If The Universe Is 13.8 Billion Years Old...

[Winston]

If The Universe Is 13.8 Billion Years Old, How Can We See 46 Billion Light Years Away?
Distances in the expanding Universe don’t work like you’d expect, unless, that is, you learn to think like a cosmologist

https://medium.com/starts-with-a-ba...-see-46-billion-light-years-away-db45212a1cd3

The explanation with graphics is followed by this conclusion:

Put that all together, and this means the distance we can see in the Universe, from one distant end to the other, is 92 billion light years across. And don’t forget: it’s continuing to expand! If we left today at the speed of light, we could only reach about a third of the way across it: approximately 3% of its volume. In other words, due to the Universe’s expansion and the presence of dark energy, 97% of the observable Universe is already unreachable, even if we left today at the speed of light.

 

[GrouchoDuke]

Just go faster than the speed of light. Easy!

 

[Worsaer]

So, “you can’t get there from here...” is a real thing. Who knew?

 

[Bat-mite]

So, “you can’t get there from here...” is a real thing. Who knew?

HA! :lol:

"Hey, Mac, how do you get to Redbud?"

"How'd you know mah name wuz Mac?"

 

[dr wogz]

what if we went 'plaid'?

 

[jlabrasca]

So, “you can’t get there from here...” is a real thing. Who knew?

I don't know about any locus bounded by the region labeled "Arkansas", but direct observation indicates that East Millinocket is, in fact, beyond some kind of event horizon.

Students in a "hybrid" astronomy class (meeting only for labs, completing all lecture work online) a couple of years ago stumbled onto some earlier version of the Starts with a Bang blog. Nothing posted there helped them understand anything, and I spent considerable time and effort typing things into the class discussion forums trying to untangle the mess it made inside their heads. It was all the fun of a pointless internet argument, multiplied by the anxiety and mistrust of antinummerate students who resented being "forced" to take a science class.

Ethan Siegle deserves some credit for trying to explain cosmology without mathematics. He also gets grudging respect for figuring out how to get money for trying to explain cosmology without mathematics. It is only unfortunate that cosmology is nothing but mathematics.

 

[OverTheTop]

If this is the discussion I think it is, then the most distant things we see today will not be observable in the future, due to expansion. Read it somewhere a while back. There is some discussion and planning about how to preserve what we see today, so when it is no longer actually visible there will be some record of it for future cosmologists and historians to pore over. Could make for an interesting "museum" experience.

 

[aerostadt]

Mind boggling stuff!

The original start of the big bang is confusing in itself. It didn't explode into space that was already there. It actually created the space that all the matter and energy moved into. I guess you could say that it made the space that it exploded into, but wait, it is more confusing than that. Not only did it create the space that it exploded into, but it created the time that it exploded into. In other words time in our universe started at the start of the big bang.

 

[jlabrasca]

Mind boggling stuff!

The original start of the big bang is confusing in itself. It didn't explode into space that was already there. It actually created the space that all the matter and energy moved into. I guess you could say that it made the space that it exploded into, but wait, it is more confusing than that. Not only did it create the space that it exploded into, but it created the time that it exploded into. In other words time in our universe started at the start of the big bang.

Its even more confusing than that. Because the Planck Length and the vacuum speed of light set a lower bound on the interval between distinguishable events, when the the universe came into existence it was already 10^-43 seconds old.

Physics is written in a grand book — I mean the Universe — which stands continually open to our gaze, but which cannot be understood unless one first learns the language and characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering around in a dark labyrinth. -- Galileo

 

[Daddyisabar]

And I thought the inflation of the late 70's was bad! My economist buddies say there is only one thing to fear: Inflation. At least cosmic inflation was really quick, that instant before Plank Time at 10-43 seconds. With no speed limits and time having not matured the math gets a little crazy. Sounds like a universe engulfed in teen age drag racing and playing chicken, leading to big trouble that only James Dean, a rebel without a cause, could truly understand.

 

[KennB]

Just go faster than the speed of light. Easy!

There was a young lady named Bright
Who traveled much faster than light.

She took off one day,
In a relative way,​

And returned the previous night.

 

[aerostadt]

And I thought the inflation of the late 70's was bad! My economist buddies say there is only one thing to fear: Inflation. At least cosmic inflation was really quick, that instant before Plank Time at 10-43 seconds. With no speed limits and time having not matured the math gets a little crazy. Sounds like a universe engulfed in teen age drag racing and playing chicken, leading to big trouble that only James Dean, a rebel without a cause, could truly understand.

Daddy,
You are so right! I remember in the late 70's under President Jimmy Carter we had crazy financial inflation. I had a money market fund that was paying 17 percent interest. If that wasn't enough, theoretical physicist Alan Guth developed his idea of the inflationary universe. About 10-36 seconds after the big bang until about 10-33 or 10-32 seconds later, there was the inflationary expansion epoch of the universe, where the boundary of the universe expanded faster than the speed. Since the boundary is not a physical object, it does not need to obey the universal speed limit.

 

[Zeus-cat]

Puppies and kittens. I thought someone should bring this back down to earth and to really important things.

 

[aerostadt]

Puppies and kittens. I thought someone should bring this back down to earth and to really important things.

What about Schrodinger's Cat?

 

[jlabrasca]

Puppies and kittens...

Yes. If we were to place a kitten beyond the comoving horizon with a small flask of poison gas, a piece of radium, and a detector which-- upon intercepting an alpha particle -- will trigger a device to break the flask... actually, why stop at one cat? A statistically valid sample might require all of the cats currently murdering song birds in my neighborhood.

 

[Charles_McG]

We went to the Adler Planetarium this Sunday. They have Alan Guth’s notebook on display, open to the page where he starts laying out supercooled inflation.


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[aerostadt]

We went to the Adler Planetarium this Sunday. They have Alan Guth’s notebook on display, open to the page where he starts laying out supercooled inflation.


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That sounds cool! I lived in the Chicago area for many years, but never made it to the Adler Planetarium. I am envious. BTW probably as you know the University of Chicago is going to close down the World's largest refracting telescope at the Yerkes Observatory this year.

Guth did work in the Grand Unified Theory with the idea of getting General Relativity and Quantum Mechanics to reconcile each other.

 

[Charles_McG]

I heard that Yerkes is being closed. I got to go last year on a special Lake Geneva Chamber of Commerce night. It was pretty awesome.


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