Quotes About Astronomy

Comets develop their distinctive tails when their surface material begins to evaporate as they approach the Sun.

If we were randomly inserted into the universe," Sagan wrote, "the chances that you would be on or near a planet would be less than one in a billion trillion trillion.

Glance at the night sky and what you see is history and lots of it—not the stars as they are now but as they were when their light left them.

In just 200 million years, possibly less, the Earth was essentially formed, though still molten and subject to constant bombardment from all the debris that remained floating about. At

lunar material, it is thought, came from the Earth's crust, not its core, which is why the Moon has so little iron while we have a lot.

The transit of Venus of 1769 finally allowed us to determine the distance from the Earth to the Sun: 149.59 million kilometres. A

galaxies of the universe are racing away from us, but that they are doing so at a rate that is accelerating.

we can't see even into the Oort cloud, so we don't actually know that it is there. Its existence is probable but entirely hypothetical.1 About

Pluto is about 40 AUs from us, the heart of the Oort cloud about fifty thousand. In a word, it is remote. But

The most remarkable part of all is your DNA. You have a metre of it packed into every cell, and so many cells that if you formed all the DNA in your body into a single fine strand it would stretch ten billion miles, to beyond Pluto.8 Think of it: there is enough of you to leave the solar system. You are in the most literal sense cosmic.

The Earth at last had a position in space.

Most star systems in the cosmos are binary (double-starred), which makes our solitary sun a slight oddity.

The current best estimate for the Earth's weight is 5.9725 billion trillion tonnes

All over the inchoate solar system, the same was happening. Colliding dust grains formed larger and larger clumps. Eventually the clumps grew large enough to be called planetesimals.

a diagram of the solar system to scale, with Earth reduced to about the diameter of a pea, Jupiter would be over a thousand feet away and Pluto would be a mile and a half distant (and about the size of a bacterium, so you wouldn't be able to see it anyway).

transits of Venus, as they are known, are an irregular occurrence. They come in pairs eight years apart, but then are absent for a century or more

that if you looked deep enough into space you should find some cosmic background radiation left over from the Big Bang.

On a diagram of the solar system to scale, with Earth reduced to about the diameter of a pea, Jupiter would be over a thousand feet away and Pluto would be a mile and a half distant (and about the size of a bacterium, so you wouldn't be able to see it anyway).

Only about 6,000 stars are visible to the naked eye from Earth, and only about 2,000 can be seen from any one spot. With binoculars the number of stars you can see from a single location rises to about 50,000, and with a small two-inch telescope it leaps to 300,000.

McDonald Observatory in Texas

The core of a neutron star is so dense that a single spoonful of matter from it would weigh 200 billion pounds.

Vesto Slipher, of the Lowell Observatory in Arizona, was the first person to notice that distant galaxies appeared to be moving away from us—evidence that the universe was not, as everyone had long assumed, static.

Astronomers today believe there are perhaps 140 billion galaxies in the visible universe.

The red shift gives the speed at which galaxies are retiring, but doesn't tell us how far away they are to begin with.