Physics/cosmology crank visits house

[Paul C. Anagnostopoulos]

Today we had the pleasure of a visit from a physics/cosmology crank. We need some work done on the water hardening system in the basement, so the installer came back to check it out. In the process, he regaled me with his paradigm-shattering theories. He had all the trappings of a crank, talking about MIT professors who wouldn't let him come give a lecture, a cosmologist from South Africa who agrees with him, forming his own publishing company to spread the word, and so forth. He didn't seem bitter about it, which was nice. Important to his theories are:

• The Earth tilts 19.5 degrees, not 23.5
• The Earth cuts a helical path through space as it orbits the moving sun.
• The accepted idea for the number of photons hitting the head of a pin each second is too low.
• The red shift may be caused by photon energy loss, not moving light sources
• The fact that the moon goes faster than the earth during part of its orbit and slower during the other part, relative to the sun.

Otherwise I had no idea what he was on about.

Fascinating.

~~ Paul

 

[Tez]

• The red shift may be caused by photon energy loss, not moving light sources

Otherwise I had no idea what he was on about.

Fascinating.

~~ Paul [/B]

This possibility has been studied in excruciating detail. Amongst the very distinguished people who spent time on it (because they did, for a time, believe it) was Emil Wolf, co-author of the bible of classical optics "Born and Wolf" (Cant even remeber its actual title!).

It was called the "tired light" theory.

So I'm quite sure the possibility has been discarded for good empirical reasons, although to be honest I have no idea what they are. Sorry.

I find it fascinating that you find cranks fascinating. Is it like watching a car accident or sometheing?

I think I have so little tolerance for them because of overexposure.

Fotunately I have graduated in the eyes of the journals I referee for - they now send me good quality papers and not just cranks. (There's some kind of rating they give referees I think, though theyd probably deny it!)

 

[Kiri]

[*]The Earth tilts 19.5 degrees, not 23.5

So, ALL of our astronomical, seasonal and navigational computations are COMPLETELY WRONG?!

You're right, that IS fascinating!

 

[Paul C. Anagnostopoulos]

Tez said:

I find it fascinating that you find cranks fascinating. Is it like watching a car accident or sometheing?

I think I have so little tolerance for them because of overexposure.

Perhaps fascinating isn't the right word, but I'd never talked to such an obvious crank before, so it was, shall we say, illuminating. I found myself trying to get him out the door after about 20 minutes, so the overexposure comes pretty quickly, I guess.

~~ Paul

 

[garys_2k]

[*]The Earth tilts 19.5 degrees, not 23.5

OK, a mental typo. But of course, the number is wrong.

[*]The Earth cuts a helical path through space as it orbits the moving sun.

I wouldn't rule that out. It could be a spiral path if the plane of the earth's orbit isn't exactly along the plane of the sun's galactic orbit. Maybe an "open" helix, but it could be a helix.

[*]The accepted idea for the number of photons hitting the head of a pin each second is too low.

This one has me, IS there an "accepted (idea for the) number?" I assume any number would involve an equation relating the size of the pin head and the brightness of the light. Anyway, this one is strange.[/b][/quote]
[*]The red shift may be caused by photon energy loss, not moving light sources[/b][/quote]
Nope, wrong. Where did all that energy go? If it turned into heat on the way, where is the heating effect?

[*]The fact that the moon goes faster than the earth during part of its orbit and slower during the other part, relative to the sun.

Well, it DOES, if you allow that it's "overtaking" the earth on the far side of the sun and its velocity relative to the sun is less than the earth's when it's on the sun side. But so what?

 

[Paul C. Anagnostopoulos]

He had a specific reason why the accepted tilt is off by 4 degrees, but I couldn't for the life of me understand it.

He even left me a poster he'd printed showing the helical path of the earth and moon. He just happened to have a huge pile of the posters in his car.

~~ Paul

 

[Tez]

[*]The red shift may be caused by photon energy loss, not moving light sources

Actually I just read this more carefully - and of course he's right in as much as its not due primarily to moving sources. We attributemost of the redshift to expansion of spacetime, and not a doppler effect of the sources (the vast majority of the shift accumulates during the photons travel). Same process accounts for how the cosmic background microwave radiation has "cooled" - at the time of recombination (300KYr after Big Bang) it was obviously at a much higher temperature and wasnt microwave! (Recombination of the charged particles is when the photons became free - the medium became transparent - and they havent interacted with anything much since)

The tired light theory I refered to was an attempt to mimic this with light that's propagation effects in vacuum were intrinsicallly such that it lost energy and became tired.

 

[garys_2k]

Re: Re: Physics/cosmology crank visits house

Actually I just read this more carefully - and of course he's right in as much as its not due primarily to moving sources. We attributemost of the redshift to expansion of spacetime, and not a doppler effect of the sources (the vast majority of the shift accumulates during the photons travel). Same process accounts for how the cosmic background microwave radiation has "cooled" - at the time of recombination (300KYr after Big Bang) it was obviously at a much higher temperature and wasnt microwave! (Recombination of the charged particles is when the photons became free - the medium became transparent - and they havent interacted with anything much since)

The tired light theory I refered to was an attempt to mimic this with light that's propagation effects in vacuum were intrinsicallly such that it lost energy and became tired.

So, police radar depends on the expansion of the universe?

 

[Tez]

Re: Re: Re: Physics/cosmology crank visits house

So, police radar depends on the expansion of the universe?

