1

Physics, Astronomy & Cosmology / Does the ability to collect microwaves for electric current cut off at some temp

« on: 09/11/2017 21:46:28 »

So, collecting microwaves/ radiowaves for electric current is relatively easy using a length of wire and a diode aka an antenna, right? The current is small, unless high power microwave source is nearby or the antenna is very big, but thats irrelevant for my question. 
What I am wondering - is there some (very low) temperature where this process ceases to?
Why am I wondering this, you might ask? Well: what if we put such an antenna in a very cold environment - 12 kelvin, where the black body radiation is microwaves?

Edit: changed "background thermal radiation" to "black body radiation"

2

Physics, Astronomy & Cosmology / Is it possible to generate electricity from infra red radiation?

« on: 05/11/2017 17:41:22 »

Sorry about the vague title - the system doesnt allow it to be very long.
The expanded question: It is possible to collect radiowaves and microwaves with a simple antenna and a diode to produce electric current, right? What if we lived in an such a cold environment where the background thermal radiation was microwaves, instead of infrared - I see no reason (other than than it being a perpetual motion of the second kind) why the background microwaves couldnt be harvested for electricity. Please explain.
In extension - what, fundamentally, disallows for a similar collection of infrared? Other than there being no diodes that work fast enough for the higher frequency of infrared, but that seems more like technical limit, not a fundamental.

3

Physics, Astronomy & Cosmology / Does very light matter make gravity appear weak?

« on: 13/09/2017 11:14:03 »

I mean, regular matter, atoms and molecules, is far, far lighter than, say, a neutron star or a black hole. How weak is gravity if we compare a proton sized black holes gravity to the electromagnetic strength of a proton?

4

Physics, Astronomy & Cosmology / Is it possible to climb out of a gravity well with less than escape velocity?

« on: 30/08/2017 13:40:43 »

I am pretty sure the answer is "yes" - thats the whole idea with space elevators, isnt it? As long as you can keep applying a force away from the well, by pulling on a cable or just having super thrusters,  you should, eventually crawl out of the gravity well.

Now, to the real question - what about black holes? Their whole thing is that the escape velocity becomes >c  below the event horizon and, since nothing can travel >c, thats that... but what about slow crawling way I mentioned above?
To avoid spaghettification lets use a supermassive BH.

5

Physics, Astronomy & Cosmology / Is the strength of the Casimir effect the same everywhere?

« on: 25/08/2017 15:57:41 »

Have there been measurements of the Casimir effect at different altitudes on Earth, in orbit, in interplanetary space? Is there even reason to think it might vary from place to place?

What got me thinking of this is "Einstein's Missing Inch" - the fact that massive objects warp space and so the circumference is smaller than pi*2R. That kinda means there is .. umm.. more space density, for a lack of a better term, in certain regions and with that might come different strengths of the Casimir effect.
if not that, maybe something else, just curious.

6

Technology / Could small, compressible balls be used to negate the effects of ice expansion?

« on: 12/11/2015 20:34:20 »

Hey, naked scientists. I am wondering about how to prevent freezing water from breaking its container (as it freezes). Of course, one way is to use anti-freeze of some sorts and not let it freeze in the first place, but, if I want it to still be drinkable, thats not really an option.

What I am pondering is - what if I fill the water container with some compressible balls (or cubes? Some other shape?), that would still be compressible at those temperatures, so they act as a pressure relief system of sorts. The freezing water/ ice would crush them instead of breaking its container.  Or coat the container walls of such material.

7

Technology / How much force can a speaker and one-way valve system produce?

« on: 09/11/2015 16:24:06 »

Greetings, naked scientists. I am wondering about alternatives to propellers for thrust production. What I have in mind is this:
The inspiration being a speaker cone, I get a square plate full with one-way valves (say, thin stripes covering the length of the square, all right next to each other. Or something.) and hook it up to a system that, similar to a speaker cone, vibrates it/ moves it back and forward. Now, if the valves open and close fast enough, it will be pushing air in one direction, producing some thrust, wouldnt it?

How much thrust could it make? Lets say, 1m^2 at 20Hz with the amplitude (that is, the total distance traveled by the plate in one sweep) of 2 cm? The air moved in one sweep would be 0.02m^3 and the mass of air would be 25.5 grams, according to WolframAlpha.

What would be the optimal frequency and amplitude before the plate or the valves just couldnt move that fast? And how much thrust would that give?

