The End of Cosmology

Deep Sky from HubbleScientific American’s feature article this month posits about the End of Cosmology, which is the study of the universe. And why should cosmology end, you may ask? Because future cosmologists will be unable to get any data, they respond.

As of the late ’90s, the universe is seen as being filled with a “dark energy” (don’t ask!) that is essentially defeating gravity and causing the universe to blow up like a balloon. The stars, galaxies, clusters of galaxies – everything – will eventually separate (an an ever expanding rate) so that all chance of communication between them is lost.

Consider that. Right now if you look at one side of the sky and point, you’re pointing at galaxies that are over 13 billion light years away. Same with the other side of the sky. They can’t communicate with each other, because light hasn’t had enough time to go from one to the other (“causally disconnected” is the proper term).

What happens when each and every galaxy is causally disconnected from every other galaxy because of this runaway expansion? What will cosmologists of the future think they know when they see only one “island universe” surrounded by nothing?

What will the scientists of the future see as they peer into the skies 100 billion years from now? Without telescopes, they will see pretty much what we see today: the stars of our galaxy. The largest and brightest stars will have burned up their nuclear fuel, but plenty of smaller stars will still light up the night sky. The big difference will occur when these future scientists build telescopes capable of detecting galaxies outside our own. They won’t see any! The nearby galaxies will have merged with the Milky Way to form one large galaxy, and essentially all the other galaxies will be long gone, having escaped beyond the event horizon.

Oddly enough, that’s exactly what cosmologists thought barely 100 years ago, before Slipher and Hubble laid the groundwork showing that other galaxies were separate entities from our own. Until then, what astronomers thought of the scale of the universe was essentially mistaken. But how then will they come to understand that the universe is expanding?

As a result, Hubble’s crucial discovery of the expanding universe will become irreproducible. All the expanding matter in the universe will have visually disappeared beyond the horizon, and everything remaining will be part of a gravitationally bound cluster of stars. For these future astronomers, the observable universe will closely resemble the “island universe” of 1908: a single enormous collection of stars, static and eternal, surrounded by empty space.

It’s possible, but unlikely that the information and knowledge that we have today will survive 100 billion years. Gee – I am not able to play 8-track tapes from the ’70s today. I hope that my CDs will be playable in 10 years.

But I have another question that this article totally ignores (and I simply can’t believe that the authors, Lawrence M. Krauss and Robert J. Scherrer, didn’t consider it). Have we already missed the opportunity to make some critical observations?

After all, if it won’t be possible to reproduce some critical observations in the distant future, observations that form the foundation of our understand of the nature of the cosmos now, then why should be think that we haven’t missed (forever!) opportunities to make other critical observations? When Steven Weinberg wrote The First Three Minutes in the early ’70s he essentially stated that we had enough information and knowledge to accurately know what was going up up to the first three minutes after the creation of the universe. Later advances and deeper understanding let physicists state that they understood the universe back to the first 10**-35 seconds (that’s one part in 1-followed-by-35-zeros seconds, which is even faster than the time between the light turning green and the guy behind you honking his horn). Any earlier than that, physicists are loath to proclaim that they understand the universe at the earliest moments (but they’re working on it).

I contend that we’ll never know some things. It’s not possible. These things are not beyond our ability to observe, but they are shielded from our eyes by the nature of the universe (and my suspicion is that it has to be that way if the universe is to be self-consistent).

I’m surprised that Scientific American avoided this line. Then again, given their history, maybe not.

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