Matter, all of it matter. Matter generates gravity.
However, that visible matter is only a small portion of what’s
really
there. From the way galaxies behave and from the way light is distorted when there’s nothing obvious there to distort it, and from other clues, cosmologists have deduced that there’s a lot more matter out there than the stuff we can see. In fact, there’s
five times
as much.
But we’re
still
not done.
I’m not going to deal with the current prevailing theory of how it all began, the Big Bang theory. I always saw it as an explosion, with everything rushing away from a center point, like you see in films of an explosion. Papa says this is only partly true, but it can be a useful way to visualize it. But the logic breaks down quickly. From where we are, in the Milky Way galaxy, everything but our very close neighboring galaxies seems to be rushing away from us. The more distant it is, the faster it is rushing away. What, was it something we said? Do we smell bad?
Since no matter which direction you look, everything is moving
away
from us, you’d think that meant we just happen to be the center of the universe. That would be a nice thing to think, wouldn’t it? Like before telescopes and such things, people thought the Earth was the center of the universe, and Old Sun and all the stars and planets revolved around it. Made them sort of special, and don’t we all want that?
But it ain’t so. Papa says that no matter where we were in the universe, everything would seem to be rushing away from us. That’s because since the universe is expanding, space
itself
is expanding. Papa used a balloon to show us how that made sense. You draw dots on the surface of a balloon, and say those are galaxies. Now blow the balloon up. All of the dots move away from all the other dots, because the balloon is stretching. That’s a two-dimensional model of what’s happening in three dimensions. The balloon’s surface is two-dimensional, but it’s curved.
So, the universe is expanding. But gravity—including all that dark matter—should be tending to slow it down. Eventually, it would stop expanding and start to collapse back on itself, like the rocks thrown in the air by an explosion on a planet eventually stop rising and fall back to the ground.
Except about a hundred years ago they found out that’s not what’s happening. Everybody expected that the rate of expansion would be slowing down, so that it would eventually stop and start contracting. Another possibility was that the rate of expansion would stay steady. The third, and what most scientists thought was the least likely to be true, was that the rate of expansion could be
increasing
.
And that’s exactly what they found. In some unimaginable future, the universe will stretch so thin that the light from one galaxy would be unable to reach any other galaxy. Eventually, all the stars would burn out, and the universe would consist of the dead cinders of stars, black holes, and uncountable googolplexes of cubic light-years of cold, empty space.
So have fun while you can, because the future is bleak. If you live forever, that is.
—
But this discovery raised more questions than it answered.
To have all those galaxies rushing away from each other faster and faster, there needs to be something pushing them away from each other, and pushing pretty hard. Remember, their own gravity is pulling them
toward
each other, and it’s helped along by the gravitational attraction of all that dark matter—four times the amount of visible matter, and thus four times as strong.
This other stuff, this dark energy, or
dark lightning
, as Papa prefers to call it, has to overcome all that, and then some.
How
it does it wasn’t solvable at the time since we didn’t have the foggiest notion of what it was or where it was hiding. We could only infer it
was
there because something had to be there to keep pushing everything apart faster and faster. But it was possible
However, that visible matter is only a small portion of what’s
really
there. From the way galaxies behave and from the way light is distorted when there’s nothing obvious there to distort it, and from other clues, cosmologists have deduced that there’s a lot more matter out there than the stuff we can see. In fact, there’s
five times
as much.
But we’re
still
not done.
I’m not going to deal with the current prevailing theory of how it all began, the Big Bang theory. I always saw it as an explosion, with everything rushing away from a center point, like you see in films of an explosion. Papa says this is only partly true, but it can be a useful way to visualize it. But the logic breaks down quickly. From where we are, in the Milky Way galaxy, everything but our very close neighboring galaxies seems to be rushing away from us. The more distant it is, the faster it is rushing away. What, was it something we said? Do we smell bad?
Since no matter which direction you look, everything is moving
away
from us, you’d think that meant we just happen to be the center of the universe. That would be a nice thing to think, wouldn’t it? Like before telescopes and such things, people thought the Earth was the center of the universe, and Old Sun and all the stars and planets revolved around it. Made them sort of special, and don’t we all want that?
But it ain’t so. Papa says that no matter where we were in the universe, everything would seem to be rushing away from us. That’s because since the universe is expanding, space
itself
is expanding. Papa used a balloon to show us how that made sense. You draw dots on the surface of a balloon, and say those are galaxies. Now blow the balloon up. All of the dots move away from all the other dots, because the balloon is stretching. That’s a two-dimensional model of what’s happening in three dimensions. The balloon’s surface is two-dimensional, but it’s curved.
So, the universe is expanding. But gravity—including all that dark matter—should be tending to slow it down. Eventually, it would stop expanding and start to collapse back on itself, like the rocks thrown in the air by an explosion on a planet eventually stop rising and fall back to the ground.
Except about a hundred years ago they found out that’s not what’s happening. Everybody expected that the rate of expansion would be slowing down, so that it would eventually stop and start contracting. Another possibility was that the rate of expansion would stay steady. The third, and what most scientists thought was the least likely to be true, was that the rate of expansion could be
increasing
.
And that’s exactly what they found. In some unimaginable future, the universe will stretch so thin that the light from one galaxy would be unable to reach any other galaxy. Eventually, all the stars would burn out, and the universe would consist of the dead cinders of stars, black holes, and uncountable googolplexes of cubic light-years of cold, empty space.
So have fun while you can, because the future is bleak. If you live forever, that is.
—
But this discovery raised more questions than it answered.
To have all those galaxies rushing away from each other faster and faster, there needs to be something pushing them away from each other, and pushing pretty hard. Remember, their own gravity is pulling them
toward
each other, and it’s helped along by the gravitational attraction of all that dark matter—four times the amount of visible matter, and thus four times as strong.
This other stuff, this dark energy, or
dark lightning
, as Papa prefers to call it, has to overcome all that, and then some.
How
it does it wasn’t solvable at the time since we didn’t have the foggiest notion of what it was or where it was hiding. We could only infer it
was
there because something had to be there to keep pushing everything apart faster and faster. But it was possible
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