11 replies to this topic

[TikiPrincess]

HINT: It's not a button on your keyboard

I was watching a NOVA program last night on gamma rays and discovered lots of interesting things, including this thing they called "red shift."
For those of you who can remember your science classes, light produces a spectrum of color: blue-green-yellow-orange-red. Since scientists can't pull out a measuring stick to measure distance in light years, they use the spectrum of light to determine approximate distances for things like stars. Stars which are close appear blue, so the stars we see in the sky are those that are closest to us. The more distant the source of light, the more it moves down the spectrum towards red. This is what they call "red shift."
The interesting thing about gamma rays is that they don't produce light, so scientists had a difficult time determining how far away the sorce is from Earth. Then they realized that the gamma rays had to pass through stuff before reaching Earth, causing explosions when it came into contact with space dust. The light emitting from these explosions could then be measured to determine the approximate distance of the gamma ray's source. When scientists used red shift to examine these explosions, they were surprised to discover that the light was coming from the red area of the spectrum. That meant that whatever was producing the gamma rays was something very distant, but still powerful enough to reach Earth.

[Tetraca]

Yep, and red shift is a good sign, for now, as it shows us that the universe is indeed expanding.

[linekill]

I believe the red shift has some connections to the Doppler effect.

[rvalkass]

Red shift is pretty much the Doppler Effect, just with a different name when used for space.

Quote

Stars which are close appear blue

A star's colour depends on its surface temperature, not on how far away it is. The Sun, for example, is our closest star and appears yellow. This is the table used to classify stars into colours and spectral type:

Surface Temperature (Kelvin)	Colour	Type
> 30,000	Blue	O
11,000 - 30,000	Blue-White	B
7,500 - 11,000	Blue-White	A
6,000 - 7,500	White	F
5,000 - 6,000	Yellow-White	G
3,500 - 6,000	Yellow-Orange	K
< 3,500	Red	M

The Sun is of spectral type G, having a surface temperature of around 5,800K. Stars much further away can be much hotter, and appear blue or white. Red shift (the Doppler Effect) is caused by the stars emitting radiation (visible or otherwise) while moving away from our relative position. This causes the wavelength of their radiation to increase, therefore shifting it towards the red end of the visible spectrum. The fact this happens is a reliable suggestion that everything is still spreading out, and the universe still expanding. If the reverse happens then the whole lot is coming back towards us!

[Jimmy]

linekill, on Jul 25 2007, 09:42 AM, said:

I believe the red shift has some connections to the Doppler effect.

er.. WHAT!!

red shift is an effect with the wavelengths of light.

the doppler effect is auditory. Working on soound principles and the wavelengths being "physically changed" by the moving object.

I'm sure you could find a link, but from what I know, the purposes of each are very different

[t3jem]

Jimmy, on Jul 25 2007, 03:18 AM, said:

er.. WHAT!!

red shift is an effect with the wavelengths of light.

the doppler effect is auditory. Working on soound principles and the wavelengths being "physically changed" by the moving object.

I'm sure you could find a link, but from what I know, the purposes of each are very different

I think he was comparing the doppler effect to the effect on light when the light source moves. If the source of light moves towards us, the light moves towards the blue side of the spectrum; however, if the light source moves away from us, then the light moves towards the red side, that is how scientists are able to determine approximatly how fast the univers is expanding. This happens because as the light source moves away the light waves get extended and the period between waves is longer, therefore it goes red, so it's just like the doppler effect except with light.

[nirmaldaniel]

I think you have stated a situation that is close to the truth.The universe can't be in a state of accelerated expansionThe Hubble constant and the red shift are errors of interpretation.The red shift is real,and it occurs in all directions.It must be due to more than an expanding universeThe farthest galaxies have gone out of existence billions of years ago.
The center of each galaxy is an end stage in the evolution of a universe I don't believe a black hole inhabits the centers of galaxies.
I believe that some sort of neutron star activity is the prime driver of the center of all galaxies.We are contracting now but it is not a true contraction of the universe,it is a diminishing of the density of space.This would account for a red shift from any direction.The universe is a finite entity and it is in the last stages of it's demise.The big crunch is not a viable end to a universe like ours,it just would not make sense.If we could slice a galaxy open and see the insides we might be surprised at how simple it might be.

[Saint_Michael]

Interesting topic, its amazing what new stuff about what happens in our universe, but a interesting note that scientists believe their is a source of energy beyond our known universe. For the life of me I cannot find that stupid website and I spent a good 45 minutes looking for it . I been watching this program on the History Channel every Tuesday called the Universe and I have been learning some new stuff about the latest happenings of it as well. I would recommend trying to watch this program its on at 9 P.M. east coast time. So far they have cover all the planets except for Neptune, Uranus and Pluto. It they have covered comets and asteroids and hopefully they will cover Gamma rays and stuff like that.

All I know about Gamma Ray's is that one burst of that radiation even your atoms won't exsist .

[TikiPrincess]

Saint_Michael, on Jul 25 2007, 01:12 PM, said:

I would recommend trying to watch this program its on at 9 P.M. east coast time. So far they have cover all the planets except for Neptune, Uranus and Pluto.

Pluto has been demoted and it's no longer considered a planet. Uranus, on the other hand, continues to mystify and amaze us all with its deep, dark depths.

[9block]

While some may and probably garenteed will debate this... I think that red shift is only a theory. While it may be true, I don't think it can be relied on as a source as in many years, or a short few years, we might find out that all of this data is incorrect...