Ask Ethan: How Do We Know The Universe Is 13.8 Billion Years Old?

A Glowing Pool Of Light

"NGC 3132 is a striking example of a planetary nebula. This expanding cloud of gas, surrounding a dying star, is known to amateur astronomers in the southern hemisphere as the "Eight-Burst" or the "Southern Ring" Nebula.

The name “planetary nebula” refers only to the round shape that many of these objects show when examined through a small visual telescope. In reality, these nebulae have little or nothing to do with planets, but are instead huge shells of gas ejected by stars as they near the ends of their lifetimes. NGC 3132 is nearly half a light year in diameter, and at a distance of about 2000 light years is one of the nearer known planetary nebulae. The gases are expanding away from the central star at a speed of 9 miles per second.

This image, captured by NASA’s Hubble Space Telescope, clearly shows two stars near the center of the nebula, a bright white one, and an adjacent, fainter companion to its upper right. (A third, unrelated star lies near the edge of the nebula.) The faint partner is actually the star that has ejected the nebula. This star is now smaller than our own Sun, but extremely hot. The flood of ultraviolet radiation from its surface makes the surrounding gases glow through fluorescence. The brighter star is in an earlier stage of stellar evolution, but in the future it will probably eject its own planetary nebula”

Credit: The Hubble Heritage Team

In engineering we talk a lot about tools. Some people have a favorite collection of software, some a metaphorical belt filled with tips, tricks, and techniques, and others a literal box or lab bench filled with instruments. In my experience, a good engineer not only maintains all three, but seeks...

I believe in free education, one that’s available to everyone; no matter their race, gender, age, wealth, etc… This masterpost was created for every knowledge hungry individual out there. I hope it will serve you well. Enjoy!

FREE ONLINE COURSES (here are listed websites that provide huge variety of courses)

Alison 

Coursera

FutureLearn

open2study

Khan Academy

edX

P2P U

Academic Earth

iversity

Stanford Online

MIT Open Courseware

Open Yale Courses

BBC Learning

OpenLearn

Carnegie Mellon University OLI

University of Reddit

Saylor

IDEAS, INSPIRATION & NEWS (websites which deliver educational content meant to entertain you and stimulate your brain)

TED

FORA

Big Think 

99u

BBC Future

Seriously Amazing

How Stuff Works

Discovery News

National Geographic

Science News

Popular Science

IFLScience

YouTube Edu

NewScientist

DIY & HOW-TO’S (Don’t know how to do that? Want to learn how to do it yourself? Here are some great websites.)

wikiHow

Wonder How To

instructables

eHow

Howcast

MAKE

Do it yourself

FREE TEXTBOOKS & E-BOOKS

OpenStax CNX

Open Textbooks

Bookboon

Textbook Revolution

E-books Directory

FullBooks

Books Should Be Free

Classic Reader

Read Print

Project Gutenberg

AudioBooks For Free

LibriVox

Poem Hunter

Bartleby

MIT Classics

Many Books

Open Textbooks BCcampus

Open Textbook Library

WikiBooks

SCIENTIFIC ARTICLES & JOURNALS

Directory of Open Access Journals

Scitable

PLOS

Wiley Open Access

Springer Open

Oxford Open

Elsevier Open Access

ArXiv

Open Access Library

LEARN:

1. LANGUAGES

Duolingo

BBC Languages

Learn A Language

101languages

Memrise

Livemocha

Foreign Services Institute

My Languages

Surface Languages

Lingualia

OmniGlot

OpenCulture’s Language links

2. COMPUTER SCIENCE & PROGRAMMING

Codecademy

Programmr

GA Dash

CodeHS

w3schools

Code Avengers

Codelearn

The Code Player

Code School

Code.org

Programming Motherf*?$%#

Bento

Bucky’s room

WiBit

Learn Code the Hard Way

Mozilla Developer Network

Microsoft Virtual Academy

3. YOGA & MEDITATION

Learning Yoga

Learn Meditation

Yome

Free Meditation

Online Meditation

Do Yoga With Me

Yoga Learning Center

4. PHOTOGRAPHY & FILMMAKING

Exposure Guide

The Bastards Book of Photography

Cambridge in Color

Best Photo Lessons

Photography Course

Production Now

nyvs

Learn About Film

Film School Online

5. DRAWING & PAINTING

Enliighten

Ctrl+Paint

ArtGraphica

Google Cultural Institute

Drawspace

DragoArt

WetCanvas

6. INSTRUMENTS & MUSIC THEORY

Music Theory

Teoria

Music Theory Videos

Furmanczyk Academy of Music

Dave Conservatoire

Petrucci Music Library

Justin Guitar

Guitar Lessons

Piano Lessons

Zebra Keys

Play Bass Now

7. OTHER UNCATEGORIZED SKILLS

Investopedia

The Chess Website

Chesscademy

Chess.com

Spreeder

ReadSpeeder

First Aid for Free

First Aid Web

NHS Choices

Wolfram Demonstrations Project

Please feel free to add more learning focused websites. 

