Albert Einstein's Theory of General Relativity By: Ethan Brzana, David Gomez, and Thi Hong Dang Trinh

Historical Background ▪ Was developed by renowned physicist Albert Einstein. ▪ Einstein used the work of scientists and mathematicians before him, including Isaac Newton’s three laws of Motion to develop his theory. ▪ E=MC^2 is the formula commonly associated with Einstein’s theory of relativity. ▪ Theory of Special Relativity Published in 1905 in a paper titled, “On the Electrodynamics of Moving Bodies”. ▪ Theory of General Relativity Published in ▪ Very broad theory that affects all aspects of physics. ▪ Theory asserts time and space are relative to position.

Predominant Thinking Before Einstein’s Theory of Relativity ▪ Galileo was the first person to study the concept of relativity. ▪ Isaac Newton studied gravity while developing his famous three laws of motion. However, Newton did not realize that gravity and time were related. ▪ Before Einstein, it was thought that time was constant and was not influenced by gravity. ▪ This misconception originated from the fact that time is constant on earth because objects on the earth do not travel fast enough to cause a noticeable change in time.

Predominant thinking before the discovery continuation ▪ Before Einstein introduced his Theory of Relativity, Newton's Three Laws of motion were the predominant thinking. The Three Laws of Motion follow: 1. An object at rest, or in uniform straight line motion, will remain at rest, or in uniform straight line motion, unless acted upon by a net external force. 2. A net force acting on a body produces on that body, an acceleration that is directly related to the force impressed upon the body and inversely related to the mass of the body. 3. For every action there is an equal but opposite reaction. ▪ In the following slides we describe how the above thinking was changed into what we know about our Universe today

What is the theory of relativity? ▪ Albert Einstein’s theory of Relativity explains the theory of space time. What exactly is space time? ▪ Space time is the idea that space and time are related. What this means is that events can occur at different times depending on a person's location or point of reference. ▪ For example, if a person drops an object from the top of a building the trajectory of the object will be different for someone standing directly above the object and for a person watching from a distance. ▪ Therefore, although two people observe two different motion paths relative to their individual position they are both correct.

Theory of Relativity Continuation ▪ In 1915, Einstein determined that "massive objects cause a distortion in space-time, which is felt as gravity" (Taylor, Space.com). ▪ Imagine setting a large body in the center of a trampoline. The result is that smaller bodies will be pulled toward the larger body "in much the same way that the gravity of a planet pulls at rocks in space" (Taylor, Space.com).

How does Space-Time Work? ▪ In his theory of Relativity, Einstein treats space and time as one single entity: space-time. ▪ To Einstein, space and time are no longer absolute, but only relative. ▪ Relativity states that "the faster you go through space, the slower you progress through time" (ScienceTV). ▪ In the next slide there is a graphical representation of this concept.

Graphical demonstration of space-time ▪ From the graph it can be seen that the faster you go through space, the slower you go through time. ▪ Theoretically, what this means is that traveling at the speed of light (highest speed possible) in the space direction produces no change in time (just as it is the case with a beam of light). ▪ These results are a caused by two unusual effects of relativity which greatly depend on velocity: time dilation and length contraction. ▪ However, "at every day speeds [time dilation and length contraction] are simply not noticeable" (ScienceTV). Space Time

How the Discovery Impacted Society ▪ Regarded as one of the most important scientific discoveries of all time, Einstein’s theory of Relativity radically changed how scientists and ordinary people understand the world and the universe. ▪ Newton's theories remained unquestioned until the beginning of the twentieth century. However, Einstein's Theory of Relativity showed that Newton's theories were "only approximately correct" (Albert Einstein and the Theory of Relativity) in the following ways: - Newton's Three Laws of Motion break down when velocities approach that of light, as we explained graphically in the example of space-time. - Newton's Theory of Gravitation breaks down in the presence of very strong gravitational fields, as we explained in the trampoline example.

How the Discovery Impacted Society Continuation ▪ The biggest impact Einstein's discovery had on society was that space and time were no longer thought of as absolute, but relative. ▪ However, Einstein's famous equation, E = mc 2, also played a pivotal role in the development of the atomic bomb. ▪ In the following slides, we show a specific example of how the Theory of Relativity plays an extremely important role in the accurate functioning of a GPS.

Applications of The Theory of Relativity ▪ There are many practical applications for the theory of relativity in science. ▪ Useful when working with situations where an object is moving at the speed of light (176,000 miles per second). ▪ One of the most common and well-known applications is its use in global positioning systems (GPS).

How Does GPS Work? ▪ To understand how the two things relate one must first understand how a GPS works. ▪ A GPS can "pinpoint your location, anywhere on Earth, to within a few yards" (ScienceTV). ▪ A GPS works by connecting to a series of twenty-nine earth orbiting satellites. ▪ To pinpoint the location of an entity the GPS sends signals to at least four of the twenty- nine satellites that are directly overhead of the user of the GPS.

Video: How Does a GPS Work? ▪ Posted below is a link to a YouTube video of how a GPS works in order to further clarify the concept. ▪ Essentially, a GPS works by applying relativity and triangulation to determine one's position. ▪

How Does GPS Relate to Relativity ▪ In a previous slide the theory of space-time was explained. ▪ The concept of space-time is extremely important to a GPS because time is slower in space relative to the time on Earth. ▪ Therefore, the difference in times must be taken into account when transmitting the time at a specific position to the user of a GPS on Earth. ▪ Without taking relativity into account the time transmitted to a GPS would be flawed. In fact, without Einstein's theory "the accuracy of the GPS would drift more than seven miles every day" (ScienceTV).

Works Cited ▪ "10 Discoveries Relativity Made Possible." Discovery Channel. N.p., n.d. Web. 27 Feb ▪ Albert Einstein and the Theory of Relativity. Web. March 2, ▪ " Einstein's Theory of Relativity." About.com Physics. N.p., n.d. Web. 01 Mar ▪ "Einstein's Theory of General Relativity." Space.com. N.p., n.d. Web. 27 Feb ▪ "How GPS Receivers Work." HowStuffWorks. N.p., n.d. Web. 28 Feb ▪ “How Does GPS Work (2005). YouTube. N.p. Web. 1 Mar ScienceTVV. Einstein's Theory of Relativit Made Easy y July 28. 5, Web. March Science TV V. Space-Time And The Speed Of Light I Einstein's Relativityy August 5. 8, Web. March < ▪ Taylor R, Nola. Einstein's Theory of General Relativity. Space.com, September 18, Web. March 1, "The Theory of Relativitye."Curious About Astronomy? N.p., n.d. Web. 01 Marb