更多"Galaxies are the major’ building bl"的相关试题:
[单项选择]Galaxies are the major’ building blocks Of the universe: A galaxy is giant family of many millions of stars, and it is held together by its own gravitational field. Most of the material universe is organized into galaxies of stars together with gas and dust.
There are three main types of galaxy: spiral, elliptical, and irregular. The Milky Way is a spiral galaxy, a flattish disc of stars with two spiral arms emerging from its central nucleus. About one-quarter of all galaxies have this shape. Spiral galaxies are well supplied with the interstellar gas in which new stars form: as the rotating spiral pattern sweeps around the galaxy it compresses gas and dust, triggering the formation of bright young stars. The elliptical galaxies have a symmetrical elliptical or spheroidal shape with no obvious structure. Most of their member stars are very old and since ellipticals are devoid of interstellar gas, no new stars are forming in them. The biggest and brightest galaxies in the universe
A. The Milky Way.
B. Major categories of galaxies.
C. How elliptical galaxies are formed.
D. Differences between irregular and spiral galaxies.
[单项选择]Atoms, the basic building blocks of matter, are made of three basic components: protons, neutrons and electrons. The protons and neutrons cluster together to form the nucleus, the central part of the atom, and the electrons orbit about the nucleus. Protons and electrons both carry an electrical charge(电荷). The charges they carry are opposite to each other; protons carry a positive electrical charge while electrons carry a negative electrical charge. Neutrons carry no charge at all.
Electricity is the movement of charged particles, usually electrons, from one place to another. Materials that electricity can move through easily are called conductors. Most metals, such as iron, copper and aluminum, are good conductors of electricity. Other materials, such as rubber, wood and glass, block the flow of electricity. Materials which prevent the flow of electricity are called insulators (绝缘体). Electrical cords are usually made with both conductors and insulators. Electricity flows throug
A. The charges of protons equal the charges of electrons.
B. The charges of neutrons equal the sum of the charges of electrons and protons.
C. The charges of protons equal the sum of the charges of electrons and neutrons.
D. The charges of electrons equal the sum of the charges of protons and neutrons.
[单项选择]Passage OneA. About equal numbers of galaxies are moving toward and away from us.
B. Almost all galaxies are moving away from us.
C. A small handful of galaxies are getting close to us.
D. The close a galaxy is the faster it is moving towards us.
[填空题]The earliest known galaxies in the universe, which formed during the universe’s "dark age" nearly 13 billion years ago, have been spied by two teams of astronomers.
The discoveries, reported separately in this week’s issue of the journal Nature. suggest that galaxies were forming just 700 million years after the birth of the universe.
Theory holds that the universe formed 13.7 billion years ago when an extremely dense concentration of mass rapidly expended in an event known as the big bang.
The universe has been expanding ever since, so astronomers are able to age galaxies by computing how much. the wavelength of their light has stretched—or redshifted—as the expansion takes the galaxies farther from Earth. The redder the light is, the older and more distant the galaxy is.
The detection of such ancient galaxies adds intrigue (神秘色彩) to theories of how the very first galaxies formed, according to astronomers.
Were there many large, young galaxies in the
