Idea #5: Electromagnetism and Relativity

Carl Friedrich Gauss: 1777-1855 (heart attack)
a. German mathematician; determined the 1st law: the total electric flux (density of flow of electric field) around a charge is proportional to the amount of charge
b. And the 2nd law: the total magnetic flux around a magnet is zero- because magnets have two poles that cannot be isolated!

Michael Faraday: 1791-1867 (natural causes, but had dementia, perhaps due to mercury posioning)
a. English physicist; determined the 3rd law: a changing magnetic field creates an electric field. It induces a current

André-Marie Ampère: 1775-1836 (pneumonia)
a. French physicist: determined 1st part of 4th law: that an electric current produces a magnetic field
b. Maxwell added the missing piece of this law- that a changing electric field can produce a magnetic field

The third and fourth laws together explain something very important:
a. A changing electric field makes a magnetic field...
b. That magnetic field makes a new electric field...
c. That electric field makes a new magnetic field...
d. That magnetic field makes a new electric field...
e. What are we describing here?
f. LIGHT!!!

Scottish; died from stomach cancer

As Newton did for forces and motion, Maxwell took laws about electricity and magnetism discovered by others, organized them, clarified them, and added to them

Maxwell taught at Marischal College from 1856-1860; when Marischal merged with King's College to form the University of Aberdeen, Maxwell, as junior professor of physics, was "downsized"

Maxwell organized the 4 laws of electromagnetism

He figured out the missing piece of the fourth law

This opened up greater understanding of science, much like when you hit the right box in Minesweeper!

He discovered light!

More specifically, he was the first person to understand the nature of light- electromagnetic radiation

Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays are all light, and travel in the same way

Constantly interchanging magnetic and electric fields

Maxwell knew that he had discovered light because he calculated the speed of these waves, and found it to exactly match the known speed of light

German (died of abdominal aortic aneurysm rupture)

Developed the Special Theory of Relativity in 1905
a. "Special" meaning only under certain circumstances; limited to uniform motion
b. "Theory" meaning scientific theory; not opinion; a law for all intents and purposes

Based on two principles:
a. Newton's first law- that rest feels the same as uniform motion; you only feel changes in motion
b. Maxwell- the speed of light is constant (at least when it's traveling in a uniform medium)

But really, these 2 principles are incompatible with one another! Newton's laws say that relative motion adds or subtracts... and Maxwell said that light doesn't do that!

Why did the turnip kill the man?
a. Because the velocity of the moving car and velocity of the thrown turnip added together, making its overall velocity much higher! If the car was going 30 m/s and they threw the turnip at 25 m/s, then it was actually moving at 55 m/s

If they were shining a flashlight from the car would the light be moving at 299,702,547 m/s + 30 m/s = 299,702,577 m/s?

No! Light cannot go faster. The speed of light is the upper limit
a. When things speed up, time slows down. At the speed of light, time stops. If light went faster, time would go backwards, which is impossible

Because of this disagreement in ideas, Einstein had to redefine time and space and mass and velocity

There are 6 consequences of the special theory of relativity

1. Consequence 1: As you travel fast, time slows down a. The faster you move through space, the slower you move through time! b. But the traveler would never know this- you only recognize what's happening inside of your frame of reference; you don't feel the motion of your frame of reference

Consequence 2: As you travel fast, inertia increases
a. The faster you go, the harder it is to go faster!
b. At the speed of light, even an electron would have infinite mass
c. All the energy in the universe couldn't make it go the speed of light!

Consequence 3: As you travel fast, distances shrink!
a. The faster you go, the shorter the distance between two points!
b. Only the direction of motion is compressed

Consequence 4: Nothing can travel the speed of light!

Consequence 5: E = mc²
a. Energy equivalent of mass
b. The = is very important- mass is energy! Crystallized energy!
c. Because c is such a huge number, tiny amounts of matter could yield HUGE amounts of energy! A paperclip (1 gram) would yield the same energy as an atomic bomb (5000 g of plutonium)!
d. After an atomic bomb, if you could gather up all the atoms, there would only be 4999 g of matter left

Consequence 6: Relative velocity isn't calculated by simply adding or subtracting
a. v DOES NOT EQUAL v1 + v2
b. v3 = (v1 +v2)/(1+((v1)(v2))/c²⁾
c. This works for the turnip thrown from the car, and for the light from a flashlight shone from the same car