The speed of light is the highest know speed in the Universe (aproximatly 300.000 km/sec.). It's the speed that light travels, radio waves and electrical waves. Only massless objects can reach this speed like photons (the particles that make up light). Even if we wanted we cuoldn't reach that speed. The maximum we could get would be 99.99999999999999% of the speed of light.
That makes us think: is the speed of light the highest speed of all? In th truth, no. Dark energy and dark matter expand the Universe at faster speeds than light, so, each year we can't see more and more of our Universe and the observable universe will het each time smaller and smaller.
A light-year is the distance that the light covers in one year, Scientists use this unit to count bigger distances like between stars and galaxies.
