Astrophysics for People in a Hurry (Astrophysics for People in a Hurry Series)

by Neil deGrasse Tyson

The Speed of Light: It’s Not Just a Good Idea It’s the Law.

Another class of universal truths is the conservation laws, where the amount of some measured quantity remains unchanged no matter what. The three most important are the conservation of mass and energy, the conservation of linear and angular momentum, and the conservation of electric charge.

And if you insert low mass and low speeds into Einstein’s equations they literally (or, rather, mathematically) become Newton’s equations—all good reasons to develop confidence in our understanding of all we claim to understand.

The power and beauty of physical laws is that they apply everywhere, whether or not you choose to believe in them.

after the laws of physics, everything else is opinion.

Our senses detect infrared only in the form of warmth on our skin. The LED revolution in advanced lighting technology creates pure visible light without wasting wattage on invisible parts of the spectrum.

Ordinary matter is what we are all made of. It has gravity and interacts with light. Dark matter is a mysterious substance that has gravity but does not interact with light in any known way. Dark energy is a mysterious pressure in the vacuum of space that acts in the opposite direction of gravity, forcing the universe to expand faster than it otherwise would.