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kjamha
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I've heard many times that the universe was the size of our solar system after 1 sec. But how is this possible if nothing can travel faster than the speed of light? Are there any theories on this?
kjamha said:Thank you - I found the article very interesting. The last paragraph says there are galaxies receding from us faster than c. Is that true? If it is, how could we ever detect the EM waves?
marty1 said:The universe wasn't complicated back then by all the machinery of atoms and molecules that take up a lot of empty space now.
kjamha said:Thank you - I found the article very interesting. The last paragraph says there are galaxies receding from us faster than c. Is that true? If it is, how could we ever detect the EM waves?
kjamha said:Thank you - I found the article very interesting. The last paragraph says there are galaxies receding from us faster than c. Is that true? If it is, how could we ever detect the EM waves?
kjamha said:Based on everything I've learned, I do have another question - If space and time are interwoven, I'm wondering if time is affected in these areas of expansion. It seems it would have to play a part in analyzing red shifts. No?
RUTA said:Special relativity (SR) holds locally in general relativity (GR), much like we can treat the surface of Earth as flat over small distances when we do projectile motion problems. According to SR, light always travels at speed c and so it does locally in GR. However, these locally flat spatial frames are carried apart by the expansion of the universe so the speed at which the light approaches us is given by c - Hd, i.e., the local frame is being dragged away from us at speed v = Hd (Hubble's law) while light is moving towards us through that frame at c, just as in simple Newtonian physics. In fact, for large red shifts, Hd for the emitting galaxy was greater than c at time of emission so the light was actually being dragged away from us. The emitting galaxy has sinced slowed, but may still be moving away faster than c. There is a nice article explaining this and other misconceptions about the big bang in Scientific American http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf. Here is a paper I wrote years earlier explaining it to physics undergrads: “Can Galaxies Exist within Our Particle Horizon with Hubble Recessional Velocities Greater Than c?” W.M. Stuckey, American Journal of Physics 60, No. 2, 142 – 146 (1992). In my paper there is a graph showing the recession velocity of the photon from emission to reception for redshift 4.73 and you can see that it starts with a positive recession velocity and ends with a recession velocity of -c in accord with SR.
marcus said:RUTA, this is a nice explanation and I would like to see your plot of the photon speed of approach that starts out negative (dragged away) and ends up arriving at us at the ordinary speed of light c.
I will look for a link to an online version of the pedagogical article you wrote for AmJPhys. If it is not at arxiv.org perhaps you could supply a link?
RUTA said:Hi, marcus. I didn't know anything about arXiv in 1991 when I submitted this paper and I don't have any Word or WP file after 20 years so I copied it to my online repository http://users.etown.edu/s/stuckeym/AJP1992a.pdf. Fig 1 shows how far away the photon is as a function of time and Fig 2 shows its recession velocity as a function of time.
marcus said:he starts out 4 billion ly from us and actually gets dragged back till almost 6 billion ly away before turning it around and beginning to make progress. A moral lesson for us all, the little photon that could .
RUTA said:Hahaha (I wanted to post a rolling laughing face, but I can't figure the code for that).
Scientists use various methods and observations, such as the cosmic microwave background radiation and the expansion of the universe, to estimate the size of the universe at different points in time. By studying these factors, scientists can make educated assumptions about the size of the universe after 1 second.
The universe experienced a rapid expansion known as inflation in the first fraction of a second after the Big Bang. This inflation caused the universe to expand exponentially, resulting in the universe being the size of our solar system after 1 second.
No, the entire universe was not condensed into the size of our solar system after 1 second. The universe continued to expand and cool down after the Big Bang, leading to the formation of galaxies, stars, and planets over billions of years.
The universe has expanded significantly since its initial size of our solar system after 1 second. It is estimated that the observable universe has a diameter of about 93 billion light-years, which is much larger than the size of our solar system.
Due to the limitations of our current technology and understanding, it is impossible to know the exact size of the universe after 1 second. However, scientists continue to gather data and make calculations to improve our understanding of the early universe and its size at different points in time.