The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

The Galaxy in which we live is composed of three ingredients: stars, interstellar gas and cosmic rays.

The bulk of the mass is in the stars. A fair estimate can now be made of the amount of gas. It is probably between 5 and 10% of the total mass of the system.

The cosmic ray particles have a negligible mass density, but a considerable energy density, comparable to the kinetic energy of the interstellar gas. Their velocities are so high that they would leave the system in a time of the order of 100 000 years if they were not constrained by magnetic fields. The current theory is that cosmic rays, except for some rare particles with exceptionally high energies, are kept in the Galactic System by magnetic fields. As the latter are frozen in the interstellar gas, the cosmic rays exert a pressure on this gas and may thus influence its motion and distribution.

The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

The Chairman, W. Fricke, President of Commission 4, opened the Joint Discussion by drawing attention to the purpose and proposed procedure for the meeting. The Joint Discussion had been arranged by the Executive Committee of the Union in order to avoid the necessity for separate discussions by each Commission that was affected by the Report of the Working Group on the IAU System of Astronomical Constants. The Organizing Committee therefore proposed the following resolution:

Radar echoes have already been detected from Venus, Mercury, Mars, and Jupiter. Time delay measurements of high precision between Earth and Venus, as well as between Earth and Mercury, have disclosed significant deviations from the published ephemerides of these planets. Although new simultaneous solutions for the A.U., the relevant planetary masses, radii, and orbital elements have not yet been carried out, preliminary analysis indicates that the light-second equivalent of the A.U. is 499.0050 ± 0.0004 and that the corresponding kilometer equivalent is about 149 598 000 ± 100 (using c = 299 792.5 km/sec). The same analysis shows that, with respect to Earth, both Venus and Mercury seem to be ahead in their orbits relative to predictions. The radius of Venus appears to be about 6100 ± 50 km, in agreement with the most accurate optical determination. Doppler spread measurements show Venus to have a retrograde rotation with a period of about 247 ± 5 days. The celestial latitude of its axis is about – 85 ± 2 degrees.