1. How do I do this assignment?

Make sure you view the main tutorial at :
http://www.anselm.edu/homepage/dbanach/spacetime1.htm

All of the results of space time diagrams depend on the speed of light being drawn at a constant 45 degrees. The main problem is insuring this 45 degree angle.

There are at least 3 ways:

1. Use a graph paper and draw the beams of light as diagonals (or parallel to diagonals). Make sure the boxes on your graph paper are square and not rectangular.

2. Use MS Draw (The Draw tool in Microsoft Word) Holding the SHIFT button down while you draw a line will click the line into standard angles and make it easy to draw 45 degree angles.

3. Use Euklid and use the grid or the angle and parallel functions to make your 45 degree angles.
See Tutorial here:
http://www.anselm.edu/homepage/dbanach/spacetime-euklid.htm



2. How do I find the point that is simultaneous with some event?

To find the event on a line that is simultaneous to some other event not on the line, it is necessary to send out a light signal to the event and wait for it to come back. (In reality, since you wouldn't know when the event was going to happen, you would have to be sending out signals continuously waiting for one to come back.) You would know the time the signal left on the line and the time it came back. The middle point between the send time and the receive time would be judged as the time when the event happened.

http://www.anselm.edu/homepage/dbanach/st3.jpg


3. How do I make 45 degree angles in Euklid?

The easiest way is to make the grid visible. (measure menu-Co-ordinate system-click on the visible and the mark grid points boxes). Then make a line segment from the point to your line and drag the endpoint until it is parallel with the diagonals of the grid.


You can also use the parallel line function. Once you have a guide beam of light (which you can make using the angle function (enter -45 degrees) you can draw a parallel line through the point using the parallel function (click the point, then the guide line). Once you have the beam of light to the point, you can use the perpendicular function to get the return beam. (Again, click the point and then the line.)

4. What are the Diagrams for?

The answers to some of the questions are at:
http://www.anselm.edu/homepage/dbanach/st.htm

You cannot cut and paste these, but they are a guide to what your answers should look like. You must draw your own diagrams and answer the questions in your own words.

5. I don't get it. What do these things mean?

There are tutorials on the basic concepts and on using Euklid here:
http://dbanach.com/course/mod/forum/discuss.php?d=119

You should make sure you do the assigned readings. Look here for some help understanding space time diagrams:
http://www.astro.ucla.edu/~wright/relatvty.htm
and
http://www.phy.syr.edu/courses/modules/LIGHTCONE/index.html

More resources can be found on our website:
http://www.anselm.edu/homepage/dbanach/ph31c.htm#qm

6. What is a simultaneity slice?
A simultaneity slice is a line (or plane in 3D) connecting all the points that are simultaneous to a given event for an observer. Once you find two points that are simultaneous for an observer in a space time diagram, you can simply connect them with a line. All of the events on that line happened at the same time for that observer; it is a simultaneity slice or moment in time for that observer. (You will note that all simultaneity slices for stationary observers are horizontal.)