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Course: Middle school Earth and space science - NGSS > Unit 1
Lesson 1: Earth's place in the universeEarth’s place in the universe
Review your understanding of Earth’s place in the universe in this free article aligned to NGSS standards.
Key points:
- Actual motion is how objects actually move. For example, Earth rotates on its axis.
- Apparent motion is how objects appear to move. For example, due to Earth’s rotation, the sun seems to rise and set each day.
- Early astronomers developed the geocentric model based on the apparent motion of the sun and stars. In this model, Earth is at the center of the universe.
- The geocentric model was later replaced by the heliocentric model. In this model, the sun is at the center of the universe.
- In reality, the sun is only at the center of our solar system, not the entire universe.
Want to join the conversation?
what is retrograde motion an example of ?(50 votes)
It's an example of the fact that we are orbiting the sun, that Mars, Jupiter, Saturn, Uranus and Neptune are orbiting further away from us and that the planets orbit the sun in ellipses rather than circles(70 votes)
why is the sun center of the solar system and not the unuverse(26 votes)
The sun is the center of the solar system because its planets, asteroids, comets, and so on all orbit it.
As Janice said, though, the solar system also orbits the center of our Milky Way galaxy, which is part of the Local group, which is part of the Virgo supercluster, and on to larger groups.
Also, as far as we know now, there isn’t actually an absolute center of the universe. Space itself is expanding, so every point is expanding away from every other point. That means we can’t trace it all back to one “center” of the Big Bang or what the Big Bang expanded to become: the universe right now.
Does that help?(33 votes)
Have we ever tried studding black holes and what is past it? This is not really on topic but what if black holes were actually like a new "dimension" like a worm hole,but the power is to strong that nothing is able to handle the pressure that it gives.(11 votes)
The term black hole is potentially misleading. Calling it a hole makes you think that it is something that you can enter, pass through, and go to the other side. More accurately, they are massive objects with intense gravitational fields similar to stars. But, unlike stars they are so massive that light can't escape. If you think of them as dark stars, rather than holes, then you'll probably have a more realistic concept of what black holes actually are.(27 votes)
why do we live on earth(15 votes)
It is the only planet we can find that gives us oxyegn and water. It is in the habital zone(13 votes)
- what is an axsis or where is the axsis?(7 votes)
- They’re talking about the axis of rotation. This is an imaginary line that something spins around. If you roll a wheel, for example, its axis of rotation would be through its center. Earth’s axis passes through its poles, and it’s the imaginary line the planet spins around every day.
Does that help?(15 votes)
When was the heliocentric model created?(13 votes)
1543 (source: google)(3 votes)
This article states that the sun is only the center of our solar system and not the entire universe so what is the center of the universe?(10 votes)
Some people say that there's a black hole in the center of our universe, but I personally disagree with that because there is scientific evidence that the universe is speeding up. Here's a quote from an article that explains it "By carefully observing distant supernovae—stellar explosions that for a brief time shine as brightly as 10 billion suns— astronomers found that they were fainter than expected. The most plausible explanation for the discrepancy is that the light from the supernovae, which exploded billions of years ago, traveled a greater distance than theorists had predicted. And this explanation, in turn, led to the conclusion that the expansion of the universe is actually speeding up, not slowing down." Black holes tend to generally suck things into their grasp, if there was truly a gigantic one in the middle of the universe, we would be slowing down.(9 votes)
- can new planets form in our universe? aslo can their be mini stars forming aslo because the moon slowly backs away from the earth will a new moon form? :O(14 votes)
- no theyeyeyeyeyeyeyeyeyeyeyeyeeyyeyeyeeyye-(1 vote)
Can new stars or black hole come into the milky galaxy?(6 votes)- Yes, new stars are constantly forming! Gravity pulls gas together, and the gas heats up. Eventually, once there's enough gas, gravity pulls on it so much that two smaller atoms can be forced together to make one bigger atom. This process is called fusion, and stars usually start by fusing hydrogen atoms to make helium atoms.
Black holes can also form in our galaxy. One common way to get a black hole happens when a large star "dies". Usually, the energy released during fusion keeps gravity from making a star collapse in on itself. Once big stars use up enough hydrogen, the reaction at the center of the star brings together the helium atoms to make even bigger atoms: carbon. The star keeps fusing bigger and bigger elements. Once the star's made iron atoms, though, it can't make any bigger atoms. Fusion doesn't work as much, then. That means the fusion loses the battle with gravity, and the star collapses in on itself. If the star is massive enough, gravity can make it collapse so much that its gravity pulls in even light. That's how a new black hole can form from an old star.
(There are also supermassive black holes, like the one at the center of our galaxy, that are much bigger than the black holes we see forming this way.)
Does that help?(11 votes)
- Why do asteroids always hit the moon instead of Earth?(5 votes)
Asteroids hit the Moon more often than Earth because the Moon has no atmosphere to protect it from meteoroids(10 votes)
