Titlebook: Invisible Matter and the Fate of the Universe; Barry Parker Book 1989 Springer Science+Business Media New York 1989 astronomy.physics.univ

freight

Black Holes,We have seen that black holes are a serious candidate for the dark matter. But I have said little about what they are. In this chapter we will look at their properties, and consider them as candidates.

镶嵌细工

Fate of the Closed Universe,f years. If, on the other hand, it is three or four times as great as the critical density it will stop expanding in about 30 billion years. Let’s assume for simplicity that it is twice the critical density; in this case the turnabout will occur in about 50 billion years.

Inexorable

率直

The Missing Mass Mystery Unfolds,ee the dimmer of the two stars, but we know it’s there when we look at the spectral lines of the system: because of the Doppler effect they move back and forth as the two stars revolve around one another. From the period of revolution of the stars we can obtain a relation between the mass of the stars and their brightness (luminosity).

秘方药

Fate of the Open Universe,rse accurately. And this, in turn, depends on how much dark matter there is. Is there, in fact, enough dark matter to close it (stop its expansion)? As we have just seen, we’re still not certain, but we do know that it is close, and because of this I will discuss both the open and closed universes. This chapter will consider the open universe.

荒唐

Introduction,ars were like tiny diamonds—some solitary, others in pairs and threes. Some were blue, others faintly red. I remember thinking as I looked at them that any one of them could have a planet orbiting it, perhaps with a civilization on it. I tried to imagine what they would be like.

合唱团

GRUEL

Magnetic Monopoles and Other Exotic Particles,with what is called the magnetic monopole. There has been a tremendous amount of interest in it the last few years, not only because it would be a good candidate for dark matter, but also because scientists have predicted that it should exist, and so far—despite extensive searches—it hasn’t been found.

Pageant

A Consensus: To Be or Not To Be, the dark matter is. True, we have a number of candidates, but each of them presents problems. Furthermore, we don’t know how the dark matter is distributed—whether it is uniform throughout the universe, or in clumps.

flex336