Cosmology in the Deep Lambda Era
We are observing the universe at an age of ~14 Gyr, where it is rich in cosmological information. What will astronomers at t ~ 100 Gyr be studying?
(First of all, they better be living around very low mass stars, or living in a lucky part of the universe that is still forming stars. Present day solar mass stars will long since have died!)
1. The Microwave Background?
At 100 Gyr, R(t) ~ 200, so TCMB~0.015 K. The CMB will be:
- Redshifted to 1m wavelengths (300 GHz frequency)
- Down in intensity by a factor of ~ 1012.
At later times (500 Gyr), the CMB is redshifted to frequencies where scattering by the ionized interstellar medium will screen it, making it invisible.
So... very hard to impossible to observe; no cosmological constraints.
2. Large scale structure?
By 100 Gyr, even the Virgo Cluster will have moved out of our horizon. No large scale structure will be visible.
No cosmological constraints.
3. The expansion history of the universe?
Not really. The density of local galaxies to sample the Hubble expansion is very small, and many will have fallen into the Local Group and not be participating in the expansion.
Not much cosmological constraint.
4. Observations of the early universe.
Nope, galaxies that are currently at high redshift will have long since been carried out of our horizon.
No cosmological constraints.
5. The abundances of the light elements.
Light elements will have been highly processed by subsequent generations of star formation. No ability to measure primordial abundances at high redshift. No CMB to compare to or even motivate the comparison!
No cosmological constraints.
6. Galaxy Evolution.
What galaxy evolution? Really only the Milkomedia to observe. And most information contained in the stellar record is lost, since the stars have died.
Very limited cosmological constraint.
What's left?
A feeble, static universe where the Milky Way (now Milkomedia) is the entire observable universe.