Science Trivia and Fact

Redshift

This thread is for those wierd science questions that really make you think.

Have a question that that's doing your head in like, What would everything look like if the speed of light was slowed right down to 1 metre per second ? Then post it here.

If you have any other examples of facinating facts or theories then add them on here.

Redshift

Imagine if you will a mirror..., and not just any mirror, but a specially designed spherical hollowed out mirror. The mirror is the surface of the sphere but on the inside. Now add some kind of light source inside (a light bulb will do for now). Turn it on and what do you think would happen?
Inside the mirrored sphere.
The moment in time just before the whole thing 'exploded' - caught myself by a special heat sensing camera (wide-focal lens) - located outside and looking into a tiny 'pin-hole' in the mirror's surface.
I only had one chance at this, considering the cost of the experiment, so I was glad it went to plan! It was important to get the image straight to the PC (milliseconds) before the heat melted the camera! Click here for a higher res.
As the light rebounds inside the sphere, the intensity grows and grows - as light is rebounded for the umpteenth time - and more light is continually being pumped out from the bulb.
It has nowhere to go!

What happens next???
Assuming the light really cannot escape, two things will start to happen...
a: The inside will become brighter and brighter as light builds up - and countless more photons are swimming inside.
b: The air and surface of the sphere will become hotter and hotter - as light is turned into heat.

Now what happens?
Well Kaboom basically! According to the brightness of the bulb, and the exact material and thickness of the sphere, it either melts away over a period of a few seconds, or the thing suddenly explodes in a great fury - as particles, photons and other stuff rushes to escape.
See pictured, the experiment itself! I was sure to choose the 'melting' option, as I didn't particularly want to set the building on fire! Also, I used an extra strong filter for the camera lens (much, much stronger than the filter in the glasses used for the eclipse), to prevent the light from 'blinding' the camera.



Inside the mirrored sphere.

The moment in time just before the whole thing 'exploded' - caught by a special heat sensing camera (wide-focal lens) - located outside and looking into a tiny 'pin-hole' in the mirror's surface.
I only had one chance at this, considering the cost of the experiment, so I was glad it went to plan! It was important to get the image straight to the PC (milliseconds) before the heat melted the camera!

Source www.skytopia.com

ISAW

Redshift wrote:

Imagine if you will a mirror..., and not just any mirror, but a specially designed spherical hollowed out mirror. The mirror is the surface of the sphere but on the inside. Now add some kind of light source inside (a light bulb will do for now). Turn it on and what do you think would happen?
Inside the mirrored sphere.

One could do this on a grand scale with the Sun. It is called a Dyson sphere. But lets us consider your light bulb. Say a normal 100 watt bulb. Most of the energy in a light bulb turns into heat already. Very little of it turns into light. Now you already know you are supplying 100 W to the system. Eventually the system would have to radiate (or conduct) away this heat. If it didn't the sphere would indeed heat up. But think about the light bulb. Most of the energy it produces is heat. If you grasp it you will burn your hand. So where does it go? It radiates heat into the air. What is to stop your sphere from doing this? There is no need to even get near the conditions necessary to "burn" a building.

Similar conditions for the Sun. Most of the energy is not light but other forms of electromagnetic radiation. If you could construct a Dyson sphere you would need to be able to radiate heat from the outside as the inside approached the melting point of whatever material you constructed it. But no doubt it would radiate it off well before that. In idealised conditions this is what a "black body" does.

nesf

Redshift wrote:

What would everything look like if the speed of light was slowed right down to 1 metre per second ?

The photon's perspective wouldn't change. Everything would still be motionless

You'd get the opposite effect to now, with sound being faster than sight. So we'd hear the thunder and then look for the lightning and such.

Redshift

Q: Where is magenta 'meant' to be in the color spectrum - after blue or before red? The 'blue' (shorter wavelength) end of the visible color spectrum contains magenta/purple/violet/indigo (red/blue mixes). It seems that red also exists after blue!
Effectively, this implies that there are 1½ reds in the color spectrum (!)
So what's going on? Did it get second helpings?




Answer:

In a very real sense, red is getting second helpings. Due to a small idiosyncrasy with the design of the eye, blue wavelengths activate the blue cone, but surprisingly also activate the red cone. The reverse doesn't happen however - red wavelengths don't stimulate the blue cone. To answer the first question, magenta itself doesn't appear in the visible spectrum. You need to mix blue and red wavelengths 'artificially' to achieve magenta.

ISAW

I think george Gamow did a book abot this called "mr Tomkins in paperback".
Go to the library and borrow it.

Gamow was famous for falling asleep in lectures and snoring. so he wrote two books about making relativity and quantum mechanics into every day expoerience. How did he do it? he made the speed of light equal to tem miles an hour and made planck's constant equal to one. Many physicists have said Gamow did better physics in his sleep than his lecturers ever did in their working lives!

ISAW

Redshift wrote:

Q: Where is magenta 'meant' to be in the color spectrum - after blue or before red? The 'blue' (shorter wavelength) end of the visible color spectrum contains magenta/purple/violet/indigo (red/blue mixes). It seems that red also exists after blue!
Effectively, this implies that there are 1½ reds in the color spectrum (!)
So what's going on? Did it get second helpings?



ther are two answers to this. One is to define particular colours by their wavelength. they you know where they all are.

However you refer to the visual "spectrum". I seem to remember ( i may be wrong) the idea of seven coulors of the rainbow the popular "specturm" of red, orange , yellow, green, blue , indigo ,violet. can be traced to the heretic Isaac Newton who had some very odd religious ideas. Seven was considered a "special" number wiuth mystical connections so I think it was he pushed the idea of seven colours in the spectrum. remember he got membership of the royal society for his telescope design and his earlier work was in Optics and not Gravity.