The speed of light is , but it still takes time for light to get to its destination. this is not usually a noticeable effect over short distances here on the earth, but as objects get farther away, the "lag time" for information becomes more . we see objects not as , but rather we see them as . for farther objects, this "lookback time" becomes . since extremely distant objects will also look incredibly to us, we need very large telescopes, which can gather and focus enough light to observe such objects.

Amethod of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.