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No antennae radiate all the power fed to them!
Jerry Stuckle wrote:
On 11/3/2014 8:53 AM, Lostgallifreyan wrote: Jerry Stuckle wrote in news:m37qbe$pgl$1@dont- email.me: Uh... "The Big Bang Theory" is a television show... Btw, I don't watch TV. :) I just got done telling the TV license people that too. Every two years or so they decide not to beleive me despite the fact that any time they visited over 15 years, the cut cable has been plastered by the same old paint on the outside front wall every time. I'm fine with radio (and first thought that Big Bang thing might have been a movie. I don't see many of those either. The last several show series I have came off eBay on disks.) I don't watch The Big Bang Theory, but I do enjoy some of the old shows. The Big Bang Theory is one of very few shows which actually get science right. -- Jim Pennino |
No antennae radiate all the power fed to them!
wrote in message
... On Monday, November 3, 2014 11:17:26 AM UTC-6, gareth wrote: wrote in message ... On Monday, November 3, 2014 11:05:11 AM UTC-6, gareth wrote: "Lostgallifreyan" wrote in message . .. How many other people who are not engineers or scientists do you see posting around here? In discussions about short antennae, quite a few from Yankland. I'm just a regular ole ham here. Never studied any of this stuff in school, and don't work in any related field. Everything I've learned, I learned on my own. It shows. Big talk from rraa's new purveyor of bafflegab Read and learn a bit more. |
No antennae radiate all the power fed to them!
On 2014-11-03 17:06:02 +0000, Lostgallifreyan said:
rickman wrote in : It takes the same amount of heat to raise a substance 1 degree at 77 °K as it does at room temperature. Ok, but when I read (or hear on BBC radio science programs) that it takes FAR more effort (energy) to pump from 2K to 1K than it does from 300K to 299K, what am I supposed to make of that given what you just said? That's energy to keep all the heat from the surrounding environment out. In a system completely separated from hot material or radiation, such as space, the energy is exactly the same, because of the way temperature is defined. -- Percy Picacity |
No antennae radiate all the power fed to them!
On 11/3/2014 12:19 PM, Jerry Stuckle wrote:
The ISS is the same. You don't see the rotation because the ISS is stationary (rotation-wise) relative to the earth, and you are observing the earth. But if the cameras were pointed into space, you would see the stars move as the ISS rotates. As I read this and pictured cameras pointed to the earth as the "space" station orbits the earth while ignoring the vastness of *space*, it seems to be that humanity is obsessed with selfies. -- Rick |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
rickman wrote:
On 11/3/2014 1:07 PM, wrote: rickman wrote: On 11/2/2014 4:11 PM, wrote: Lostgallifreyan wrote: wrote in : The only external heat source in space is the Sun; solution, sun shade. Maybe not. I just did a bit of Googling for 'superconductors in space' minus quotes. There's a lot of statements abotu space missions ended because required helium or hydrogen coolant ran out, Yeah, the coolent ran out for the things that GENERATE a lot of heat and need to be cooled more than radiation can provide. Radiative cooling does not provide for a lot of cooling. and also of space having latent temperatures up to 100K, so a sun shade won't help a lot there with current materials. There really is no such thing as temperature in space as it is a vacuum. That is a gross oversimplification. The temperature of space is the temperature of the background radiation, even in a near vacuum. That is also an simplification. But not a gross oversimplification. True. Shall we go into why an ordinary thermometer exposed to the Sun at about Earth's distance from the Sun allowed to stabilze will read the tempurature of space as about 7 C and what are the unstated assumptions for this to happen? -- Jim Pennino |
No antennae radiate all the power fed to them!
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No antennae radiate all the power fed to them!
On 11/3/2014 12:06 PM, Lostgallifreyan wrote:
rickman wrote in : It takes the same amount of heat to raise a substance 1 degree at 77 °K as it does at room temperature. Ok, but when I read (or hear on BBC radio science programs) that it takes FAR more effort (energy) to pump from 2K to 1K than it does from 300K to 299K, what am I supposed to make of that given what you just said? Ok, I'll grant that few who have not had thermodynamics really understand heat. Thermo was not an easy part of the curriculum in school. The reason why cooling something gets harder as it approaches absolute zero is because the heat flow is proportional to the difference in temperature. Even if your pump is perfect and acts as if you put the thing being cooled in contact with a heat sink at 0 °K, the rate of heat flow decreases as that temperature delta diminishes. The reality is that thinking 77 °K is especially cold is a bit of an exaggeration. Yes, it is cold by human experience, but in the world of cryogenics it is just a step stool to board the rocket. Thinking that any little heating effect would warm a high temperature superconductor is thinking with your feelings and not your brain. Not that we don't all do that. But you need more experience with this stuff to let your instinct guide you. -- Rick |
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