I did some simple calculations on my own, but I am not sure if they are correct:
 I assumed the final air velocity would be the speed at which the plate moves, which is, in case of 20Hz and 2cm amplitude, 20*2=40 cm per second. Or is it twice as fast since it moves 20 times in one direction and 20 times back making it 40*2? I am not quite sure, but I want to know.
 If the air is exiting the device 0.4m/s and it took just 1/20 (or is it 1/40) of a second to accelerate it to that speed, then the acceleration would be 8m/s/s (assuming the lower estimates).
 Knowing acceleration and mass of the air pushed we get 8*0.0255=0.204 Newtons (or 204 grams?). But since its pushing only half of the time the total force decreases to 0.102 Newtons (?)

Not particularly much, using the lover estimates, it might be 2 or even 4 times as much as this, depending to answers to the questions above. But what if it revs up to 100Hz? Would the force be 5 times as much? 10 times as much? How much could the amplitude be increased? 4 cm?

8

Technology / Can we pull heat from the ceiling with materials that shrink when heated?

« on: 07/04/2015 00:21:03 »

Can we pull heat from the ceiling with materials that shrink when heated that are suspended in a carefully chosen fluid in which the material (like Zirconium tungstate) floats when at the temperature of the floor, but sinks (shrinks - gets denser) when at the temperature of the ceiling? That is, ceiling is usually quite a bit noticeably warmer than the floor, due to the fact that hot air rises.
If a material would sink to the floor level when heated, absorbing the heat energy from the ceiling, then rise again, when cooled a bit, giving the heat energy to the floor level (perhaps pipes under the floor) and expanded, that would make a passive system that puts the heat where its most needed, instead where it wants to go, wouldnt it?
(I am talking about about houses in the kind of climate where we would actually want to heat our houses, of course)

9

Physics, Astronomy & Cosmology / Can we steal energy from the Earths rotation?

« on: 30/03/2015 21:17:38 »

Greetings. If we take some mass from the equator and push it to one of Earths rotational poles trough some tubing (idk, say, super-fluid filled to prevent friction loss or something, just bare with me please), the piece of mass would accelerate in the direction of Earths rotation relative to the ground that now underneath it (Coriolis effect). Its like ice skater pulling in arm while rotating to rotate faster, but in this case, the mass thats pulled in is not rigidly attached and can accelerate on its own without accelerating the whole planet.
Now, that the mass is moving relative to the ground (and the initial energy that was used to push to the pole is not lost/ is absorbed), it can be absorbed and converted how we like (electricity).

Now, how about the angular momentum of the planet?
I understand that if the object we are moving to the pole is rigidly attached to the planet (like arms to an ice skater), the planet would in fact rotate faster, but angular momentum would be conserved.
But what about the scenario about the energy stealing? The mass in question would still end up at one of the rotational poles, but, in this case, we also have some energy extracted. I guess I could think that the planet would slow down (after speed up) and the energy we extract would not come from nowhere, but what about the angular momentum?
Edit: Changed title to a question.

10

Physics, Astronomy & Cosmology / Muon catalyzed fusion of heavy, iron+, elements

« on: 24/03/2015 18:40:26 »

Greetings. I wonder - if fusion of iron and heavier elements absorb more energy than the reaction releases, what if the fusion event is muon catalyzed, "cold" fusion? Would the medium become colder? That is, there would be nothing to push the nuclei together like in hot fusion and the absorbed energy would not come from that pushing/ kinetic energy of hot particles. Well, there would be kinetic energy and some pushing, but much, much less, since one could irradiate a cold (think room ~temperature or , heck, even 1 Kelvin) iron plate with muons.

11

Physics, Astronomy & Cosmology / How long to to equalize the temperature of aerogel sealed, supercooled box

« on: 17/03/2015 12:24:32 »

If I have a, say 2*20*30 (cm) box completely surrounded/ insulated by aerogel, where the inside is cooled to 77 Kelvin  and the outside is 293 kelvin (room tempeature) - how long would it take for the temperature to equalize (practically, for the inside temperature to reach 293 Kelvin) ? And how much power would it require using, say, peltier coolers, to exactly negate the outside heat leaking inside?

12

Geek Speak / HDMI cable weirdness - help me understand

« on: 25/02/2015 15:08:41 »

Greetings. I dont really want this to be a "fix my pc" thread, but, well, I have a weird problem and I dont understand how can it possibly happen.
That is - I had an HDMI cable that worked fine until, after two months or so, my monitor just started to disconnect randomly. Sometimes for a second, sometimes for minutes, sometimes just kept on connecting and disconnecting until it drove me mad and I pulled the cable and unsed my laptops smaller screen.
I took the cable back to the shop and they replaced it with a new one. So far so good.

But the funny thin is - this new cable, after a month or so of usage, started to exhibit the same symptoms.
As if the monitor just goes to sleep, but not really, because mouse and keyboard doenst wake it up, but not the same as unplugging the cable (although the pc does play the unplug sound), because there is no "check signal cable" message.

