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Planck Telescope Is Coolest Spacecraft Ever
Hugh Pickens writes "Launched in May, BBC reports that Europe's Planck observatory has reached its operating temperature, a staggering minus 273.05C — just a tenth of a degree above what scientists term "absolute zero." and although laboratory set-ups have got closer to absolute zero than Planck, researchers say it is unlikely there is anywhere in space currently that is colder than their astronomical satellite. This frigidity should ensure the bolometers will be at their most sensitive as they look for variations in the temperature of the Cosmic Microwave Background (CMB) that are about a million times smaller than one degree — comparable to measuring from Earth the heat produced by a rabbit sitting on the Moon. Planck has been sent to an observation position around the second Lagrange point of the Sun-Earth system, L2, some 1.5 million km from Earth and Planck will help provide answers to one of the most important sets of questions asked in modern science — how did the Universe begin, how did it evolve to the state we observe today, and how will it continue to evolve in the future. Planck's objectives include mapping of Cosmic Microwave Background anisotropies with improved sensitivity and angular resolution, determination of the Hubble constant, testing inflationary models of the early Universe, and measuring amplitude of structures in Cosmic Microwave Background. 'We will be probing regimes that have never been studied before where the physics is very, very uncertain,' says Planck investigator Professor George Efstathiou from Cambridge University. 'It's possible we could find a signature from before the Big Bang; or it's possible we could find the signature of another Universe and then we'd have experimental evidence that we are part of a multi-verse.'"
Uh, yea. Atmopheric distrotion is bad enough for visible radiation...thermal would basically be a second level of distortion.
According to Japanese and Aztek folklore, a rabbit has been there for a long time. I could never really make out the face or the rabbit in the moon's craters when I look.
Ryan Fenton
heat != temperature.
The summary said "heat produced by a rabbit sitting on the Moon". Somehow that went through your brain and came out as "measuring the temperature of a rabbit on the moon". So the problem is you, not the metaphor.
L2 is behind the earth, as seen from the sun. And the distance given is correct.
Wikipedia has an excellent article describing each of the Legrangian points and why each of them is pseudo-stable.
Don't Bogart the fish sticks
For your statement to make sense, you assumed the same property "time" exists within and outside the universe, and that it made sense to connect the two. It is like saying since Earth existed within something larger, there might be something due North of Earth's North Pole.
Unfortunately, North/South is a local property of Earth, while there is plenty space above the North Pole, you cannot go more north from the North Pole. Similarly, spacetime is a property of our observable universe, and that property breaks down at Big Bang. Trying to simply extrapolating spacetime from the universe to beyond is like trying to reach space by just keep going North on the Earth.
Oliver.
Well, let's say 1 Library of Congress is about 20TB, a measure of information. If we want to convert that into Rabbits * arc length, a unit of temperature * arc seconds, we can use the laws of entropy.
We know that entropy=k*ln(O) where k is the Boltzmann constant and O is the number of microstates of the system. If we really wanted, we could express the number of microstates as 1 LoC, since both are really just measuring information in one way or another.
Now if you recall temperature = change in heat/change in entropy. The average body temperature of a rabbit is about 312 degrees kelvin according to google.
To get a change in entropy and heat, we can look at both over an arbitrary time step t, so 312 K [one rabbit]=(heat/t)/(k*ln(2TB [one Library of Congress])/t)
Solving for one Library of Congress, we get one Library of Congress = e^(k*heat [in joules]/312 degrees K)=e^(4.4252x10^-26 joules^2/(degree kelvin)^2)
Now assuming a rabbit is about 0.2 meters in diameter, at a distance of about 384,000 km, that's about 3*10^-8 degrees.
So, putting that all together, the conversion factor is about e^(4.4252x10^-26 joules^2/(degree kelvin)^2)*1.1*10^5 arc seconds.
Hope that clears things up for you!
For more information you can catch up with Planck on the mission blog on Planck's twitter, and on the Planck outreach website.
I help maintain the blog and work on both the Planck and Herschel missions.
Just to clarify: -273.05C equals 0.1 Kelvin. That looks much more impressive, as it
indicates how close to absolute zero it is - and even is easier to grasp in my opinion.
Come on, we're on Slashdot, dammit!