1. Different Views on the World? Arecibo - a giant radio observatory. It can point only straight up,
but it's the largest dish in the world, so can detect sensitive
signals. Old technology, brute force, and works well.
Keck - the premier optical (& infrared) telescopes in the world.
Although they don't have the resolution of Hubble, their mirrors are
much bigger and they can gather more light (25x) in a shorter time.
Since they're on the ground, they're cheaper -- you could build
25 Kecks for the price of one Hubble.
Galileo - not a large telescope (only a few inches across), but it's
the only one which can get near Jupiter to look at it. It can look
from different angles than we can from Earth, can look close up, and
can also directly measure quantities like the magnetic field.
2. Evidence of our Civilization Over a period of 10,000 years, there will probably be many remains
from human civilization. Buildings, roads, airports, rusted Chevys,
oil tankers, cemetaries - you name it. Erosion from wind, air, and water
will be the major processes -- in addition to chemical breakdown, such as
rusting of metals (until they dissolve completely). Evidence like
paper will probably be gone quickly. We know that a lot of these
buildings, roads, etc. will stick around for 10,000 years, because we
see them preserved from previous cultures already: Pompeii (2000 years
ago), ancient Greece (2500 years ago), and so forth.
Over a 10 million year period, we might have a harder time. The
Earth resurfaces by plate tectonics over about 200 million years, so
the evidence will still be on the surface -- but erosion will have
taken a dramatic toll on most of it. Structures such as buildings and
roads will be long gone -- except for the ones that are buried beneath
sand, water, or mud, just like dinosaur bones are today. Some evidence
for radioactive materials may still be around, since these metals
usually differentiate and fall toward the center of the Earth, and
don't usually concentrate themselves on the surface. In the geologic
record, there may also be evidence of changes in carbon dioxide levels
or global pollution -- seen as a thin layer put down in the rocks on
the surface and the ocean.
3. What is life?
Some characteristics of life on Earth:
If a robot fits enough of these definitions, it might be considered
life. But some people might impose another criterion: that it's not
`artificially made' by humans.
The difference between plants and animals? Perhaps arbitrary or
not, depending on your own definition.
Last modified 6-Jul-2000
The largest telescope in the world is the Arecibo Radio Observatory in
Puerto Rico, 1000 feet across (one of the ones Jodi Foster used). The
largest optical telescope (using visible light) are the 10-meter Keck
telescopes in Hawaii. The largest telescope in space is the 2.4-meter
Hubble Space Telescope. The highest resolution images of the Jovian
satellites, however, are from the Galileo spacecraft. Explain how
these four telescopes are different, and how they are the same.
Discussion Question 1, Ch. 13 in the text (p. 397)
Write your own definition of life, in several sentences. Is there a
difference in your definition between plants and animals - or other
kingdoms? Should there be? Would a self-replicating robot (a robot,
which is built to build another robot from scratch, which builds
another one, each of them getting better and better) fit your
definition of life? Should it?
Dr. Henry Throop, University of Colorado / throop@broccoli.colorado.edu