Physics 1010

Elementary Physics

General Education Requirement

Physical Sciences (PS)

Semester

Fall 2018

Signature Assignment

Part 1: Star Identification

Star 1: Vega

  1. Name: Vega (Alpha Lyrae)
  2. Distance: 25 Light Years
  3. The light from this star now reaching earth would’ve left in approximately 1993.
  4. Size: 2.3x the Sun
  5. Luminosity: 40x the Sun

Star 2: Sheliak

  1. Name: Sheliak (Beta Lyrae Aa1)
  2. Distance: 960 Light Years
  3. The light from this star now reaching earth would’ve left in approximately 1058.
  4. Size: 6x the Sun
  5. Luminosity: 26,300x the Sun

Star 3: Sulafat

  1. Name: Sulafat (Gamma Lyrae)
  2. Distance: 620 Light Years
  3. The light from this star now reaching earth would’ve left in approximately 1398.
  4. Size: 15.4x the Sun
  5. Luminosity: 2,430x the Sun

Star 4: Delta-2 Lyrae

  1. Name: Delta-2 Lyrae
  2. Distance: 899 Light Years
  3. The light from this star now reaching earth would’ve left in approximately 1121.
  4. Size: 286x the Sun
  5. Luminosity: 12,900x the Sun

Part 2: Equation Analysis

Equation 1: E=mc2

  1. E = energy (variable), m = mass (variable), c2 = the speed of light squared (constant).
  2. c, the speed of light, is 299,792,458 meters per second. Therefore, c2 = 8.986 x 1,016 m2/s2.
  3. Yes, mass and energy are related, and based on the way the equation is written, they are interchangeable. Using mass at the speed of light, it is possible to calculate the speed of light, and from energy, one can calculate mass. Given the proper inertia conditions, it is possible to convert the forms from one to another.
  4. Yes, a little bit of mass can produce a lot of energy. In the equation E=mc2, energy is calculated by multiplying mass by the speed of light squared, a high number. The speed of light squared can produce a large amount of energy from a small mass.

Equation 2: E=-mc2

  1. Einstein’s equation doesn’t allow for a negative mass. However, if the equation is viewed as a formula which can be manipulated mathematically, then negative mass is a possibility. Some physicist believe negative mass does exist, in the form of dark matter.
  2. Yes, c could be negative, because both positive and negative signs can be used to designate c’s direction. However, there are physicists that believe c cannot have a negative value, as a scalar constant it must be positive.
  3. No, because c2 and -c2 are both positive numbers.
  4. Yes, but only if m is given a negative value.

Equation 3: E=±mc2

  1. There are mixed opinions within physics on whether or not energy can be negative. With negative mass, negative energy (or dark energy) is possible. But with normal mass, energy is always positive.
  2. Energy is a scalar, and can act in any direction.
  3. No, because negative energy can also act in any direction.
  4. Yes, because the negative sign can just be a theoretical convenience that has no correlation with the physical world.
  5. Einstein’s equation is intended to represent reality, but is not reality itself. Therefore, in using the equation to dark energy, the negative sign has meaning for those who believe it exists.

Part 3: Learning about a Law of Physics

1. An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction, unless acted upon by an external unbalanced force. This is Newton’s first law of motion, also referred to as the law of inertia. The greater the object’s mass, the more it resists a change in velocity, or the more inertia it has.

2a. When the driver steps hard on the brake pedal, the car’s occupants feel themselves thrust forward. When the driver steps hard on the accelerator, the car’s occupants feel themselves thrust backward. If a car stops suddenly in a crash, and the occupant isn’t wearing a seatbelt, their continued forward motion may be enough to send them through the windshield.

2b. A skateboard hits a curb, which causes it to abruptly stop. The skateboarder’s continued forward motion causes him to fly forward and land in front of the board.

2c. After a fan is switched off, the blades continue to spin. They are slowed by external forces of friction in the motor and air resistance, and eventually come to a stop.

