Large Hadron Collider

Biohazard said:
He said 300 millions years after big bang, the universe was big enough to become transparent and light started to travel across it.

Yet he said it wasn't until 100 million years (400 million after BB) after then that the first stars were born.

Where does light come from if not from stars? noob question? :confused:
Click to expand...

Background radiation

EDIT* :o how far behind am I :o
 
Tefal said:
because it is light...



There is light, just not very bright compared to stars.
Click to expand...

sorry yeah getting mixed up, I just took what he said literally. I thought when he said light it to be bright. I suppose a glow is still 'light'! :p

But wouldn't the lack of intensity effect its travel?
 
Biohazard said:
So why did he say light travels when there is no light to be had at that stage then?
Click to expand...

It's not just stars that emit light, and light doesn't have to be of the wavelength visible to us to be considered light, light can refer to any part of the EM spectrum, ranging from radio waves to gamma waves. It's all light.

I wasn't there at the time but i'm guessing the big bang would have produced quite a bit radiation.
 
yak.h'cir said:
Yup that's my understanding of what the current theories say will happen as well.

For anyone actually entering the black hole they'll fall into it pretty quickly and time will flow for them as expected. However if they were to look out at something far away from the black hole it would appear that time there was running very fast. For someone far away watching this person fall into the black hole they would observe the persons time running slower and slower, until stopping altogether at the event horizon where they would appear to be frozen in time. It would in theory appear as though they never entered the black hole. Of course this ignores all the lovely effects like spaghettification!
Click to expand...

assuming that this guy falling into the BH does so 'in a straight line', ie not spiralling, he will be accelerating away from some objects, and towards others. Surely this affects whether he sees one ticking fast or slow?
 
nokinidea said:
He will feel acceleration maybe but not time compressing or stretching
Click to expand...

Disagree. Assume the following configuration:

Star twinkling at 1HZ(relative to the star) ........... person accelerating this-a-way ->.............. BH


The person will receive the star's signal at lower and lower frequencies. ie to him, time on that world seems to be slowing down.

That's why I dont think someone falling into a BH will see 'the outisde' speeding up.
 
Last edited:
That would be the doppler shift, but would that be counteracted by the time dilation caused by the black hole? So, time would pass faster for the unfortunate person falling into the BH, but because he is travelling into the BH, the doppler shift would slow the flickering of the light from the star.
 
Last edited:
lord filbuster said:
That would be the doppler shift, but would that be counteracted by the time dilation caused by the black hole? So, time would pass faster for the unfortunate person falling into the BH, but because he is travelling into the BH, the doppler shift would slow the flickering of the light from the star.
Click to expand...

Faster time for the person relative to what? In my configuration, the BH is irrelevent - all that matters is the acceleration.
 
Faster time relative to anything that is in a weaker gravitational field. Mass distorts space, and the more that space is distorted, the slower time flows in that region. I think it is part of general relativity.
 
just read this:
In special relativity, the time dilation effect is reciprocal: as observed from the point of view of any two clocks which are in motion with respect to each other, it will be the other party's clock that is time dilated. (This presumes that the relative motion of both parties is uniform; that is, they do not accelerate with respect to one another during the course of the observations.)

In contrast, gravitational time dilation (as treated in general relativity) is not reciprocal: an observer at the top of a tower will observe that clocks at ground level tick slower, and observers on the ground will agree. Thus gravitational time dilation is agreed upon by all observers, independent of their altitude.
Click to expand...
http://en.wikipedia.org/wiki/Time_dilation
so you're right :)
 
My head of year was on the news earlier talking about the LHC; turns out he's the UK project leader for one of the LHC's four detectors (ALICE)!

That was cool :cool:
 
You must log in or register to reply here.
Back
Top Bottom