Since looking in one direction the universe looks 13.7 Billion light-years deep...?

Question

... does that mean it is at least 27.4 Billion lightyears in diameter?
And, if we can see back 13 Billion years, how come it took this long for light from then to arrive, when at the time the size of the universe would at most have been 1.5 Billion light years?

Answer 1

http://www.sciam.com/print_version.cfm?articleID=0009F0CA-C523-1213-852383414B7F0147

http://www.astro.ucla.edu/~wright/cosmo_01.htm
http://en.wikipedia.org/wiki/Physical_cosmology

no, this is actually a common misconception about the big bang. depending on what mathematical model of the expansion astronomers use to analyze the observations of nasa's microwave anisotropy probe, the cosmic microwave background seems to be at least 78 billion light-years away, but the universe is only 13.7 billion years old.

the cmb comes from a time when the universe was 380 000 years old. at that time, the universe had expanded and cooled enough for electrons to combine with atomic nuclei to form atoms (about 76 percent hydrogen and 24 percent helium). light could then pass unscattered by the free electrons, and the universe became transparent. before this time the universe had been like a heavy fog. we see this light today stretched to microwave wavelengths. we see it in every direction in which we look, but the universe was much smaller then. the big bang was the entire universe and everywhere in the universe was once the big bang.

incidentally, anything with a cosmological redshift of 1.7 is receding at c, light-speed, and anything with a greater cosmological redshift is receding faster than c. the redshift of the cmb is 1089. redshift has three causes 1) recession of a light source, 2) an extremely massive, dense light source, and 3) the stretching of light due to the expansion of the universe.

the inflationary era occurred while the universe was a tiny fraction of a second old and lasted for an even tinier fraction of a second. during this time, the expansion rate was hyper-fast. when it was over the universe was about one meter across. the expansion began to slow after this, but about five billion years ago, the expansion rate seems to have begun to accelerate.

Answer 2

I think the 13.7 billion light years referred to is a distance. The most distant objects we have seen thru our telescopes are 13.7 billion light years away (a distance). That means the universe would be if anything 13.7 billion light years in dia, not 27.4 billion. This is assuming that the most distant objects we see are on the far side of the universe. I don't understand the 2nd part of your question at all. What do you mean, "at the time"... "the universe would have been 1.5 billion light years"? at what time?

Answer 3

The age of the universe doesn't have anything to do with the size of the universe - you are mixing apples and oranges so to speak. During the first minute of the big bang the universe inflated from the size of a grapefruit to nearly the size it is now, i.e., at a trillion trillion times the speed of light No one knows the diameter of the universe, or even if it has a diameter, and there are no theories as of yet. Ask again in 10 years and there may be an answer.

Answer 4

Honestly, finding a close measure of distance of the diameter is highly unlikely. Even if many scientists hypothesize this. The size is so great that man kind would never be able to find out it's estimated diameter. If the Earth is in theory 13.7 billion years old, then that would explain it. Light can only travel so fast, even if it is extremely fast the time it would take to travel from over 10 billion years would provide an immediate affect on your question. In space the speed of light is much more spread out, because the universe has alot of "space" to travel in, and is continuously growing in size.

Answer 5

The light that we are seeing now theoretically left whatever object it came from 13.7 billion light years ago. Other light from not as far away has already passed us. We are only able to see dispersed light from some things that left that long ago with modern telescopes. We spent millions of years not being able to see most of what we can see today. That doesn't mean that it wasn't there.

According to these guys, http://www.space.com/scienceastronomy/mystery_monday_040524.html, the known universe is some 150 billion light years wide.

What will happen now if, as they say, the universe is inflating at the speed of light? Will things start to fade from view?

Answer 6

What we can see is the "observable" universe. Anything farther than 13.7 billion years from us is receding at more than the speed of light. It can do that because the speed of expansion is accelerating. The universe might be trillions of times that big, but the rest of it is forever cut off from us.
The light emitted from objects that far out took13 or so billion years to reach us even though it was emitted when the object was much closer because that object isn't just traveling away from us in space. The space in between us is actually expanding. It's like driving on a road that's stretching out so fast you can barely get closer to your destination.

Answer 7

Good question.
I have read that its at least 156 billion light years wide:
http://www.space.com/scienceastronomy/mystery_monday_040524.html
As for your second question, one theory is that after the Big Bang there was an inflationary period in which the Universe initially expanded at a rate faster than the speed of light, so the stars were travelling away faster than the light they emitted was able to travel.
Here is a great article about the expansion of the Universe:
http://www.sciam.com/print_version.cfm?articleID=0009F0CA-C523-1213-852383414B7F0147
Someone from this site sent it to me.

Answer 8

universe "diameter" estimated at 150 billion light years. Reason light can reach us after having travelled only for 14ish billion years, is that, if you want, space grew under its feet, as the universe expended.

I find that trying to think about an ant (or better, a snail) walking towards you on an elastic band, as you stretch the band further and further, helps to visualise that effect.

Answer 9

certainly, if the galaxy is ninety 3 billion mild years away, you're seeing because it became ninety 3 billion years in the past, no longer 13 billion years in the past. a mild year is the area mild travels in a year. the elementary answer on your question is not any. you could't see a similar component in 2 distinctive places or circumstances no count how a strategies away that's. the undeniable fact which you're seeing it 'now' ability that the mild that left it ninety 3 billion years in the past has merely arrived on earth. mild that left it 50 billion years in the past (whilst it became closer) reached us 50 billion years in the past and might't be seen to any extent further.

Answer 10

You know... When we talk about such great numbers, does it really matter?

People take these estimates like Gospel and assume they are right.

When you say 13.7 B I ask. Have we made measurements in all directions. Your 27.4 assume we are at the center. Why?

And just because the farther we can see is 13 B doesn't mean that that's the edge.

Again, when dealing with large numbers and distances our techniques might be wrong.

No one can say for sure how big it is or where we are, so everything else is inconsequential.