The closer they `zoom in" on an object the fainter it appears, and so they need to collect as much of the radio emissions from the object they are studying as possible. 
The concept of Merlin depends on astronomers being able to measure the minute differences in arrival time at the different telescopes of the signals from distant stars and galaxies. 
As the radiowave washes over the telescopes, they can compare its intensity and phase and can add and subtract the amplitudes of the wave to <tag "515647">derive</> more information than would be obtainable by one telescope alone.   