Part 4: The Fermi Paradox

1. Given the billions of stars in our galaxy, and the high probability some of these stars have Earth-like planets, the possibility of intelligent life having evolved somewhere other than Earth is high. Yet, we have not discovered any evidence that such intelligent life exists. This is the basis for the Fermi Paradox, named after physicist Enrico Fermi.

2a. Intelligent extraterrestrial life may not yet have developed the technology necessary to communicate with Earth over a long distance. A more primitive civilization may exist somewhere in the galaxy, but it won’t be transmitting radio signals we can detect, and it won’t be easily visible from space. Such a civilization is nearly impossible to detect using our current methods.

2b. Intelligent extraterrestrial life may transmit signals that are too weak or in the wrong frequency to detect. For us to receive a signal from an extraterrestrial civilization, it must be strong enough for us to detect and in a detectable frequency. It is often assumed that an intelligent civilization would be purposefully sending out detectable radio signals at long-range frequencies, but it’s just as likely that this isn’t the case, or that they are using methods of communication we can’t detect.

2c. Intelligent extraterrestrial life may have destroyed itself, or been destroyed by a natural event. One possibility is that intelligent life was often made extinct before or shortly after it developed the technology necessary to communicate with Earth, through a natural event such as a meteor impact. Another is that after intelligent civilizations developed technology sufficient to communicate with Earth, they also developed the technology sufficient to destroy themselves in a war or conflict, and hence they were gone long before we ever started listening.

Reflection

In the process of searching for answers to the various parts of the signature assignment project, I came to several realizations. One is the disagreement in the physics community over issues I thought were settled, such as Einstein’s equation E=mc2. Another is the need for speculation and debate to explain issues we have yet to observe an answer to, such as the Fermi Paradox.

Part 1, Star Identification, involved researching and labeling four stars within the constellation Lyra. Researching the stars was fairly straight-forward, though finding the required information was particularly difficult for the fourth star I researched, Delta-2 Lyrae, with the Wikipedia entry offering conflicting information from two different sources.

Interestingly, although the stars all appear as part of the same constellation from Earth, they are actually separated by vast distances, hundreds of light years. The star that appears brightest, Vega, is simply the closest to Earth; the other stars I researched are actually much brighter, but also much farther away, and hence they appear dimmer. All four stars are many times brighter than the Sun.

Part 2, Equation Analysis, was by far the hardest portion of the project. Researching Einstein’s equation E=mc2, I found many disagreements among those in the physics community over its meaning. For example, is the nature of mass energy or matter; is there negative as well as positive mass?

Some physicists believe in negative mass and negative energy. Negative energy provides an explanation for the continued expansion of the universe, as it counteracts positive attracting forces. However, Einstein never accounted for the existence of negative mass or energy in his equation, and the equation has held up well both mathematically and experimentally.

For part 3, Learning about a Law of Physics, I chose Newton’s first law of motion, also referred to as the law of inertia, because it is a law that has many practical and real-world consequences. Safety systems such as seat belts are designed with the sole purpose of providing a resisting force to counteract inertia.

I found part 4, The Fermi Paradox, to be the most interesting part of the project. Due to the large number of stars and planets in our galaxy, science fiction writers have envisioned many intelligent civilizations much like our own existing and evolving throughout the galaxy. Star Trek alone has depicted dozens. The problem is, we have yet to detect any evidence that other civilizations actually exist elsewhere in the galaxy.

Researching the Fermi Paradox, I found plenty of speculation concerning the lack of evidence. The most plausible reason to me involves the limitations of our current detection methods. An intelligent civilization would have to broadcast a signal in a specific range of frequencies and in the direction of Earth for us to detect it. Depending on the distance, the signal may also take hundreds of years to reach Earth, much longer than we’ve been listening.

In conclusion, though some parts of this project were more challenging or intersting than others, researching them ultimately strengthened my understanding of the importance of speculation, mathematical calculation, observation, analysis, and debate in physics.