What keeps the stars suspended in space?
All the stars that we see with our eyes are in our Galaxy. In fact, in a small part of the Galaxy. All the stars, including our own, are in orbit around the centre of the Galaxy. As far as these local neighbours are concerned, the ‘bottom’ is the Galactic centre (25,000 light-years away); our orbital speed — 230 km/s — is what keeps us in orbit around the centre (it is what keeps us from falling to the “bottom’ of our Galaxy). For us on Earth (and the few astronauts around Earth), the ‘bottom’ is Earth’s centre. The astronauts are not falling because they have enough speed to stay in orbit. We do not fall because the ground stops us. For all objects in the Solar system, the ‘bottom’ is the Sun (it has over 98% of the mass of the solar system). Our speed around the Sun (29.8 km/s) is what keeps us from falling. Our Sun travels at 230 km/s on its orbit around the centre of the Galaxy. In the Local Group, the ‘bottom’ is somewhere at the centre of the group, about halfway between oursel