Where did I say the doppler effect didnt exist?

I said its not the primary cause of galactic redshifts. If you dont believe me, read a book...

 

[Paul C. Anagnostopoulos]

Now I'm confused. The red shift caused by the expansion of the universe is a Dopler effect, no? Not due to the movement of the source, but to the "movement" of the entire universe. This guy was suggesting that the light actually loses energy as it travels, shifting toward the red.

~~ Paul

 

[Tez]

Thinking of it as movement of the entire universe is somewhat misleading.

Thinking of it as like the doppler effect of a police siren etc is equally misleading.

There are basically three ways to get a redshift - a moving source (relative to a fixed background or to you), a gravitational field and expansion of spacetime.

The shift to the red that we see from far galaxies is primarily due to the fact that as these photons have travelled, the spacetime has stretched, their wavelengths have stretched and a longer wavelength implies a "redder" photon. (MartinM would probably pull me apart for the impreciseness of this statement). Note that since the spacetime is expanding the sources of that light also appear to be moving away from us - not in the sense that particles in an explosion move away from us, but in the sense that the dots painted on the balloon also move away from us.

The amount of redshift is basically just a measure of how long theyve been propagating through this expanding medium.

We do also measure effects of local velocities of the sources - a standard doppler redshift on top of the spacetime expansion redshift so to speak. This effect is generally much smaller. The recession velocity astronomers refer to is not this motion through space, but rather the apparent motion caused by expansion of space.

So yes - the photons are losing energy as they propagate - just as the CMB photons have lost energy and are now microwave - they were originally super-ultraviolet (or whatever a Planck spectrum peaks at for whatever the temperature of the universe at 300KYr was).

Here are some of the first few google hits I got on redshift and expansion of the universe...

http://isaac.exploratorium.edu/~pauld/activities/astronomy/expansionoflight.html

http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit5/expand.html

this one mentions the tired light theory:

http://nedwww.ipac.caltech.edu/level5/Peebles1/Peeb2_3.html

 

[Paul C. Anagnostopoulos]

I see why the cosmo redshift isn't a Doppler effect. It's hard to picture how the expansion of space effects individual photons' wavelengths. Can you give an intuitive explanation for this? Does it involve the expansion of time (in addition to space)?

~~ Paul

 

[garys_2k]

Thanks, Tez; got it!

 

[BillyJoe]

It's hard to picture how the expansion of space effects individual photons' wavelengths.

And why doesn't the expansion of spacetime stretch out the objects within it (like the dots on an expanding balloon)? Why empty space and wavelengths but not solid objects?

 

[Jethro]

And why doesn't the expansion of spacetime stretch out the objects within it (like the dots on an expanding balloon)? Why empty space and wavelengths but not solid objects?

Because those solid objects are being held together. Likewise, the solar system and our galaxy and all the galaxies in our local group are gravitationally bound. They are not moving apart. It's just objects that are very far away from each other that are moving apart from eachother.

 

[BillyJoe]

Because those solid objects are being held together. Likewise, the solar system and our galaxy and all the galaxies in our local group are gravitationally bound. They are not moving apart. It's just objects that are very far away from each other that are moving apart from eachother.

Still not sure if I understand.....

Those "objects that are very far away from each other" are still gravitationally attracted to each other aren't they even if only very weakly? So why aren't galaxies being stretched out by spacetime, even if only very weakly?

 

[garys_2k]

And why doesn't the expansion of spacetime stretch out the objects within it (like the dots on an expanding balloon)? Why empty space and wavelengths but not solid objects?

I assumed that WERE growing, too.

For instance, if we'd setup a lightspeed test with mirrors that bounced a beam of light around the entire earth a billion years ago, would we have measured a different speed? IOW, would the earth itself have grown in the past billion years from the expansion of space? I think it would have. I can't imagine anything "gluing" a solid together to any particular size.

 

[Martin]

The shift to the red that we see from far galaxies is primarily due to the fact that as these photons have travelled, the spacetime has stretched, their wavelengths have stretched and a longer wavelength implies a "redder" photon. (MartinM would probably pull me apart for the impreciseness of this statement)

Oh, it's not that bad - in the infinitesimal limit, at least.

The recession velocity astronomers refer to is not this motion through space, but rather the apparent motion caused by expansion of space

Does that annoy you as much as it annoys me? Talking about recession velocities as they do can only contribute to the common misconceptions about cosmological redshift.

they were originally super-ultraviolet (or whatever a Planck spectrum peaks at for whatever the temperature of the universe at 300KYr was)

Last scattering surface is around z = 1065, IIRC. So if I could remember where the CBM spectrum peaks now, I could work it out. But I can't, and I'm too lazy to look it up

 

[Martin]

I see why the cosmo redshift isn't a Doppler effect. It's hard to picture how the expansion of space effects individual photons' wavelengths. Can you give an intuitive explanation for this? Does it involve the expansion of time (in addition to space)?

You might have more luck considering the wave nature of light. Thinking of it in terms of particles won't help.

 

[Martin]

Those "objects that are very far away from each other" are still gravitationally attracted to each other aren't they even if only very weakly? So why aren't galaxies being stretched out by spacetime, even if only very weakly?

Gravitational attraction falls off with distance sqared. The Hubble flow increases with distance. So at small distances gravity (and the other forces, for that matter) will overwhelm the expansion, and at large distances the expansion will overwhelm gravitational attraction.