61

That CAN'T be true! / Fir tree in lung

« on: 15/05/2009 18:05:07 »

Think I'll just pack my trunk but then wood that sap all my strength?

62

That CAN'T be true! / Fir tree in lung

« on: 15/05/2009 16:27:07 »

Yew appear to have resurrected this old thread and are barking up the wrong tree.

Now you really are begining to needle me..

63

Guest Book / new to all this.

« on: 15/05/2009 13:07:55 »

No,  I just followed the instructions on a tinned pudding it said  "Pierce lid and stand in boiling water for 20 minutes".

64

Guest Book / new to all this.

« on: 15/05/2009 13:00:39 »

Don't make me laugh, I am sitting here with both legs severely bandaged from my feet to my thighs.

65

That CAN'T be true! / Fir tree in lung

« on: 15/05/2009 12:58:55 »

I think this thread is begining to branch away from it's roots, it needs a bit of sprucing up.

(Now having seen what I just wrote I wanna be sick...)

66

Guest Book / new to all this.

« on: 15/05/2009 12:56:06 »

Hmmm...

As I said I sold kitchens, (also appliances) I am no cook though!

67

Physics, Astronomy & Cosmology / Could the Hubble telescope see astronaut footprints?

« on: 15/05/2009 12:54:14 »

I just read the NASA link posted by Fortran. As I suspected it says:

"There are six landing sites scattered across the Moon. They always face Earth, always in plain view. Surely the Hubble Space Telescope could photograph the rovers and other things astronauts left behind. Right?

Wrong. Not even Hubble can do it. The Moon is 384,400 km away. At that distance, the smallest things Hubble can distinguish are about 60 meters wide. The biggest piece of left-behind Apollo equipment is only 9 meters across and thus smaller than a single pixel in a Hubble image."

So it looks like a footprint is indeed beyond the scope of Hubble's resolving power.

Chris

If it were possible for Hubble to photograph a footprint on the moon I'm not sure conspiracy theorists will take the word of NASA that any picture was genuine, they could suggest the pictures are 'doctored'.  The principle conspiricists have a living to make.  It is impossible to prove who made a print on the moon and when, it is up to each person to decide for themselves whether or not they believe NASA,  I once published an article which rebutted the conspiricists and since none of them could prove me wrong, it is clear the landings happened!

68

Physics, Astronomy & Cosmology / Re: What is the temperature in space?

« on: 15/05/2009 12:41:35 »

And for the second part a thermometer dipped in hot coffee will only measure it's own temperature, and it's the same in space, a thermometer will only indicate it's own temperature.  Even a rarified gas is unlikly to alter the thermometer temperature (much)which will settle at a point where energy absorbed, balances with energy lost.

Either way I feel it is technically incorrect to say astronauts go from +200 to -200 when moving into the shade.

69

General Science / When will there be the technology for wireless electricity?

« on: 15/05/2009 12:30:02 »

If you have a source of wireless power in your home then how can you be sure that there is nothing around which will be dissipating that power - either by chance or by design, by your thieving neighbour?

You do it the normal way. You measure the current drawn, and compare it with the amount used. If there's a significant difference you investigate.

Any leech would have to have a circuit that resonates at a particular frequency; it's not hard to track that down. TV license vans do much the same thing.

The only show stopper that I'm aware for this kind of thing is the frequency- you'd have to operate it at a frequency that wasn't in use.

It's not particularly expensive, it's not outrageously inefficient, it seems to be safe (you can design it within current occupational limits) and it's more convenient. [O8)]

Only to find that your neighbors ornate ring fence is glowing white hot....

70

Physics, Astronomy & Cosmology / Re: Could the Hubble telescope see astronaut footprints?

« on: 14/05/2009 23:40:26 »

I am not sure I understand "500 feet at 250,000 miles" and why this is okay for seeing footprints.

Does this mean that it can spot something 500 feet across at a distance of 250,000 miles?

How far is Hubble from the moon?

Chris

Hubble is about 242,648 miles from the moon which others (being less pedantic than I) have rounded up to 250K Miles. I think the 500 feet is either the smallest object hubble can 'see' at that distance or it is the field width of the image (ie like a picture of an object 500 feet across) in which case the smallest object would be around 12 inches, to resolve a footprint you would probably need a resolution better than 1 pixel per centimetre.


Edit: Here's a piece from Nasa on that very subject

http://science.nasa.gov/headlines/y2005/11jul_lroc.htm

71

Physics, Astronomy & Cosmology / Re: What is the temperature in space?

