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The current accepted estimate for,
Cosmic
time scales are hard to make sense of.
The moon we see, is always around 1 second in the past. That is only a slight distortion.
The farthest galaxy observed is 13.4 billion light-years from Earth. That doesn't mean it is that many light years away.
Instead, it is probably more than 30 billion light years away now due to the accelerating expansion of the universe. The galaxy we see though, is as it was 400 million years after the Big Bang.
The light has been travelling for 13 billion years to reach us.
Most of what we see in
the sky, is the past...
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There are definitely parts of the universe that have expanded away from us and the light has not had enough time to reach us.
All the matter that we do
see, including all those galaxies, make up only 5 percent of the
universe. If that isn't strange enough, we do not know what the
other 95 percent of it is!
We see this in our solar system. This is why Mercury takes 87 days to go around the sun once while Neptune takes 165 years. Stars at edge of galaxies however, rotate just as fast as the ones near the centre.
There's not nearly enough mass in the galaxies to cause this effect so astronomers came to the conclusion that there was something massive causing the gravitational field to extend and keep the stars moving just as fast.
Something we couldn't
see, hence the term, dark matter. It makes up 25% of the universe.
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And so, some theories suggest maybe we don't understand gravity and dark matter doesn't really exist.
Either way, behavior of galaxies and the motion of the stars in it, tells us we are missing something. We have found the Dragonfly 44 galaxy, which is 99 percent dark matter.
We have also found a galaxy with no dark matter in it. The fascinating thing is that the galaxy with no dark matter strengthens the case that dark matter, whatever it may be, exists...
But as of this today, it still remains a mystery.
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In a sense, it's a fight between the expansion of the space and gravity of the matter in it. And expansion wins. There's not enough matter in the universe for the gravity to reverse the expansion. So it will go on. We assumed that at some point, this expansion would slow down and stop.
When it was actually
measured though, it was shocking to see that the expansion had
actually sped up...
Slowing down of the expansion was what we expected. But something was making it go faster than it was in the past.
The cause of this accelerating expansion has come to be called dark energy. Other than knowing that it must be a property of empty space itself, we don't know too much about it.
It makes up 70 percent of
the universe. The biggest part of it. And as it stands it will
continue to grow exponentially. Which means in a distant future, it
will be a very dark universe.
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Words fail when you try to express how big the universe is. It came in to being and almost 14 billion years later, we showed up. Our existence may be just an accident. Irrelevant in the grand scheme of things.
In any case, we are
linked to it.
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If it is a good answer, it should lead to more questions. The kind of which we never even thought to ask.
We may never really find
out everything. But that has never stopped us from trying.
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