Headphones, refrigerator magnets, and compasses
Hope that was helpful.
Answer:
- The separation will be spacelike.
- The first event can't cause the second event, as there exist an frame of reference in which both happens at the same time, in different positions, so, if there were causally connected, it will imply an instant connection, this is faster than light.
Explanation:
We can define the separation between two events (using the + - - - signature) as :

where the separation will be lightlike if is equal to zero, timelike if is positive and spacelike if is negative.
For our problem








So the separation will be spacelike, and the first event can't cause the second event, as there exist an frame of reference in which both happens at the same time, in different positions, so, if there were causally connected, it will imply an instant connection, this is faster than light.
Answer:
Elements are made up of only one type of atom. Each element has a unique chemical symbol. Elements can be identified by their atomic number.
I think the correct answer from the choices listed above is option D. Scientists would use a control sample that has no dna from bighead carp in edna surveillance in order to to verify that no dna has contaminated the gel. It would eliminate certain errors in the experiment.