Question: Can the brightness from the sun reach the hole universe ?

Stephen Davitt answered on 4 Nov 2016:

Very good question! So we can think of this in two ways; first the light from the sun. Light can travel great distances and as it travels at nearly 300 million meters in just one second however when we think of the whole universe there are so many planets, asteroids and other stars to get in the way I think sadly the light from the sun couldn’t reach all of the universe as it will eventually be blocked out from reaching areas.

Secondly your question specifically said the BRIGHTNESS of the sun, if we think of how bright our sun is to us, it lights up everything around us and this is daylight. The sun is actually a star (and not even the biggest or brightest of stars) so even our closest stars at night are not nearly as bright as the sun! Therefore to planets around those stars our sun wouldn’t be very bright at all either. So sadly no I don’t think the brightness from the sun can reach the whole universe.