Understanding Earth's Core: Iron, Heat, and Atmosphere Insights
School
CUNY Hunter College**We aren't endorsed by this school
Course
ASTRO 100
Subject
Astronomy
Date
Dec 11, 2024
Pages
9
Uploaded by JudgeGalaxy9885
Class 2 notes | made into my own slides because professor doesn’t use slide for online class Class Today Today’s class was about “How we know there is Iron at the core of the Earth”, “‘How we know it’s hot at the core?”, Earth’s atmosphere and the age of the Earth. Seriously this guy is all over the place. *Professor kept mentioning the question “Why is the iron at the core of the earth hot?” but | don’t think he actually answered that today.* The Earth Earth’s Radius ~ 4000 miles Iron Core’s Radius ~ 2000 miles Iron Core’s Temperature ~ 6000°C (11,000°F) How come there is so much Iron? How come it's so hot?
How did people find out what things are made of? As a basic concept, people find out what things are made of by “hitting” them. If you hit a wooden door with your knuckles, versus if you hit a metal door, the sounds will be different. *Professor didn’t say this, but from my understanding sound is carried through vibrations. Different materials send out different vibrations therefore they make different sounds* So how do you hit the Earth hard enough to find out what’s inside? How do you hit the Earth hard enough? The answer is Earthquakes. Earthquakes create waves of vibrations that go through the earth. Scientists use a kind of vibration recording device to determine what those waves went through and consequently telling us what is inside the Earth. Earthquake Vibrations Devices used to record the vibrations
Why Iron? The core of the Earth is Iron. Iron can also be found throughout the other layers of the Earth. So needless to say, there’s a lot of iron. But why specifically iron? Iron is made in the stars. Basically everything in our galaxy, except hydrogen and helium was made from the “junk” of previous exploding stars. Near the end of a star’s explosion, it stops making the other elements and just mostly makes iron. For some reason that’s all it can make at that point. So we end up with a lot of iron to use up in the making of our galaxy. Earth’s Density *p = density” p of Water = 1 The difference in the density of the Earth’s surface p of Earth’s Surface ~ 3 and the density of the Earth as a whole is due to p of Whole Earth ~ 5 the inside of the Earth has a higher density that the surface. The interior density is great because lron has a density. **o of water = 1 = 1 gram per cm”3 (centimeter cubed)*
Earth’s Atmosphere Earth’s Atmosphere Composition (2 things mainly) Nitrogen ~ 78% Oxygen ~ 21% Carbon Dioxide ~ 0.03 % Other There is 0% hydrogen in the Earth’s atmosphere despite that fact that the universe was made from hydrogen and Earth itself has an abundance of hydrogen.
Why is there no Hydrogen in the Earth’s Atmosphere? **Note from Professor: Don’t say “gravity” in class. Gravity is too broad of a term. Instead say “Force due to ..."”. For example if you're talking about Earth’s gravity say “force due to Earth”.** Is it possible to throw something high enough that it doesn’t come back? That is called Escape Velocity. Escape velocity is because how hard you have to “throw” something, so that it going beyond the reach of Earth’s gravitational pull back down to earth. There actually used to be hydrogen in the atmosphere, but they would collide with the other molecules in the atmosphere and be knocked away. They were too light to pulled back by earth’s gravity once they got knocked away. Why do things fall? Things fall because of the Earth, not the object itself. When two objects of different masses are dropped from the same height they reach the ground at the same time. All objects fall at the same rate regardless of its weight or mass. This statement however does not take into consideration the interference of “air” into account. Falling from a resting point: e 1stsecond = 32 ft/ sec e 2nd second =64 ft/ sec e 3rd second = 96 ft/ sec All objects follow this gradual acceleration when falling on the earth. The acceleration is dependent on the “force due to earth” and not how much an object weighs.
Galileo’s Leaning Tower of Pisa Experiment Galileo was the one to make this discovery. His famous experiment was dropping two objects of different masses from the top of the Leaning Tower of Pisa and observing that they both landed at the exact same time. |11 Old idea Galileo Ridges on a Coin (I don’t know why this was relevant) In ancient times money was made of gold and silver. People used to cut off small unnoticeable bits of coins around the edges and were essentially paying less for things. This was apparently a big problem so Newton came up with a solution. His solution was puting ridges around the coin so if any bit was cut off you could easily tell. That is why even today coins like the quarter has ridges around them.
Age of the Earth We have know the age of the Earth for about 50 to 60 years now. When it was first discovered, it sparked a lot of debate among religious people, philosophers, and scientists. People didn’t believe in the new findings. Timeline of People “discovering the age of the Earth” Around the 1300’s a monk used the bible and the stories in it to estimate the age of the earth and placed it at about 5000 year ago. And the church accepted that. Around the early 1800’s fossils were discovered, which lead to the discovery that the Earth has layers. Archaeologists at the time estimated that the fossils were from 250,000 years ago. That estimation wasn’t correct but they were getting closer. Between 1800 to 1850 Darwin came and brought the in the idea of evolution. Animals weren't just created, they evolved over time. For example, dinosaurs evolved into birds. 1900’s : Kelvin estimated the age of the Earth.
Kelvin Kelvin theorized that the Earth used to be very hot, and have been cooling down over time. He believed you could determine the age of the Earth using it’s temperature. 8 - geothermal gradient (degrees Celsius per kilometer) S i S— 10 20 50 100 200 500 1.000 2,000 5,000 predicted age (millions of years)
Pan Analogy for Kelvin's Age of the Earth Theory Let's say someone put a pan on the stove and brought it up to 400°. At 400° they turned off the fire and let the pan cool down naturally. The Pan’s Temperature After: 1 min = 300 degrees® 2 min = 200 degrees® 3 min = 100 degrees® Now let's say you came in while it was cooling down and you don’t know when the fire was turned off. You check the temp of the pan and it's at 200°. Logically you can estimate that the fire was turned off 2 minutes ago because that’s how long it would take for the pan to have reached 200°. The idea was that we can use the Earth’s temperature now and work our way backwards to figure out how long the Earth has been cooling. Therefore telling us the age of the Earth. This was Kelvin’s initial thought process. He later found out however, that there was an error in this though process. The Error: Pan Analogy Before we assumed the pan was cooling down without any disruptions. However what if every once in a while, someone comes in and turns the fire back on? Now the pan is heating up again. And when the fire gets turned off, the pan starts to cool down again. And this keeps on happening. The pan starts to cool down but then someone keeps turning on the fire. Kelvin realized later that as the Earth was cooling, something else was heating it up again. Professor didn’t say what was heating up the Earth, just that it was some radioactive stuff.