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Universe may not do that thing we think it does : any physicists?
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Snagletooth Johnson
Center for Advanced Studies
Gallente Federation
#21 - 2013-08-18 09:19:33 UTC  |  Edited by: Snagletooth Johnson
Akita T wrote:
Mathematically, from our view point, it's the same thing, having photons generated at shifted energies due to different initial conditions, or perceived as shifted due to speed, the end result is still the same.
Not even sure yet how we could tell which one of those is true at this time, and that type of experiment is not exactly something to think up in a hurry, but I bet somebody will try to come up with such an experiment eventually.
It never hurts to try and explore alternate possibilities whenever mathematically sound.

Snagletooth Johnson wrote:
If that theory worked correctly as Hubble believed, a car would change color as it drove away from you.

It does. But not enough for you to notice with the naked eye.
For the average person, something would need to move away at a speed of at least 25 million kilometers per hour (or, if you prefer, roughly 7000 kilometers per second) to really notice a difference.

On the other hand, for SOUND, it's a lot easier to notice. You can easily hear the difference between the sound of an approaching and departing car.


In theory in a perfect enviroment, you can tell a car moving away by sound. The farther away it gets the more drop off their is of certain tones. But that theory fails to work in real world as echos can create false sounds. natural blocks such as thick tres and buildings can also create a false block to certain sound waves even though the vehicle is approaching, not pulling away..or even just driving around in circles, keeping the same distance. But anyone with a trained ear can always tell if that car has a 350 chevy or a 1.8 Toyota as the depth (rumble, rpm yada yada) is the same.
Light can also be distorted by a mass cluster or a closer star infront of a farther star. So, what the scientist is suggesting is, the rumble of the motor isn't so much and indicator of it's distance/velocity, but more a rumble of it's engine type (Mass/density, yayda yada).
Ishtanchuk Fazmarai
#22 - 2013-08-18 09:59:41 UTC
Snagletooth Johnson wrote:
Inokuma Yawara wrote:
Hold on a minute, here! I thought red-shift = "going away from", not distance, and the more red-shifted, the faster it was going away from us. The inverse of that is blue-shift = "moving towards to", again not distance, and the more blue-shifted, the faster the object is moving towards us.....

I thought distance was measured by calculating how fast an object moved across the sky in relation to the other star's locations, and the number of degrees that the object moved compared from the last time it was measured, from Earth's view point.


And how would you know if it's heading towards or moving away unless you the distance?
What I still havent figured out is, how do they know the distance of the stars to decipher whether red-shift is true? It's not like we can go out with a tape measure, check it and say "7.5468 LY, hmmm....OK, Hubble, what's the color now?"
We know haw far Jupiter is, we've sent probes there. We have hard numbers to check theories against. But that little red dot way oof there? Not so much.


That's exactly what Hubble was doing. He was measuring distances through a "rule meter", the cepheid variable stars.

Cepheid variable stars are stars whose brightness varies upon several days/weeks. Astronomists had determined that a cepheid which took X days to complete its cycle would always have the same absolute brightness i.e., every cepheid shines the same according to its variable cycle. This provides a rule to measure brightness and estimate distance, if we see two cepheids with the same cycle and one is brighter than the other, then the brighter one is closer.

So you see how far are some cpeheids and then measure other cepheids and determinate their distance. As some cepheids are bright enough to be seen from another galaxy, Hubble began chasing those cepheids with a new giant telescope, but then he found that something was wrong with their spectrum. The absortion lines of known elements in extra-galactic cepheids were all closer to the red end of the spectrum than the those from stars in our own galaxy. And also was the spectrum of every other star in those distant galaxies. That's the famous "red shift", which eventually would become a way to estimate distances.

But it all started by measuring distances with cepheid stars as "rule meter".

Roses are red / Violets are blue / I am an Alpha / And so it's you
Karak Terrel
Foundation for CODE and THE NEW ORDER
#23 - 2013-08-18 10:12:41 UTC
What Ishtanchuk said, just a small addition to this explanation. I linked it before, but looks like Snagletooth missed it.

Today there is a whole catalog of different methods to measure distances on an extragalactic scale:
http://en.wikipedia.org/wiki/Cosmic_distance_ladder#Extragalactic_distance_scale
Karak Terrel
Foundation for CODE and THE NEW ORDER
#24 - 2013-08-18 10:38:51 UTC
Snagletooth Johnson wrote:

In theory in a perfect enviroment, you can tell a car moving away by sound. The farther away it gets the more drop off their is of certain tones. But that theory fails to work in real world as echos can create false sounds. natural blocks such as thick tres and buildings can also create a false block to certain sound waves even though the vehicle is approaching, not pulling away..or even just driving around in circles, keeping the same distance. But anyone with a trained ear can always tell if that car has a 350 chevy or a 1.8 Toyota as the depth (rumble, rpm yada yada) is the same.
Light can also be distorted by a mass cluster or a closer star infront of a farther star. So, what the scientist is suggesting is, the rumble of the motor isn't so much and indicator of it's distance/velocity, but more a rumble of it's engine type (Mass/density, yayda yada).


Distortions change the direction of a sound wave or a photon, but not the pitch or the sound or the frequency of the photon.

There are certain markers in light that comes from a star, like the emission lines of hydrogen or helium, they are always at the same frequencies. Except if the frequency gets changed, then the whole set of markers get shifted towards the red spectrum or towards the blue spectrum, that's why it's called red and blue shift.

http://en.wikipedia.org/wiki/Emission_spectrum

If that signal was somehow distorted in some wavelengths one would notice the difference because of the change in the gaps between this lines.

Hope that covered your question, lost it a bit whit all that car analogies :-)
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