In the vastness of space, if supernovas and other explosions happen often, why can't we simply look up and see them?

Question

Elena Antonova · Accepted Answer

Yes, explosions happen and emit tremendous amounts of energy but there are many reasons we can't see it.

Yes, novas, supernovas, and other similar phenomena occur frequently in the immense expanse of space. So why are most of them invisible to us? People cannot see most electromagnetic waves (we cannot see the microwaves from the microwave oven, the infrared from the convection oven, the x-rays from the dentist, or the gamma waves from the Sun). And most of the energy released from those explosions is not visible light wave. One reason for this is that the visible light spectrum within the total electromagnetic spectrum is extremely tiny. Another reason is the distance involved. Think of this - an explosion will happen in a sphere (it'll explode in a 3-dimensional spherical way). As the energy moves through space, the amount of energy in each unit of space decreases exponentially. The equation for the surface of a sphere is #A=4pir^2#, so as the energy moves one unit towards us, the energy is #1/4# as dense. Now take that over vast amount of distances and see that the energy will dissipate quickly. Another reason is that there is a lot of material between Earth and the explosion site; far from being empty, space is full of objects that can both bend light (both towards and away from us) and block light (such as gas clouds and massive gravitational fields, such as galaxies, stars, etc.).

Owen Atkinson · Answer

undefined Although supernovas and other explosions happen often in the universe, telescopes and other astronomical instruments are used to detect and study these phenomena. Supernovas and other explosions are often obscured by factors like distance, interstellar dust, and the vastness of space. In addition, many supernovas occur in distant galaxies, making them difficult to observe with the naked eye from Earth.