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Space and Time: Which One are We Able to See Further Back

Space

Space and Time are totally twisted together and the things that go on in an expanding universe are bent and stretched into incomprehension. To modern astronomers, it makes perfect sense to talk about objects we can see 41.6 billion light-years away in a universe that’s only 13.78 billion years old. It only adds up when you factor in what happens while you’re not looking.

Warping space and time

When Isaac Newton worked out his laws of motion, he had no idea they only worked locally. Albert Einstein came up with not just one, but two versions of relativity. His rough draft case of “special” relativity laid the groundwork but his “general” version is the one in use today describing the elusive “force” we know as gravity.

Space and time are intertwined and any object in the universe bends the fabric of spacetime around it. Everyone knows that light photons and other massless particles fly through the universe at “the speed of light.” That means, since light moves 9.46 trillion kilometers a year, a star “one light year away” would be 9.46 trillion kilometers from Earth. That only works for the close ones.

Space, it says in the Hitchhikers Guide to the Galaxy, “is big, really big.” Not only is it big, it keeps getting bigger all the time. The effect isn’t even noticeable until you get out past 5 billion light years in distance or so.

Ever since the big bang, which physicists are convinced happened right around 13.78 billion years ago, the universe has been inflating like a big balloon. Astrophysicists prefer to use the “raisin bread model.” They want you to imagine a ball of dough with raisins in it.

Pick a direction, any direction. Push the button on that little laser pointer you use to play with the cat. If you pick a direction like down, the red dot photons will light up the planet at your feet and stop.

If you pick something in the up direction it will go a lot further. If your batteries are fresh and you pick just the right direction, you’ll miss all the matter in the solar system, the intergalactic dust, galaxies, quasars and, at the edge of space and time itself, eventually meet “the cosmic microwave background, which is thought to be the leftover radiation from the early stages of the hot Big Bang.”

Space

It also currently appears to be 41.6 billion light-years away in every direction from here. That makes people who aren’t astrophysicists want to reach for a nice glass of Bourbon or a bong or something. How can it be that far away when the universe isn’t that old? Inflation.

Expansion greater at the edges

When we see light from far away in space, its been traveling between where it was emitted and here. In the amount of time it took to get here, the object that emitted it was dragged farther away.

The raisins in the center of the dough ball don’t notice much difference in distance from each other as the dough ball rises but the ones on the outside move quite a bit. You have to have a really huge dough ball before you see major differences.

The way space curves affects the observations. If a triangle is drawn on a sphere the internal angles will add up to a whole lot more than 180 degrees. One drawn on a horse saddle will produce smaller internal angles. Only on a flat surface will all the angles add to 180. Because our universe is expanding, light from distant objects shifts red.

“Within our own galaxy or our own Local Group, the expansion of the universe is completely negligible. It is only on large cosmic scales — where we observe objects that might be bound to one another in a larger structure, but not bound to the same structure we are part of — that the expansion of the universe rears its head.”

As explained in detail by BigThink, “Light arriving from 1 billion years ago in time corresponds to an object presently 1.036 billion light-years away” in space. That’s not much of a difference.

“Light arriving from 10 billion years ago corresponds to an object presently 16.03 billion light-years away.” At the extreme, “Light arriving from 13.78 billion years ago corresponds to an object presently 41.6 billion light-years away.”

What do you think?

Written by Mark Megahan

Mark Megahan is a resident of Morristown, Arizona and aficionado of the finer things in life.

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