Suppose there is a planet in our solar system that moves with respect to the sun with the same speed and direction as the earth, only it is exactly on the other side, would we have discovered it already?
And also: how can something (space) expand at an accelerated rate, if it is already infinitely large?
Answer
Hi Paul,
The chance that an undiscovered planet will be found has become a lot smaller a few years ago. Then the definition of ‘planet’ was changed to such an extent that Pluto is no longer even considered a planet. There are probably still undiscovered celestial bodies in our solar system that are larger than Pluto, but they probably won’t be able to claim the title of planet. Those celestial bodies are very far from the sun, and they don’t have a stable, wiped-clean disk in which they have formed their orbit as the only object. And for that reason they could not be called a planet.
The chance that a planet at exactly the same distance, with exactly the same weight, orbits the sun at exactly the opposite location from the earth, is very small. In fact, thanks to accurate measurements of other celestial bodies and thanks to spacecraft, we can even study that part of our solar system.
And as for your last question: space is not infinite! It would be a growing, but finite number of cubic kilometers. Just like the surface of a balloon you inflate is a finite number of cubic centimeters.
Regards,
Ward
Answered by
Dr. ir. Ward Blondé
Physics Bioinformatics
http://www.ugent.be
.