Can you tell me what are comets & when will they hit
earth?
NUPUR, AGE 14, MUMBAI
Answer: Comets are objects that orbit the Sun
much further away than Pluto. Because they are so far away there is barely
any heat or light reaching them from the Sun. As a result, they freeze
up.
Sometimes the objects crash into each other sending one
of them in toward the Sun and toward the planets. As they get closer to
the Sun, the Sun heats the ice and causes it to melt which then forms
the amazing tail you see in pictures.
Unfortunately I do not know when one will hit the Earth.
We are looking out for them but we are lucky to have the big planet Jupiter
in the Solar System.
Jupiter is so big that it attracts many of the comets
that head are way. It works like a cosmic vacuum cleaner.
Venus in transit across the sun |
Do other planets experience eclipses as we do here
on Earth? If so, do the planets eclipse each other?
ALEXANDREA WAGNER
Answer: Other planets do experience eclipses although
they are not as spectacular as the solar eclipses we have here on Earth.
Any planet that has a moon will experience a solar eclipse
as the moon blocks sunlight from reaching the planet and a lunar eclipse
as the planet blocks sunlight from reaching the moon.
We do see planets eclipsing the Sun, even from Earth.
Over the last 10 years there have been two events called transits where
Mercury and Venus have passed between the Earth and Sun.
The picture shows Venus passing in front of the disk
of the Sun in 2004. Venus is the tiny black disk.
On Earth there are living things. Do any of the other
planets have grass/water and all those kind of stuff that support life?
ROHAN SOLANKI, AGE 10, NEW ZEALAND
Answer: We have found water ice on the Moon, Mars
and on comets but we have not found it as a liquid, such as rivers or
seas anyway other than Earth.
Some patterns on Mars make us believe that water has
been running across the surface millions of years ago but not any more.
Can you explain how the earth experiences different
seasons?
NIKKI, AGE 12, AUSTRALIA
Planet Earth |
Answer: As you know, the Earth spins once everyday,
that gives us day and night. The axis that the Earth spins on is tilted
over at an angle so it鈥檚 not quite spinning upright.
When the Southern hemisphere has its summer then the
Southern hemisphere is pointing toward the Sun.
At the same time, the Northern hemisphere is pointing
away from the Sun and so has winter. The opposite is the case six months
later.
Why is it difficult to leave the Earth?
DARA OBAKIN, AGE 12, SURREY
Answer: It's difficult to leave the Earth because
gravity keeps us pressed against the surface. To escape from the gravity
of Earth, we must fly rockets at 11km per second, otherwise they will
fall back to the Earth.
Can you push a 10 ton block of metal in space? Since
there's no gravity in space you should shouldn't you?
RYAN, AGE 12, CANADA
Answer: You could easily push a 10 ton block of
metal in space because neither gravity nor friction will try to stop you.
However because there is no friction or gravity, however
hard you push the block of metal, you will go back by the roughly the
same amount.
If we fell through our solar system when and how would
we land?
ELLA, AGE 9, FOREST HILL, LONDON
Answer: We only fall on the Earth because something
called gravity pulls us down to the surface. The Sun and all the other
planets in the Solar System have their own gravity but space doesn't have
gravity.
You would not fall through the solar system. If you flew
through it in a rocket you would just go straight through into deep space.
How hot is the sun?
RUTH, AGE 12, DUNEDIN, NEW ZEALAND
Answer: The Sun is just
like all the other stars in the sky, it's a big ball of gas. The temperature
at the visible surface of the Sun is about 6,000 degrees but is much hotter
in the centre at 15 million degrees.
Black Hole |
How do we know black holes are there if light can't
escape it?
AILISH, AGE 8, GLASGOW
Answer: You are right that
black holes are black and impossible to see, but we can see what they
do on the area around them. For example we can see material glowing brightly
as it is being sucked into the black hole.
Are there any other planets in our solar system past
Pluto? I keep getting contradictory results when I try to search for information
on this.
ALEC, AGE 11 FROM MILWAUKEE, WI
Answer: The reason you
are getting contradictory results is that there is no real difference
between a planet and an asteroid.
Planets tend to be bigger than asteroids but there is
no official definition. Even Pluto is sometimes called an asteroid rather
than a planet.
But in answer to your question, there are two other objects
beyond Pluto; Sedna and Quaoar which have been suggested are planets.
Both are quite small, certainly smaller than Pluto but until there is
an official definition some astronomers will come them planets and others
will call them asteroids.
Who was the first person to discover how far the Earth
is away from the Sun and how did they do it?
JASON, AGE 18 FROM NORMAN, OK
Answer: The two key people
who together enabled us to understood how we could measure the distance
to the Sun were Edmund Halley (of comet fame) and Johannes Kepler.
Halley realised that if we found accurately, the distance
to Venus during one of its passes in front of the Sun that we could use
that information along with Keplers laws of planetary motion to calculate
the Sun's distance from the Earth.
This essentially relied on no more than fairly simple
trigonometry. Observations of the events were made in following years
by a number of different astronomers and the value was fine tuned as the
years progressed.
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