if light travels thru space ,why does space appear black?

Answer 1

There is nothing in space to reflect the light. The gases in our atmosphere reflect light and that is what you see, not the light itself.

Answer 2

There are two things to think about here. Let's take the easy one first and ask "why is the daytime sky blue here on Earth?" That is a question we can answer. The daytime sky is blue because light from the nearby Sun hits molecules in the Earth's atmosphere and scatters off in all directions. The blue color of the sky is a result of this scattering process. At night, when that part of Earth is facing away from the Sun, space looks black because there is no nearby bright source of light, like the Sun, to be scattered. If you were on the Moon, which has no atmosphere, the sky would be black both night and day. You can see this in photographs taken during the Apollo Moon landings.

So, now on to the harder part - if the Universe is full of stars, why doesn't the light from all of them add up to make the whole sky bright all the time? It turns out that if the Universe was infinitely large and infinitely old, then we would expect the night sky to be bright from the light of all those stars. Every direction you looked in space you would be looking at a star. Yet we know from experience that space is black! This paradox is known as Olbers' Paradox. It is a paradox because of the apparent contradiction between our expectation that the night sky be bright and our experience that it is black.

Many different explanations have been put forward to resolve Olbers' Paradox. The best solution at present is that the Universe is not infinitely old; it is somewhere around 15 billion years old. That means we can only see objects as far away as the distance light can travel in 15 billion years. The light from stars farther away than that has not yet had time to reach us and so can't contribute to making the sky bright.

Another reason that the sky may not be bright with the visible light of all the stars is because when a source of light is moving away from you, the wavelength of that light is made longer (which for light means more red.) This means that the light from stars that are moving away from us will become shifted towards red, and may shift so far that it is no longer visible at all. (Note: You hear the same effect when an ambulance passes you, and the pitch of the siren gets lower as the ambulance travels away from you; this effect is called the Doppler Effect).

Answer 3

You can't see light. Think about it, if there was a laser beam travelling across your line of vision now you could only see it if it reflected off something.

We (the guys in the PhD office) were discussing this earlier, why space appears black if there are an infinite number of stars and in every direction you look there will, eventually, be a star. We decided that it is due to the contrast in intensity of light. Closer stars appear brighter because the light from them enters our eyes with a greater solid angle than further stars, so obviously they appear brighter. It is due to this contrast that space appears black, there are billions of stars but their brightness falls off as 1/r^2, so the further they are the lower the solid angle (and it too drops off quickly).

Daanzig, this is the explanation for the Olbers' paradox. The stars are visible with a telescope (like the Hubble) and that proves that the light DOES reach us from everywhere, but the contrast is such that it is undetectable to our eyes.

Answer 4

Let's go with the terms in which the question was posed for now, rather than quibble about them. I am sure you can imagine being in the middle of "nothing" but still feeling a force pulling on you. For example, you could be in space and be pulled towards a planet by its gravity. Also, I am sure you are familiar with the idea of waves. Water waves travel across the surface of a pond as the surface level at each point in their journey are move up and down in combination. The surface at each point is "too high" - higher than an equilibrium level - and falls, and this falling takes it beyond the equilibrium level to the point where it is too low, so it moves back - continuing back and forth a little less each time as it loses energy. There are different kinds of "pull" - of force. Gravity is an obvious one. Magnets are another. Electrical fields are another - in fact the description of how magnetic and electric fields work is combined into something called "electromagnetism". Light is an electromagnetic wave. The strength of the electric and magnetic "pull" at a point in space that the wave passes through oscillates about an equilibrium just like the water wave oscillates about an equilibrium. If you were to put something that responds to that kind of pull, like an electrically charged object such as an electron, it would actuallt vibrate as it is pulled one way then the other. This is how the aerial of your radio gets the signal that it can amplify and produce from its speakers as sound - electromagentic waves moving the electrons in the metal to create currents...

Answer 5

Light must enter our eyes before we can 'see' anything. This usually happens by reflection like the light of the Sun being reflected off of the Moon. Space appears 'black' because it does not reflect any light.

Answer 6

Because space is so massive no amount of light cam illuminate the entire galaxy, its amazing I, so facinated with all this. Did you know depending on where a star is out there that, if the star exploded or destroyed we will still see that star in the sky for about 8 years. due to the time it would take for that image and the speed of light to hit us.

Answer 7

Black is the absence of light. Space is not uniformly illuminated and light is also absorbed/diffracted. Thus, at night, blackness surrounds light sources in space.

Answer 8

because light isn't visible unless it hits something (since it space and there is pretty much nothing around earth then we arent seeing light travel, but we can see it land on the light side of the moon)

Answer 9

If light comes directly at you then space wont appear black.

Answer 10

Theres no light there. You see the light coming from the stars in the form of dots in the sky, but you can't see actual light rays.