Date Vocabulary Word: Announcements:

Space Travel, Time Machines, and Einstein

PA Standards S8.A.1.3.1 Use ratio to describe change (e.g., percents, parts per million, grams per cubic centimeter, mechanical advantage). S8.A.2.2.1 Describe the appropriate use of instruments and scales to accurately and safely measure time, mass, distance, volume, or temperature under a variety of conditions. S8.A.2.2.2 Apply appropriate measurement systems (e.g., time, mass, distance, volume, temperature) to record and interpret observations under varying conditions.

PA Standards S8.A.2.2.3 Describe ways technology (e.g., microscope, telescope, micrometer, hydraulics, barometer) extends and enhances human abilities for specific purposes. S8.C.3.1.1 Describe forces acting on objects (e.g., friction, gravity, balanced versus unbalanced). S8.D.3.1.3 Compare and contrast characteristics of celestial bodies found in the solar system (e.g., moons, asteroids, comets, meteors, inner and outer

Albert Einstein 1879-1955 Born in Germany. Was visiting the US in 1933 when Hitler took power and so never returned to Germany (He was Jewish). Einstein is regarded as one of the most brilliant people ever to live. Though he was incredibly smart, it was his imagination and creativity that allowed him to develop the ideas he did.

Einstein’s Theory of Relativity Einstein said that the laws of motion work at all speeds. He also predicted that light always moves at it’s own speed. If you were running along side a beam of light, as you approached the speed of light (300,000 Km/s) you would say that light sped away from you as fast as you’d expect. However a person watching you run would say that you caught up to the speed of light!

Relativity Continued… “Relativity” then means that space (distance) and time are relative to your motion or frame of reference. Time and distance are not absolute (as they would seem to us to be). The faster you travel relative to the speed of light, the shorter your unit of length becomes and the slower your measurement of time becomes. This is called time dilation and it means the faster you travel, the slower time passes.

Proof of Relativity Three very accurate atomic clocks were compared in 1971. One clock was on the ground in Washington DC. One clock was on a plane flying west and one clock was on a plane flying east. When the clocks were compared, the airborne clocks were a teensy bit behind the clock on the ground showing that the faster you move, the slower time passes (to the observer, not to you!)

The Twin Paradox Einstein said imagine a set of 25 year old twins. One twin stays on earth, the other twin goes on a mission in outer space where he travels at 90% the speed of light. When the astronaut twin returns after 20 years in space he returns (now 45 years old) and is shocked to find that his twin is now 71! Since the astronaut twin was moving very fast, time passed more slowly.

One More Thing Einstein also showed that as an object moved faster, it’s mass increased. This meant that the energy of motion was somehow being transformed into the increasing mass of the object. Thus matter and energy are interchangeable. You can calculate how much energy is converted to mass with the equation…

Distances in Space Light Year: A measure of distance and not time. The distance light travels in a vacuum in one Earth Year. This amounts to just under 10 trillion Km! The nearest star with a potentially habitable planet is Alpha Centauri, a mere 4.36 light years away!

Space-Time Continuum Space exists in 3 dimensions. Einstein’s theories predict that time adds a 4th dimension. Space and time are woven together in this “fabric” called spacetime. Objects of mass cause spacetime to curve (the more massive the greater the curve or dimple. Theoretically (remember, Einstein had a great imagination) this fabric can be folded or warped.

Hyper Drives Based on science fiction. An engine on a spacecraft that warps or rumples the space/time fabric to shorten distances in space. Space is curved so instead of traveling that entire curve, you can travel through hyperspace, in a straight line, to your destination.

Time Travel (To the Future) Remember Einstein said time passes more slowly the faster you move (relative to someone else), so in a way that in itself is time travel. The problem is moving that fast.

Time Travel (To the Past) It is not theoretically impossible since we move forward in time all the time and forward and back in space as well. Stephen Hawking points out that time travelling to the past is not possible. Why? Because if we could, we’d have time tourists coming to tell us about it! Most physicists feel it’s unlikely. However…

Wormholes A machine using energy greater than the sun *could* open a path in space time to a point in the past relative to the time the machine were used. You could go back no further than when the machine was invented. Thus physicist Stephen Hawking says a time machine could be built but hasn’t yet since we haven’t had any visitors…yet.

Recap 1. What does Einstein’s Theory of Relativity basically say? 2. What does E=mc2 mean? 3. What is the trick to travelling to the future?