I Why Schwarzschild metric?

1. Jun 25, 2017

davidge

Why one uses Schwarzschild metric instead of FLRW metric when deriving things such

- deflection of light by the sun
- precession of perihelia of planets

Also, as our solar system is not isotropic nor static, it seems that by using the Schwarzschild metric we would get only an approximation on the results. So why we still get accurate result for the precession of perihelia of Mercury?

2. Jun 25, 2017

Ibix

Because the FLRW metric assumes that spacetime is filled with uniformly distributed matter. A bad approximation on the scale of the solar system.
Because it's a very good approximation because the mass of the Sun is such a huge percentage of the total mass of the solar system.

3. Jun 25, 2017

davidge

Ah, ok. Thanks.

A bit off topic... but, the name precession of perihelia is due to the fact the we use the nearest distance $r$ of the planet from the sun when computing the angle? Is there a special motivation for non using the aphelion distance instead?

4. Jun 28, 2017

vanhees71

No, it's just common use in astronomy.

5. Jun 28, 2017

Thanks.