Stellar distances are measured in

Fill in the blanks: Steller distances are measured in __________.

All the distances are measured from the ………….. Of the lens.

In case of spherical mirrors, all distances are measured from………. .

In spherical lenses, all distance are measured from ___________.

State units of larger distances measured in astrononers.

Why could you not use an elastic measuring tape to measure distance ? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape ?