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--------------------- 2455 - ASTRONOMY - making sense of science?
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- Why isn’t everyone bothered by the strangeness of the universe? Science keeps giving us more questions.
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- The current accepted estimate for the age of the universe is 13.8 billion years. Our galaxy, the Milky way, 13.5 billion years. The Sun, 4.6 billion years. Planet Earth, 4.5 billion years.
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- The Moon is the closest to earth. 384,400 kilometers away. In other words, 1.282 light seconds away. The Moon we see, is always around 1 second in the past.
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- The farthest galaxy observed is 13.4 billion lightyears 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 is as it was 400 million years after the Big bang. The light has been traveling for 13 billion years to reach us. All that we see in the sky, is the past.
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- Our Milky Way Galaxy is part of the 100 to 200 billion galaxies that we estimate exist in the “observable universe“. There are definitely parts of the universe that have expanded away from us and the light has not had enough time to reach us.
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- All the matter that we do see 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!
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- Gravity weakens as you go further from the center and the object moves slower. Stronger the pull, faster the movement. 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.
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- However, stars at edge of galaxies rotate just as fast as the ones near the center. There is 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, called dark matter. It makes up 25% of the universe.
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- We can’t see it but we measure its effects. It only interacts gravitationally. And so, some theories suggest maybe we don’t understand gravity and dark matter doesn’t really exist.
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- Either way, the motion of galaxies and the motion of the stars in it, tells us we are missing something. We have found the Dragonfly 44 galaxy, to have 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.
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- The universe has been expanding since it all began but how does it end?
Knowing the amount of matter and its gravity and the rate at which parts of the universe are expanding, we can answer this question. In a sense, it’s a fight between the expansion of the space and gravity of the matter in it. And expansion wins.
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- There is not enough matter in the universe for the gravity to reverse the expansion. So expansion will go on forever. We had assumed that at some point, this expansion would slow down and stop. When it was actually measured it was shocking to see that the expansion had actually sped up.
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- If space was expanding at a constant rate, it would not have been surprising to most astronomers. 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.
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- 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 mass/energy in the universe. 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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- We know a lot about our world but the majority of it is still unknown to us. 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.
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- We might not be around forever to witness end of our planet or the death of the Sun. We might ever learn where did it all come from?
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- Solving the unanswered questions in science may or may not lead to a deeper understanding of the precise nature of reality. 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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- The universe makes us feel small, insignificant and gives you an existential crisis. At its best, it makes us feel like a child in front of a giant puzzle, never ending for a solution.
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- October 21, 2019.
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--------------------- Monday, October 21, 2019 -------------------------
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