At the bottom of this entry, I give the Weekly Pondering 7 assignment, for those of you in ASTR 1/2.  Any text that you need to read is on Blackboard or linked to here.

7: Personally Exploring the Universe?

I’ve previously mentioned that, with our current technology, it would take many thousands of years to reach even the closest stars. For instance, the closest star system to Earth is Alpha Centauri, which is 4.37 light years away. How far is this? One light year is the distance that light travels in space, in a straight line, during one (Earth) year. Since the year consists of 365.25 days × 24 hours/day x 60 minutes/hour × 60 seconds/minute = 31,600,000 seconds, light travels 31,600,000 seconds × 300,000,000 meters/second = 9.5 × 1015 meters during one year. The number 1015  is 106  × 109, which is a million times a billion. Thus, one light year is about 9.5 million billion meters. Suppose that we wish to travel one light year at 40,000 miles per hour, noting that this is slightly faster than the fastest human craft. This corresponds to about 18,000 meters per second. How long will it take to travel one light year? The number of seconds it would take would be 9.5 million billion divided by 18,000, which is about 528 billion seconds, or almost 17,000 years. It would thus take us at least about 70,000 years to get to the closest star system. 

It would seem that the challenges we must overcome are overwhelming. However, there are some ideas that might work—at least, insofar as sending tiny craft to the stars. A solar sail is a sail that is designed to absorb the momentum of light. By using lasers, we might be able to send craft to nearby stars within a human lifetime. Such craft will have to be very low-mass and will not be able to carry humans, but they might still be able to send data back to Earth. Watch the two linked videos. The second is an interview with Dr. Jim Gates, who is a theoretical physicist best-known for his work on String Theory; please watch this from the beginning to 13:55. The first is about a potential future solar sail mission. Do a little research on the Viking 1 and 2 spacecrafts to determine when they were launched and when they landed on Mars. Now, do the same for the Perseverance rover. Is there a marked difference between these two travel times? It’s important to note that these missions are separated by about 45 years. In a paragraph or two, write your answers to these questions. Also, briefly research and comment on the IKAROS mission.