Photonics? / frequency multiplier,

Be interesting to make, perhaps a metamaterial, which doubles or multiplies the frequency of fields in space. A lens or dish could be made out of this material, to transmit or reflect light generated by the interaction with incident radio waves, perhaps THz radiation. Bias could be incorporated to provide amplification; this would be the bulk equivalent of the zero-dimensional frequency tripler (which distorts the original signal, producing 2nd harmonic, which gets implicitly mixed with the original, making a fairly linear tripler).

Such material can probably be fabricated today from layers of SiO2, amorphous silicon and aluminum interconnects -- amorphous transistors suck, but it would be an interesting proof-of-concept that might work into the GHz. I don't know if schottky diodes can be made with any performance with amorphous silicon, but regular MOS structures should still do fine. Good enough for TFTs.

Can Al2O3 be grown by epitaxy on Si? I know the opposite way works. Annealing probably isn't possible; growth from solution (Al2O3 is soluble in Na3AlF6 and similar salt 'alloys') is probably necessary. Hmm, making reliable MOS gates after soaking in a sodium ion bath would be... interesting?

Tim

The information barrier is literally the edge of the universe. The red-shifted things you see at around 14G light-years were created at the birth of this universe.

..which leads to the possibility that we are IN a black hole.

The 'edge', if there is one, seems to be found by linearly extrapolating the recession velocity described by Hubble's constant to where it reaches c. That's just silly.

There is no need to have EM energy in the visible range to make images, either. We can make images using infrared and radio waves just fine. Of course, we need huge apertures to get interesting resolution, but that's needed for raw sensitivity too, anyway.

Jeroen Belleman

The Big Bang is silly, too.

But you can't make very good images of something that doesn't exist. It's redshifted to zero Hertz.

Well, it appears that there are two things going on.

1. As the Universe is expanding, the galaxies and all are flying out. So the optical Doppler Effect or 'Red Shift'
2. Light coming in from from the extremities of the Universe are 'bent' from their straight paths by massive galaxies and 'dark matter' and this is 'gravitational lensing'. Very fascinating stuff.

It's the other way around, actually: Remote objects have their observed spectra increasingly red-shifted, which is explained by positing they are moving away.

One problem with this is that when you extrapolate that sufficiently far backwards, you end up with something that present-day physics cannot explain.

Then again, there are quite a few things in the universe that present-day physics has trouble with, and most 'explanations' are merely unbridled fantasy.

Jeroen Belleman

In cosmology, like religion, I agree with everybody else, the model is your choice.

A standard telescope can increase the brightness, which is actually increasing the Number of photons in an image.

Total Energy = Number x (Plancks h) x frequency

My curiosity is to boost the Total Energy by

Total Energy = Number x (Plancks h) x Frequency

where Frequency = frequency x multiplier.

Not quite the same as 'heterodyning' or a photo multiplier, which increases Number. Regards Ken

At sufficient power densities, some materials will behave in a non-linear way and produce sum and difference frequencies. Even a "transparent" fiber might do this at sufficient (close to melting) power levels.

Of course, this is unusable for image generation purposes, in which the power levels are _far_ too low.

Well let say you have such frequency multiplier, and you travel to get close to the information barrier (let say 2 feet away) what happens then? will you see multiple universes ?

I'll ask you, what if we can see more of the universe, perhaps out to 15GLys, what would that mean?

The 'device' theorized, would have applications to earthly photonics, (cosmology was just an example). Ken

Well allow me to be incremental, and start with Doppler Shifted Audio. Of course we've all experienced that. One has a spectrum of audio ranging from 0-10Khz, and then simulates approaching that source to Doppler shift to 0-20Khz, linearly, so that would be frequency x2, and one can select x3 x4 ... Off hand, I haven't done that using either analog or digital computer, so that's where I'd need to start. Regards Ken

Tim Williams wrote:

Not quite. We actually see back to the surface of last scattering where the universe first became transparent to electromagnetic radiation which corresponds to the inevitable 4K background radiation noise in radio and microwave receiver electronics that will not go away.

The patterns in that region reflect the tiny perturbations from perfect uniformity that will eventually lead to the formation of stars, galaxies and clusters of galaxies.

The surface of last scattering is still well before the position where our observable part of the universe runs out. And you do have to be very careful how you define the horizon of our universe too...

Yet another thing that John doesn't understand so it must be wrong.

You can make very good aperture synthesis images at radio wavelengths. All it takes is a load of dishes and some very low noise front ends, phase compensators, correlators and associated electronics. Aperture synthesis has been done down to tens of MHz. The VLA surveyed ground is currently retrofitted to do aperture synthesis at 74MHz see for example.

The tricky bit is in compensating for the atmospheric and ionospheric distortions in these low frequency wavebands. Resolution isn't exactly great at 4m wavelength even with a 27km baseline.

The most interesting detectors in astronomy at the moment are in the largely unexplored terahertz band. I have seen some preliminary results.

I don't understand it either. It has too many ad-hoc patches. What would an infinitely deep background of red-shifted galaxies at the observed average density look like? Any chance it might look like a uniform 3K background? Like Olbers thought it should, but after correction by Hubble or Lemaitre and Einstein?

Jeroen Belleman

Do you understand the Big Bang? Explain it to us.

The big bang is a theory / model that tries to explain several observations. Expansion of the universe and 4 degree cosmic background radiation. Did you every read "The First Three Minutes" by Steven Weinberg

George H.

hnology.com=A0 jlarkin at highlandtechnology dot com

Of course. I have it around here somewhere, old and yellow by now. They teach that stuff in high school these days.

The original question remains, can we build better radio telescopes to see 30-billion year old galaxies?

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My copy 'grew legs' a long time ago.

Not according to my understanding... For the same reason we can't dig deeper on the Earth and find 1 billion year old dinosaur fossils.

There are none.

George H.

hnology.com=A0 jlarkin at highlandtechnology dot com

My point exactly.