Light, Observable Universe, Finite or infinite

[Tom B]

I am a retired engineer (EE) with a general interest in many of the questions raised by physics and astronomy.

 

I would like to post a few questions and offer a thought experiment or two. I do not have an extensive background in these fields, but I enjoy reading and watching science shows.

 

First, there is widespread agreement on the Big Bang Theory and the age of the universe.

 

The age of the universe is largely based upon the residual microwave radiation that is thought to be the oldest observable portion of our universe. We are surrounded by this radiation and it is the same in all directions.

 

First question. In some respects, that seems to put us at the center of the universe. We can see the same distance in every direction. Does that seem mathematically probable?

 

Though experiment.

 

A solar system exists 10 billion light years from earth. Scientist in this solar system have the same understanding, theories, and tools that we have. If they were to look in our direction and could detect us, they would see us as we were 10 billion years ago. If the universe is 13 billion years old, they would observe the background microwave radiation about 3 billion light years beyond us.

 

Now, they look in the opposite direction. What do they see? Is it the background radiation at a distance of 3 billion light years? Would they be unable to see beyond it?

Might it have dissipated or evolved into something else? If everything was born from this energy, why not? Now, if they do see more galaxies, can you keep extrapolating this out into infinity?

 

If the universe is finite, might an object leaving from their side of the universe enter our side? If these other galaxies exist in a finite universe, but are beyond where we can see them, could there mass explain the "Dark Flow?" Could these galaxies be the same ones that we can see, but seen from a different point of view?

 

Could it be that the universe is finite and the region of microwave radiation is the boundary? At the boundary you simply move in a similar manner as you do when you fly east from New York long enough. You end up back in New York.

 

If this radiation is 13 billion light years from us and has been traveling towards us at the speed of light, how did it get so far away in 13 billion years? Was the early period of expansion so extreme to account for these great distances?

 

Another property of light that I have long known, but little understood is the constant speed of light. Light is always measured at the same speed regardless of the velocities of the source and observer. That raises the question of why can't the speed of light be infinitely variable such that the sum of the velocities of the light, the source, and the observer are constant?

 

Another question is, "If time slows as you travel faster, why can't photons be standing still in a timeless "bubble" and be warping space time around them? I think that implies that they would have to be infinitely massive.

 

Thanks for any help. I'm probably missing some key facts.

[nrobinson_12]

I have no clue about all the other stuff, but I recently read an article about the twin paradox and light speed and this is what is explained. Photons have no mass, they are both a particle and antiparticle, and they are around everywhere all the time. Light itself, doesn't really have anything to do with time slowing down, just it's speed. Standing still we, are already traveling at the speed of light. Time spent traveling + distance traveled = light speed. Thus, when we don't move any distance, it doesn't take any time and equals light speed. So the faster your speed, the more distance is traveled, and the more time slows for the person traveling. Obviously, the amount of time is miniscule down here. But as the twin paradox states, one twin stays here on Earth, while the other travels in a rocket ship traveling near the speed of light, when the twin in the rocket returns three months later, 80,000 years would have passed on Earth. That is because, the twin on the rocket ship was moving at almost twice the speed of light, since he himself is traveling at the speed of light inside the rocket, while the rocket itself is also traveling at near light speed, and would cover a very large distance, in a very short amount of time, and time would slow because speed traveling + distance traveled, also equals time. Meanwhile, the twin on Earth is traveling a just light speed with time progressing as normal. It would take the twin on Earth 80,000 years to walk the same distance. The article also went on to say that nothing with mass, that they know of, can travel faster than the speed of light. E=mc^2 means that anything with mass traveling at the speed of light would have to have infinite mass and infinite energy.

[ACG52]

I am a retired engineer (EE) with a general interest in many of the questions raised by physics and astronomy.

 

I would like to post a few questions and offer a thought experiment or two. I do not have an extensive background in these fields, but I enjoy reading and watching science shows.

 

First, there is widespread agreement on the Big Bang Theory and the age of the universe.

 

The age of the universe is largely based upon the residual microwave radiation that is thought to be the oldest observable portion of our universe. We are surrounded by this radiation and it is the same in all directions.

 

No, the age of the universe is based upon both observation and calculation.

 

First question. In some respects, that seems to put us at the center of the universe. We can see the same distance in every direction. Does that seem mathematically probable?

 

No, there is no center of the universe. The BB was not an expolsion of matter and energy moving in all directions from a central point. The BB was the expansion of space, occuring at every point in space. So at every point in space, you would see everything moving away from you, and the further something was, the more space was being created between it and you, so the faster it would appear to be receeding.

 

 

 

Though experiment.

 

A solar system exists 10 billion light years from earth. Scientist in this solar system have the same understanding, theories, and tools that we have. If they were to look in our direction and could detect us, they would see us as we were 10 billion years ago. If the universe is 13 billion years old, they would observe the background microwave radiation about 3 billion light years beyond us.

 

Now, they look in the opposite direction. What do they see? Is it the background radiation at a distance of 3 billion light years? Would they be unable to see beyond it?

 

No, as I explained above, there is no center. And the CMB is everywhere, equally, throughout space. So when you train your microwave detector out into space, you are receiving photons which are 13.7 billion years (-380000 years) old, but they are not that far away. They are right here, running into your microwave detector.

 

Might it have dissipated or evolved into something else?

 

That's exactly what happened. At the time of the photon decoupling the photons were very hot, and have cooled to 2.73 K and stretched to microwave lengths.

 

If everything was born from this energy, why not? Now, if they do see more galaxies, can you keep extrapolating this out into infinity?

 

This is not the energy everything was created from, these are just the photons which were suddenly free to travel forever through expanding space.

 

Our observable universe is 13.7 billion light years in any direction. And anything we see that we measure as 13.7 billion lys away is actually at present 48 billion lys away (space has been expanding while the light has been getting to us). Beyond that we can't see, but theory does say that the actual universe is far larger than our observable one. Infinite? Maybe. At least into the future.

 

 

If the universe is finite, might an object leaving from their side of the universe enter our side? If these other galaxies exist in a finite universe, but are beyond where we can see them, could there mass explain the "Dark Flow?" Could these galaxies be the same ones that we can see, but seen from a different point of view?

 

 

Maybe. We wouldn't have had time to see these galaxies though.

 

Could it be that the universe is finite and the region of microwave radiation is the boundary? At the boundary you simply move in a similar manner as you do when you fly east from New York long enough. You end up back in New York.

 

 

Remember that there is no region of the microwave background radiation. It is equally everywhere, to 1 part in 100,000. There are about 400 million photons of the CMB in every cubic meter of space, including your body.

 

If this radiation is 13 billion light years from us and has been traveling towards us at the speed of light, how did it get so far away in 13 billion years? Was the early period of expansion so extreme to account for these great distances?

 

 

See above answers.

 

 

Another property of light that I have long known, but little understood is the constant speed of light. Light is always measured at the same speed regardless of the velocities of the source and observer. That raises the question of why can't the speed of light be infinitely variable such that the sum of the velocities of the light, the source, and the observer are constant?

 

 

You are now leaving the realm of cosmology and entering that of Relativity. It's Maxwell's electromagnetic equations which says that the speed of light is fixed and constant. Einstein incorporated this into Special Relativity gave us space/time, time dilation and length contraction.

 

Another question is, "If time slows as you travel faster, why can't photons be standing still in a timeless "bubble" and be warping space time around them? I think that implies that they would have to be infinitely massive.

 

 

Nah.