U.S. CitiesCity-Data Forum Index
Go Back   City-Data Forum > General Forums > Science and Technology > Space
 [Register]
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
View detailed profile (Advanced) or search
site with Google Custom Search

Search Forums  (Advanced)
Reply Start New Thread
 
Old 11-03-2019, 07:39 PM
 
22,786 posts, read 17,260,808 times
Reputation: 9491

Advertisements

Quote:
Originally Posted by Milky Way Resident View Post
It's estimated to be approximately 13.8 billion years, but due to expansion it's got a radius of over 46 billion, which leads to a current diameter of 92-93 billion ly. I haven't heard of the 96 figure myself.
That's the observable universe. While it can't be known for sure, physicist Alan Guth has said that the universe beyond what we can see is 10²³ bigger. That's a hundred billion trillion times bigger than the observable universe. He bases that on, if I'm understanding him correctly, (because we don't really know how much inflation took place) a two hundred fold doubling of the size of the universe in less than a micro second. That's twice the one hundred fold minimum that is required to make his inflationary theory work. So a two hundred fold doubling of the size of the universe is about 10²³.

Alan Guth - How Vast is the Cosmos?


https://www.youtube.com/watch?v=Fto2HTtnz6g
Reply With Quote Quick reply to this message

 
Old 11-04-2019, 05:16 PM
 
2,959 posts, read 1,123,920 times
Reputation: 1992
Quote:
Originally Posted by Mike555 View Post
That's the observable universe. While it can't be known for sure, physicist Alan Guth has said that the universe beyond what we can see is 10²³ bigger. That's a hundred billion trillion times bigger than the observable universe. He bases that on, if I'm understanding him correctly, (because we don't really know how much inflation took place) a two hundred fold doubling of the size of the universe in less than a micro second. That's twice the one hundred fold minimum that is required to make his inflationary theory work. So a two hundred fold doubling of the size of the universe is about 10²³.

Alan Guth - How Vast is the Cosmos?
Yeah, I was thinking about the observable universe. Beyond that, it's hard to tell as we don't know it's topology. Current observation suggests a flat universe, but it could curve beyond our horizon.
Reply With Quote Quick reply to this message
 
Old 11-07-2019, 09:22 AM
 
Location: Haiku
5,613 posts, read 2,974,582 times
Reputation: 8057
Quote:
Originally Posted by HouseBuilder328 View Post

But would that really explain why there is hardly any light throughout space? Or is it as simple as that the Universe is so large, that stars' light is not enough to light it up. Such as a weak flashlight would just be a shining spot in a dark NFL stadium?
The even, diffuse light that we have here on earth in the day is due to scattering of the the sun's light by the atmosphere. At night there is still scattering of the faint starlight but it is too weak for our eyes to see the scattered light and all we see are the stars. So the universe is full of points of light but unless you are on a planet with an atmosphere to diffuse those points it is going to look like it does for us at night - mostly black with stars here and there.

But technically, the universe is filled with photons, however our eyes only "see" photons in a very narrow bandwidth. But if we were able to see photons across the entire electromagnetic spectrum, the universe would look much brighter. In particular, if we could see CBR (cosmic background radiation) the universe would appear as a uniform glow in all directions. The fact that is looks black to us is just our visual limitation.
Reply With Quote Quick reply to this message
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.

Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.


Reply

Quick Reply
Message:

Over $104,000 in prizes was already given out to active posters on our forum and additional giveaways are planned!

Go Back   City-Data Forum > General Forums > Science and Technology > Space
Similar Threads
Follow City-Data.com founder on our Forum or

All times are GMT -6.

© 2005-2019, Advameg, Inc. · Please obey Forum Rules · Terms of Use and Privacy Policy · Bug Bounty

City-Data.com - Archive 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 - Top