Question

it has been more than 80 years since the astronomer edwin hubble discovered that the universe is expanding. he was able to determine that fact by observing the speed and direction that galaxies are moving. nearly all galaxies are moving away from our galaxy, and the more distant galaxies are moving away faster. that means that all of the galaxies in the universe (or at least the material from which they were formed) were all together around 14 billion years ago, and they have been moving apart ever since. that is a scientific fact. but the question of what is expanding is part of the big bang theory. according to this theory, what, exactly, is expanding?
circle the answer that best matches your interpretation of the big bang theory.
a. matter is expanding into a huge empty void.
b. space is expanding or stretching, so the distance between galaxies is growing.
c. space and matter are expanding, so galaxies are getting bigger and moving apart.
explain your thinking. describe what you know about the big bang theory to support your answer.

Explanation:

For the multiple - choice part:

The Big Bang theory states that the universe began as a singularity and has been expanding ever since. It is not that matter is expanding into pre - existing empty space (so A is wrong), and galaxies themselves are not expanding in size as part of the Big Bang's expansion mechanism (so C is wrong). The expansion is of space itself, which causes the distance between galaxies to increase. Galaxies are like "markers" in the fabric of space, and as space stretches, the distance between these markers (galaxies) grows.

Answer:

B. Space is expanding or stretching, so the distance between galaxies is growing.

For the explanation part: