A Quote by Isaac Newton

Gravity explains the motions of the planets, but it cannot explain who sets the planets in motion.

Isaac Newton

Quote Topics

Cannot Explain Explains Gravity Motion Motions Planets Sets

Quote Author

Isaac Newton
English - Mathematician
December 25, 1642 - March 20, 1727

Just as the system of the sun, planets and comets is put in motion by the forces of gravity, and its parts persist in their motions, so the smaller systems of bodies also seem to be set in motion by other forces and their particles to be variously moved in relation to each other and, especially, by the electric force.

Isaac Newton

We're just learning that a lot of planets are small planets, and we didn't know that before, fact is, in planetary science, objects such as Pluto and the other dwarf planets in the Kuiper Belt are considered planets and called planets in everyday discourse in scientific meetings.

Alan Stern

But what exceeds all wonders, I have discovered four new planets and observed their proper and particular motions, different among themselves and from the motions of all the other stars; and these new planets move about another very large star [Jupiter] like Venus and Mercury, and perchance the other known planets, move about the Sun. As soon as this tract, which I shall send to all the philosophers and mathematicians as an announcement, is finished, I shall send a copy to the Most Serene Grand Duke, together with an excellent spyglass, so that he can verify all these truths.

Galileo Galilei

The motions of the comets are exceedingly regular, and they observe the same laws as the motions of the planets, but they differ from the motions of vortices in every particular and are often contrary to them.

Isaac Newton

Gravity may put the planets into motion, but without the divine Power, it could never put them into such a circulating motion as they have about the Sun; and therefore, for this as well as other reasons, I am compelled to ascribe the frame of this System to an intelligent Agent.

Isaac Newton

A major puzzle for which nobody has an answer is this: is there some size at which the planets change their nature from water-rich planets like Neptune, to rocky planets like the Earth? We have found two planets that are the size of the Earth in radius, but they are very close to their host star, so water on the surface would evaporate away.

Geoffrey Marcy

A 'serious' scientist in 1992 or 1993 had to admit the possibility that planets were really rare, that most stars might not have planets. We've gone from there to here - where most stars have planets.

Debra Fischer

Planets are the big bullies of the planetary system that are, that basically ignore everybody else around them. And everybody else has to deal with the planets. Those are what the planets are.

Mike Brown

Ocean planets might be very common in the universe because water is very common in the low-temperature environments where planets form and evolve. This might be especially true for super-Earths, which can retain volatiles more easily thanks to their larger mass and surface gravity.

Dimitar Sasselov

There's no doubt that the search for planets is motivated by the search for life. Humans are interested in whether or not life evolves on other planets. We'd especially like to find communicating, technological life, and we look around our own solar system, and we see that of all the planets, there's only one that's inhabited.

Debra Fischer

Before 1995, the only planets we knew about were the planets in our solar system.

Debra Fischer

When I grew up as a kid, we didn't know there were any other planets outside of our own solar system. It was widely speculated that planet formation was an incredibly rare event and that it's possible that other planets just don't exist in our galaxy, and it's just this special situation where we happen to have planets around our sun.

John M. Grunsfeld

Our sun enlightens the planets that belong to him; why may not every fixed star also have planets to which they give light?

Bernard le Bovier de Fontenelle

Earlier generations of stars in the galaxy could well have had planets. But really, there was only hydrogen and helium to work with, so they'd all be gas giants and not small, rocky planets.

Jill Tarter

The planets and moons of our solar system are blatantly visible because they reflect sunlight. Without the nearby Sun, these planets would be cryptic and dark on the sky.