« on: 14/05/2009 23:34:39 »

If you put a thermometer in space it will only read it's own temperature and not that of free space, as I said temperature is an attribute of matter, radiation from the sun may heat up a thermometer but even in strong sunlight space has no temperature, the thermometer will though.

72

Physics, Astronomy & Cosmology / Re: Could the Hubble telescope see astronaut footprints?

« on: 14/05/2009 22:41:14 »

There is no hope that Hubble's resolution could be increased a hundredfold, assuming everything is made perfectly the resolution is determined by the size of the mirror and the frequency of the light it is operating at, Hubble is already at that limit.

It seems I remember that the CCD's of the early Hubble had a resolution of 800 by 800 pixels. They must do some tricks with those because the images we see are much more detailed.

I'm not sure what the news cast was claiming was a hundred times better. What ever tricks they use to capture images have probably improved over the last 20 years or so.

I'm sure I remember reading that there was some redundancy in the hubble in terms of the 800 x 600 ie 0.48 megapixel - it was known that camera technology would improve thus the resolution was much smaller than a single pixel, by how
much I do not know but also remember a lot of the processing is done on board
and improvements in software algorhythms will also improve 'effective resolution'  I think I read about it in Scientific American at some point.

73

Physics, Astronomy & Cosmology / What is the temperature in space?

« on: 14/05/2009 22:03:24 »

I heard it again, and it really gets to me,

"The astronauts experience a temperature change from +200C to -200C"  - BOllocks"

The temperature of space is NOT 10 or 50 or 100 Kelvin, it is space, it has no temperature.
Temperature is a parameter of matter, it's about how atoms wobble about!, space does not wobble about!

When an astronaut does a space walk energy from the sun is absorbed by his/her suit and may indeed raise the temperature then, when in shade, heat will be radiated from the suit but like a vacuum flask heat is only lost through radiation and not convected or conducted away.

There, I got that off my chest! now who agrees with me?

74

Geek Speak / What level of EM radiation does the average desktop generate?

« on: 14/05/2009 21:43:59 »

Q1. traditional PCs are in metal cases, which act as a Faraday cage, but so-called modded PCs use a whole host of materials; do these ruin the screening properties of the case?

Q2: In theory, would it be possible to make a case out of mesh (or a material with a mesh embedded in it - like the window on a microwave) with zero EM emissions?

Q3: Are PC's unstable if separate parts are not all earthed to a chassis? (ie mainboard, PSU, HDD were just bolted to wood, say). [case designers must have to meet specifications I'm sure, but how problematic would such Heath Robinson systems be, huh?]

Thanks!

Answer 1 to a certain extent YES.

Answer 2  NO not ever

Answer 3 It will work but might just fail occasiaonally due to induced spikes, possible ground loops and as above potential coolong issues.


EM emissions covers from DC to way past xrays, since all energy eventually ends up as heat (a form of EM energy) the amout of EM radiation will be the same as the input power.

75

General Science / When will there be the technology for wireless electricity?

« on: 14/05/2009 18:05:09 »

And what of efficiency of these systems?  just how much power would you need to transmit over 100 feet to light a 100 watt bulb at the far end of your garden? how big would the transmitter and reciever be?  a receiver for each appliance?  and remember the transmitter would need to be plugged in, it would need to transmit energy for the receiver to power up.

At the end of the day a single piece of copper wire across the floor must be a better deal than a transmission system the size of the empire state building.

This is another one of those ideas from  "The raving lunatics and Tesla society"

76

That CAN'T be true! / Fir tree in lung

« on: 14/05/2009 17:47:20 »

maybe the sun shines out of his ass and that's why the sprigg was green?

77

That CAN'T be true! / when we shut off the light in a room, what is the "speed" of darkness?

« on: 14/05/2009 17:40:08 »

I measured the speed of darkness last night, it was light for about an hour and a quarter after the sun went down  so I estimate the speed of sdarkness to be around 34mph.

78

That CAN'T be true! / Latest news on Stephen Hawking.

« on: 14/05/2009 17:36:43 »

He has now left hospital, having been admitted with a broken nose, two broken wrists, a broken ankle and shattered jaw after his girlfriend stood him up.

79

Physics, Astronomy & Cosmology / Re: Could the Hubble telescope see astronaut footprints?

« on: 14/05/2009 17:13:20 »

1 OSSP Per 26 miles 385 yards to keep with the same system []

80

Physics, Astronomy & Cosmology / Re: How far back in time can we see with powerful telescopes?

« on: 14/05/2009 17:08:45 »

Wouldn't it be great if we could see ourselves out there and our own galaxy appeared as it is today!  - that'd be a head scratcher!