Questions mark the beginning of every space science journey. So if you've
ever wondered why, where, what, who or how — click the "Ask A Question"
button below to find out from the Athena Mission scientists. Read on
to discover what other kids have found out!
Why do things look bigger when they are in water?
This phenomenon is caused by the difference in the speed of light when it passes through different materials.
Light travels faster in air than in water (e.g. ~4/3 times faster for yellow light). When an object is immersed
in water and viewed by a person looking at it from outside in the air, the light from it (for example, reflected
sunlight) has to pass through the water-air boundary. The light bends away from an imaginary line that
perpendicular to the surface of the water (we call it "the normal" of the surface), and thus the object looks
bigger than it looks in air. Think about it from the other side; a person will look smaller than he/she is when
viewed by a fish in water! Note also that a fish in water is not quite where you think you see it, again because
of the bending of the light. People who hunt fish with spears of bows and arrows have to aim below where the
fish appears to be.
Can't you make a atmosphere clone on mars so that we could live there in the future?
I think that is possible, and it seems fascinating. Creating an Earth-like environment on another planet is
called "terraforming," and you can find out about terraforming at your library. Human beings have long dreamed
of living on other planets. Scientists have seriously discussed in detail many issues involved in building and
maintaining a space stations on the Moon and Mars. Some scientists regard Mars as a more human-friendly place
than the Moon. It has a thin atmosphere consisting mainly of CO2, and because the atmosphere can carry heat from
warmer locations to colder ones, the day-night temperature difference is much smaller (~80¡C) than on the Moon
(>250¡C). Mars has water ice on both its south and north poles, and recent images from the Mars Global Surveyor
suggest that there might be more water beneath the Mars surface. With both water and CO2, we can build a livable
world. Other scientists point out, however, that there are adequate resources on the Moon, so that people could
live there, too. Both Mars and the Moon are extremely harsh environments for humans, however, and enclosed
environments would have to be built in order for humans to live comfortably. Practical terraforming will likely
prove to be an indoor activity, for example, inside a glass dome.
Why are planets formed round?
Most scientists believe that planets are formed hot, so hot they are somewhat plastic. By "plastic," we mean it
can be easily deformed. Thus, gravity makes them round. This is because the center of gravity becomes the center
of the planet, and the gravitational force is sufficient to bring every part of the planet as close to the
center as possible. The more dense the material in a planet, the closer to the center it goes. This is why the
Earth's dense, metallic core is at the center, and the least dense types of rock like granite are at the
surface. Most of Earth's core is still liquid. Earth's mantle, which makes up most of the Earth and lies
outside the core is not molten, but it is very hot and so it is still somewhat plastic. Note that many
asteroids are not round in shape. That is because they are not plastic and their gravity fields are too small
to force them into spherical shapes. You can easily observe the effect of Earth's gravity on a plastic
material. Silly putty is a plastic material that you can readily form into any shape you like. Make a ball of
silly putty. Put it in a container and leave it alone for a long time. You will see the ball flatten out and
conform to the shape of the container. That is the effect of Earth's gravity on the plastic material, the same
effect that made Earth round.
