ISS in orbit

    Caption: "Backdropped by Earth, the horizon, and the blackness of space, the International Space Station (ISS, mission length 1998--, mean vertical altitude 418.5 km) is featured in this image photographed by an STS-130 crew member on the space shuttle Endeavour after the ISS and the space shuttle began their post-undocking relative separation. Undocking of the two spacecraft occurred at 7:54 pm EST on 2010 Feb19." (Slightly edited.)

    The stars are NOT seen because they are too dim for the contrast range of the image.

    Re orbits: In low-Earth-orbit (< 2000 km vertical altitude), the Earth's gravity is almost as strong as on the Earth's surface. However, a spacecraft is in free-fall since it is falling perpetually toward the Earth, but keeps missing. In a free-fall frame, there is weightlessness since gravity pulls on everything equally. Hence, weightlessness. The spacecraft, in fact, consitutes a very exact elementary inertial frames.

    Credit/Permission: NASA 2010 (uploaded to Wikimedia Commons by User:Ras67, 2010) / Public domain.
    Image link: Wikimedia Commons: File:STS-130 Endeavour flyaround 5.jpg.
    Local file: local link: iss_orbit.html.
    File: Orbit file: iss_orbit.html.