mirror's own reference frame the photons reflecting from the mirror have a lower energy / longer wavelength after their elastic collision with it- the mirror receives a small bit of momentum from each photon in the collision. And in the sun's frame, the mirror is receding and the reflected photons are doppler shifted. He can't assume that the incident and reflected energy are the same and run off making derivations from that. They are extremely close, but the difference between them is not zero like he assumes.
This is true, but not the reason why the Carnot analogy fails.
The main point is that the mirror is not receiving "heat energy" (a scalar quantity), but a constant radiation directed radiation pressure ( I hate the term "pressure", because pressure to me seems to be a local scalar quantity but such is jargon.), a directed constant force (i.e. a vector quantity.) So the MIrror is NOT a heat engine. A battle analogy is that the Sun is the engine powering the "mirror".
The sail temperature will rise to some intermediate temperature between 3 and 300K and reach thermal equilibrium with all available radiation.
Not 300k. The Sun is approximately a Blackbody at 6000k, so the mirror sees a Planck spectrum of radiation at 6000k in one side, and cosmic microwave 3K on the other. THe rest your explanation is spot on.
...they are trying to raise a nice headline to publicise their work.
"Marriage tames Genius" is so much better a headline than "Genius burns out, then gets married."
Remember, causality is very hard to prove either way.