How come light can travel through space for millions of years but cannot penetrate > 100 yds under the sea?

Answer 1

because space is a vaccum. meaning there is little or no matter (or air if you prefer) in space. light will continue until it meets a nebula, another star, planet, moon, astroid, dust cloud or other types of matter. (or even a strong gravitational pull)

water consists of practically nothing but hydrogen and oxygen. which is matter. Lots of it.
water is even reflective (wink wink). so light bounces (scatters) off each atom or molecule to the next, then it does it again and again. eventually the light looses clarity as it is dispersed. thats why water kinda glows when you shine a light into it.


btw. light is not slowed by matter (at least to where we can't notice it). it is dispersed. meaning its reflected, yet not evenly thusly the light is less focused and less intense. - each time it hits matter

only a Bose-Einstein condensate can slow down light. we still can't stop it yet
http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate

duh......... who ever voted against me must not believe in or understand physics. maybe I should ask you what 2+2 is and when you answer 4 I'll vote against you too. its 2+2 = 2x2

Answer 2

Some light energy gets refracted back to the surface of the water and whats left gets dissapated into heat. That is why water temperature is much colder as you get deeper. Space is a vaccum and thus offers no resistance to light energy.

Answer 3

In space, there isn't anything blocking or diluting the beams of light. Water molecules, as you get deeper, are more tightly compacted due to the weight of the water at that depth (which is why the pressure increases as you go deeper). The light has to penetrate denser and denser layers of water and at some point, the water molecules are so tight together it begins to block the beams of light.

Light in space is only passing through minimum density gasses at most in space. Since space acts like a vacuum, nothing exists to impede the beams of light.

Answer 4

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Answer 5

Because the sea aborbs the light energy. Light only travels through space until it hits something to absorb or reflect it.

Answer 6

Space is a vacuum, there is nothing impeding light. Through it passes through the void easily enough, it is still blocked by gas and dust.

We can't see to the other side of our own galaxy or even to the edge of the galactic plane no matter what direction we look because there is just too much gas and dust in the way.

Answer 7

The same reason it can't penetrate through 1 mm of steel. In space, there is nothing for light to interact with. Light, like all electromagnetic radiation, interacts with matter.

Answer 8

well due to the fact that the index refraction of water is higher then air, whose index of refraction is higher then space, light can not penatrate any further then 100yds under the sea. Plus the light has alredy traveled millions of mile. This is the reason behind this phenominoum.

Answer 9

Of all the answers, the one explanation rendered by Josh M is the nearest to the correct. It is well-known that all forms of energy, like heat, light and electricity are 'stopped' or resisted by objects of denser mass, and so, it is true that light is resisted by water too.

Answer 10

Light is slowed by matter. In addition, there are particles in the sea just like in our atmosphere which aid in slowing and stopping altogether lights' ability to penetrate.