A Sense of Time and Scale
in the Universe
Our modern perception of the Universe has been drastically reshaped from the
corresponding perception of only a few hundred years ago.
Changing Perceptions of the Universe
of the Universe with respect to it size, temporal duration, the
kinds of events that take place in it, and the kinds of objects that it
contains has undergone serious revision in the last few centuries:
Thus, the Universe of the modern astronomer would be largely unrecognizable to
her counterpart from a few centuries ago. We can only speculate whether
our present understanding of the Universe will appear as quaint 400 years from
now as the views from 400 years ago appear to us.
- Only in the last 400
years or so have we realized that the earth is not the "center", and that the
Universe is immense.
- The Sun would hold
1.3 million Earths.
- There are
200 billion "Suns" in a galaxy like our own Milky Way Galaxy.
- Astronomers can see
billions of galaxies.
- We don't know whether the Universe has an "end" or not; we are not
completely sure even of the full meaning of the question.
- Only in the last 50 years have we realized that the Universe is not static.
- The entire Universe is
- Events of
fantastic violence take place in the Universe.
- In the last half-century we have come to
believe that the Universe contains objects that are truly bizarre
as measured in human terms.
- Neutron Stars and
- Black Holes
- Only in the last 200 years have we begun to appreciate the age of the
- The Universe is probably 10-20 billion years old.
- Our Solar System is probably 4-5 billion years old.
A Sense of Scale
If the solar system were the size of a table, the Andromedae Galaxy would lie
at 10 times the distance to the moon and the most distant galaxies would lie at
60 times the distance to the Sun.
A Sense of Time
If we were to compress the time since the Big Bang into one year, and make the
time of the Big Bang January 1,
Thus, all of human history is but a fleeting instant on the cosmic timescale.
- The Earth was formed in mid-September.
- The mammals appeared on December 26.
- All human prehistory (from the first known stone tools) and history have
occurred in the last 1/2 hour of New Year's Eve.