- Scale of the Universe
- Stars, black holes and galaxies
- Earth geological and climatic history
- Life on Earth and in the Universe
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Scale of the Universe
Things in our universe can be unimaginably large and small. In this topic, we'll try to imagine the unimaginable!
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Scale of the small and large
We humans have trouble comprehending something larger than, say,
our planet (and even that isn't easy to conceptualize) and smaller than,
say, a cell (once again, still not easy to think about). This tutorial
explores the scales of the universe well beyond that of normal human
comprehension, but does so in a way that makes them at least a little
more understandable.
How does a bacteria compare to an atom? What about a galaxy to a star?
Turn on your inertial dampeners. You're in store for quite a ride!
Light and fundamental forces
This tutorial gives an overview of light and the fundamental four
forces. You won't have a degree in physics after this, but it'll give
you some good context for understanding cosmology and the universe we
are experiencing. It should be pretty understandable by someone with a
very basic background in science.
Scale of earth, sun, galaxy and universe
The Earth is huge, but it is tiny compared to the Sun (which is
super huge). But the Sun is tiny compared to the solar system which is
tiny compared to the distance to the next star. Oh, did we mention that
there are over 100 billion stars in our galaxy (which is about 100,000
light years in diameter) which is one of hundreds of billions of
galaxies in just the observable universe (which might be infinite for
all we know). Don't feel small. We find it liberating. Your everyday
human stresses are nothing compared to this enormity that we are a part
of. Enjoy the fact that we get to be part of this vastness!
Time scale of the cosmos
Not only is the universe unimaginable large (possibly infinite),
but it is also unimaginably old. If you were feeling small in space,
wait until you realize that all of human history is but a tiny blip in
the history of the universe.
Big bang and expansion of the universe
What does it mean for the universe to expand? Was the "big bang"
an explosion of some sort or a rapid expansion of space-time (it was the
latter)? If the universe was/is expanding, what is "outside" it? How
do we know how far/old things are?
This tutorial addresses some of the oldest questions known to man.
- Big Bang Introduction
- Radius of Observable Universe
- (Correction) Radius of Observable Universe
- Red Shift
- Cosmic Background Radiation
- Cosmic Background Radiation 2
- Hubble's Law
- A Universe Smaller than the Observable
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Stars, black holes and galaxies
Our universe is defined by stars. This
topic explores how they came to be and where they end up. This includes
a discussion of black holes and galaxies.
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Life and death of stars
Stars begin when material drifting in space condenses due to
gravity to be dense enough for fusion to occur. Depending on the volume
and make-up of this material, the star could then develop into very
different things--from supernovae, to neutron stars, to black holes.
This tutorial explores the life of stars and will have you appreciating
the grand weirdness of our reality.
Quasars and galactive collisions
Quasars are the brightest objects in the universe. The gamma rays
from them could sterilize a solar system (i.e. obliterate life). What
do we think these objects are? Why don't we see any close by (which we
should be thankful for)? Could they tell us what our own galaxy may
have been like 1 billion or so years ago?
Stellar parallax
We've talked a lot about distances to stars, but how do we know?
Stellar parallax--which looks at how much a star shifts in the sky when
Earth is at various points in its orbit--is the oldest technique we
have for measuring how far stars are.
It is great for "nearby" stars even with precise instruments (i.e, in
our part of our galaxy). To measure distance further, we have to start
thinking about Cepheid variables (other tutorial).
Cepheid variables
Stellar parallax can be used for "nearby" stars, but what if we
want to measure further out? Well this tutorial will expose you to a
class of stars that helps us do this. Cepheids are large, bright,
variable stars that are visible in other galaxies. We know how bright
they should be and can gauge how far they are by how bright they look to
us.
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Earth geological and climatic history
What is the Earth made up of and how do we know? What causes the seasons? Are there longer-ranging cycles in Earth's climate?
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Plate tectonics
Is it a coincidence that Africa and South America could fit like
puzzle pieces? Why do earthquakes happen where they do? What about
volcanoes and mountains? Are all of these ideas linked? Yes, they are.
This tutorial on plate-tectonics explains how and why the continents
have shifted over time. In the process, we also explore the structure
of the Earth, all the way down to the core.
- Plate Tectonics-- Difference between crust and lithosphere
- Structure of the Earth
- Plate Tectonics -- Evidence of plate movement
- Plate Tectonics -- Geological Features of Divergent Plate Boundaries
- Plate Tectonics-- Geological features of Convergent Plate Boundaries
- Plates Moving Due to Convection in Mantle
- Hawaiian Islands Formation
- Pangaea
- Compositional and Mechanical Layers of the Earth
- How we know about the Earth's core
Seismic waves and how we know Earth's structure
How do we know what the Earth is made up of? Has someone dug to
the core? No, but we humans have been able to see how earthquake
(seismic) waves have been bent and reflected through our planet to get a
reasonable idea of what is down there.
Earth's rotation and tilt
What causes the seasons? Even more, can Earth's climate change
over long period just to "wobbles" in its orbit? This tutorial explains
it all. You'll know more about orbits (and precession and Milankovitch
cycles) than you ever thought possible. Have fun!
- Seasons Aren't Dictated by Closeness to Sun
- How Earth's Tilt Causes Seasons
- Are Southern Hemisphere Seasons More Severe?
- Milankovitch Cycles Precession and Obliquity
- Precession Causing Perihelion to Happen Later
- What Causes Precession and Other Orbital Changes
- Apsidal Precession (Perihelion Precession) and Milankovitch Cycles
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Life on Earth and in the Universe
When and how did life emerge on Earth? How did humanity develop a civilization? Is there other intelligent life out there?
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History of life on Earth
Earth is over 4.5 billion years old. How do we know this? When
did life first emerge?
From the dawn of Earth as a planet to the first primitive life forms to
our "modern" species, this tutorial is an epic journey of the history of
life on Earth.
Humanity on Earth
Where do we think humans come from? How and why have we developed
as a species. This tutorial attempts to give an overview of these
truly fundamental questions.
From human evolution (which is covered in more depth in the biology
playlist) to the development of agriculture, this tutorial will give you
an appreciation of where we've been (and maybe where we're going).
- Human Evolution Overview
- Understanding Calendar Notation
- Correction Calendar Notation
- Development of Agriculture and Writing
- Firestick Farming
- Collective Learning
- Thomas Malthus and Population Growth
- Land Productivity Limiting Human Population
- Energy Inputs for Tilling a Hectare of Land
- Random Predictions for 2060
Measuring age on Earth
Geologists and archaeologists will tell you how old things are or
when they happened, but how do they know? This tutorial answers this
question by covering some of the primary techniques of "dating" (not in
the romantic sense).
Life in the Universe
Are dolphins the only intelligent life in the universe? We don't
know for sure, but this tutorial gives a framework for thinking about
the problem.
- Detectable Civilizations in our Galaxy 1
- Detectable Civilizations in our Galaxy 2
- Detectable Civilizations in our Galaxy 3
- Detectable Civilizations in our Galaxy 4
- Detectable Civilizations in our Galaxy 5
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