*There are a lot more learning websites out there, but I picked the ones that are, as far as I’m aware, completely free and in my opinion the best/ most useful.

Quantum Tunneling 

Quantum tunneling refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. This plays an essential role in several physical phenomena, such as the nuclear fusion that occurs in main sequence stars like the Sun. It has important applications to modern devices such as the tunnel diode, quantum computing, and the scanning tunneling microscope. The effect was predicted in the early 20th century and its acceptance as a general physical phenomenon came mid-century.

Tunneling is often explained using the Heisenberg uncertainty principle and the wave–particle duality of matter. Pure quantum mechanical concepts are central to the phenomenon, so quantum tunneling is one of the novel implications of quantum mechanics.

source

Windswept by Charles Sowers

Though we cannot physically hold wind or see its swirling forms around us, we can definitely feel it.

In order to help visualize wind-currents, artist Charles Sowers created a kinetic installation consisting of 612 aluminum weather vanes called “Windswept” (2011). These were then meticulously placed on the side of the Randall Museum in San Francisco. Through this installation, we are able to see the patterns in the wind; where the currents go, how they turn, and sometimes how wind can abruptly change direction. This gives us a visual representation of the natural, invisible, force which moves around us, and sometimes with enough force, pushes and pulls us.

As the artist states: “Our ordinary experience of wind is as a solitary sample point of a very large invisible phenomenon. Windswept is a kind of large sensor array that samples the wind at its point of interaction with the Randall Museum building and reveals the complexity and structure of that interaction.”

This sort of installation creates a better understanding, and appreciation, of the wind. It is not just one large gust; a single wave can be made up of smaller currents, going in their own directions from the main flow. A dialogue begins to form between the building and the wind, the weather vanes acting as translators.

-Anna Paluch

In the garden. Värmland, Sweden (October 23, 2015).

HIV virus particle, budding influenza virus and HIV in blood serum as illustrated by David S. Goodsell. 

Goodsell is a professor at the Scripps Research Institute and is widely known for his scientific illustrations of life at a molecular scale. The illustrations are usually based on electron microscopy images and available protein structure data, which makes them more or less accurate. Each month a new illustrated protein structure can be found in Protein Data Bank molecule of the month section and you can read more on how his art is made here.

Theories about the Origins of Space and Time. 1. Gravity as Thermodynamics Entropic gravity is a theory in modern physics that describes gravity as an entropic force - not a fundamental interaction mediated by a quantum field theory and a gauge particle, but a consequence of physical systems’ tendency to increase their entropy.  2. Loop Quantum Gravity According to Einstein, gravity is not a force – it is a property of space-time itself. Loop quantum gravity is an attempt to develop a quantum theory of gravity based directly on Einstein’s geometrical formulation. The main output of the theory is a physical picture of space where space is granular. More precisely, space can be viewed as an extremely fine fabric or network “woven” of finite loops. These networks of loops are called spin networks. The evolution of a spin network over time is called a spin foam. The predicted size of this structure is the Planck length, which is approximately 10−35 meters. According to the theory, there is no meaning to distance at scales smaller than the Planck scale. Therefore, LQG predicts that not just matter, but space itself, has an atomic structure. 3. Causal Sets Its founding principles are that spacetime is fundamentally discrete and that spacetime events are related by a partial order. The theory postulates that the building blocks of space-time are simple mathematical points that are connected by links, with each link pointing from past to future. Such a link is a bare-bones representation of causality, meaning that an earlier point can affect a later one, but not vice versa. The resulting network is like a growing tree that gradually builds up into space-time. 4. Causal Dynamical Triangulations The idea is to approximate the unknown fundamental constituents with tiny chunks of ordinary space-time caught up in a roiling sea of quantum fluctuations, and to follow how these chunks spontaneously glue themselves together into larger structures. The space-time building blocks were simple hyper-pyramids (four-dimensional counterparts to three-dimensional tetrahedrons) and the simulation’s gluing rules allowed them to combine freely. The result was a series of bizarre ‘universes’ that had far too many dimensions (or too few), and that folded back on themselves or broke into pieces. 5. Holography In this model, the three-dimensional interior of the universe contains strings and black holes governed only by gravity, whereas its two-dimensional boundary contains elementary particles and fields that obey ordinary quantum laws without gravity. Hypothetical residents of the three-dimensional space would never see this boundary, because it would be infinitely far away. But that does not affect the mathematics: anything happening in the three-dimensional universe can be described equally well by equations in the two-dimensional boundary, and vice versa.

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