162 Chapter 3 The Universe Was Born With a Big Bang
Hubble’s Theory of the Expansion of the Universe Was
Although Hubble discovered that the universe is expanding, it seems highly likely that he
would have encountered fierce opposition from people around him, especially from his fel-
low researchers in the astronomical community. In fact, many accounts say that Hubble very
prudently kept his ideas to himself.
The value that determines the expansion velocity of the universe is called Hubbles
constant, and it is represented by H
. Hubble obtained a value of 500 km/sec/Mpc for this
velocity; this is approximately seven times the currently accepted value (74 km/sec/Mpc).
But if Hubble’s value is used to calculate how long ago the birth of the universe (that is, the
Big Bang) occurred, it would indicate that the universe began 2 billion years ago, at most.
Since scientists have found the age of Earth to be approximately 4.6 billion years (based on
observations of rocks and fossils), then if we use Hubbles initial value, the universe would
be younger than Earth, which it clearly cannot be.
Even Hubble himself did not obtain the correct value for Hubbles constant. It would
take a very long time for the theory of the expansion of the universe to be widely accepted.
Hubbles experiments indicated that the entire universe was only 2 billion years old...
but that didn’t make sense, as scientists had estimated that Earth itself was 4.6 billion years old!
Hule’s Theory of the Expansion of the Universe Was Imperfect 163
Now—13.7 biion years
after the big bang
Aroximately 9 biion
years after the Big Bang
Formation of the solar system and
Uncertain period
Formation of galaxies, clusters
of galaxies, superclusters of
galaxies, and the Great Wall
Aroximately 1 biion years
after the Big Bang
Formation of the Milky Way galaxy
Aroximately 200 miion years
after the Big Bang
Stars and galaxies appear, and light begins to
shine in space.
Aroximately 380,000 years
after the Big Bang
Electrons that had been flying about join
with nuclei to form atoms. As a result, space,
which had previously been opaque like a
cloud, clears up, and visibility gets better.
Aroximately 3 minutes after the Big Bang
Elementary particles (the basis of all matter) come into existence,
and the universe continues to grow so that protons and neutrons
form nuclei.
From 10
to 10
seconds after the Big Bang
The universe continues to expand and cool, and quarks (which
make up protons and neutrons) are formed.
From 10
to 10
after the Big Bang
The universe cools and expands dramatically,
and the energy created through inflation causes
the creation of particles of matter and antimatter.
From the Big Bang until 10
seconds after it
This is called the Planck epoch, a state in which time cannot be defined.
Some scholars believe that everything, including gravity and time, was
in a state of flux.
The Big Bang
Chronology of the Universe
Space is born
Look at the following chronology, which shows how
the universe evolved from the Big Bang to its current
164 Chapter 3 The Universe Was Born With a Big Bang
So there was a history of the universe even before the
Big Bang?
This part is still not perfectly understood. A particularly mysterious interval
is the time from when the universe was born until it was 10
of a second
old, which is called the Planck epoch. Since nothing at all existed to measure
time or gravity, no physics has been created yet for describing what occurred
and how the universe evolved during this period. Therefore, nothing can be
said other than that the universe was born and took a certain form by the
time 10
seconds had elapsed.
So there is even something that the Professor doesn’t
understand very well!
You seem so happy to
hear that!
There are a great many things I don’t understand. In terms of the balloon
we talked about earlier, the birth of the universe corresponds to the time
when the rubber that the balloon is made from was formed. However,
there are various hypotheses about why that rubber suddenly expanded.
That period of expansion is called inflation, right?

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