Albert Einstein

• Born in 1879 died in 1955• Father of Modern Physics• Relativity – describes the very large• Quantum mechanics – describes the very

small• Newtonian physics works for “normal”

speeds• Changed how we view space• Proved the existence of the atom

Einstein Quote

• “When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity.”

Special Relativity

• Speed of light is constant, no matter how fast you move! In any reference frame the speed of light is constant.

• For this postulate to be true time must get slower the faster you move. Time is relative.

• Called ~ Time dilation

Practice Problem

• Consider two twins 25 years old. One twin steps on a space ship (after studying physics in college) and travels through space at 0.95 c for 4 years according to her. How old is each twin after 4 years?

• 37.8 years old for Twin on Earth

• 29 years old for Twin on space ship

Length Contraction

• Lengths contract as you approach the speed of light as viewed by an outside observer.

• The contraction of speeding objects is the contraction of space itself.

• Space only contracts in one direction – the direction of motion. (so if moving horizontally, there is no contraction vertically)

Practice Problem

• A rocket ship is 100 meters long on the ground. When it is in flight its length is 99 meters to an observer on the ground. What is its speed (as a fraction of the speed of light)?

• 0.14C

• 4.2 X107m/s

• 94,000,000 mi/hr

Special Relativity Mass & Energy

• E=mc2 c = 3 x 108 m/s• Even at rest, an object has energy, which is

locked in its mass.• As an object moves faster, its mass increases.• As an object approaches the speed of light, itsmass approaches infinity• Because masses approach infinity with

increasing speed, it is impossible to accelerate a material object to (or past) the speed of light. To do so would require an infinite force.

General Relativity

• Newton said that gravity was instantaneous.

• Why would Einstein disagree with this?

General Relativity

• Anything that has mass warps space

• Planets move around the sun not because of a gravitational pull but because the sun has warped the space around it, and space itself pushes the planets.

The Consequences of General Relativity

• Big Bang Theory.

• Expanding universe.

• Prediction of black holes

• Worm holes

Other Contributions from Einstein

• Light has a dual nature – it exists as a wave and a particle. This quantum theory of light has lead to modern electronics including TV, lasers and fiber optics.

• Solid justification to the existence of atoms.

Einstein Quotes

“The release of atom power has changed everything except our way of thinking. The solution to this problem lies in the heart of mankind. If only I had known, I should have become a watch maker” Albert Einstein