Think Small - The Scale of the Universe

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Visible vs Actual

erin's picture

The confusion can be cleared up by realizing that the stuff we can see at the limit of the visible universe is actually about three times as far away, presently. That's even more confusing when you do the math in detail because you end up with an equation describing something that looks like faster than light travel. :)

So the visible universe is about 14 B light-years in radius and the actual universe just happens to work out to be 14 B parsecs in radius. Quite a coincidence since the definition of a parsec involves the diameter of the orbit of the earth; but then the definition of a light year involves the circumference of the Earth's orbit, too.

The site you referenced didn't use parsecs at all; they are out of fashion for measuring anything further away than our local grouping of stars. But the diameter they give for the actual universe, 93 B light-years, works out to a radius of about 14 B parsecs.

Hugs,
Erin

= Give everyone the benefit of the doubt because certainty is a fragile thing that can be shattered by one overlooked fact.

= Give everyone the benefit of the doubt because certainty is a fragile thing that can be shattered by one overlooked fact.

Wow!

This would have made a great resource for when I was teaching science/chemistry.

Thanks for sharing it Edeyn.

Thank you too Erin for clearing up the parsec/light year thing.

Phenomenal Size


Bike Resources

Practical travel in the Universe.

Well, in truth there is none for us humans. Still, if you are writing a Sci Fi story, one needs to get around the science stuff somehow. For the purposes of my story, I finally decided that it would need access to a hundred or so other galaxies. So one day I sat down and tried to come up with a numerical way of stating such speed. Well, the numbers and accelerations quickly make even scientific notation useless, and rather than come up with another system, I just decided to ignore scientific fact.

David Weber is good with that.

The problem is that I can't even find the story I was working on now. :(

Gwendolyn

reminds me

Many, many moons ago, when I was young, a lot of the knowledge we now find on the Internet was passed around as photocopies in offices and universities around the globe. Some was useful, some was funny, some was even pornographic! (Imagine that, porn existed before the Interwebs!) Anyway, one was called something like "The Universal Knowledge Test". Under the category "Astronomy" the question was "Define the Universe. Give three examples." Of course, Star Trek hadn't come out at that time, and science fiction was something only certifiably crazy people (like me) read.

Thanks for the link, Edeyn.


I went outside once. The graphics weren' that great.

Think Big

Puddintane's picture

Hubble Ultra Deep Field Square

Warning: This is a big file, 3100x3100 pixels. It may take a while to load if you have a slow connection.

This picture is the furthest we've probed into deep space, a very small portion of the night sky, about a tenth the diameter of the Moon, 11.5 square arcminutes.

The picture is 5.167 inches square, roughly 26.7 square inches. Almost everything you see in it is a galaxy, not a star, even those tiny points of light in the really deep field.

Because your computer uses pixels which are larger than the tiny pixels used in the picture, at full resolution you won't be able to fit it on your screen, even if you're using a High Definition TV screen, which is around two thirds as many pixels wide, and around a third as many pixels tall.

It would require 12,913,983 pictures of this size to cover the entire sky, 344,776,085 square inches of photos, 2,394,278 square feet, roughly 55 acres, which is a lot of wallpaper.

There are approximately 10,000 galaxies in the picture. The average galaxy contains roughly 100,000,000,000 stars. If you do the math, that works out to approximately 123,000,000,000,000,000,000 stars in the visible universe. That's a lot of stars.

In fact, it's roughly a hundred times more than the number of grains of sand on all the beaches on Earth. And those are just the stars we can see, or have a hope of seeing. The universe is much bigger than that.

Cheers,

Puddin'

A tender heart is an asset to an editor: it helps us be ruthless in a tactful way.
--- The Chicago Manual of Style

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Cheers,

Puddin'

A tender heart is an asset to an editor: it helps us be ruthless in a tactful way.
--- The Chicago Manual of Style