# Time flow & Cosmic Background Radiation

1. Aug 12, 2004

### J79

Hi,
I was wondering if somebody could tell me in what way the following paragraph is incorrect (if it is). Thanks.

According to Einstein’s theory, when radio waves travel from one place to another, and both places have a different time flow, the frequency will appear to change. When measured, the frequency of Cosmic Background Radiation appears to be lower, since the flow of time on earth is faster than it was soon after the big bang. Time flows faster on earth, because earth has such little gravity, and soon after the big bang the whole universe was packed into such a relatively small area, making for an enormous amount of gravity. The difference in gravity causes a difference in the flow of time.

2. Aug 19, 2004

### J79

No comments? Does anybody think it is correct?

3. Aug 19, 2004

### chroot

Staff Emeritus
It is meaningless to talk about the speed of a clock's ticking without comparing it to another clock's ticking. You can't say anything about the speed of an isolated clock, because you have nothing to compare it to.

A more accurate description of the CMBR is that the photons themselves have suffered elongation by the expansion of the universe. The elongation results in the photons having a larger wavelength (lower frequency) today than they did in the past.

- Warren

4. Aug 19, 2004

$$f = \frac{v}{\lambda}$$
The article is correct, it is talking about the expansion of the universe. This change in frequency is because of a gravitational doppler effect. At the beginning, the universes gravity was so high that the frequency was enourmous. Now that space is so spread out and gravity is much lower, the wavelength is red shifted, changing the frequency.

5. Aug 19, 2004

### chroot

Staff Emeritus

I don't believe that is a proper explanation. It's not a Doppler effect, and the original CMBR frequency was set by the thermal energy of the plasma that radiated it, not by "gravity being high."

- Warren

6. Aug 19, 2004

### Nereid

Staff Emeritus
The Cosmic Microwave Background Radiation (CMBR) is extremely close to a perfect black body, of temperature ~2.73K. In the concordance model of cosmology, the CMBR is the highly redshifted radiation from the 'surface of last scattering', which is the time in the universe when it cooled sufficiently for H atoms to form (i.e. the protons captured electrons); when that happened, matter and EM radiation 'decoupled', which essentially means that the universe became transparent to electromagnetic radiation.

The universe has been expanding since the Big Bang (more accurately, since the first 'Planck second', which is ~10-43 s); the expansion of space results in light being 'redshifted', i.e. we perceive light from distant objects as having a lower frequency (longer wavelength) than that at which it was emitted.

So, you see that the CMBR has nothing to do with gravity directly; indirectly it has a lot to do with gravity - it's the gravity of the mass in the universe which causes the universe's expansion to slow down (well, it would, if it weren't for 'dark energy'; but that's a different story )

7. Aug 19, 2004

my bad, Im just trying to give him one reason of why light is redshifted when coming from long distances.

8. Aug 20, 2004

### J79

What about the accuracy of this?

Thanks. Could you tell me about the following two paragraphs? I know they may not go in depth enough to fully explain things. And some things may be over generalized, but is there anything about the following two paragraphs that are simply false? Thanks again.

“Isn’t a day the same on the moon as it is on earth?” According to Albert Einstein’s theory it is not the same. When you compare the time flow at two different places (in this example the earth and the moon) there will often be a difference, albeit usually an extremely small difference. The difference in time flow between two places, if there is a difference, depends on how much faster something is traveling, and how much more gravity there is (which depends on how big a planet or star is. A bigger planet or star will have more gravity.) Now the speed of the earth and of the moon are pretty close, and compared to the rest of the universe they are also similar in size. Because the moon and the earth are close in size and speed, the difference in time flow on the moon compared with earth is only a tiny fraction of a second every day. Now with all the comparative differences in time flow throughout the universe, it would be convenient if there were a universal time, or clock. Fortunately there is. After the big bang the flow of time was the same everywhere (since after all, “everywhere” was a relatively small area at the time). Ever since then time flow has often been different when comparing one place to another. But when time flow was the same everywhere, an echo was created. That echo wasn’t sound. It is electromagnetic energy, like radio waves. We now call that echo Cosmic Background Radiation (or CBR for short). CBR still echoes throughout the universe today, and has been studied at universities around the world.
According to Einstein’s theory, when radio waves travel from one place to another, and both places have a comparatively different time flow, the frequency will appear to be different at one place than at the other. When measured, the frequency of CBR appears to be lower, since the flow of time in this solar system today is faster when compared to the flow of time just after the big bang. Time flows faster here today than it did after the big bang, because our solar system has such little gravity, and during the big bang the whole universe was packed into the same relatively small area, making for an enormous amount of gravity. Using simple algebra, the difference in the original frequency of CBR, and the frequency that it appears to be, can be used to calculate just how much the flow of time here on earth today differs from that of the universe just after the big bang. By knowing how comparatively different the flow of time is between the earth today, and the universe just after the big bang, we can make the necessary transition from earth time to universal time, or from universal time to earth time. We could calculate, somewhat accurately, how many seconds according to the “universal clock” would be equivalent to a year (for example) according to the “earth clock.”

9. Aug 20, 2004

### chroot

Staff Emeritus
There are many misconceptions in that last post, J79. Let's see here...

1) The term "time flow" is not recognized in mainstream science. You should use more precise language, such as discussing the time elapsed on clocks.

2) Clocks do not run slow because they are moving -- this is perhaps the single most common misconception with special relativity. Again, the only way you can speak of a clock's speed is to compare it with another clock. In the situation of two clocks in relative motion, both appear to the other to be running slow. It is not correct to speak of a clock running slowly because it is moving faster.

3) The CMBR does not represent a universal standard of rest at all! It's no more special a frame of reference than any other. In fact, it's not the same everywhere in the universe. Two distant galaxies, both moving along with the Hubble expansion, have zero velocity relative to the local CMBR photons, but are actually moving away from each other.

4) The term 'echo' is quite poorly used here. The CMBR are the photons which were bouncing around in the plasma of the early universe at the moment that the universe became transparent to radiation, and haven't ever hit anything in the 13.4 billion years since. The CMBR isn't an "echo" of anything.

5) The "flow of time" is not faster in the solar system than in the early universe. This sentence doesn't even make any sense.

6) The redshift of the CMBR photons can be calculated by considering the change in the scale factor of the universe over time -- not any sort of "time flow."

7) Again, there is no universal time. Period. This is one of the most fundamental features of relativity. There cannot be such a thing.

- Warren

10. Aug 20, 2004

### J79

Gerald Schroeder

Ok thanks. I wrote those two paragraphs from the information I got from reading a book by Gerald Shroeder. I think there is a good chance that I didn't get all my information right. Anyway, has anybody heard of Gerald Shroeder? His website is www.geraldschroeder.com

11. Aug 20, 2004

Staff Emeritus
I don't know his ideas in detail, but in general I would be cautious of learning physics from someone wiith a non-physics agenda. They are frequently basing their physical statements on popularizations which they twist to their purposes. You can do better than that.

12. Aug 20, 2004

### J79

The Science of God - book

I agree. I could just quote the book and not care wether it's the truth or not. (Actually I sold it, so I would have to borrow it from the library, but anyway...) I'm not willing to use deception for any reason. That's why I'm researching this, to see whether it's a lie, an honest theory, or something else. If I find that deception is used in this theory, then I will have no problem dropping my interest in it. On the other hand, for all I know right now (or don't know), it may be truth. I need to research more to find out.

13. Aug 20, 2004

### pervect

Staff Emeritus
Some of what you post does sound like it's on the right general track - so it doesn't strike me as total nonsense, though the language is non-standard.

But I wouldn't rel;y on it being exactly correct, either.