# Long-Term Forecast

This xkcd cartoon is undeniably awesome as-is, but the cosmologist in me couldn’t resist adding one more row at the bottom.

Looks like the forecast calls for Boltzmann Brains! I guess Hilbert space is finite-dimensional after all.

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### 12 Responses to Long-Term Forecast

1. James Goetz says:

Hey Sean, that;s funny. But seriously, when do you think that the average temperature of the universe will first reach -459 Fahrenheit?

2. Trevor says:

Not this Boltzmann brain bullshit.

3. Bill Johnson says:

How are you measuring time in 10^10^35?

4. JR says:

Hey, Bill Johnson, does it make any difference in what unit of time do you measure 10^10^35?! What is the difference between 10^35 and 10^35-8 or 10^35-14?? (Notice, however, that I am a firm advocate of units in the axes!)

5. Ken K says:

Thanks for the laugh!

6. Max says:

If one BB, why not many in a row? Why not an infinite number of them? Why not whole universes of experience? Seems like this line of reason can lead to some bizarre conclusions… So why not 0 BBs?

7. Elizabit says:

Funny thing about time is that it’s dependent upon the frame of reference…. A photon of light exists without time…. meanwhile space-time is inseparable. And light propagates in the same timeless manner is all frames of reference…. So, when light is gone what happens to all those frames of reference? Without an observer to intercept, qualify and quantitate the missing observable waveforms, would nothing really exist? Gives new meaning to vacuum packed!

8. Elizabit says:

Opps, correction to my statement above.. a photon of light is particulate…. which is the observable state of light

9. John Barrett says:

Has an oscillating universe really become out of the question? I had always thought that an oscillating universe would be more likely to produce life, since there would be more chances for it to be able to do so. Therefore, it would be more likely, since life exist here on Earth. Then I never really held much merit into that type of reasoning anyways… If there is no more room for the oscillating universe, life must have been much more likely than I have thought it to be.

10. Kasuha says:

I don’t really like the Boltzmann brains idea. It’s ill defined – they may be everywhere around us without us ever noticing, or they may never appear in whatever future the universe has, based on how strict are we with the definition.

My opinion is that the Universe’s phase space has two kinds of states: reachable and unreachable. And there is no proof that the set of reachable states contains any Boltzmann brains.

If we play with the idea that all states are reachable in the future if we wait long enough, then the Universe is inevitably cyclic and will return to the Big Bang state as that’s also one state in the phase space, reachable, and will be reached.

11. Roy says:

If a Boltzmann brain comes into existence then must there also be an anti-Boltzmann brain created at the same time? Because otherwise we would be violating the conservation of baryon number. If a Boltzmann and anti-Boltzmann brain mind melded then how much of the matter and anti-matter would annihilate before the intense heat blew both their minds apart? How long would it take for only a neutron and anti-neutron to come into existence? Maybe the universe is older than we realize and full of intelligent life playing video games and not trying to contact us. Sean please insert more credits to continue.

12. David Brown says:

10^(10^35) years —> string theory with the infinite nature hypothesis.
String theory with the finite nature hypothesis? Google “witten milgrom”.