*I tested the old and new cable with two laptops and two different monitors (+a tv) and a different cable I had for another purpose - the problem seemed to be the cable (plus the fact BOTH cables worked fine for some time)
*All the ports on all devices are in good condition and nothing wiggles
*The cable gets rarely moved/ unplugged and there is external damage to the pins or the cable itself

I am a bit baffled. What could possibly be the cause for this? What could happen to a cable over such short time of use? And the fact tat BOTH cables have exactly the same problem.

13

Physics, Astronomy & Cosmology / How are windows letting a lot of heat escape from homes if glass is an insulator

« on: 22/02/2015 16:27:30 »

Even a double pane window, if I put my hand to it, I can feel it is very much colder then every other part of the outer wall and the rim of the window (in a cold climate, ofc), though glass is a poor conductor of heat.
Is it only because of how thin the glass piece is? If I would have a window glass as thick as my outer walls, would the insulation be as good (or even better than) .. the wall itself?

14

Technology / Hydrogen cars with built in water splitters?

« on: 21/01/2015 02:16:13 »

With the recent announcement of a new hydrogen car, that seems to be getting pretty popular, I am wondering - couldnt they have built in water slitter tech so the cars can be charged up BOTH from the specialized stations that are yet to be built (faster) and/ or any electric power outlet (charging at home overnight and using the infrastructure we already have)?
Would it be terribly impractical somehow? Or expensive? Or they already work that way and I just missed that?

15

Technology / How can I optimise an electric generator with a shaking magnet inside a coil?

« on: 25/12/2014 15:05:16 »

Greetings. I was wondering if it would be a good idea to simply loosly put a strong magnet inside a copper (or other) coil to generate electric energy from the shaking of the system (say, in smartphone in a pocket while walking), BUT with the so called "Liquid metal" material coating inside to minimize energy loss and keep the magnet bouncing for longer to extract a bit more energy.. what do you think? Or is the "Liquid Metal" magnetic and the magnet will just stick? In that case - perhaps the magnet can be fixed in position and the coil be bouncing between the very kinetic energy reflecting  material plates? ..

16

Physics, Astronomy & Cosmology / Do subatomic particles actually make up matter or are created in interactions?

« on: 22/12/2014 16:21:41 »

Do subatomic particles actually make up matter or they are created in interactions?
Something like - we can chip of smaller rocks from a larger rock, but that doesn't mean the larger rock is actually made of lots of smaller rocks.

17

Physics, Astronomy & Cosmology / Does gravity only work on moving objects?

« on: 18/12/2014 00:26:50 »

I think I have discussed this somewhere on forum. This or another, but cant find the thread anymore and I want to learn more about this.
If gravity is the curvature of space and objects "fall" in to the gravity well because they are following a curved path, then, well, that can only happen if the object is moving, isn't it so? I understand there is still molecular and sub-atomic motion in matter and this would be the major contributing factor if this is true.
But then escape velocities exist and I get really confused.

18

Physics, Astronomy & Cosmology / would it make sense to think of space-time as 3.5 dimensional instead of 4?

« on: 17/12/2014 23:41:29 »

That is, if one dimension adds two possible directions to move in, would a half a dimension add only one direction to move in? That is - one way in time.

19

Physics, Astronomy & Cosmology / Can a heat pump system generate electricity from temperatures over 0 Kelvin?

« on: 20/10/2014 22:03:49 »

I am wondering - can a heat pump system be used to generate electricity from T>0K (temperature larger then 0 kelvin)?
That is - if a heat pump system consumes 1 energy unit and gives back 3 units (that includes the input unit), where the excess energy is taken from somewhere, decreasing that places temperature - using a thermoelectric converter with efficiency of 40%, then 1 unit can be pushed back to repeat the process, 1,8 is lost (non-converted) heat and 0.2 can be harnessed as electrical energy. With the mechanical parts and the compression chamber in the same place, surrounded by the thermoelectric converter system not to loose heat energy at mechanical inefficiency. It almost seems as if a system could be built that just keeps on cooling its surroundings and generating electricity as long as there is T>0K in the surroundings. Cant it?

20

Physics, Astronomy & Cosmology / Molten snow, indentations around objects in/ on the snow

« on: 06/10/2014 09:10:55 »

Greetings. I have noticed that pretty much any object on the surface of the snow or partly sticking out, will have a indentation around it where the snow has, presumably, melted. I find it fascinating and I think it is to to the fact that those materials absorb the Suns radiation more and get warmer than the snow. Is that right?
Snow melts at 0C (273.15 K?), so the objects temperature should be at least that high to actually melt the snow, not just warm it up a bit making it -9C from -10C?
How high can the temperature get just by leaving the most absorbing material lying in the snow (or somewhere on Earth)?