charges repel each other.

What would the difference of spectral lines emitted by hydrogen gas in distant galaxies which is normally found at a wavelength of 21 cm on earth, be observed at 21.1 centimeters?

Abox is sliding on a frictionless surface when it suddenly begins to rain heavily. if the downpour of rainfall falls vertically into the box

There are 3 ways heat can be transferred: through solids, called , through liquids and gases , called , and through electromagnetic waves, called