Space Barometry and Thermometry 101 ( Q & A )

[jatslo]

<blockquote><font class="small">In reply to:</font><hr /><p>Where can I find space barometry and thermometry output stockpiles?<br /><br /><b>Barometry and Thermometry:</b><br /><br />Edme Mariotte (1620-1684), French physicist. His De la nature de l'air (1676) includes a statement of Boyle's law, which he discovered independently and which is sometimes called Mariotte's law in France. One of the founders of experimental physics, Mariotte investigated a wide range of phenomena, including the motion of bodies, sound, hydrodynamics, <b>barometry</b>, color, and vision (Encyclopedia).<br /><br />Gas Laws: Physical laws describing the behavior of a gas under various conditions of pressure, volume, and temperature. Experimental results indicate that all real gases behave in approximately the same manner, having their volume reduced by about the same proportion of the original volume for each drop of 1° on the Celsius temperature scale . Graphs drawn to describe this behavior can be extrapolated, and all converge to a point corresponding to about -273°C (-459°F)—this point is called absolute zero . A temperature scale defined so that zero degrees corresponds to this zero-volume temperature coordinate is known as an absolute scale. The Kelvin temperature scale begins at this absolute zero and has degrees the same size as those of the Celsius scale (Encyclopedia).<p><hr /></p></p></blockquote>

 

[jatslo]

Does the Cassini Spacecraft have a barometer, because I am curious about barometer telemetry, but I have not found any evidence? I see that the Cassini and Galileo probes were fitted with thermometers and barometers, but no sign of onboard systems that measure space anomalies related to space pressure and temperature.

 

[CalliArcale]

Barometers built for use on Earth do not work in space. They will continually register zero even as the average density fluctuates in space. So instead, spacecraft measure particles. This is a very direct way of measuring density. Instead of measuring the pressure exerted by a medium, it measures how many particles are in it. So a spacecraft like Cassini tells if space is becoming more dense by observing more particle hits. There is definitely data on this, but it rarely gets put up on the Cassini website because there isn't as much public interest in this sort of esotheric data. But it is available. Voyager data is available, although you have to go through certain channels to get it. (It's easiest if you're working for a university, because then you have access to academic channels.) Cassini data probably won't be broadly available for a while; since the mission is in such an active phase, the team is more focused on data acquisition and archiving than they are on packaging it up for broad dissemination.<br /><br />Thermometers built for use on Earth also don't work the way you'd expect in space. This is because they don't actually measure the temperature of a thing -- instead, they measure their own temperature, which over time should cool down or warm up to match the surrounding environment. In space, a thermometer can be heated up to very high temperatures by the Sun, and can then cool down tremendously as it radiates heat away. This doesn't tell you much of anything about the temperature of space, so it's not really useful except for maintaining spacecraft health. (Cassini does have thermometers for taking the temperature of various subsystems so it can thermoregulate and so systems can be shut down if they're getting too hot.) However, Cassini does have instrumentation useful for deducing the temperature of planetary surfaces, by measuring how much infrared radiation it gives off. I don't believe it's as accurate as the infrared imaging instrume <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[jatslo]

Were stuck in the middle. <img src="/images/icons/wink.gif" /> I am exploring a different gas, super-fluid, etc. as opposed mercury, because length is an issue, as in velocity affects: length, mass, and time. Did you know that gravity is velocity? How convenient for my theories. <img src="/images/icons/laugh.gif" /> We can do this, but first; you have to believe that you can.<br /><br /><font color="yellow">Barometers built for use on Earth do not work in space. They will continually register zero even as the average density fluctuates in space. So instead, spacecraft measure particles. This is a very direct way of measuring density. Instead of measuring the pressure exerted by a medium, it measures how many particles are in it. So a spacecraft like Cassini tells if space is becoming more dense by observing more particle hits. There is definitely data on this, but it rarely gets put up on the Cassini website because there isn't as much public interest in this sort of esotheric data. But it is available. Voyager data is available, although you have to go through certain channels to get it. (It's easiest if you're working for a university, because then you have access to academic channels.) Cassini data probably won't be broadly available for a while; since the mission is in such an active phase, the team is more focused on data acquisition and archiving than they are on packaging it up for broad dissemination. </font><br /><br />Yeah, okay, so observatories are good, because we can utilize that information and speculate pressure localities relative to whatever. I would be curious to look and permeations of light and dark areas of the space surrounding the Earth’s moon in various faces of eclipse, because I would imagine that the dark cooler regions would involve lower pressures over time. We have some perplexing velocity issues; that is for sure. <br /><br /><font color="yellow">Thermometers built for use on Earth also don't work the way you'd expect in space. This</font>

 

[yevaud]

A Barometer in space would be a transducer, that would measure the differential between the pressure inside of the sensor and without.<br /><br />A thermometer would be a bimetallic strip, in which the two different metals would have different temperature responses. Changes in temperature would flex the two strips differently, resulting in a resistive change.<br /><br />Simple, really. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[jatslo]

What would be the most sensitive metal? Or something else; what would something else do? Something like a porcupine barometer? Space-time = X, Y, Z, and Time -(t). We can charge the spines, so that when the spines touch do the low-pressure we could harvest info.

 

[yevaud]

Not certain. That'd be materials science versus Space Physics. I know the latter, but not really the former. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[igorsboss]

It is important to define what exactly is meant by pressure and temperature.<br /><br />Pressure is the average force exerted (by a fluid or substance) on a surface, per unit area.<br /><br />On Earth, ideal gas pressure at rest is the same in all directions. Space particles are not idea, not at rest, not confined, and experience a microgravity field. In space, pressure may be very different in different directions, due to real or apparent bulk material flows (ie. solar wind, spacecraft motion, interplanetary dust). The answer is... not simple.<br /><br />For example, the shuttle flew the "wake shield" experiment which created the best vaccuum conditions ever observed.<br /><br />The temperature (of a sample of matter) is the average kenetic energy of the consituent molecules in the sample, due to the random (heat) motion of the molecules.<br /><br />Temperature does not include the kenetic energy due to the bulk flow of the molecules. However, for a moving spacecraft in solar wind, there are bulk flows of material which should be discounted. (ie. Solar wind, and spacecraft motion)<br /><br />Perhaps a bimetallic strip would measure the temperature of the solar wind, but only if it were on a spacecraft which was travelling along with the solar wind. I doubt it's precision, because the mass of the strip would be much larger than the mass of the space it enountered. I fear the strip would measure the temperature of the spacecraft (by heat conduction) rather than the temperature of space itself.<br /><br />For engineering purposes, however, it is important to measure the temperature of the spacecraft to keep the spacecraft itself from getting too hot or cold. This information is vital to spaceflight, and can be gathered by the bimetallic strip.<br /><br />It may be easier to CALCULATE the temperature of space than to measure it.

 

[jatslo]

Same shebang, just more sensitive to relativity.

 

[jatslo]

Okay, I figured it out, but I have class tonight, and I need to do my homework. I will leave you with something to think about: Doppler effect is barometry, so I need to suspend my porcupine barometer in fluid that prevents thermals from permeating my readings: Great early warning detection system(s). Yep, the laws of motion break down: Where are the Voyager spacecrafts now, and are they sending telemetry still?<br /><br />I will resurect something that died: Ether and Tether.

 

[igorsboss]

<font color="yellow">Doppler effect is barometry</font><br /><br />How is the doppler effect barometry?<br /><br />http://www.weatherforyou.com/weather/south+dakota/porcupine.html

 

[yevaud]

Of course. That was merely a starting point (pressure transducer). It was the first non-thermometer I could think of that would work.<br /><br />The bimetallic strip idea is the basis for many thermocouples. It's actually a very elegant solution. Although, it wouldn't give you a lot of information - just the temperature differential between the spacecraft and the background temperature. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[jatslo]

I did not see a porcupine barometer on the web site; I better hurry and apply for a patent. <img src="/images/icons/wink.gif" /> Think of gravity as pressure for a second, and then exert that pressure on a ball of liquid; what will it do? It will wobble, and it will wibble, as in wibble wobble. <img src="/images/icons/laugh.gif" />

 

[igorsboss]

No, thank you, I will NOT think of Gravity as pressure, not for even a moment.<br /><br />Gravity is an acceleration field. Pressure is average force per unit area.<br /><br />Do wibble wobbles obey superposition?

 

[yevaud]

No offence intended, but once...just once, I'd like to be able to begin to explain something to someone in a somewhat "dumbed down" fashion - slowly leading them towards more complex answers - WITHOUT someone coming out of the goddamned woodwork and trying to correct me. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[yevaud]

Sorry. Lately, I'm very disgusted, depressed, and disappointed with SDC. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[igorsboss]

Don't I get to play here too? All posts are fair game, are they not?

 

[igorsboss]

I understand... I've been having long discussions with jatslo lately, too.

 

[jatslo]

What happened; I don't see it.

 

[jatslo]

That's cool, it will work for gravity too; anyway, as I was saying wibble wobble, as in doppler effect.<br /><br />Pressure is not gravity alone, I have to jazz it up (look, no strings). <img src="/images/icons/wink.gif" />

 

[jatslo]

Helium-II might be the barometer super-fluid that I seek.<blockquote><font class="small">In reply to:</font><hr /><p>Okay, I figured it out, but I have class tonight, and I need to do my homework. I will leave you with something to think about: Doppler effect is barometry, so I need to suspend my porcupine barometer in fluid that prevents thermals from permeating my readings: Great early warning detection system(s). Yep, the laws of motion break down: Where are the Voyager spacecrafts now, and are they sending telemetry still? I will resurect something that died: Ether and Tether.<p><hr /></p></p></blockquote>

 

[jatslo]

“<font color="yellow">Ether or aether, in physics and astronomy, a hypothetical medium for transmitting light and heat (radiation), filling all unoccupied space; it is also called luminiferous ether. In Newtonian physics all waves are propagated through a medium, e.g., water waves through water, sound waves through air. When James Clerk Maxwell developed his electromagnetic theory of light, Newtonian physicists postulated ether as the medium that transmitted electromagnetic waves. Ether was held to be invisible, without odor, and of such a nature that it did not interfere with the motions of bodies through space. The concept was intended to connect the Newtonian mechanistic wave theory with Maxwell's field theory. However, all attempts to demonstrate its existence, most notably the Michelson-Morley experiment of 1887, produced negative results and stimulated a vigorous debate among physicists that was not ended until the special theory of relativity, proposed by Albert Einstein in 1905, became accepted. The theory of relativity eliminated the need for a light-transmitting medium, so that today the term ether is used only in a historical context (Encyclopedia).</font>#8221;<br /><br />Okay, there is something out there that looks like ether; I can see it, so it is not invisible, or is it? F = ma breaks down as we get further and further from the Earth's Sun. Density? Viscosity?