Compare the advantages and disadvantages of a space-based satellite and the sr-71 blackbird.

Space-based satellites

Advantages:

•difficult to shoot down

•HD resolution pictures

•safe

•cost effective

Disadvantages

•hard to maintain

•unreliable at times (signal interference)

SR-71 blackbird

Advantages

•high quality imagery (can be infrared)

•demand-based usability

•high propagation delay

Disadvantages

•costly

•demand-based usability

•less safer

answer: the time zones used to be whatever the local authority wanted them to be. one town might have 6am whenever the sun came up and another town had 6am 10 minutes later.  

the trains had a hard time when their orders said to be at a certain point at 6am.  

6am, but who's 6am.  

the railroads got together and set the time zones more or less along the longitude lines across the country.

explanation: