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Course: Middle school Earth and space science > Unit 1
Lesson 1: Earth's place in the universeIntroduction to Middle school Earth and space science
Dive into the mysteries of our universe with Middle School Earth and Space Science! Discover why we have seasons, explore the wonders of gravity, learn about lunar and solar eclipses, and uncover the secrets of water and the rock cycle. Understand how our actions impact the Earth and its climate. Get ready for an exciting journey from the cosmos to Earth! Created by Iman Howard.
Want to join the conversation?
- If scientists discovered for a fact that dark matter and energy is real would we have a hypothesis on how it would affect our universe? If so how would it?(29 votes)
- We actually have observed both dark matter and dark energy! We first discovered dark matter from its gravitational effects on galaxies. People calculated that galaxies were spinning so fast that the gravity from their visible matter wasn’t enough to keep them from flying apart. That means there must be some mass that isn’t just regular matter: dark matter.
Since (as far as we can tell) dark matter only interacts with the rest of the universe via gravity, that’s what we have to use to study it. Another gravitational effect is gravitational lensing. This happens when light bends when it travels around massive objects. General relativity predicts gravitational lensing, and we first confirmed it by measuring where stars around the sun appeared during solar eclipses. Their light does appear to come from different directions when the sun is near them. For dark matter, we also observe that the light coming around it appears distorted as well.
Dark energy makes the expansion of the universe speed up. We’ve observed the light from distant stars and discovered that the further a star is from us, the faster it appears to be moving away from us. This happens because space itself is expanding. We know the universe is expanding, but for a while we didn’t know if its expansion was getting slower or faster with time, or if it was just expanding at pretty much the same rate.
Gravity makes things with mass pull together. Specifically, it makes massive things that are moving apart (like they are in our expanding universe) start to move apart more slowly and eventually start moving together. People thought, then, that gravity might be slowing its expansion down. So, they set out to observe more distant stars again to test this prediction.
The universe’s expansion wasn’t slowing like they thought, though! It was speeding up. We call the thing that counteracts gravity (over very long distances) and makes the universe expand faster and faster dark energy.
Does that answer your questions at all? There’s still a lot we don’t know about dark matter and energy, so people are studying them!(44 votes)
- why didn't the sun cool down(12 votes)
- Stars don't usually cool down. They usually get hotter and hotter over a long period of time. So instead of the sun cooling down it will most likely end up heating up.(12 votes)
- What was the first other planet found other than Earth, it seems that there are so many out there and it's just crazy!(5 votes)
- The first planets to be discovered were Mercury, Venus, Mars, Jupiter, and Saturn. They were discovered more or less at the same time because they all can be seen with the naked eye. Uranus and Neptune weren't discovered until after the invention of the telescope.(20 votes)
- do you believe that there are other sources of life on different planets in our solar system(6 votes)
- The only evidence that we have of potential life elsewhere in the solar system comes from Martian meteorite "Allan Hills 84001". It's a rock from Mars that appears to contain fossilized bacteria. Most scientists reject the hypothesis that the structures in the meteorite are fossils and instead believe that they were produced abiotically. But, it is still debated and at this point we don't know for sure.(9 votes)
- I have heard rumors saying that if the sun is any closer to us we would burn to death. If the sun was any farther we would freeze to death. Is this information I have been told true?(5 votes)
- If the Earth got closer to the Sun then the Earth would burn because it is too hot. If Earth got further away from the sun, it would be too cold to support life. Earth is in the "Goldilocks" zone meaning it is the right distance from the sun in order to support life.(2 votes)
- Hi!
I'm really excited about this (Earth and Space Science)
I am especially curious on black holes and am wondering if there is anything called a white hole. I would love to learn more about space science (astronomy) and dark matter. And really, about that season thing? I'm really caught by that hook. 👌🏻👍🏻😊(6 votes)- A white hole is purely theoretical. There is no evidence on its existence(1 vote)
- How does the same water dinosaurs drank and other animals from the past drank not diteriate over time considering the waters been on the earth for trillions of years.(3 votes)
- When water evaporates, it goes back into the atmosphere and forms clouds, it later falls back down as rain. The water cycle keeps water moving, but never gone.(4 votes)
- Why is the pun nessacery(4 votes)
- My video wont re play after all the times i try(4 votes)
- If scientists discovered for a fact that dark matter and energy is real would we have a hypothesis on how it would affect our universe? If so how would it?(4 votes)
Video transcript
- Hi everyone. Sal Khan here and I'm with
Iman Howard, who is our manager for all of our stem
content on Khan Academy. And we wanted to welcome you to the Middle school Earth
and Space Sciences course. Iman, why should folks
be excited about this? - So Middle school Earth and Space Science is really exciting because it's one of those areas of science that answers what's
happening in our universe. And then like when you dig in, you're like "What is happening in our universe? This is why we have seasons." And so we start like really
big, we go all the way to outer space and we figure
out sort of earth's position in our solar system and the relationship to gravity and our inner
planets and our outer planets. And then we keep digging
in and we finally figure out how Earth's position answers seasons. It's not because we get closer to the sun or how based on earth's
position, we look up at the moon and you'll see a lunar eclipse
or how you don't look up and look at a solar
eclipse, like seriously don't look up because
it'll hurt your corneas. And then we keep going
and we talk about water and how the same water
that you're drinking right now is the exact same
water that dinosaurs drink. And then we get into the
rock cycle and we figure out why mountains are here and
how we're moving right now. Literally the plates below
us are moving and how at one point we could walk
across all the way from the US to Africa and how plate
tectonics really changed that. And then finally,
finally, we talk about us. We talk about us on this planet and how there's so many amazing
resources here and how well how we use them really impacts the earth and how that could impact our climate. And really awesome things that you can do as a learner to change all that and make this earth really awesome. What are you excited about, Sal? - Well, I'll just double
down everything you said and I like how you said
we're gonna dig into it 'cause it's very appropriate
pun for earth, earth and space. This starts to answer the questions of, the from the cosmos to earth. Over billions of years, as you
mentioned, the earth is alive in certain ways with the
plates are still moving it's active and we should
say at least, and you know we are part of the earth. Your point, the, the water in our bodies the air that we breathe,
it's the same water and earth that has been
been here and the air for billions and billions of years. So to be able to actually
understand that it, it actually gives me, gives me goosebumps. So I think folks will be very
excited about this course. - Absolutely. (upbeat music)